KR100992499B1 - Semiconductor light-emitting diode - Google Patents

Abstract

The semiconductor light emitting diode 20 is formed of a silicon single crystal substrate 201, a group III nitride semiconductor and an intervening layer 203 stacked on the silicon single crystal substrate 201, and a pn junction heterojunction structure. The light emitting parts 205, 206, and 207 stacked on the intervening layer 203 are provided. The intervening layer 203 is formed of an aluminum-containing group III nitride semiconductor. A superlattice structure 204 formed of a plurality of group III nitride semiconductor layers containing aluminum and having different aluminum composition ratios is disposed between the intervening layer 203 and the light emitting portions 205, 206, and 207. The DBR film formed of the superlattice structure 204 may improve reflectance and improve light emission characteristics.

Semiconductor light emitting diode

Description

Semiconductor Light Emitting Diodes {SEMICONDUCTOR LIGHT-EMITTING DIODE}

The present invention provides a semiconductor light emitting diode comprising a silicon single crystal substrate, an intervening layer formed of a group III nitride semiconductor and stacked on the silicon single crystal substrate, and a light emitting part formed of a pn junction heterojunction structure and stacked on the intervening layer. It is about.

Until now, group III nitride semiconductor materials such as gallium nitride (GaN) have been used to form light emitting portions of semiconductor light emitting devices (semiconductor light emitting diodes) such as short wavelength visible light emitting diodes (LEDs) and laser diodes (LDs) (Japanese Patent) See notice 55-3834). The expression "light emitting portion of a semiconductor light emitting device" denotes a region including a light emitting layer formed of a semiconductor material capable of causing light emission, and a functional layer such as a clad layer accompanying the light emitting layer. As one example of the above semiconductor material used to form the light emitting layer, gallium indium nitride (Ga _X In _{1 - X} N, where 0≤X≤1) is known (see Japanese Patent Publication 55-3834).

The light emitting portion formed of the group III nitride semiconductor is made of sapphire (α-Al ₂ O ₃ single crystal) (see Japanese Patent Publication No. 55-3834) or silicon single crystal (silicon) (see Japanese Patent Publication No. 49-122294) as a substrate. It is obtained by using. In the case of forming a group III nitride semiconductor layer on such a substrate, it is common to dispose a buffer layer between these layers in view of alleviating lattice mismatch that may cause their interface (see Japanese Patent Laid-Open No. 60-173829). ). For example, a technique using a boron phosphide (BP) layer as a buffer layer is known to form a group III nitride semiconductor layer on a silicon substrate (see Japanese Patent Laid-Open No. 4-084486).

As a method of forming a silicon carbide layer as a buffer layer on a silicon substrate, a technique including carbonizing the surface of the silicon substrate is described (J. Electrochem. Soc. (USA), Vol. 137, No. 3, 1990, pp. 989-992). It is reported that a good quality aluminum gallium indium nitride (AlGaInN) layer can be formed on the silicon carbide layer disposed on the surface of the silicon substrate (see Japanese Patent Laid-Open No. 4-223330). Therefore, it is presumed that formation of a functional layer such as a distributed Bragg reflector (DBR) having a superlattice structure of a group III nitride semiconductor layer on such a layer is preferable.

On the other hand, an example of the prior art for forming the DBR layer having GaN and AlN of a superlattice structure in which sapphire is used as a substrate is described (Appl. Phys. Lett (USA), Volume 74, No. 7, 1999, pp. 1036-1038).

For example, an attempt to arrange a superlattice structure in which an AlN layer stacked on a silicon carbide buffer layer is used as an underlayer has been made as long as the structure is formed of a combination of a GaN thin film and an AlN thin film, which are all Group III nitride semiconductor layers. It causes a problem that the superlattice structure can not be formed stably. This is because the GaN thin film, which has a flat surface without pit and is continuously and uniquely oriented toward a specific crystal direction, cannot be formed by being bonded to the AlN thin film due to condensation of Ga on the AlN film.

