Embodiment
Explanation is from introducing the manufacture method according to the first scheme III group-III nitride semiconductor crystal of the present invention.
Be included in the first step of the particulate of deposit III family metal on the substrate surface according to the manufacture method of the first scheme III group-III nitride semiconductor crystal of the present invention, being second step of nitrogenize particulate in containing the atmosphere of nitrogenous source afterwards, is the third step of growth III group-III nitride semiconductor crystal then.
The manufacture method that comprises three steps can make the III group-III nitride semiconductor crystal be formed on the substrate with having well-crystallized.In addition, this method can easily be made high-quality III group-III nitride semiconductor crystal, needn't need accurately to create conditions as the art methods of using low temperature buffer layer simultaneously.Here the III group-III nitride semiconductor crystal In that mentions
xGa
yAl
zN represents, (wherein x+y+z=1,0≤x≤1,0≤y≤1,0≤z≤1).
The substrate that uses in above manufacture method can be glass, SiC, Si, GaAs, sapphire or other similar substance.Use sapphire (Al
2O
3) advantage of substrate is to obtain high-quality crystal and can obtain material at low cost.When using sapphire, the plane of use comprises m, a and c face.The preferred c face ((0001) face) that uses also needs the vertical axis and<0001 of substrate surface〉direction has the inclination angle.Before also preferably using substrate in first step substrate being carried out the similar preliminary treatment of organic washing or corrosion or other, is owing to can keep substrate surface to be in the normal state like this.
The III family metal particle that is deposited in first step on the substrate can be the particulate of Al, Ga, In etc.In the present invention, preferably use In
uGa
vAl
wParticulate (wherein u+v+w=1,0≤u≤1,0≤v≤1 and 0≤w≤1).Use In
uGa
vAl
wAdvantage be it and the III group-III nitride semiconductor that forms subsequently has good affinity.The impurity that can add III family metal particle to comprises the similar non-III of Si, Be, Mg and other family metal.When using the decomposition deposit III family metal of metallic compound, III family metal particle can contain the impurity just like carbon, hydrogen and halogen etc., but they also can be used as metal particle.
Can make the deposit particulate that ins all sorts of ways, for example the thermal decomposition of metal-organic material or metal halogen compound, vapour deposition and sputter.The preferred thermal decomposition deposition III family metal particle that uses metal-organic material.For metal-organic material, operable compound is trimethyl gallium (TMG), triethyl-gallium (TEG), trimethyl aluminium (TMA), trimethyl indium (TMI) and bicyclic pentadiene indium (Cp for example
2In).Using an advantage of the thermal decomposition deposition III family metal particle of metal-organic material is original position to carry out deposit.
If in containing the nitrogenous source atmosphere of ammonia for example, carry out first step, can produce the problem that for example stops surface migration etc. so.For this reason, preferably in the atmosphere that does not contain nitrogenous source, carry out first step.Here do not consider to use and extensively be used as the N that inertia is carried gas
2Gas is as nitrogenous source.N
2Gas can not be because its decomposition temperature is higher than the decomposition temperature as nitrogenous sources commonly used such as ammonia or hydrazines as effective nitrogenous source.Therefore, for the first step in these methods, in atmosphere, comprise N
2Gas can impact effect.Operable gas comprises hydrogen, rare gas and nitrogen.Need or be higher than under the temperature of III family melting point metal and carry out first step, be because this helps the migration of metallic atom on the substrate.
The III family metal particle that is deposited in first step on the substrate surface is the deposit that distributes discontinuously.Particulate is combination in position.Can use atomic force microscope (AFM) to observe the deposit state of particulate on the substrate surface.About 50 of III family metal particle that form in this first step are to 1000 height, and about 100 that pass through are long to 10000 , and when from top when vertically observing, the superficial density scope of particulate is from about 1 * 10
6Cm
-2To 1 * 10
10Cm
-2
If carry out second step in containing the atmosphere of metal material, the crystallinity of the III group-III nitride semiconductor crystal of growing in third step so can be degenerated, so should carry out second step in the atmosphere that does not contain metal material.For second step, can use and contain ammonia or hydrazine atmosphere as nitrogenous source.Preferably 1000 to 1 * 10
5Carry out second step under the atmospheric pressure of Pa.The III family metal particle that uses the profile analysis of transmission electron microscope (TEM) to be presented at nitrogenize in second step have polycrystalline and/structure of amorphous and comprise unreacted metal.
Need carry out second step under the temperature of carrying out first step being not less than.The experiment demonstration that the inventor carries out is done like this and can be produced the III group-III nitride semiconductor crystal with well-crystallized.Promote the particulate nitridation reaction, preferably or be higher than 700 ℃ temperature and carry out second step, more preferably or be higher than 900 ℃ and carry out.By with on it the fine-grained substrate of deposit or be higher than in 700 ℃ of atmosphere that contain nitrogenous source and keep carrying out in 1 to 10 minute the nitrogenize of III family metal particle in second step.
Need carry out third step under the temperature of carrying out second step being not less than.The favourable part of doing like this is the III group-III nitride semiconductor of growing in high quality.Particularly, preferably or be higher than 700 ℃ temperature and carry out third step, more preferably or be higher than 900 ℃ and carry out.
In third step, can form the III group-III nitride semiconductor crystal by various vapor growth methods, comprise metal-organic chemical vapour deposition (MOCVD) method, molecular beam epitaxy (MBE) method and vapor phase epitaxy (VPE) method.Because mocvd method can be used for growing film, therefore especially preferably use mocvd method to form the III group-III nitride semiconductor crystal.Known mocvd method is 1000 to 1 * 10
5Contain grown layer in the gas of metal-organic material and nitrogenous source under the pressure of Pa.Existing knownly use mocvd method to carry out the compound semiconductor that third step can obtain having well-crystallized being higher than under 1000 ℃ the temperature based on gallium nitride.This is considered to because different with other temperature, or be higher than 1000 ℃, become strong horizontal growth pattern based on the growth pattern of the compound semiconductor of gallium nitride.At this moment, can form crystal layer with the low dislocation of good surface morphology.
In the manufacture method of the III of alternative plan group-III nitride semiconductor crystal according to the present invention, in first step, in the atmosphere that does not contain nitrogenous source, be not less than the temperature T 1 time of metal 1 fusing point, comprise that the thermal decomposition that is selected from the metal-organic material of at least a metallic element among In, Ga and the Al is used on Sapphire Substrate depositing metal 1 (by In
uGa
vAl
wExpression, u+v+w=1 wherein, 0≤u≤1,0≤v≤1 and 0≤w≤1), metal 1 comprises one or more metallic elements that are selected from In, Ga and Al.Carry out second step afterwards, do not containing metal-organic material and containing in the atmosphere of nitrogenous source in temperature T 2 (the nitrogenize metals deposited 1 down of T2 〉=T1) wherein.Carry out third step then, temperature T 3 (wherein under the T3 〉=T2), use the metal-organic chemical vapor deposition method thereon on the Sapphire Substrate of depositing metal 1 extension ground growth III group-III nitride semiconductor (use In
xGa
yAl
zN represents, x+y+z=1 wherein, 0≤x≤1,0≤y≤1,0≤z≤1) crystal.
By above method, the III group-III nitride semiconductor crystal with well-crystallized can be grown on the Sapphire Substrate to extension.In addition, this method can easily be made high-quality III group-III nitride semiconductor crystal, needn't need accurately to create conditions as the art methods of using low temperature buffer layer simultaneously.
The inventor also finds can strengthen by the Sapphire Substrate of using (0001) face the preferred steps flow process growth of III group-III nitride semiconductor crystal, and wherein the vertical axis of (0001) face tilts with<0001〉direction in specific direction.The specific direction that tilts when vertical axis is<1-100〉and apart from<0001 inclination angle when being 0.2 ° to 15 °, the steps flow chart growth is maximum, so they can be used as creating conditions of high-quality III group-III nitride semiconductor crystal.
For thermally decomposable metal-organic material effectively, preferred temperature T 1 is at least 200 ℃, but also is not less than the fusing point of metal 1.More preferably the T1 more than 900 ℃ is so that decompose and guarantee that metals deposited 1 melts near 100% metal-organic material.The temperature T 3 of extension ground growth III group-III nitride semiconductor crystal should be at least 700 ℃, more preferably is at least 900 ℃ to guarantee the decomposition fully of nitrogenous source.
Confirm because metal 1 is being higher than deposit under the temperature of fusing point that by atomic force microscope observation surface tension makes metal form particulate rather than layer on Sapphire Substrate.Even after the nitrogenize of second step, metal 1 particulate still keeps their shape.A tree name is estimated because the use particulate carries out the epitaxial growth of III group-III nitride semiconductor crystal as nuclear, therefore the III group-III nitride semiconductor crystal that can obtain having well-crystallized.
Use the profile analysis of transmission electron microscope confirm in second step III family metal particle of nitrogenize be polycrystalline and polycrystal be not (the composition In that this is regional in 1: 1 the zone in the stoichiometric proportion of nitrogen and metal
uGa
vAl
wN
kExpression, u+v+w=1 wherein, 0≤u, v, w≤1 and 0<k<1).A tree name estimate to have its source in metal-organic material and nitrogenous source provide simultaneously form low temperature buffer layer make by high-temperature heat treatment after the low temperature deposition layer crystallization prior art growth pattern and according to the difference between the method for metal nitride 1 of the present invention.
According to third party's case, the manufacture method of III group-III nitride semiconductor crystal comprises and III family metal material is provided to the substrate of heating and deposit III family's metal material and/or decompose the first step of its product on substrate, be second step of heat treatment substrate in containing the atmosphere of nitrogenous source afterwards, then for using III family's metal material and nitrogenous source by on substrate, the grow third step of III group-III nitride semiconductor of vapour phase processes.
Metal-the organic material that contains in the atmosphere of using in first step can be metal-organic compound, metal halogen compound or metal or analog.Wherein preferably use metal-organic compound.In first step, the metal-organic compound of operable III family element comprises trimethyl gallium (TMG), triethyl-gallium (TEG), trimethyl aluminium (TMA), trimethyl indium (TMI) and bicyclic pentadiene indium (Cp
2In).In order to mix as element rather than the III family metal of Si or Mg etc., with monosilane (SiH
4), disilane (Si
2H
6) and bis-cyclopentadienyl magnesium (Cp
2Mg) etc. add in the atmosphere.
In first step, the also atmosphere in preferred nonnitrogenous source.If comprise the nitrogenous source as ammonia in first step, Sheng Chang the compound semiconductor layer based on gallium nitride can not have the minute surface form so.This introduces in the prior art of JP-C 3026087 and JP-A-HEI 4-297023.N
2Gas extensively is used as inertia and carries gas, but is not considered as nitrogenous source here.N
2Gas is not effective nitrogenous source, is because its decomposition temperature is higher than the decomposition temperature as nitrogenous sources commonly used such as ammonia or hydrazines.Therefore, for the first step in these methods, in atmosphere, comprise N
2Gas can the appreciable impact effect.Operable gas comprises hydrogen, nitrogen and rare gas.
The experiment that the inventor carries out is presented at or is higher than to be carried out second step and can produce the III group-III nitride semiconductor crystal with well-crystallized under the temperature of carrying out first step.Particularly, promote the particulate nitridation reaction, preferably or be higher than 700 ℃ and carry out second step, more preferably or be higher than 900 ℃ and carry out.Particularly, use the temperature more than 1000 ℃ can obtain good crystallinity.Need in third step, use mocvd method growth III group-III nitride semiconductor crystal.Use this method to use identical epitaxial reactor from first to third step.When using mocvd method, the ideal temperature that uses for third step more than 1000 ℃ or 1000 ℃.Using the temperature more than 1100 ℃ or 1100 ℃ better, is because this helps to obtain the minute surface crystal.Preferably carrying out third step in containing the atmosphere of hydrogen, is because so easily crystallization control and configuration of surface.
As mentioned above, sapphire is desirable substrate.Need to use to have the Sapphire Substrate of (0001) face, wherein vertical axis tilts with<0001〉direction in specific direction.As mentioned above, the preferred orientations that tilts of this vertical axis is<1-100〉and be 0.2 ° to 15 ° apart from<0001〉direction preferred angled angle.
When use has vertical axis at<1-100〉in the direction with<0001 when tilting 0.2 ° to 15 ° the Sapphire Substrate of (0001) face, be grown in III group-III nitride semiconductor crystal on the substrate have vertical axis in specific direction with<0001〉direction (0001) face that tilts.Here, the specific direction of the surface tilt of III group-III nitride semiconductor crystal will be<11-20 〉, be owing to compare with the planar orientation of substrate, crystal is with 30 ° curl growth.When apart from<0001〉inclination angle when being 0.2 ° to 15 °, strengthened the steps flow chart growth, can be used as creating conditions of high-quality III group-III nitride semiconductor crystal.
Manufacture method is included in first step known heat treatment before, is called thermal annealing.One type the clean of widely used thermal annealing when using sapphire in epitaxial reactor, carrying out.Be usually included in the atmosphere that contains hydrogen or nitrogen 1000 ℃ to 1200 ℃ heated substrate.
In manufacture method, first step also can be divided into a plurality of steps, is contained in the metal-organic material type in the atmosphere, its composition and its mixed proportion and all changes at every turn.Other condition also can change, for example the temperature and time length of substrate processing.When first step was divided into a plurality of step, preferred atmosphere in a first step contained the metal-organic material that comprises Al.This is because in III family metal, Al has high-melting-point and combines with substrate easily.
The step of annealing in the atmosphere of metal-containing material neither also nonnitrogenous source is included between first and second steps, and/or second and third step between.Annealing has promoted the distribution of metal particle.Any this annealing all should be carried out under the temperature that is not less than III family metal particle fusing point.Temperature should be at least 900 ℃, more preferably is at least 1000 ℃.Annealing also should be carried out in nitrogen atmosphere.
Carry out second step and change underlayer temperature simultaneously.This moment, same second step also should be carried out more than the temperature in the decomposition temperature of nitrogenous source or this.Second step should be carried out at least 700 ℃, and more preferably at least 900 ℃, preferably at least 1000 ℃.The beginning temperature of second step should be higher than end temp.Second step begins with the uniform temp that first step uses, and finishes at the uniform temp that carries out third step.When changing temperature during second step, change by changing the carry gas type and flow velocity and chamber pressure that use.
Below with reference to the detailed content of accompanying drawing introduction according to the manufacture method of the compound semiconductor that the present invention is based on gallium nitride.
Fig. 1 shows formation based on the growth mechanism in the step of gallium nitride compound semiconductor layer, and Fig. 2 shows an example of the heating mode that formation uses during based on gallium nitride compound semiconductor layer.
Use following steps on substrate, to form based on gallium nitride compound semiconductor layer.As shown in Figure 1a, in steps A (first step), metallic element, metal nucleus (drop) Sa of preferred III family metallic element is attached to substrate 1.Needn't also can be the liquid form of covering surfaces for isolated non-conterminous particulate at this stage metal nucleus Sa.Next, in step B (second step), annealed metal nucleus Sa (Fig. 1 (b)).Even in first step, particulate is not required isolated fully state, but after the annealing is.Next, in step C (third step), the metal nucleus Sa1 of nitrogenize annealing forms growth nucleus Sb (Fig. 1 (c)).The nucleus Sb that no matter grows is any shape, as long as have suitable distribution, they can be as the growth nucleus.Yet by experiment, the inventor determines that the shape of growth nucleus Sb is influential to the crystalline nature based on gallium nitride compound semiconductor layer really.Preferably, the III group-III nitride semiconductor crystal is essentially trapezoidal, and smooth end face is parallel to substrate 1, and smooth side and substrate 1 have a certain degree.By gas, reactor pressure, underlayer temperature and the substrate heating mode of considering to use during the nitrogenize, growth nucleus Sb can form the shape that needs.
In step D (the 4th step), growth is based on the compound semiconductor layer (Fig. 1 (d)) of gallium nitride on the substrate 1 with growth nucleus Sb.Flatly grow,, guarantee enough layer depth (for example 2 μ m), the compound semiconductor layer 2 based on gallium nitride (Fig. 1 (e)) smooth, level is provided thus usually with dislocation.
In epitaxial growth device, carry out steps A continuously to D by mocvd method.Carry out before the steps A, under 1000 ℃ to 1200 ℃ the temperature in the MOCVD device thermal cleaning Sapphire Substrate for example, (illustrate 1170 ℃) as shown in Figure 2 as the temperature of using.Do like this is in order to remove any oxide-film or the analog of substrate surface.Temperature with epitaxial growth device is reduced to for example 5 ℃ to 200 ℃ then, and remains on this temperature (among Fig. 2 being 1100 ℃).Carry out steps A, B and C in this temperature.Form growth nucleus Sb midway by nitriding process in step C, the temperature in the grower raises and remains on the temperature (among Fig. 2 being 1160 ℃) of this rising: this temperature carry out step D with further growth on growth nucleus Sb based on the compound of gallium nitride.
More than introduce with the step shown in Fig. 1 only be an example of the inventive method, method of the present invention is not limited to this.For example, can use thermal cleaning if desired.Similarly, heating mode is not limited among Fig. 2 shown, is owing to wishing that use is suitable for type, the nitrogenous source of the shape of epitaxial reactor, metal-organic material and carries the flow velocity of gas, use and the condition of other similar factor.Can use different temperature in each of steps A, B and C, or steps A can be used different temperature with B and step B with C.In addition, step D can be than the steps A temperature low to C or carry out under identical temperature.
Thus, in these examples of the present invention, the first metal nucleus Sa is attached to substrate 1, forms the basis of growth nucleus Sb, and compound based on gallium nitride is used to grow.Can control the growth of the metal nucleus Sa that is attached to substrate 1 by the flow velocity, the time span of gas flow, the technological temperature of use etc. of control metal-organic gas, control the density of metal nucleus Sa on the substrate 1 thus.
By in the part that does not have metal nucleus Sa, generating metallic vapour, and in adhering to the space of exposing between the part of Sa1, form substrate surface, because with the wetting generation caking of substrate, annealed metal nucleus Sa has increased the vertical dimension (Sa1 among Fig. 1 (b)) of metal nucleus Sa, has reduced adhesive force.This can control to the state that needs, i.e. the density of the growth nucleus Sb that is obtained by nitrogenize.Particularly, gas that uses during the annealing and temperature, pressure, duration and other conditions of similarity control of density effectively.Can suitably select these conditions according to the metal types of the metal nucleus Sa use that is attached to substrate, the shape of reactor etc.According to the experiment that the inventor carries out, think that the gas that uses should be hydrogen, temperature should be at least 900 ℃, and the time that annealing continues is not less than 5 minutes.
Next, metal nitride nucleus Sa1 changes them into form nitride-based semiconductor growth nucleus Sb.As mentioned above, the shape of growth nucleus Sb should be trapezoidal, has the flat top that is parallel to substrate 1 and smooth side.The condition of using during the nitriding process by control can control growing nucleus Sb shape.Particularly, the gas that uses during the nitrogenize, temperature and pressure and other conditions of similarity can both be controlled shape effectively.Can suitably select these conditions according to the metal types of the metal nucleus Sa use that is attached to substrate, the shape of reactor etc.According to the experiment that the inventor carries out, think that the gas that uses should be hydrogen, temperature should be at least 900 ℃, answers elevated temperature between nitriding step.
More the compound semiconductor based on gallium nitride is grown on the growth nucleus Sb, so filled space between the adjacent growth nucleus Sb based on the compound growth of gallium nitride, forms flatness layer.Therefore finally, can form and need thickness and crystalline compound semiconductor layer 2 based on gallium nitride.
This surface based on the compound semiconductor layer of gallium nitride is covered by the compound based on gallium nitride, keeps very excellent lattice matching characteristic with the upper strata.Thus, by the compound semiconductor layer 2 based on gallium nitride, can form the compound semiconductor layer of multilayer based on gallium nitride on substrate 1, every layer all has good crystallinity.This has improved the characteristics of luminescence of using the light emitting semiconductor device of making based on the compound semiconductor of gallium nitride.Light emitting semiconductor device by above method manufacturing also can be used for electronic equipment, the vehicles, traffic signals etc., as the light source with favorable luminance and other similar characteristics of luminescence.
The substrate that uses in above method can be glass, SiC, GaAs, sapphire etc.Use Sapphire Substrate (Al
2O
3) advantage be that crystal mass is high and can obtain at low cost.When using sapphire, m, a and c face are operable plane.Wherein, preferably use c face ((0001) face).Before also preferably using substrate in first step substrate being carried out organic washing or corrosion or other preliminary treatment, is because can make substrate surface remain on normality like this.
The metal that is attached to the metal nucleus use of substrate in first step comprises Al, Ga and In.In the present invention, preferably use the nucleus of III family metal, use In
uGa
vAl
wExpression (wherein u+v+w=1,0≤u≤1,0≤v≤1 and 0≤w≤1).In
uGa
vAl
wHas the advantage that good affinity is arranged with the compound semiconductor based on gallium nitride that forms thereafter.The impurity that doped with II I family metal particle can add comprises the similar non-III of Si, Be, Mg and other family metal.When decomposing metal compound during with deposit III family metal, III family metal particle can contain just like impurity such as carbon, hydrogen and halogens, also can be used as the metal nucleus.
Can the metal nucleus be attached to substrate by the whole bag of tricks, comprise thermal decomposition, vapor deposition and the sputter of metal-organic material or metal halogen compound.For the present invention, preferably use the thermal decomposition of metal-organic material, be owing to can easily control the density and the shape of metal nucleus.Operable metal-organic material comprises trimethyl gallium (TMG), triethyl-gallium (TEG), trimethyl aluminium (TMA), trimethyl indium (TMI) and bicyclic pentadiene indium (Cp
2In).Use the metal-organic material that for example contains gallium, aluminium or indium to adhere to as In
uGa
vAl
wThe metal nucleus of III family metal.
In containing the atmosphere of the nitrogenous source of ammonia for example, carry out first step and can produce the problem that for example stops the metallic atom surface migration.Therefore preferably in the atmosphere that does not contain nitrogenous source, carry out first step.Here, do not consider to use and extensively be used as the N that inertia is carried gas
2Gas is as nitrogenous source.N
2Gas can not be because its decomposition temperature is higher than the decomposition temperature as nitrogenous sources commonly used such as ammonia or hydrazines as effective nitrogenous source.Therefore, for the first step in these methods, in atmosphere, comprise N
2Gas can impact effect.Operable gas comprises hydrogen, rare gas and nitrogen.
Should carry out first step under the temperature that is not less than metal nucleus fusing point, be because this helps the migration of metallic atom on the substrate.The metal nucleus that is deposited in first step on the substrate surface is the deposit that distributes discontinuously.Particulate is combination in position.Can use atomic force microscope (AFM) to observe the deposit state of metal nucleus on the substrate surface.Observation shows about 50 of the metal nucleus that forms to 1000 height in first step, about 100 that pass through are long to 10000 , and when from top when vertically observing, the superficial density scope of particulate is from about 1 * 10
6Cm
-2To 1 * 10
10Cm
-2
For annealing steps, preferred use both nonnitrogenous source also not containing metal-organic material carry gas annealing metal nucleus, be owing to can make nucleus become piece effectively like this.Hydrogen, rare gas and nitrogen can be used as and carry gas, but preferably use hydrogen, and hydrogen has the effect of removing oxide from the metal nucleating surface.Also being not less than the annealing of carrying out the metal nucleus under 700 ℃ the temperature being not less than metal nucleus fusing point, is owing to can make nucleus become piece effectively like this.
Should carry out annealing steps under the temperature of carrying out first step being not less than.The experiment that the inventor carries out shows to do like this can make the compound semiconductor crystal based on gallium nitride with well-crystallized.Even when under the uniform temp that first step uses, annealing, can produce good crystallinity and easy using system device with the condition in the control reactor.
If the step of metal nitride nucleus occurs in the atmosphere that contains metal material, the crystallinity based on the compound semiconductor of gallium nitride of growing in the step so afterwards will be degenerated.Therefore, nitriding step should carry out in the atmosphere that does not contain metal material.In the present invention, for the metal nitride nucleus contain nitrogenous source atmosphere, can use the atmosphere that contains ammonia or hydrazine.Should be 1000 to 1 * 10
5Carry out this step under the pressure of Pa.Use the profile analysis of transmission electron microscope (TEM) to be presented at the growth cores that the metal nitride nucleus forms in the above nitriding step and be structure polycrystalline and/or amorphous, and comprise unreacted metal.
Be to promote the nitridation reaction of metal nucleus, nitriding step should carry out more than 700 ℃ or 700 ℃, preferably carries out more than 900 ℃ or 900 ℃, so that produce the compound semiconductor crystal based on gallium nitride with well-crystallized.By with on it the substrate of depositing metal nucleus in containing the atmosphere of nitrogenous source, form the growth nucleus in the nitrogenize that keeps more than 700 ℃ or 700 ℃ carrying out the metal nucleus in 1 to 10 minute.
The temperature of carrying out nitriding step should be not less than the temperature of annealing steps, is owing to can produce the compound semiconductor crystal based on gallium nitride with well-crystallized like this.Even with the identical temperature of annealing under when carrying out nitrogenize, can produce and have good crystalline compound semiconductor based on gallium nitride, and easily the using system device with the condition in the control reactor.
Be not less than 700 ℃ more preferably be not less than the favourable part of carrying out on the substrate that has the growth nucleus under 900 ℃ the temperature based on the growth step of the compound semiconductor of gallium nitride be like this can growing high-quality the compound semiconductor based on gallium nitride.Can adopt various vapor growth methods to carry out growth step, comprise metal-organic chemical vapour deposition (MOCVD) method, molecular beam epitaxy (MBE) method and vapor phase epitaxy (VPE) method based on the compound semiconductor of gallium nitride.Because mocvd method can be used for growing film, therefore especially preferably use mocvd method.For the present invention, known mocvd method is 1000 to 1 * 10
5Under other pressure of Pa level in the atmosphere that contains metal-organic compound and nitrogenous source growing semiconductor.
The growth step that carries out under the temperature of carrying out nitriding step based on the compound semiconductor of gallium nitride should be not less than.The experiment that the inventor carries out shows can produce the compound semiconductor crystal based on gallium nitride with well-crystallized like this.Even when under the temperature identical, carrying out the growth step of compound semiconductor, can produce good crystallinity and easy using system device with the condition in the control reactor with nitrogenize.
Above introduction is that relevant metal nucleus Sa is attached on the substrate 1 and annealed metal nucleus Sa.Yet repeatedly adhesion metal nucleus Sa is to replace annealing.Repeatedly adhesion metal nucleus Sa is with the density of the growth nucleus Sb that forms among the controlled step C.At this moment, in the second stage step of phase I step of adhering to first metal core and the adhesion metal nucleus second time, select fluent material to help density and the shape of control growing nucleus Sb according to the adhesiveness of substrate 1.For the present invention, preferred phase I step contains the step that is selected from metal-organic material of containing aluminium, contains the metal-organic material of gallium and contain the gas of at least a steam in the metal-organic material of indium for flowing, second step contains the step with the gas of phase I step different metal-organic material steam for flowing.At this moment, in the phase I step, for example, fluent material contains and combines well Al with substrate, so that on substrate, form the metal nucleus Sa of predetermined density, in the second stage step, mobile for example Ga or In etc. to make metal nucleus Sa, form Ga or the In structure around Al in conjunction with not so good material.Though phase I step and second stage step can replace once, preferably alternately twice or repeatedly.