As described above, when arranging the superlattice structure formed of the group III nitride semiconductor layer through the silicon carbide buffer layer formed on the silicon substrate, the prior art is made from the group III nitride semiconductor layer which is persistent and exhibits regular orientation. A superlattice structure cannot be formed, and the light emission characteristic of the semiconductor light emitting diode cannot be improved.

SUMMARY OF THE INVENTION The present invention has been proposed in view of overcoming the problems in the prior art as described above, and an object thereof is to provide a semiconductor light emitting diode having excellent reflectance and improved light emitting characteristics for a DBR film made of a superlattice structure. do.

In order to achieve the above-mentioned object, 1) the present invention is an interlayer, pn junction heterojunction structure formed of a silicon single crystal substrate and an aluminum-containing group III nitride semiconductor and laminated on the silicon single crystal substrate as a first embodiment. And a superlattice structure formed of a plurality of group III nitride semiconductor layers including aluminum and disposed between the intervening layer and the light emitting portion and including aluminum and having different aluminum composition ratios. Provided is a semiconductor light emitting diode.

In a second embodiment of the present invention comprising the embodiment of the first embodiment of the present invention, the intervening layer has an aluminum composition ratio of X ₁ (0 <X ₁ ≦ 1), and the semiconductor layer of the superlattice structure. The aluminum composition ratios of X ₂ and X ₃ are different from each other without exceeding X ₁ (0 <X ₂ <X ₃ ≤ X ₁ ).

A third embodiment of the present invention, including the form of the second embodiment of the present invention, further comprises an intermediate layer formed of an aluminum-containing group III nitride semiconductor, and disposed between the intervening layer and the superlattice structure. the intermediate layer is an aluminum composition ratio of X ₄ is greater than X ₂ X ₃ or less has a _{(0 <X 2 <X 4} ≤X 3).

In the fourth embodiment of the present invention including any one of the first to third embodiments of the present invention, the intervening layer, the semiconductor layer and the intermediate layer of the superlattice structure are each formed of aluminum gallium nitride. .

The fifth embodiment of the present invention, which includes any one of the first to fourth embodiments of the present invention, further includes a gamma (?)-Like aluminum film disposed between the silicon single crystal substrate and the intervening layer.

According to the first embodiment of the present invention, a silicon single crystal substrate, an intervening layer formed of a group III nitride semiconductor and stacked on the silicon single crystal substrate, and a pn junction heterojunction structure and stacked on the intervening layer A semiconductor light emitting diode comprising a light emitting portion, wherein the intervening layer is formed of an aluminum-containing group III nitride semiconductor, and a plurality of group III nitride semiconductor layers containing aluminum and having different aluminum composition ratios between the intervening layer and the light emitting portion. Since the superlattice structure formed of the structure is disposed, the superlattice structure may include a group III nitride semiconductor layer having excellent continuity.

According to the second embodiment of the present invention, the intervening layer has an aluminum composition ratio of X ₁ (0 <X ₁ ≦ 1), and the semiconductor layer of the superlattice structure has an aluminum composition ratio of X ₂ and X ₃ of X ₁ . Since the superlattice structure is excellent in continuity and is used as a distributed Bragg reflector capable of reflecting light emission with high efficiency since it satisfies each other (0 <X ₂ <X ₃ ≤ X ₁ ) without exceeding, high luminance light emission Allow the device to be manufactured.

According to a third aspect of the invention, the intermediate layer formed of aluminum-containing Ⅲ nitride semiconductor disposed between the intervening layer and the superlattice structure, the intermediate layer is less than the aluminum composition ratio of X ₄ is large and X ₃ than X ₂ (0 Since <X ₂ <X ₄ ≤ X ₃ ), the group III nitride semiconductor layer excellent in continuity can be stably formed, and the superlattice structure when used as a distributed Bragg reflector is suitable for the manufacture of a high brightness light emitting device. Make it stable.

According to the fourth embodiment of the present invention, since the intervening layer, the semiconductor layer of the superlattice structure, and the intermediate layer are each formed of aluminum gallium nitride, an aluminum-containing group III nitride semiconductor advantageous for obtaining a group III nitride semiconductor layer having excellent continuity. It is possible to improve the effect of forming the intermediate layer and the like formed in the above, and to form the distributed Bragg reflector which is suitable for reflecting shortwave light emission with high efficiency, and to manufacture a high brightness short wavelength light emitting device.