Be that nitrogenize formation growth nucleus does not carry out any annealing after this.Identical, same during with use annealing control metal nucleus Sa1 density, can form growth nucleus Sb by suitably controlling nitrogenize with excellent in shape.During annealing, the gas that uses during the nitrogenize, temperature and pressure all are the conditions of influence control shape.Can suitably select these conditions according to the nitrogen material that uses in the material of metal nucleus Sa, the nitrogenize, shape of reactor etc.According to the experiment that the inventor carries out, think that the gas that uses should be hydrogen, temperature is at least 900 ℃, should increase temperature during the nitriding step.
This moment is same, should be not less than the growth step that carries out under the temperature of nitrogenize based on the compound semiconductor of gallium nitride.The experiment that the inventor carries out shows can make the compound semiconductor crystal based on gallium nitride with well-crystallized like this.Even growth is based on the compound semiconductor crystal of gallium nitride under the uniform temp of nitrogenize, the result still has good crystallinity, also the condition in the reactor of using system device control easily.
As mentioned above, in the manufacture method according to the compound semiconductor that the present invention is based on gallium nitride, the metal nucleus is attached to substrate and growth.Be formed with based on the Sapphire Substrate of the low growth rate mask layer of the compound semiconductor crystal of gallium nitride on it and optionally grow by using, form film with fine crystalline phase volume property based on the compound semiconductor of gallium nitride.
Fig. 9 (a) is used to introduce the formation mechanism based on the compound semiconductor film of gallium nitride with well-crystallized to 9 (b).
Shown in Fig. 9 (a), the source gas 3 that contains Si and ammonia 4 that flows makes two kinds of compound reactions and form silicon nitride film 5 on the Sapphire Substrate 1 that is heated to predetermined temperature.Because the available point that the formation of film 5 starts from disperseing on the substrate, therefore initial film 5 can not cover entire substrate equably.There is the zone that is covered by silicon nitride film 5 in the control growing time and exposes sapphire regional 6 (Fig. 9 (b)) so that on substrate 1.Then, by the III family material gas 3 ' that flows, the droplet-shaped particulate 7 of III family element is provided to zone 6 (Fig. 9 (c)), and mobile ammonia is reflected at and generates III group-III nitride 8 (Fig. 9 (d)) in the zone 6.Thus, the growth nucleus in the zone that silicon nitride film 5 covers can not grown, and grows crystal 9 in sapphire regional 6 and expose, and (Fig. 9 (f)) flatly grows on silicon nitride film 5.Thus, crystal 9 covers the whole surface (Fig. 9 (g)) of Sapphire Substrate 1.Can control because the sapphire and the direction of growth based on the different screw dislocations that cause of the compound semiconductor lattice constant of gallium nitride, most dislocation forms the loop of sealing, and can upwards not spread.Reduce the density of screw dislocation like this, thereby formed high-quality crystal.
By Si source gas with as the method that flows simultaneously of the nitrogenous source gas of ammonia, and the sapphire surface of the part nitrogenize in advance ammonia that flows, the Si source gas manufacturing of flowing then is used to form the method manufacturing mask layer of scattered 1 individual layer of the silicon nitride of mask layer.When forming silicon oxide layer as mask layer, use the oxygen atom on the thermal cleaning activation sapphire surface, the Si source gas that flows then forms 1 individual layer of silicon oxide layer.
Is flow simultaneously on the Sapphire Substrate of heating Si source gas and III clan source gas with different growth rates at cambial effective ways on the Sapphire Substrate, and ammonia then flows.Figure 10 (a) shows the growth technique of this method to 10 (f).At first, Si source gas 3 and III family material gas 3 ' on the substrate 1 of heating mobile (Figure 10 (a)).Decomposing gas, the droplet-shaped particulate 7 of the aggregate 10 of silicon atom and III family metal adheres to Sapphire Substrate 1 (Figure 10 (b)) with the spacing that is provided with.Then by they each of ammonia 4 nitrogenize that flows, thereby on substrate 1, form mask layer, form (Figure 10 (c)) by the slow growth part 5 of silica with based on the quick growth part 8 of the compound semiconductor of gallium nitride.When growth was based on the compound semiconductor 9 of gallium nitride on this mask layer, in example shown in Figure 9, crystal 9 optionally was grown on the compound semiconductor film 8 based on gallium nitride.This selective growth has improved crystallinity.
For the methods of introducing with reference to figure 9 and 10, processing and growth after under at least 1000 ℃ temperature, forming mask layer.This is owing under 600 ℃ low temperature for example, form III family metal particle 7 and insufficient based on migration during the compound semiconductor film 8 of gallium nitride.Thus, growth nucleus even in the zone of substrate 1 that covers by silica and silicon nitride and resilient coating, begin growth, selective growth properties is degenerated.Even when being formed on this mask layer based on the compound semiconductor layer 9 of gallium nitride, under 600 ℃ low temperature for example, migration is insufficient during the initial growth, grow thus nucleus even begin growth in the zone of substrate 1 that is covered by silica and silicon nitride and resilient coating, selective growth properties is degenerated.Silane (SiH
6) and disilane (Si
2H
6) be used as Si source gas.The step that forms mask layer can be carried out in the grower that the compound semiconductor of growing subsequently based on gallium nitride uses.
As mentioned above, according to the present invention, by the step of the metal-organic material that flows on the substrate of heating, growth can obtain having the crystalline semiconductor film that well-crystallized is used for semiconductor device application based on the compound semiconductor of gallium nitride on substrate thus.The film that so obtains has smooth minute surface, the good crystallinity of the film that obtains than low temperature buffer layer method.The emissive porwer that can suppress the leakage of current that pit defect that crystal growth causes causes, be caused by dislocation is degenerated and to disadvantageous other the similar performance of semiconductor device, has been improved the emission output variable.
Introduce the semiconductor crystal of III group-III nitride below and based on the object lesson of the manufacture method of the compound semiconductor of gallium nitride.Yet, the invention is not restricted to these examples.Below each example use Sapphire Substrate and use mocvd method to form compound semiconductor layer based on gallium nitride.
Example 1
The embodiment of the method for III group-III nitride semiconductor crystal is made in explanation now.Used substrate is for having the sapphire single-crystal substrate on (0001) plane.Substrate carries out organic washing with acetone and is placed on carborundum (SiC) support, and support is placed in the MOCVD device subsequently.RF introduces heating system and is used for controlling temperature at the MOCVD device.The thermocouple that is enclosed in the quartz ampoule inserts in the support, with increasing of temperature in the measurement mechanism.
After substrate is placed in the device, in nitrogen atmosphere, is heated to 1180 ℃, and kept this temperature 10 minutes, to remove any oxide-film from substrate surface.Temperature is reduced to 1100 ℃ then, and does not comprise nitrogenous source in identical nitrogen atmosphere, and metal-organic material, trimethyl aluminium (TMA) were added to substrate 1 minute with flow velocity 12 μ mol/min.So the TMA thermal decomposition causes Al to be deposited on sapphire surface.Close after the TMA, temperature is raised to 1180 ℃, applies the nitrogenous source (NH of ammonia form with flow velocity 0.2mol/min
3) 3 minutes, aluminium nitride.Then, NH
3Constant and the temperature of flow velocity remains on 1180 ℃, applies metal-organic material, trimethyl gallium (TMG) with flow velocity 140 μ mol/min, to be implemented in the GaN epitaxial growth 1.1 μ m on the substrate with Al deposit.Subsequently, the device cool to room temperature, substrate shifts out from reactor.
The epitaxial wafer of Zhi Zaoing has mirror surface thus, and half peak value width of the X-ray swing curve of epitaxial layer of gallium nitride is 959 seconds.This has shown the outstanding degree of crystallinity of epitaxial loayer.
Example 2
In the situation of example 1, in grower, the sapphire single-crystal substrate with (0001) plane is carried out organic washing and heat treatment.Then, substrate keeps 1180 ℃ in the nitrogen atmosphere that does not comprise nitrogenous source, applies TMA and TMG 1 minute with flow velocity 12 μ mol/min, the alloy of deposit Al and Ga on the sapphire single-crystal substrate.Temperature keeps 1180 ℃, and TMA and TMG close, and apply ammonia (NH with flow velocity 0.2mol/min
3) 3 minutes, nitrogenize Al-Ga alloy.Then, apply ammonia and temperature and remain on 1180 ℃, apply metal-organic material, trimethyl gallium (TMG), to be implemented in the GaN epitaxial growth 1.1 μ m on the substrate with Al-Ga alloy deposition thing with flow velocity 140 μ mol/min.
The epitaxial wafer of Zhi Zaoing has mirror surface thus, and half peak value width of the X-ray swing curve of epitaxial layer of gallium nitride is 720 seconds, demonstrates the outstanding degree of crystallinity of epitaxial loayer.Check that by atomic force microscope the platform that the surface of gallium nitride layer demonstrates the atom step shows the growth of step stream.These atom step platforms demonstrate by epitaxial wafer center more consistent spacing and depth of parallelism to the specific direction of periphery.This step stream growth of (0001) planar section that is illustrated in the periphery of wafer is reinforced, wherein vertical axis at specific direction by<0001 tilt.This direction is<1-100 〉.
Tem observation at the section of the Sapphire Substrate of wafer and the contact-making surface between the gallium nitride layer is shown the thermal decomposition of the metal-organic material by the contact-making surface between substrate and gallium nitride layer, the metal polycrystal of deposit nitrogenize.Crystal is a hexagon, the 5-10nm height.μ-EDS analyzes demonstration, and Al in polycrystal and Ga element are inconsistent, and (compound in the zone is by In in this zone
uGa
vAl
wN
kRepresentative, u+v+w=1 wherein, 0≤u, v, w≤1,0<k<1) in nitrogen and the stoichiometric proportion of metal departed from 1: 1.
Carry out subsequently experiment with research example 2 mechanism of crystal growth.
In example 1, the sapphire single-crystal substrate with (0001) plane carries out organic washing and heat treatment in grower.Then, substrate remains on 1180 ℃ in the nitrogen atmosphere that does not comprise nitrogenous source, applies TMA and TMG to form the alloy deposition of Al and Ga on Sapphire Substrate.Temperature remains on 1180 ℃, and TMA and TMG close, and applies ammonia 3 minutes with flow velocity 0.2mol/min, nitrogenize Al-Ga alloy.Then, device cool to room temperature.
Surface with the atomic force microscope inspection wafer of making like this.Can be observed the nitrogenize polycrystal of the metal particle of about 50nm height and the about 0.1 μ m of diameter.Polycrystal does not cover the whole surface of Sapphire Substrate; Flat gap is arranged between polycrystal.The epitaxial growth that it is believed that the gallium nitride layer in the example 2 is that core is carried out with the polycrystal.
Similarly, carry out subsequently experiment is deposited on the III family metal of substrate surface with research the state of particulate.
In example 1, the sapphire single-crystal substrate with (0001) plane carries out organic washing and heat treatment in grower.Then, adopt with example 2 in identical condition, substrate remains on 1180 ℃ in the nitrogen atmosphere that does not comprise nitrogenous source, apply TMA and the TMG alloy deposition with formation Al and Ga on Sapphire Substrate.Then, the device cool to room temperature, and check surperficial with atomic force microscope.The table of discovery mask has the long particulate of high about 500 of about 100 ; The superficial density of particulate is 1 * 10
8Cm
-2Part in the particulate links together.
Example 3
Adopt the method identical with example 1, the sapphire single-crystal substrate with (0001) plane carries out organic washing and heat treatment in grower.Subsequently, in the nitrogen atmosphere that does not comprise nitrogenous source and temperature be reduced to 1100 ℃, on substrate, apply TMA, TMG and trimethyl indium (TMI), another kind of metal-organic material 30 seconds with flow velocity 6 μ mol/min, 18 μ mol/min and 18 μ mol/min respectively, on Sapphire Substrate, to form the alloy of Al, Ga and In.Close the supply of metal-organic material, temperature remains on 1180 ℃, applies ammonia 3 minutes with flow velocity 0.2mol/min, nitrogenize Al/Ga/In alloy.Then, remain under the identical flow velocity and apply ammonia, and the device temperature remain on 1180 ℃, 140 μ mol/min apply TMG with flow velocity, the 1.1 μ m so that the gallium nitride on the substrate with Al/Ga/In alloy is grown.
The epitaxial wafer of Zhi Zaoing has mirror surface thus, and half peak value width of the X-ray swing curve of epitaxial layer of gallium nitride is 620 seconds.This has shown the outstanding degree of crystallinity of epitaxial loayer.Though above-mentioned example 1 to 3 has illustrated the epitaxial growth with the III group-III nitride semiconductor crystal of gallium nitride layer form, also can be by In
xGa
yAl
zThe form growth III group-III nitride semiconductor crystal of the mixed crystal of N representative.
Example 4
Example 4 is used to illustrate the method for the method manufacturing of employing manufacturing III group-III nitride semiconductor crystal based on the compound semiconductor light emitting device of gallium nitride.
Fig. 6 shows the epitaxial structure that is used to make luminescent device according to example 4.On c-plane sapphire substrate 11, adopt the lattice mismatch epitaxial growth method to form and have 1 * 10
17Cm
-3The GaN layer 12 that the low Si of the 2-μ m of electron concentration mixes is afterwards for having 1 * 10
19Cm
-3The GaN layer 13 that the high Si of the 1-μ m of electron concentration mixes has 1 * 10
17Cm
-3The 100-A In of electron concentration
0.1Ga
0.9N coating 14, by the GaN barrier layer to start with finish and comprise six 70-A GaN barrier layers 15 and five non-doping In of 20-A
0.2Ga
0.8The multi-quantum pit structure of N trap layer 16,30-A Al
0.2Ga
0.8The N diffusion prevents layer 17, has 8 * 10
17Cm
-3The 0.15-μ mMg Doped GaN layer 18 of hole concentration and have 5 * 10
18Cm
-3The 100-AMg doping In of hole concentration
0.1Ga
0.9N layer 9.Fig. 7 is the plane graph of electrode structure of this luminescent device embodiment of example 4.