According to the fifth embodiment of the present invention, a gamma (?) Phase aluminum film is disposed between the silicon single crystal substrate and the intervening layer, so that the silicon single crystal forming the substrate and the aluminum-containing group III nitride semiconductor layer Mismatch can be alleviated and an intervening layer with good quality can be formed. By using an intervening layer of excellent quality as an underlayer, the superlattice structure formed of the group III nitride semiconductor layer having excellent crystallinity is formed thereon, and as a result, high luminance light emission is achieved by using the superlattice structure as a distributed Bragg reflector. The device can be manufactured.

The above and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings.

1 is a schematic diagram illustrating a laminated structure devised by the present invention.

FIG. 2 is a schematic plan view of the LED of Example 1. FIG.

3 is a schematic cross-sectional view of the LED along the broken line (III-III) of FIG.

4 is a schematic sectional view of the LED of Example 2. FIG.

The semiconductor light emitting diode devised by the present invention is formed of a silicon single crystal substrate, an aluminum-containing group III nitride semiconductor and an intervening layer laminated on the silicon single crystal substrate, a pn junction heterojunction structure, and laminated on the intervening layer. And a superlattice structure which is disposed between the intervening layer and the light emitting portion, and includes a plurality of group III nitride semiconductor layers containing aluminum and having different aluminum composition ratios.

In order to form an aluminum-containing group III nitride semiconductor as the intervening layer on the silicon substrate, for example, an organic metal chemical vapor deposition (MOCVD) method and a molecular beam epitaxial (MBE) method may be used. For example, in the MOCVD method, the aluminum-containing group III nitride semiconductor layer is, for example, trimethyl aluminum ((CH ₃ ) ₃ Al) as the Al source and trimethyl gallium ((CH ₃ ) ₃ Ga) as the Ga source. It is formed by using.

For example, on the surface of a silicon substrate formed of {001} or {111} crystal plane, a group III nitride semiconductor layer having a desired Al composition ratio is supplied on the basis of the total amount of the raw materials of group III components. It is formed by adjusting the amount. The Al-containing III-nitride semiconductor layer formed on the silicon substrate may be formed of either a wurtzite hexagonal crystal or a zincite cubic crystal. In either case, a group III nitride semiconductor layer of good quality having an Al composition ratio of X ₁ (0 <X ₁ ≦ 1) and having pitless continuity can be formed.

By determining the arrangement of the Al-containing III-nitride semiconductor layer on the silicon substrate through the buffer layer that mitigates the lattice mismatch as the intervening layer, a higher-quality Group III nitride semiconductor layer can be obtained.

For example, the buffer layer may be formed of silicon carbide (SiC). The buffer layer formed of silicon carbide may be obtained by chemical vapor deposition (CVD) (see XM Zheng et al., J. Crystal Growth, 233 (2001), pp. 40-44). In addition, a method of carbonizing the surface of the silicon substrate by using a hydrocarbon such as acetylene (C ₂ H ₂ ) can be used for this purpose (A. Yamada et al., J. Crystal Growth, 189/190 (1998)). , pp. 401-405).

Preferably, the silicon carbide layer constituting the buffer layer forms a surface of the silicon substrate with a substantially equal thickness. In particular, the buffer layer is preferably a silicon carbide layer exhibiting a simple integer ratio with respect to the lattice constant (0.5431 nm) of the silicon single crystal. The silicon carbide layer having a lattice constant ratio of silicon single crystal to the silicon carbide layer, for example, 4: 5, may be preferably used because of long term domain matching with the silicon substrate (J. Narayan, J. Appl. Phys., 93 (1) (2003), pp. 278-285). The appearance of domain matching achieved by the silicon carbide layer and the silicon substrate is observed with a cross-sectional TEM image obtained by, for example, a high resolution transmission electron microscope (HR-TEM).