By the wafer with above-mentioned epitaxial structure of MOCVD method manufacturing, as described below.
At first, Sapphire Substrate is placed in the RF coil of the induction heater in the quartz reaction stove (reactor).The glove-box that is filled with nitrogen is used for substrate is placed on carbon template, and the nitrogen inflow reactor is to purify its inside subsequently.After inflow nitrogen 10 minutes, start induction heater and also make it that substrate is heated to 1170 ℃, the temperature rise time was above 10 minutes.Simultaneously, the pressure in the reactor is adjusted to 50hPa.Underlayer temperature remains on 1170 ℃, and hydrogen and nitrogen flow into 9 minutes, with the thermal cleaning substrate surface.During thermal cleaning, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses the bubbler that is connected to reactor, to begin foaming.Adopt heating bath to make bubbler keep stationary temperature.Up to beginning the operation of growing, TMGa and the TMAl steam that produces is discharged into outside the system by (deharmanizing) system that removes the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature reduced to 1100 ℃ and reactor pressure and is transferred to 100hPa.Be stabilized in after 1100 ℃ in definite temperature, TMGa and TMAl valve open for the reactor supply contains the source of the gas of TMGa and TMAl steam, and begin the metal nucleus is adhered to the operation on Sapphire Substrate surface.Be used for the mol ratio between TMGa and the TMAl is adjusted to 2: 1 at the flow controller on the foaming line.After 90 seconds, operation TMGa and the stop supplies of TMAl valve contain the steam of TMGa and TMAl.After suspending 10 seconds, the ammonia valve is opened, and ammonia is supplied in beginning in reactor.
After 10 seconds, ammonia is still flowing, and backing temp is brought up to 1160 ℃.Regulate the flow velocity of TMGa between the rising stage in temperature.Equally, start SiH
4Air-flow.SiH
4Continuously flow into the system of removing the evil,,, be discharged into the outside with carrying gas up to beginning to form low Si Doped GaN layer.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, and operates TMGa and SiH subsequently
4Valve begins to reactor supply TMGa and SiH
4Gas.About 75 minutes of the growth of the low Si Doped GaN layer of continuation.According to existing research, control SiH
4Flow velocity so that the electron concentration in the GaN layer reaches 1 * 10
17Cm
-3In this way, forming thickness is the low Si Doped GaN layer of 2 μ m.
On this low Si Doped GaN layer, form high Si Doped n-GaN layer.After the low Si Doped GaN layer of growth, stop to reactor supply TMGa and SiH
4Gas one minute changes SiH during this period
4Flow velocity.According to existing research, control SiH
4Flow velocity so that the electron concentration in high Si Doped GaN layer reaches 1 * 10
19Cm
-3Continue to reactor supply ammonia with identical flow velocity.After one minute, recover supply TMGa and SiH
4And this layer growth 45 minutes.Thereby forming thickness is the high Si Doped GaN layer of 1 μ m.
After forming high Si Doped GaN layer, operation TMGa and SiH
4Valve interrupts supplying these materials to reactor.Carry gas and change nitrogen into, keep ammonia flow simultaneously by hydrogen.Underlayer temperature drops to 800 ℃ by 1160 ℃ subsequently, and reactor pressure becomes 200hPa by 100hPa simultaneously.During the temperature change in waiting for reactor, change SiH
4Flow velocity.According to existing research, control SiH
4Flow velocity so that the electron concentration in Si doping InGaN coating reaches 1 * 10
17Cm
-3Continue to reactor supply ammonia with identical flow velocity.Begun in bubbler, to supply trimethyl indium (TMIn) and triethyl-gallium (TEGa) carries gas.Up to beginning to form coating, SiH
4TMIn and TEGa steam that gas and foaming produce are discharged into the system outside together with carrying gas by the system of removing the evil.Then, after stabilization time, beginning is to reactor supply TMIn, TEGa and SiH at given reactor
4Gas also kept about 10 minutes, to form the thick Si doping In of 100
0.1Ga
0.9The N coating stops afterwards to reactor supply TMIn, TEGa and SiH
4
Make then by GaN barrier layer and In
0.2Ga
0.8The multi-quantum pit structure that N trap layer is formed.At first at Si doping In
0.1Ga
0.9Form the GaN barrier layer on the N coating, on the GaN barrier layer, form In then
0.2Ga
0.8N trap layer.Repeat 5 times again to form after the necessary sandwich construction, at the 5th In
0.2Ga
0.8Form the 6th GaN barrier layer on the N trap layer, be created in the structure that every end has the GaN barrier layer.
More specifically, finish Si doping In
0.1Ga
0.9After the formation of N coating, suspend 30 seconds, begin subsequently, keep identical underlayer temperature, reactor pressure simultaneously, carry gas type and carry gas flow rate to reactor supply TEGa.After 7 minutes, stop supplies TEGa stops the formation on GaN barrier layer, constitutes the thick film of 70 .
During the formation on GaN barrier layer, the mole flow velocity that flows to the TMIn of the system that removes the evil is compared with the flow velocity during forming coating and is doubled.After finishing the GaN barrier layer, the supply of III family material stops 30 seconds, operates TEGa and TMIn valve then to reactor supply TEGa and TMIn, the type and the flow velocity that keep identical underlayer temperature, reactor pressure simultaneously and carry gas.After 2 minutes, stop supplies TEGa and TMIn stop In
0.2Ga
0.8The formation of N trap layer.Form the thick In of 20
0.1Ga
0.9The N coating.
Finish In
0.2Ga
0.8Behind the N trap layer, the supply of III family material stops 30 seconds, begins afterwards to reactor supply TEGa, and the type and the flow velocity that keep identical underlayer temperature, reactor pressure simultaneously and carry gas are with another GaN barrier layer of growing.This step repeats 5 times to make five GaN barrier layers and five In
0.2Ga
0.8N trap layer.Then at last In
0.2Ga
0.8Form the GaN barrier layer on the N trap layer.
On last GaN barrier layer, make non-doped with Al
0.2Ga
0.8The N diffusion prevents layer 17.Stop supplies TEGa with one minute after finishing the GaN barrier layer in, reactor pressure becomes 100hPa, the type and the flow velocity that keep identical underlayer temperature simultaneously and carry gas.The trimethyl aluminium (TMAl) that flows to bubbler carries gas stream to begin.Prevent that up to the formation diffusion step of layer from beginning, the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.Then, after stabilization time, beginning is to reactor supply TEGa and TMAl at given reactor pressure.About 3 minutes of this layer growth, stop supplies TEGa and TMAl subsequently are to stop non-doped with Al
0.2Ga
0.8The N diffusion prevents the formation of layer.In this way, forming thickness is the non-doped with Al of 30
0.2Ga
0.8The N diffusion prevents layer.
In non-doped with Al
0.2Ga
0.8The N diffusion prevents upward manufacturing Mg Doped GaN layer of layer.At stop supplies TEGa and TMAl, to stop non-doped with Al
0.2Ga
0.8N diffusion prevents that underlayer temperature is elevated to 1060 ℃ in the growth 2 minutes of layer, and reactor pressure becomes 200hPa.Equally, carry gas and become hydrogen.Dicyclopentadiene magnesium (Cp
2Mg) carry gas flow and begun to flow through bubbler.Up to the step that begins to form Mg Doped GaN layer, the Cp that foaming produces
2Mg steam is discharged into the system outside by the system of removing the evil together with carrying gas.After changing temperature and pressure, give reactor pressure stabilization time and begin to supply TMGa and Cp to reactor
2Mg.Cp
2The flow velocity of Mg is studied in advance, and regulates so that the hole concentration in Mg Doped GaN layer reaches 8 * 10
17Cm
-3After approximately growing 6 minutes, stop supplies TMGa and Cp
2Mg is to stop the formation of Mg Doped GaN layer.The final thick Mg Doped GaN layer of thick 0.15 μ m that forms of this operation.
On Mg Doped GaN layer, form Mg doping InGaN layer.Stop supplies TMGa and Cp
2After the Mg, stop the growth of Mg Doped GaN layer, be reduced to 800 ℃, and carry gas and change nitrogen into 2 minutes time chien shih substrate temperatures.Reactor keeps the identical pressure of 200hPa.Adjust Cp
2The flow velocity of Mg is with to Mg doping In
0.1Ga
0.9The Mg amount of impurities that the N layer is identical with Mg Doped GaN layer.Think that according to existing research the quantity of impurity makes Mg doping In
0.1Ga
0.9Hole concentration in the N layer reaches 5 * 10
18Cm
-3After waiting for that underlayer temperature is stable, beginning is to reactor supply TMIn, TEGa and Cp
2Mg.After growing 10 minutes, stop to reactor supply TMIn, TEGa and Cp
2Mg is to stop Mg doping In
0.1Ga
0.9The growth of N layer finally forms the Mg doping In of thick 100
0.1Ga
0.9The N layer.
Finish Mg doping In
0.1Ga
0.9Behind the N layer, close induction heater, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor only is made up of nitrogen.Behind definite substrate cool to room temperature, from reactor, take out wafer.Therefore, according to aforementioned operation, make wafer with the epitaxial structure that is used for light emitting semiconductor device.Even it is not annealed to activate p type charge carrier, Mg Doped GaN layer and Mg doping In
0.1Ga
0.9The N layer all shows as p type characteristic.
Then, the wafer with epitaxial structure that forms on Sapphire Substrate is used to make light-emitting diode, and it is light emitting semiconductor device or device one type.By forming the p electrode bonding welding pad of being made up of by the laminated construction of this order titanium, aluminium and gold layer 12, known lithography process is used at Mg doping In
0.1Ga
0.9N layer 18a goes up and makes p side (side) electrode, only is bonded on the pad 12 by the transparent p electrode that Au forms.Adopt dry corrosion to be used to expose the part 23 formation n lateral electrodes of high Si Doped GaN layer then, and make the n lateral electrode 22 of Ni and Al at expose portion.Fig. 7 shows the shape of the electrode of so making on wafer.
Then, the reverse side of Sapphire Substrate is ground and polishes with mirror finish, and wafer is cut into the square chip of every limit 350 μ m.Subsequently each chip electrode towards on be installed on the lead frame, and be connected on the lead frame with gold thread, form luminescent device.When the forward current of 20mA flow through electrode, forward voltage was 3.0V.The radiative wavelength that sees through p side transparency electrode is 470nm, and device is output as 6cd.The light-emitting diode of any part of the wafer that can be made by reality obtains consistent this light-emitting diode characteristic, does not change.
Example 5
This example is for making the method based on the compound semiconductor crystal of gallium nitride, and is as described below.
Steps A shown in Figure 1 is used for forming compound semiconductor layer based on gallium nitride to the order of D on Sapphire Substrate.In steps A, the metal nucleus is sticked on the substrate by flowing through 1: 2 the gaseous mixture of mol ratio that contains trimethyl aluminium (TMAl) steam and trimethyl gallium (TMGa) steam.In step B, in hydrogen, anneal; In step C, the gaseous mixture of hydrogen and ammonia flows into, with the metal nucleus of nitrogenize annealing and make it form the growth nucleus.In step D, TMGa and ammonia flow into further growth gallium nitride on the growth nucleus, thereby make the compound semiconductor layer based on gallium nitride with gallium nitride film on Sapphire Substrate.
More specifically, at first, Sapphire Substrate is placed in the RF coil of the induction heater in the quartz reactor.The glove-box that is filled with nitrogen is used for substrate is placed on carbon template, and nitrogen inflow reactor 10 minutes is to purify after its inside subsequently.Then, start induction heater and make it that substrate was heated to 1170 ℃ above 10 minutes.Underlayer temperature remains on 1170 ℃, and hydrogen and nitrogen flow into 9 minutes, with the thermal cleaning substrate surface.
During thermal cleaning, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses bubbler, to begin foaming.Adopt heating bath to make bubbler keep stationary temperature.The bubbler pipeline is connected to reactor.Up to the step that begins to grow based on the compound semiconductor layer of gallium nitride, TMGa steam and the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.After gas was carried in change, underlayer temperature reduced to 1100 ℃.Be stabilized in after 1100 ℃ in definite temperature, operation TMGa and TMAl valve contain TMGa and TMAl steam for the reactor supply, to begin that the metal nucleus is adhered to Sapphire Substrate.Be used for the mol ratio between TMGa and the TMAl is adjusted to 2: 1 at the flow controller on the foaming line.This technology stopped to contain to the reactor supply steam of TMGa and TMAl after 1.5 minutes with TMGa and TMAl valve.This state kept 3 minutes, to carry annealed metal nucleus in the gas at hydrogen.Anneal after 3 minutes, operation ammonia line valve begins to reactor supply ammonia, and the metal nucleus of nitrogenize annealing also makes it form the growth nucleus.Still after flowing 10 seconds, backing temp is brought up to 1160 ℃ to ammonia.Regulate the flow velocity of TMGa between the rising stage in temperature.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, and operates the TMGa valve subsequently and begin to reactor supply TMGa gas with further growth gallium nitride on the growth nucleus.
In growth based on the compound semiconductor crystal film of gallium nitride after 1 hour, by stopping to stop the growth operation to reactor supply TMGa.Behind the compound semiconductor crystal film that finishes to form based on gallium nitride, close induction heater, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor is made up of ammonia, nitrogen and hydrogen, with identical during the growth operation, but when definite substrate is cooled to 300 ℃, close ammonia and hydrogen, and nitrogen continues to flow into, up to the substrate cool to room temperature, at this moment wafer is taken out from reactor.By the method for above-mentioned steps, on Sapphire Substrate, form the thick gallium nitride film of 2 μ m.By the substrate that takes out in the reactor is water white, and epitaxial loayer has specular surface.
Non-doped gallium nitride crystal to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.In general, under the situation based on gallium nitride semiconductor, half peak value width of the XRC spectrum on (0002) plane is floor coefficient (mosaicity), and (10-12) half peak value width of the XRC spectrum on plane is the dislocation density coefficient.Measuring the half peak value width value that shows (0002) plane is 230 seconds, and (10-12) the half peak value width value on plane is 350 seconds.The both is worth preferably.
Check the surface of the superiors' film of gallium nitride with atomic force microscope.The table of discovery mask has form preferably, does not observe the growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 5 * 10 then
7Cm
-2
Adopt identical step to make wafer, up to operation midway, when sample was moved out of reative cell before the growing gallium nitride crystal film.When checking wafer, find to have the crystal group of the trapezoidal cross-section of the aluminum gallium nitride of forming the growth nucleus on sapphire surface with atomic force microscope.
Example 6
As shown in Figure 3, in this embodiment, continue step C and D then three times, on Sapphire Substrate, form compound semiconductor layer based on gallium nitride by repeating step A and B.In steps A, contain trimethyl aluminium (TMAl) steam the metal nucleus is sticked on the substrate by flowing through, in step B, the metal nucleus is annealed in hydrogen.Repeating step A and B three times then, in step C, the gaseous mixture of hydrogen and ammonia flows into, with the metal nucleus of nitrogenize annealing and make it form the growth nucleus; In step D, TMGa and ammonia flow into further growth gallium nitride on the growth nucleus, thereby make the compound semiconductor layer based on gallium nitride with gallium nitride film on Sapphire Substrate.
At first, thermal cleaning substrate surface.Along with the carrying out of cleaning, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses bubbler, to begin foaming.The pipeline of each bubbler is connected to reactor.Adopt heating bath to make bubbler keep stationary temperature.Up to the step that begins to grow based on the compound semiconductor layer of gallium nitride, TMGa steam and the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature was reduced to 1160 ℃.Be stabilized in after 1160 ℃ in definite temperature, operation TMAl valve contains the steam of TMAl for the reactor supply, so that the metal nucleus is adhered on the Sapphire Substrate.This technology stopped to contain to the reactor supply steam of TMAl after 3 minutes.This state kept 30 seconds, to carry annealed metal nucleus in the gas at hydrogen.After annealing in 30 seconds, operation TMAl line valve begins to contain for the reactor supply steam of TMAl, with the adhesiving metal nucleus.As for the first time, after 3 minutes, stop to contain the steam of TMAl in this technology, to carry annealed metal nucleus in the gas at hydrogen to the reactor supply.Carry out once this step subsequently again, the formation of repetition metal nucleus and annealing (steps A → step B) three times altogether.For the third time after the annealing, beginning is to reactor supply ammonia, with the metal nucleus of nitrogenize annealing and make it form the growth nucleus.After 10 seconds, operation TMGa valve begins to reactor supply TMGa gas with further growth gallium nitride on the growth nucleus at inflow gas.
After 1 hour, stop the growth operation at the growing gallium nitride crystal film by stopping to supply TMGa to reactor.Close induction heater then, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor is made up of ammonia, nitrogen and hydrogen, with identical during the growth operation, but when definite substrate is cooled to 300 ℃, close ammonia and hydrogen, and nitrogen continues to flow into, up to the substrate cool to room temperature, at this moment wafer is taken out from reactor.By the method for above-mentioned steps, on Sapphire Substrate, form the thick gallium nitride film of 2 μ m.By the substrate that takes out in the reactor is water white, and epitaxial loayer has specular surface.
Non-doped gallium nitride crystal to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.Measuring the half peak value width value that shows (0002) plane is 300 seconds, and (10-12) the half peak value width value on plane is 320 seconds.The both is worth preferably.Check the surface of the superiors' film of gallium nitride with atomic force microscope.The table of discovery mask has form preferably, does not observe the growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 7 * 10 then
7Cm
-2
Adopt the identical step perparation of specimen, up to operation midway, when wafer was moved out of reative cell before the growing gallium nitride crystal film.When with the atomic force microscope sample for reference, find to have the crystal group of the trapezoidal cross-section of the aluminum gallium nitride of forming the growth nucleus on sapphire surface.Therefore, in the case of this example, repeat the formation and the annealing steps of metal nucleus, increased the chance of the shape of the density of the metal nucleus that is controlled on the substrate and the nucleus after the annealing.Thereby increase the precision of technology, and can make compound semiconductor layer be endowed desirable shape and character based on gallium nitride based on these metal nucleus.
In example 6, the formation of metal nucleus and annealing triplicate.Yet, also can only repeat twice as required or repeat four times even more.
Example 7
As shown in Figure 4, in this embodiment, continue step D then twice, on Sapphire Substrate, form compound semiconductor layer based on gallium nitride by repeating step A, B and C.In steps A, by flowing through the steam that mixed in 1: 2: 4 in molar ratio that contains trimethyl aluminium (TMAl) steam, trimethyl gallium (TMGa) steam and trimethyl indium (TMIn) the metal nucleus is sticked on the substrate, in step B, in hydrogen, the metal nucleus is annealed; In step C, the gaseous mixture of hydrogen and ammonia flows into, with the metal nucleus of nitrogenize annealing and make it form the growth nucleus.Behind twice of repeating step A, B and C, in step D, TMGa and ammonia flow into further growth gallium nitride on the growth nucleus, thereby make the compound semiconductor layer based on gallium nitride with gallium nitride film on Sapphire Substrate.
At first, the thermal cleaning substrate surface, during this period, the hydrogen that contains trimethyl gallium (TMGa), trimethyl aluminium (TMAl) and trimethyl indium (TMIn) carries gas stream and crosses bubbler, to begin foaming.The pipeline of each bubbler is connected to reactor, and makes bubbler keep stationary temperature with heating bath.Up to the step that begins to grow based on the compound semiconductor layer of gallium nitride, TMGa, TMAl and the TMIn steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature was reduced to 900 ℃.Be stabilized in after 900 ℃ in definite temperature, operation TMGa, TMAl and TMIn line valve contain the steam of TMGa, TMAl and TMIn for the reactor supply, so that the metal nucleus is adhered on the Sapphire Substrate.Be used for the mol ratio between TMGa, TMAl and the TMIn is adjusted to 2: 1: 4 at the flow controller on the foaming line.
This technology stopped to contain to the reactor supply gas of TMGa, TMAl and TMIn steam after 3 minutes.This state kept 30 seconds, to carry annealed metal nucleus in the gas at hydrogen.After annealing in 30 seconds, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.Flowing into ammonia after 1 minute, operated valve stops to reactor supply ammonia.This state kept 30 seconds, supplied the steam that contains TMGa, TMAl and TMIn again with valve subsequently, once more the metal nucleus is adhered on the Sapphire Substrate.This technology stopped to contain to the reactor supply gas of TMGa, TMAl and TMIn steam after 3 minutes, and this state kept 30 seconds, to carry annealed metal nucleus in the gas at hydrogen.After annealing in 30 seconds, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.The sequence of steps of the formation of metal nucleus, annealing and nitrogenize (steps A → step B step C) is carried out twice.
After gas flowed into 10 seconds, backing temp was brought up to 1160 ℃.Regulate the flow velocity of TMGa between the rising stage in temperature.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, and operation TMGa valve begins to reactor supply TMGa gas with further growth gallium nitride on the growth nucleus.After 1 hour, stop the growth operation at the growing gallium nitride crystal film by stopping to supply TMGa to reactor.Close induction heater then, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor is made up of ammonia, nitrogen and hydrogen, with identical during the growth operation, but when definite substrate is cooled to 300 ℃, close ammonia and hydrogen, and nitrogen continues to flow into, up to the substrate cool to room temperature, at this moment wafer is taken out from reactor.
Above-mentioned steps is used for forming the gallium nitride film of the thick non-doping of 2 μ m on Sapphire Substrate.By the substrate that takes out in the reactor is water white, and epitaxial loayer has specular surface.
Non-doped gallium nitride crystal to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.Measuring the half peak value width value that shows (0002) plane is 250 seconds, and (10-12) the half peak value width value on plane is 300 seconds, and the both is worth preferably.Check the surface of the superiors' film of gallium nitride with atomic force microscope.The table of discovery mask has form preferably, does not observe the growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 3 * 10 then
7Cm
-2
Adopt the identical step perparation of specimen, up to operation midway, when wafer was moved out of reative cell before the growing gallium nitride crystal film.When checking wafer, find to have the crystal group of the trapezoidal cross-section of the aluminum gallium nitride of forming the growth nucleus on sapphire surface with atomic force microscope.Therefore, under the situation of example 7, repeat the formation step of formation, annealing and the metal nucleus of metal nucleus, increased the chance of the shape of the density of the metal nucleus that is controlled on the substrate and the nucleus after the annealing.Thereby increase the precision of technology, and can make compound semiconductor layer be endowed desirable shape and character based on gallium nitride based on these metal nucleus.
In example 7, the formation of the formation of metal nucleus, annealing and metal nucleus repeats twice.Yet, if desired also can triplicate or more times.
Example 8
As shown in Figure 5, in this embodiment, the compound semiconductor layer steps A that forms based on gallium nitride on Sapphire Substrate is divided into two stages, and steps A 1 and steps A 2 are step B, C and D subsequently.In steps A 1,, in steps A 2, the metal nucleus is sticked on the substrate by containing trimethyl gallium (TMGa) steam by containing trimethyl aluminium (TMAl) steam.In step B, in hydrogen, anneal, in step C, the gaseous mixture of hydrogen and ammonia flows into, with the metal nucleus of nitrogenize annealing and make it form the growth nucleus.In step D, TMGa and ammonia flow into further growth gallium nitride on the growth nucleus, thereby make the compound semiconductor layer based on gallium nitride with gallium nitride film on Sapphire Substrate.
At first, the thermal cleaning substrate surface, during this period, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses bubbler, to begin foaming.The pipeline of each bubbler is connected to reactor, and makes bubbler keep stationary temperature with heating bath.Up to the step that begins to grow based on the compound semiconductor layer of gallium nitride, TMGa steam and the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.
After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.After gas was carried in change, underlayer temperature was reduced to 1100 ℃.Be stabilized in after 1100 ℃ in definite temperature, operation TMAl line valve contains the steam of TMAl for the reactor supply, to begin that metal (Al) nucleus is adhered to technology on the Sapphire Substrate.This technology stopped to contain to the reactor supply steam (steps A 1) of TMAl after 1 minute with valve.Then, begin to reactor supply TMGa steam to begin that metal (Ga) nucleus is adhered to technology on the Sapphire Substrate with the TMGa valve.This technology stopped to contain to the reactor supply steam (steps A 2) of TMGa after 2 minutes with valve.In the method, the formation of metal nucleus is divided into two stages, steps A 1 and A2.
This state kept 5 minutes, to carry annealed metal nucleus in the gas at hydrogen.After annealing in 5 minutes, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.
After gas flowed into 10 seconds, backing temp was brought up to 1160 ℃.Regulate the flow velocity of TMGa between the rising stage in temperature.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, and operation TMGa valve begins to reactor supply TMGa gas with further growth gallium nitride on the growth nucleus.
After 1 hour, stop the growth operation at the growing gallium nitride crystal film by stopping to supply TMGa to reactor.Close induction heater then, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor is made up of ammonia, nitrogen and hydrogen, with identical during the growth operation, but when definite substrate is cooled to 300 ℃, close ammonia and hydrogen, and nitrogen continues to flow into, up to the substrate cool to room temperature, will serve as a contrast from reactor at this moment and take out.
Above-mentioned steps is used for forming the gallium nitride film of the thick non-doping of 2 μ m on Sapphire Substrate.By the substrate that takes out in the reactor is water white, and epitaxial loayer has specular surface.
Non-doped gallium nitride crystal to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.Measuring the half peak value width value that shows (0002) plane is 180 seconds, and (10-12) the half peak value width value on plane is 290 seconds.When the superiors' film of checking gallium nitride with atomic force microscope surperficial, the table of discovery mask has form preferably, not observing the growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 1 * 10 then
7Cm
-2
Also adopt the identical step perparation of specimen, up to operation midway, when wafer was moved out of reative cell before the growing gallium nitride crystal film.When checking wafer, find to have the crystal group of the trapezoidal cross-section of the aluminum gallium nitride of forming the growth nucleus on sapphire surface with atomic force microscope.
Therefore, under the situation of example 8, the formation of metal nucleus is divided into two stages, thereby can adopt different kinds of metals to form the metal nucleus, and can be controlled at the density of the metal nucleus on the substrate more accurately.Therefore, the compound semiconductor layer based on gallium nitride based on these metal nucleus is endowed desirable shape and character.
In example 8, though the formation of metal nucleus is divided into two stages, each carries out once, and each of two stages all can be repeated twice even more times.In addition, the present invention not restriction form step and be divided into two stages and carry out.This step can be divided into the three or more stages and carry out.The metal nucleus that the number of times that increase repeats and the quantity in stage can make formation has higher precision.Equally, in example 8, though after dividing two stages to form the metal nucleus, the metal nucleus carries in the gas at hydrogen and anneals, this annealing steps can omit.But, in this case, the material that must select suitable type is as the metal nucleus, and comes the nitrogenize nucleus with suitable gas temperature and pressure.
Example 9
With under the situation of example 8 (Fig. 5) the same, in example 9, the steps A that forms on Sapphire Substrate based on the compound semiconductor layer of gallium nitride is divided into two stages, steps A 1 and steps A 2 are step B, C and D subsequently.In steps A 1, flow into the steam that contains trimethyl aluminium (TMAl), in steps A 2, flow into the steam that mixed in 1: 2 in molar ratio that contains trimethyl gallium (TMGa) and trimethyl indium (TMIn) the metal nucleus is sticked on the substrate.Steps A 1 is carried out under different temperature with A2.In step B, the metal nucleus is annealed in hydrogen; In step C, the gaseous mixture of hydrogen and ammonia flows into, with the metal nucleus and the formation growth nucleus of nitrogenize annealing.In step D, TMGa and ammonia flow into further growth gallium nitride on the growth nucleus, thereby make the compound semiconductor layer based on gallium nitride with gallium nitride film on Sapphire Substrate.
At first, the thermal cleaning substrate surface, during this period, the hydrogen that contains trimethyl gallium (TMGa), trimethyl aluminium (TMAl) and trimethyl indium (TMIn) carries gas stream and crosses bubbler, to begin foaming.The pipeline of each bubbler is connected to reactor, and makes bubbler keep stationary temperature with heating bath.Up to the step that begins to grow based on the compound semiconductor layer of gallium nitride, TMGa, TMAl and the TMIn steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature was reduced to 1160 ℃.Be stabilized in after 1160 ℃ in definite temperature, operation TMAl line valve contains the steam of TMAl for the reactor supply, to begin that metal (Al) nucleus is adhered to technology on the Sapphire Substrate.This technology stopped to contain to the reactor supply steam (steps A 1) of TMAl after 1 minute with valve.Then, backing temp becomes 950 ℃.Waiting 10 seconds so that after the temperature stabilization, begin to contain the gas of TMGa and TMIn steam to begin that metal (Ga and In) nucleus is adhered to the technology on the Sapphire Substrate to the reactor supply with TMGa and TMIn valve.Be used for the mol ratio between TMGa and the TMIn is adjusted to 1: 2 at the flow controller on the foaming line.This technology stopped to contain to the reactor supply steam (steps A 2) of TMGa and TMIn after 2 minutes with valve.In the method, the formation of metal nucleus is divided into two stages, steps A 1 and A2.
This state kept 5 minutes, to carry annealed metal nucleus in the gas at hydrogen.After annealing in 5 minutes, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.
After gas flowed into 10 seconds, backing temp was brought up to 1160 ℃.Regulate the flow velocity of TMGa between the rising stage in temperature.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, and operation TMGa valve begins to reactor supply TMGa gas with further growth gallium nitride on the growth nucleus.
After 1 hour, stop the growth operation at the growing gallium nitride crystal film by stopping to supply TMGa to reactor.Close induction heater then, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor is made up of ammonia, nitrogen and hydrogen, with identical during the growth operation, but when definite substrate is cooled to 300 ℃, close ammonia and hydrogen, and nitrogen continues to flow into, up to the substrate cool to room temperature, at this moment substrate is taken out from reactor.
Above-mentioned steps is used for forming the gallium nitride film of the thick non-doping of 2 μ m on Sapphire Substrate.By the substrate that takes out in the reactor is water white, and epitaxial loayer has specular surface.
Non-doped gallium nitride crystal to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.Measuring the half peak value width value that shows (0002) plane is 190 seconds, and (10-12) the half peak value width value on plane is 260 seconds.When the superiors' film of checking gallium nitride with atomic force microscope surperficial, the table of discovery mask has form preferably, not observing the growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 1 * 10 then
7Cm
-2
Also adopt the identical step perparation of specimen, up to operation midway, when wafer was moved out of reative cell before the growing gallium nitride crystal film.When checking wafer, find to have the crystal group of the trapezoidal cross-section of the aluminum gallium nitride of forming the growth nucleus on sapphire surface with atomic force microscope.
Therefore, under the situation of example 9, the formation of metal nucleus is divided into two stages, and each stage is set different temperature.Thereby can adopt a greater variety of metals to form nucleus, and bonding with respect to the metal nucleus, can control temperature more accurately according to employed metal.Also can be controlled at the density of the metal nucleus on the substrate more accurately.Therefore, the compound semiconductor layer based on gallium nitride based on these metal nucleus is endowed desirable shape and character.
In example 9, though the formation of metal nucleus is divided into two stages, nucleus carries in the gas at hydrogen and anneals then, and this annealing steps can omit.If do like this, the formation of metal nucleus and nitriding step can carry out twice or more times.
Comparative example 1
Manufacturing is used for and the comparison sample wafer of comparing according to the sample of 1 to 3 and 5 to 9 each example manufacturing.Comparative sample adopts in the prior art as the low temperature buffer layer method described in the flat 4-297023 of above-mentioned JP-A is made.This method is used for making the gallium nitride film of the thick non-doping of 2 μ m on substrate.Therefore, the sample of preparation is water white, and epitaxial loayer has specular surface.
To the non-doped gallium nitride crystal film of above-mentioned art methods growth carry out XRC measure show (0002) plane and (10-12) the half peak value width value on plane be respectively 400 seconds and 500 seconds.When the superiors' film of checking gallium nitride with atomic force microscope surperficial, the table of discovery mask has the growth depression of dispersion and the step of short arch, illustrates to have a large amount of dislocations.In order to measure the density of corrosion pitting, adopt the technological preparation sample identical with example 5.The density that shows corrosion pitting with the atomic force microscope inspection is 2 * 10
9Cm
-2
Example 10
In example 10, used method forms the compound semiconductor layer based on gallium nitride in the employing reference example 8 on substrate, forms other gallium nitride layer then thereon, to make light emitting semiconductor device.
Fig. 6 shows the cross-section structure of the light emitting semiconductor device of making according to example 10.In example 10, adopt the MOCVD method to form the sandwich construction of light emitting semiconductor device by following operation.Contain the steam of trimethyl aluminium (TMAl) by inflow, flow into the steam that contains trimethyl gallium (TMGa) subsequently, on the substrate 11 that is heated to high temperature, form the metal nucleus.The metal nucleus is in hydrogen annealing and nitrogenize in ammonia then.Form succeeding layer by following order at substrate then: have 1 * 10
17Cm
-3The GaN layer 12 that the low Si of the 2-μ m of electron concentration mixes; Have 1 * 10
19Cm
-3The GaN layer 13 that the high Si of the 1-μ m of electron concentration mixes; Have 1 * 10
17Cm
-3The 100- In of electron concentration
0.1Ga
0.9N coating 14; By the GaN barrier layer to start with finish and comprise six 70- GaN barrier layers 15 and five non-doping In of 20-
0.2Ga
0.8The multi-quantum pit structure of N trap layer 16; 30- Al
0.2Ga
0.8The N diffusion prevents layer 17; Have 8 * 10
17Cm
-3The 0.15-μ m Mg Doped GaN layer 18 of hole concentration; And have 5 * 10
18Cm
-3The 100- Mg doping In of hole concentration
0.1Ga
0.9N layer 19.The wafer of being made up of Sapphire Substrate and above-mentioned sandwich construction is used to make light-emitting diode.
The wafer with above-mentioned epitaxial structure by the manufacturing of MOCVD method adopts following step.
At first, Sapphire Substrate 11 is placed in the RF coil of the induction heater in the quartz reaction stove (reactor).The glove-box that is filled with nitrogen is used for substrate is placed on carbon template, subsequently at the nitrogen inflow reactor to purify its inside.After inflow nitrogen 10 minutes, start induction heater and also make it that substrate is heated to 1170 ℃, the temperature rise time was above 10 minutes.Simultaneously, the pressure in the reactor is adjusted to 50hPa.Underlayer temperature remains on 1170 ℃, and hydrogen and nitrogen flow into 9 minutes, with the thermal cleaning substrate surface.
During thermal cleaning, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses the bubbler that is connected to reactor, to begin foaming.Adopt heating bath to make bubbler keep stationary temperature.Up to beginning the operation of growing, TMGa and the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature reduced to 1100 ℃ and reactor pressure and is transferred to 100hPa.Be stabilized in after 1100 ℃ in definite temperature, operation TMAl valve begins metal (Al) nucleus is adhered to the operation on Sapphire Substrate surface for the reactor supply contains the gas of TMAl steam.After this technology 1 minute, contain the gas of TMAl steam with the stop supplies of TMAl valve.Then, operation TMGa valve begins metal (Ga) nucleus is adhered to the operation on Sapphire Substrate surface for the reactor supply contains the gas of TMGa steam.After this technology 2 minutes, contain the gas of TMGa steam with the stop supplies of TMGa valve.In the method, the formation of metal nucleus is divided into two stages.
This state kept 5 minutes, to carry the metal nucleus that annealing so forms in the gas at hydrogen.After annealing in 5 minutes, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.By this, identical in operation and the example 4.
After ammonia flowed into 10 seconds, backing temp was brought up to 1160 ℃.Regulate the linear flow speed of TMGa between the rising stage in temperature, and begin to flow into SiH
4During this period, up to the growth operation that begins low Si Doped GaN layer, SiH
4Be discharged into the outside by the system of removing the evil.Reach after 1160 ℃ at definite backing temp, it is stable that temperature keeps, operation TMGa and SiH
4Valve begins to reactor supply TMGa and SiH
4Gas continues about 75 minutes, to form low Si Doped GaN layer.According to existing research, control SiH
4Flow velocity so that the electron concentration in the GaN layer reaches 1 * 10
17Cm
-3In this way, forming thickness is the low Si Doped GaN layer 12 of 2 μ m.
Subsequently on this low Si Doped GaN layer the growth high Si Doped n-GaN layer.Especially, after the low Si Doped GaN layer 12 of growth, stop to reactor supply TMGa and SiH
4Gas one minute changes SiH during this period
4Flow velocity.According to existing research, control SiH
4Flow so that the electron concentration in high Si Doped GaN layer reaches 1 * 10
19Cm
-3Continue to reactor supply ammonia with identical flow velocity.After pausing in one minute, recover supply TMGa and SiH
4And this layer forms and continues 45 minutes, is the high Si Doped GaN layer 13 of 1 μ m thereby form thickness.
After forming high Si Doped GaN layer 13, with TMGa and SiH
4Valve interrupts supplying these materials to reactor, and carries gas and change nitrogen into by hydrogen, keeps ammonia flow simultaneously.Underlayer temperature drops to 800 ℃ by 1160 ℃ subsequently, and reactor pressure becomes 200hPa by 100hPa simultaneously.
During the temperature change in waiting for reactor, change SiH
4Flow velocity.According to existing research, control SiH
4Flow velocity so that the electron concentration in Si doping InGaN coating reaches 1 * 10
17Cm
-3Continue to reactor supply ammonia with identical flow velocity.Begun in bubbler, to supply trimethyl indium (TMIn) and triethyl-gallium (TEGa) carries gas.Up to beginning to form coating, SiH
4TMIn and TEGa steam that gas and foaming produce are discharged into the system outside together with carrying gas by the system of removing the evil.Make reactor after stabilization time, beginning is to reactor supply TMIn, TEGa and SiH
4Gas also kept about 10 minutes, to form the thick Si doping In of 100
0.1Ga
0.9N coating 14 stops afterwards to reactor supply TMIn, TEGa and SiH
4
Make then by GaN barrier layer 15 and In
0.2Ga
0.8The multi-quantum pit structure that N trap layer 16 is formed.At first at Si doping In
0.1Ga
0.9Form GaN barrier layer 15 on the N coating 14, on GaN barrier layer 15, form In then
0.2Ga
0.8N trap layer 16.Repeat 5 times again to form after the necessary sandwich construction, at the 5th In
0.2Ga
0.8Form the 6th GaN barrier layer 15 on the N trap layer 16, be created in the structure that every end has GaN barrier layer 15.
Finish Si doping In
0.1Ga
0.9After the formation of N coating, suspend 30 seconds, begin subsequently, keep identical underlayer temperature, reactor pressure simultaneously, carry gas type and carry gas flow rate, to form a GaN layer to reactor supply TEGa.After 7 minutes, stop supplies TEGa stops the formation on GaN barrier layer 15 when 70 are thick.
During the formation on GaN barrier layer 15, the mole flow velocity that flows to the TMIn of the system that removes the evil is compared with the flow velocity during forming coating 14 and is doubled.After finishing GaN barrier layer 15, the supply of III family material stops 30 seconds, and operation TEGa and TMIn valve are to reactor supply TEGa and TMIn, the type and the flow that keep identical underlayer temperature, reactor pressure simultaneously and carry gas.After 2 minutes, stop supplies TEGa and TMIn finish the thick In of 20
0.2Ga
0.8The formation of N trap layer 16.
Finish In
0.2Ga
0.8Behind the N trap layer 16, the supply of III family material stops 30 seconds, begins afterwards to reactor supply TEGa, and the type and the flow velocity that keep identical underlayer temperature, reactor pressure simultaneously and carry gas are with another GaN barrier layer of growing.This step repeats 5 times to make five GaN barrier layers 15 and five In
0.2Ga
0.8N trap layer 16.At last, at final In
0.2Ga
0.8Form GaN barrier layer 15 on the N trap layer 16.
Process subsequently is to form non-doped with Al on final GaN barrier layer 15
0.2Ga
0.8The N diffusion prevents layer 17.Stop supplies TEGa with one minute after finishing GaN barrier layer 15 in, reactor pressure becomes 100hPa, the type and the flow velocity that keep identical underlayer temperature simultaneously and carry gas.The trimethyl aluminium (TMAl) that flows to bubbler carries gas stream to begin.Prevent that up to the formation diffusion step of layer from beginning, the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.Then, after stabilization time, beginning is to reactor supply TEGa and TMAl at given reactor pressure.Subsequently about 3 minutes are used for continuing to form this layer, and stop supplies TEGa and TMAl subsequently are to stop non-doped with Al
0.2Ga
0.8The N diffusion prevents the growth of layer 17, is the non-doped with Al of 30 thereby obtain thickness
0.2Ga
0.8The N diffusion prevents layer 17.
Then in non-doped with Al
0.2Ga
0.8The N diffusion prevents growth Mg Doped GaN layer 18 on the layer 17.At stop supplies TEGa and TMAl, to finish non-doped with Al
0.2Ga
0.8N diffusion prevents that underlayer temperature is elevated to 1060 ℃ in the growth 2 minutes of layer 17, and reactor pressure becomes 200hPa.Equally, carry gas and become hydrogen.Dicyclopentadiene magnesium (Cp
2Mg) carry gas flow and begun to flow through bubbler.Up to the step that begins to form Mg Doped GaN layer, the Cp that foaming produces
2Mg steam is discharged into the system outside by the system of removing the evil together with carrying gas.After changing temperature and pressure, give reactor pressure stabilization time and begin to supply TMGa and Cp to reactor
2Mg.Cp
2The flow of Mg is studied in advance, and regulates so that the hole concentration in Mg Doped GaN coating reaches 8 * 10
17Cm
-3After approximately growing 6 minutes, stop supplies TMGa and Cp
2Mg is to stop the formation of Mg Doped GaN layer.The final thick Mg Doped GaN layer 18 of thick 0.15 μ m that forms of this operation.
On this Mg Doped GaN layer 18, form Mg doping InGaN layer 19.At stop supplies TMGa and Cp
2After the Mg, stop the growth of Mg Doped GaN layer 18, be reduced to 800 ℃, and carry gas and change nitrogen into 2 minutes time chien shih substrate temperatures.Reactor keeps the identical pressure of 200hPa.Adjust Cp
2The flow of Mg is with to Mg doping In
0.1Ga
0.9The Mg amount of impurities that N layer 19 is identical with Mg Doped GaN layer.Think that according to existing research the quantity of impurity makes Mg doping In
0.1Ga
0.9Hole concentration in the N layer reaches 5 * 10
18Cm
-3
After waiting for that underlayer temperature is stable, beginning is to reactor supply TMIn, TEGa and Cp
2Mg.After growing 10 minutes, stop to reactor supply TMIn, TEGa and Cp
2Mg is to stop Mg doping In
0.1Ga
0.9The growth of N layer 19.Thereby form the Mg doping In of thick 100
0.1Ga
0.9N layer 19.
Finish Mg doping In
0.1Ga
0.9Behind the N layer 19, close induction heater, thereby make substrate cool to room temperature in 20 minutes time.During this period, the atmosphere in the reactor only is made up of nitrogen.Behind definite substrate cool to room temperature, from reactor, take out the wafer that forms thus.Wafer is transparent, and color and luster and epitaxial loayer with little Huang have specular surface.Therefore, according to aforementioned operation, make wafer with the epitaxial structure that is used for light emitting semiconductor device.Even it is not annealed to activate p type charge carrier, Mg Doped GaN layer 18 and Mg doping In
0.1Ga
0.9N layer 19 all shows as p type characteristic.
Then, the wafer with above epitaxial structure that forms on Sapphire Substrate is used to make light-emitting diode.By forming the p electrode bonding welding pad of being made up of by the laminated construction of this order titanium, aluminium and gold layer 20, known lithography process is used at 100 Mg doping In
0.1Ga
0.9The surperficial 18a of N layer 18 goes up and makes p lateral electrode, the only transparent p lateral electrode 21 that is formed by gold.Adopt dry corrosion to expose the part 131 of high Si Doped GaN layer 13 then, forming the n lateral electrode, and make the n electrode 22 of Ni and Al at expose portion 131.Fig. 7 shows the shape of the electrode of so making on wafer.
Then, the reverse side of Sapphire Substrate is ground and polishes with mirror finish, and wafer is cut into the square chip of every limit 350 μ m.Subsequently chip electrode towards on be installed on the lead frame, and be connected on the lead frame with gold thread, form luminescent device.When the forward current of 20mA flow through electrode, forward voltage was 3.0V.The radiative wavelength that sees through p side transparency electrode is 470nm, and emission is output as 6cd.
Example 11
This example describes with reference to being used to form based on the compound semiconductor of gallium nitride and the step of manufacturing light emitting semiconductor device.Alternately form the metal nucleus twice by TMAl stream (steps A 1) and TMGa stream (steps A 2), the metal nucleus carries out nitrogenize (step C) without any annealing (step B) then, and forms the compound semiconductor layer based on gallium nitride on the nucleus of nitrogenize.The device of making has the structure identical with device shown in Figure 6.
The following describes example by the device with said structure of MOCVD method manufacturing.Sapphire Substrate 11 is placed in the RF coil of the induction heater in the quartz reaction stove (reactor).The glove-box that is filled with nitrogen is used for substrate is placed on the carbon template that is used to heat, and the nitrogen inflow reactor is to purify its inside subsequently.As the situation of example 6, before the step of adhesiving metal nucleus, the thermal cleaning substrate surface.During thermal cleaning, adopt with example 6 identical materials to begin to bubble, consequent steam is discharged into the outside by the system of removing the evil.After thermal cleaning was finished, nitrogen carried gas trap and closes, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature reduced to 1100 ℃ and reactor pressure and is transferred to 100hPa.Be stabilized in after 1100 ℃ in definite temperature, contained the gas of TMAl steam with the TMAl valve for the reactor supply, so that the metal nucleus is adhered on the Sapphire Substrate.After this technology 2 minutes, stop to reactor supply TMAl.After 1 second kind, begin to contain the gas of TMGa steam with TMGa line valve for the reactor supply.Thereby begin gallium is adhered on the aluminium nucleus on the substrate.After 4 minutes, stop supply to the TMGa of reactor.Operation to reactor supply TMAl and TMGa repeats twice.
Stopping for the second time when reactor is supplied TMGa steam, beginning to reactor supply ammonia, with the metal nitride nucleus with ammonia line valve.After 10 seconds, backing temp is brought up to 1160 ℃, keeps ammonia flow simultaneously.Hang down the manufacturing of Si Doped GaN layer then.With hanging down GaN layer 13, the In of the GaN layer 12 of Si doping, high Si doping with example 10 described identical operation growths
0.1Ga
0.9N coating 14, by six GaN barrier layers 15 and five non-doping In
0.2Ga
0.8Multi-quantum pit structure, Al that N trap layer 16 is alternately formed
0.2Ga
0.8The N diffusion prevents layer 17, Mg Doped GaN layer 18 and Mg doping In
0.1Ga
0.9N layer 19.
Finish the Mg doping In that is formed on the wafer top layer
0.1Ga
0.9Behind the N layer, close induction heater, thereby make substrate cool to room temperature in 20 minutes time, during this period in, nitrogen is only arranged in the reactor.Behind definite substrate cool to room temperature, from reactor, take out wafer.Wafer is transparent, have the color and luster of little Huang, and epitaxial loayer has specular surface.
Therefore, according to aforementioned operation, make wafer with the sandwich construction that is used for the light emitting semiconductor device application.The operation that is used for example 6 is used for forming electrode on wafer, and wafer is cut into chip, and chip is installed in forms luminescent device on the lead frame.When the forward current of 20mA was added on the electrode of light-emitting diode of manufacturing like this, forward voltage was 3.2V.The radiative wavelength that sees through the p lateral electrode is 470nm, and emission is output as 5cd.
Example 12
In this embodiment, method of the present invention is used for forming the compound semiconductor layer based on gallium nitride on substrate, and forms other compound semiconductor layer based on gallium nitride on ground floor, thereby forms the laminated construction that constitutes light emitting semiconductor device.
Fig. 8 shows the cross-section structure of the light emitting semiconductor device of making according to example 12.As follows, adopt the MOCVD method to be formed for the wafer with this sandwich construction of light emitting semiconductor device.Contain the steam of trimethyl aluminium (TMAl) by inflow, flow into the steam that contains trimethyl gallium (TMGa) subsequently, on the substrate 11 that is heated to high temperature, form the metal nucleus.The metal nucleus is in hydrogen annealing and nitrogenize in ammonia then.Form succeeding layer by following order then: have 1 * 10
17Cm
-3The GaN layer 12 that the low Si of the 2-μ m of electron concentration mixes; Have 1 * 10
19Cm
-3The GaN layer 13 that the high Si of the 1-μ m of electron concentration mixes; By GaN barrier layer 15 to start with finish and comprise six 70-A GaN barrier layers 15 and five non-doping In of 20-A
0.2Ga
0.8The multi-quantum pit structure of N trap layer 16; 30-AAl
0.2Ga
0.8The N diffusion prevents layer 17; Have 8 * 10
17Cm
-3The 0.15-μ m Mg Doped GaN layer 18 of hole concentration.The wafer of being made up of Sapphire Substrate and above-mentioned sandwich construction is used to make light-emitting diode.
The wafer with above-mentioned multilayer epitaxial structure by the manufacturing of MOCVD method adopts following step.
At first, Sapphire Substrate 11 is placed in the RF coil of the induction heater in the quartz reaction stove (reactor).The glove-box that is filled with nitrogen is used for substrate is placed on the carbon template that is used to heat, and uses the nitrogen purge inside reactor subsequently.After inflow nitrogen 10 minutes, start induction heater and also make it that substrate is heated to 1170 ℃, the temperature rise time was above 10 minutes.Simultaneously, the pressure in the reactor is adjusted to 50hPa.Underlayer temperature remains on 1170 ℃, and hydrogen and nitrogen flow into 9 minutes, with the thermal cleaning substrate surface.
During thermal cleaning, the hydrogen that contains trimethyl gallium (TMGa) and trimethyl aluminium (TMAl) carries gas stream and crosses the bubbler that is connected to reactor, to begin foaming.Adopt heating bath to make bubbler keep stationary temperature.Up to beginning the operation of growing, TMGa and the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After thermal cleaning was finished, nitrogen valve was closed, thereby had only hydrogen to be added in the reactor.
After gas was carried in change, underlayer temperature was reduced to 1160 ℃ and reactor pressure and is transferred to 100hPa.Be stabilized in after 1160 ℃ in definite temperature, operation TMAl valve begins metal (Al) nucleus is adhered to the operation on Sapphire Substrate 11 surfaces for the reactor supply contains the gas of TMAl steam.After this technology 3 minutes, contain the gas of TMAl steam with the stop supplies of TMAl valve.Then, operation TMGa valve begins metal (Ga) nucleus is adhered to the operation on Sapphire Substrate surface 11 once more for the reactor supply contains the gas of TMGa steam.After this technology 3 minutes, contain the gas of TMGa steam with the stop supplies of TMGa valve.In the method, the formation of metal nucleus is divided into two stages.
This state kept 5 minutes, carried the metal nucleus that annealing so forms in the gas at hydrogen.After annealing in 5 minutes, begin to reactor supply ammonia with ammonia line valve, with the metal nucleus of nitrogenize annealing and make it form the nucleus of growing.Regulate flow with the TMGa flow controller, keep ammonia flow simultaneously, and begin to flow into SiH
4During this period, up to the growth operation that begins low Si Doped GaN layer, SiH
4Be discharged into the outside with carrying gas by the system of removing the evil.Stablize TMGa and SiH
4Flow, use TMGa and SiH subsequently
4Valve begins to reactor supply TMGa and SiH
4Gas continues about 75 minutes, to begin the low Si Doped GaN layer of growing.According to existing research, control SiH
4Flow so that the electron concentration in the GaN layer reaches 1 * 10
17Cm
-3In this way, forming thickness is the low Si Doped GaN layer 12 of 2 μ m.
Subsequently, growth high Si Doped n-GaN layer on this low Si Doped GaN layer 12.Especially, after the low Si Doped GaN layer 12 of growth, stop to reactor supply TMGa and SiH
4Gas one minute changes SiH during this period
4Flow.According to existing research, control SiH
4Flow so that the electron concentration in high Si Doped GaN layer reaches 1 * 10
19Cm
-3Continue to reactor supply ammonia with identical flow.After pausing in one minute, recover supply TMGa and SiH
4And this layer growth 45 minutes is the high Si Doped GaN layer 13 of 1 μ m thereby form thickness.
After forming high Si Doped GaN layer 13, with TMGa and SiH
4Valve interrupts supplying these materials to reactor, and carries gas and change nitrogen into by hydrogen, keeps ammonia flow simultaneously.Underlayer temperature drops to 800 ℃ by 1160 ℃ subsequently, and reactor pressure becomes 200hPa by 100hPa simultaneously.During the temperature change in waiting for reactor, continue to reactor supply ammonia with identical flow.Begun in bubbler, to supply trimethyl indium (TMIn) and triethyl-gallium (TEGa) carries gas.Up to beginning to form active layer, TMIn and TEGa steam that foaming produces are discharged into the system outside together with carrying gas by the system of removing the evil.
Make then by GaN barrier layer 15 and In
0.2Ga
0.8The multi-quantum pit structure that N trap layer 16 is formed.Manufacturing comprises at first formation GaN barrier layer 15 on Si Doped GaN contact layer 13, forms In then on GaN barrier layer 15
0.2Ga
0.8N trap layer 16.This structure repeats 5 times, at the 5th In
0.2Ga
0.8Form the 6th GaN barrier layer 15 on the N trap layer 16, be created in the structure that every end has GaN barrier layer 15.
Supply TEGa with the TEGa valve to reactor, keep identical underlayer temperature, reactor pressure simultaneously, carry gas type and carry gas flow, to form a GaN layer.After 7 minutes, stop supplies TEGa stops the formation on GaN barrier layer 15 when 70 are thick.
After finishing GaN barrier layer 15, the supply of III family material stops 30 seconds, and operation TEGa and TMIn valve are to reactor supply TEGa and TMIn, the type and the flow that keep identical underlayer temperature, reactor pressure simultaneously and carry gas.After 2 minutes, stop supplies TEGa and TMIn finish the thick In of 20
0.2Ga
0.8The formation of N trap layer 16.Finish In
0.2Ga
0.8Behind the N trap layer 16, the supply of III family material stops 30 seconds, begins afterwards to reactor supply TEGa, and the type and the flow that keep identical underlayer temperature, reactor pressure simultaneously and carry gas are with another GaN barrier layer 15 of growing.This step repeats 5 times to make five GaN barrier layers 15 and five In
0.2Ga
0.8N trap layer 16.At last, at final In
0.2Ga
0.8Form GaN barrier layer 15 on the N trap layer 16.
Process subsequently is to form non-doped with Al on the final GaN barrier layer 15 of quantum well structure
0.2Ga
0.8The N diffusion prevents layer 17.Stop supplies TEGa with one minute after finishing GaN barrier layer 15 in, reactor pressure becomes 100hPa, the type and the flow that keep identical underlayer temperature simultaneously and carry gas.The trimethyl aluminium (TMAl) that flows to bubbler carries gas stream to begin.Prevent that up to the formation diffusion step of layer from beginning, the TMAl steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.After stabilization time, operation TEGa and TMAl valve begin to reactor supply TEGa and TMAl at given reactor pressure.Subsequently about 3 minutes are used for continuing to form this layer, and stop supplies TEGa and TMAl subsequently are to stop non-doped with Al
0.2Ga
0.8The N diffusion prevents the growth of layer 17.Thereby obtaining thickness is the non-doped with Al of 30
0.2Ga
0.8The N diffusion prevents layer 17.
Step subsequently is in non-doped with Al then
0.2Ga
0.8The N diffusion prevents growth Mg Doped GaN layer 18 on the layer 17.At stop supplies TEGa and TMAl, to finish non-doped with Al
0.2Ga
0.8N diffusion prevents that underlayer temperature is elevated to 1060 ℃ in the growth 2 minutes of layer 17, and reactor pressure becomes 200hPa, and carries gas and become hydrogen.Dicyclopentadiene magnesium (Cp
2Mg) carry gas flow and begun to flow through bubbler.Up to the step that begins to form Mg Doped GaN layer, the Cp that foaming produces
2Mg steam is discharged into the system outside by the system of removing the evil together with carrying gas.
After changing temperature and pressure, give reactor pressure stabilization time and begin to supply TMGa and Cp to reactor
2Mg.Cp
2The flow of Mg is studied in advance, and regulates so that the hole concentration in Mg Doped GaN coating reaches 8 * 10
17Cm
-3After about 6 minutes of the layer growth, stop supplies TMGa and Cp
2Mg is to stop the formation of Mg Doped GaN layer.The final thick Mg Doped GaN layer 18 of thick 0.15 μ m that forms of this operation.
As follows, on this Mg Doped GaN layer 18, make Mg doping InGaN layer 19.At stop supplies TMGa and Cp
2After the Mg, stop the growth of Mg Doped GaN layer 18, be reduced to 800 ℃, and carry gas and change nitrogen into 2 minutes time chien shih substrate temperatures.Reactor keeps the identical pressure of 200hPa.Close induction heater then, thereby make substrate cool to room temperature in 20 minutes time.During cooling, the atmosphere in the reactor is to comprise 1% ammonia composition in nitrogen.Behind definite substrate cool to room temperature, from reactor, take out the wafer that forms thus.Wafer is transparent, have the color and luster of little Huang, and epitaxial loayer has specular surface.Therefore, according to aforementioned operation, make wafer with the epitaxial structure that is used for light emitting semiconductor device.Even not annealed to activate p type charge carrier, Mg Doped GaN layer 18 shows as p type characteristic.
The wafer with above-mentioned epitaxial structure that forms on Sapphire Substrate 11 is used to make light-emitting diode.By forming p electrode bonding welding pad of being made up of by the laminated construction of this order titanium, aluminium and gold layer 20 and the transparent p lateral electrode 21 that is only formed by gold, known lithography process is used at 100- Mg doping In
0.1Ga
0.9The surperficial 18a of N layer 18 goes up and makes the p lateral electrode.Adopt dry corrosion to expose the part 131 of the high Si Doped GaN layer 13 that is used for the n lateral electrode then, and make the n electrode 22 of Ni and Al at expose portion 131.Fig. 7 shows the shape of the electrode of so making on wafer.
Then, to Sapphire Substrate carry out that reverse side grinds and polishing with mirror finish, and wafer is cut into the square chip of every limit 350 μ m.Subsequently chip electrode towards on be installed on the lead frame, and be connected on the lead frame with gold thread, form luminescent device.When the forward current of 20mA flow through electrode, forward voltage was 3.0V.The radiative wavelength that sees through p side transparency electrode is 472nm, and emission is output as 5.9cd.
Comparative example 2
In comparative example 2, wafer adopts low temperature buffer layer method of the prior art manufacturing.This method is used for making the gallium nitride film of the thick non-doping of 2 μ m on substrate.Therefore, the wafer of preparation is water white, and epitaxial loayer has specular surface.In the method identical, on wafer, form p-and n-electrode, and the reverse side of Sapphire Substrate is ground and polishes with mirror finish, and wafer is cut into the square chip of every limit 350 μ m with example 10.Subsequently chip electrode towards on be installed on the lead frame, and be connected on the lead frame with gold thread, form luminescent device.When the forward current of 20mA flow through electrode, forward voltage was 4.0V.The radiative wavelength that sees through p side transparency electrode is 470nm, and emission is output as 3cd.
The method according to this invention be formed on the substrate based on the good improvement in performance of the compound semiconductor layer of gallium nitride the crystallinity of emission layer, improved the output of emission quantum.
Example 13
This example explanation is with being formed on slow growth mask layer growth on the substrate based on the compound semiconductor layer of gallium nitride.In this embodiment, according to step shown in Figure 9 grown crystal on substrate.By flowing into ammonia and disilane (Si
2H
6), flow into the mixture of TMG and TMA then, flow into ammonia then, adopt the MOCVD method to make the extension sample on the substrate of high temperature, have the mask layer in zone of zone that covers by silicon nitride and the Sapphire Substrate that is stained with aluminium nitride and gallium nitride and the non-Doped GaN layer that on this layer, forms being heated to.
As described below, have the sample of above-mentioned GaN layer with the manufacturing of MOCVD method.
Sapphire Substrate 11 is placed in the RF coil of the induction heater in the quartz reactor, and substrate is placed on the carbon template that is used to heat there.Air is by extracting out in the reactor then, thereby nitrogen is flowed into purification reactor inside.After inflow nitrogen 10 minutes, start induction heater and also make it that substrate is heated to 1170 ℃, the temperature rise time was above 10 minutes.Underlayer temperature remain on 1170 ℃ 9 minutes, simultaneously hydrogen and nitrogen flow into, with the thermal cleaning substrate surface.
During thermal cleaning, the hydrogen that contains trimethyl gallium (TMG) carries gas stream and crosses the bubbler that is connected to reactor, to begin foaming.Adopt heating bath to make bubbler keep stationary temperature.Up to beginning GaN layer growth operation, the TMG steam that produces is discharged into outside the system by the system of removing the evil with carrying gas by bubbling.
After thermal cleaning is finished, when making ammonia and disilane stop supplies with valve, make ammonia and disilane flow to Sapphire Substrate last 1 minute with ammonia and disilane valve.Then, carrying gas valve with nitrogen begins to reactor the supply of nitrogen.After 1 minute, open TMA and TMG valve and contain the gas 1 minute of TMA and TMG steam for the reactor supply, then, stop supplies TMA and TMG begin to reactor the supply of nitrogen with carrying gas valve.After 1 minute, beginning is supplied ammonia to reactor, and continues 10 minutes, when it is closed, opens nitrogen supply (NS).The mask layer that is formed by these steps comprises nitrogenize silicon area 5 and aluminum gallium nitride district 8.
Form after the mask layer, underlayer temperature is reduced to 1160 ℃.Be stabilized in after 1160 ℃ in definite temperature, operation ammonia line valve begins to reactor supply ammonia 4.After 1 minute, operation TMG line valve contains the gas of TMG steam to the reactor supply, with growing GaN layer 9 on mask layer.After about 2 hours, stop supplies TMG is to stop growth at the growing GaN layer.Close induction heater then, adopt the process in the example 1 to take out sample.Therefore,, on Sapphire Substrate 1, form mask layer, and on mask layer, form the thick GaN layer of 2-μ m with the perparation of specimen according to aforementioned operation.The substrate that takes out from reactor is water white; Epitaxial loayer has specular surface.
Non-Doped GaN layer to the said method growth carries out the XRC measurement.Adopt Cu β line and X line source, measure with symmetry (0002) plane and asymmetric (10-12) plane.In general, under the situation based on gallium nitride compound semiconductor, half peak value width of the XRC spectrum on (0002) plane is the crystrallographic plane coefficient, and (10-12) half peak value width of the XRC spectrum on plane is the dislocation density coefficient.Measuring the half peak value width value that shows (0002) plane is 280 seconds, and (10-12) the half peak value width value on plane is 300 seconds.
The surperficial display surface of checking the superiors' film of gallium nitride with atomic force microscope has form preferably, not growth depression.For the density of the corrosion pitting of measuring film, sample was immersed in 280 ℃ sulfuric acid and the phosphoric acid solution 10 minutes.Check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 9 * 10 then
6Cm
-2
Example 14
In this embodiment, by step as shown in figure 10, with MOCVD method grown crystal on substrate.By at high temperature flowing into ammonia nitrogenize Sapphire Substrate surface.By flowing into the mixture of disilane and TMG, flow into ammonia then, have the zone that covers by silicon nitride and be stained with the mask layer in zone of the substrate of gallium nitride with formation.The non-Doped GaN layer that on mask layer, forms then.
As described below, have the sample of above-mentioned GaN layer with the manufacturing of MOCVD method, used identical in MOCVD device and the example 13.With with example 13 in identical method thermal cleaning Sapphire Substrate, begin during this period to bubble.After thermal cleaning was finished, ammonia flow to substrate last 20 minute, stops then.Then, operation nitrogen carries gas valve and begins to reactor the supply of nitrogen.Then, open disilane and TMA valve and carried gas 30 seconds for what the reactor supply contained disilane and TMA steam, subsequently, stop supplies disilane and TMA begin to reactor the supply of nitrogen with carrying gas valve.After 1 minute, beginning is supplied ammonia to reactor, and continues 10 minutes, closes it subsequently and opens nitrogen supply (NS).The mask layer that this technology forms on Sapphire Substrate comprises nitrogenize silicon area 5 and gallium nitride district 8.
Form after the mask layer, underlayer temperature is reduced to 1180 ℃.Be stabilized in after 1180 ℃ in definite temperature, opened the ammonia source and begin to reactor supply ammonia.After 1 minute, open TMG line valve and contain the gas of TMG steam, on mask layer, to form the GaN layer to the reactor supply.After about 2 hours, stop supplies TMG is to stop the growth operation at the growing GaN layer.Close heater then, adopt the process in the example 1 to take out sample.Therefore,, on Sapphire Substrate 1, form mask layer (5,8), and on mask layer, form the thick GaN layer of 2-μ m with the perparation of specimen according to aforementioned operation.The substrate that takes out from reactor is water white; Epitaxial loayer has specular surface.
Non-Doped GaN layer to the said method growth carries out the XRC measurement.(0002) the half peak value width value on plane is 290 seconds, and (10-12) the half peak value width value on plane is 420 seconds.The surperficial display surface of checking the superiors' film of GaN layer with atomic force microscope has form preferably, not growth depression.For the density of the corrosion pitting of measuring film, use the method identical to prepare sample with example 13, check that with atomic force microscope the surface to measure the density of corrosion pitting, is approximately 6 * 10
7Cm
-2
Example 15
This example is used for illustrating that use makes the method for luminescent device based on gallium nitride compound semiconductor, comprising according to the step of method manufacturing shown in the example 13 based on the compound semiconductor of gallium nitride.As shown in Figure 8, the cross-section structure of the luminescent device of so making is identical with structure in the example 12.By flowing into ammonia and disilane (Si
2H
6), flow into TMG and TMA mixture subsequently, be ammonia then, adopt the MOCVD method to be formed for the wafer with this sandwich construction of light emitting semiconductor device being heated on the Sapphire Substrate of high temperature, have the mask layer in the zone that the zone that covered by silicon nitride and GaAlN cover.Form succeeding layer thereon by following order then: have 1 * 10
17Cm
-3The GaN layer 12 that the low Si of the 2-μ m of electron concentration mixes; Have 1 * 10
19Cm
-3The GaN layer 13 that the high Si of the 1-μ m of electron concentration mixes; By GaN barrier layer 15 to start with finish and comprise six 70- GaN barrier layers 15 and five non-doping In of 20-
0.2Ga
0.8The multi-quantum pit structure of N trap layer 16; 30- Al
0.2Ga
0.8The N diffusion prevents layer 17; Have 8 * 10
17Cm
-3The 0.15-μ m Mg Doped GaN layer 18 of hole concentration.
Adopt MOCVD method and the operation identical with example 13, the ground floor of formation is the thick plane of 2-μ m, has 1 * 10
17Cm
-3The GaN layer 12 that the low Si of electron concentration mixes.Then, adopt the operation identical, on GaN layer 12, form the GaN layer 13 of high Si doping, the multi-quantum pit structure that then is, Al with example 12
0.2Ga
0.8The N diffusion prevents layer 17 and Mg Doped GaN layer 18.
On the wafer that from reactor, takes out, known lithography process is used to make that the lamination that begun by the surface of p type InGaN layer by this order by titanium, aluminium and gold layer constitutes, and the transparent p lateral electrode that forms by gold and nickel oxide layer press this tactic bonding welding pad.Adopt dry corrosion to expose the part of the n-type GaN layer that is used for the n lateral electrode then, and make the n lateral electrode of aluminium at expose portion.Then, the reverse side of Sapphire Substrate is ground and polishes with mirror finish, and wafer is cut into the square chip of every limit 350 μ m.Subsequently chip electrode towards on be installed on the lead frame, and be connected on the lead frame with gold thread, form luminescent device.When the forward current of 20mA flow through electrode, forward voltage was 3.0V.The radiative wavelength that sees through p side transparency electrode is 465nm, and emission is output as 3cd.