Subsequently, the buffer layer may be formed of a metal Al layer, in particular a gamma (γ) Al layer. The γ-Al layer may be particularly preferably formed on a silicon substrate (111-Si) having a (111) crystal plane as its surface. This may be preferably formed by, for example, a growth method such as an MBE method or a chemical beam epitaxial (CBE) growth that forms a film under a high vacuum environment. In this case, this formation is such that the (7 × 7) rearrangement structure (eg, The Physical Society of Japan, Dec. 10, 1992, Baifukan Co., Ltd.) on the surface of the (111) -Si substrate. When done after the appearance of "Surface New Substance and Epitaxy," first edition, Chapter 8) published by, a good quality γ-Al layer can be produced.

By using the above buffer layer as described above, it is possible to form a group III nitride semiconductor layer formed of, for example, gallium nitride (GaN) without containing Al. In this case, however, the prepared layer lacks continuity and exhibits a state in which crystal grains are dispersed. When the group III nitride semiconductor layer (intervention layer) disposed on the buffer layer is formed of an Al-containing group III nitride semiconductor layer, a crystal layer having continuity and containing almost no pit can be obtained. For example, continuity can be excellent in forming the mixed crystal of aluminum gallium nitride having an Al composition ratio of _{X 1 (Al x1 Ga 1 -x1} N, where 0 <X ₁ ≤1). (In the case of X ₁ = _1, AlN) buffer layer of aluminum nitride crystal that is specifically oriented toward the specific crystal orientation of the layers constituting the may also be desirable to form a continuous film.

Use of the intervening layer formed of a group III nitride semiconductor having excellent continuity and having an Al composition ratio of X ₁ as the under layer enables the formation of a superlattice structure formed of a group III nitride semiconductor layer having excellent continuity thereon.

In addition, the superlattice structure has a mixed crystal of gallium nitride indium containing no Al (Ga In _{Q 1 - Q} N, where 0 <Q <1) is or can be formed in Ⅲ nitride semiconductor layer of GaN. On the other hand, the Al-containing III-nitride semiconductor layer grown on the Al-containing III-nitride semiconductor layer as an under layer contains almost no pits and is excellent in continuity. Further, the Al-containing III-nitride semiconductor layer produced by using an Al-containing III-nitride semiconductor layer as an under layer is a GaN layer or Ga _Q In _{1 -Q} N (0 <Q <1) formed on the same underlayer. Compared with the layer, the specificity of the orientation is excellent.

As a result, the fact that the constituent layer of the superlattice structure is necessarily formed of a group III nitride semiconductor layer containing Al as a component has the advantage of obtaining a superlattice structure having a flat surface with almost no pits. The superlattice structure formed of the group III nitride semiconductor layer having excellent continuity proves to be superior in forming the light emitting portion having the p-n junction structure having excellent flatness of the junction boundary.

When the superlattice structure is formed by alternately laminating group III nitride semiconductor layers that exhibit continuity and a flat surface and have different Al composition ratios, the superlattice structure is disposed therefrom, for example, from the light emitting portion having a pn junction structure. It can be a distributed Bragg reflector (DBR) layer that proves advantageous for reflecting light emission.

Such a superlattice structure is formed by alternately laminating, for example, a group III nitride semiconductor layer having an Al composition ratio of X ₂ and a group III nitride semiconductor layer having an Al composition ratio of X ₃ (X ₂ <X ₃ ). . Preferably the constituent layer has a layer thickness (nm) set to λ / 4n (nm). Here, the symbol lambda (nm) represents the wavelength of light emission from the light emitting layer constituting the light emitting portion disposed on the superlattice structure. The symbol n represents the refractive index at the wavelength? Of the group III nitride semiconductor layer having an Al composition ratio of X ₂ or X ₃ . In the case of forming the superlattice structure of the DBR layer, an attempt to make the numerical values as large as possible different for the Al composition ratios X ₂ and X ₃ enables the expansion of the bandwidth in which the light emission is reflected at high reflectivity.

The superlattice structure formed of a group III nitride semiconductor layer having an Al composition ratio (X ₂ <X ₃ ) of X ₂ and X ₃ may be used not only as a DBR layer but also as a structure for alleviating deformation due to a difference between Al composition ratios. . The superlattice structure used for alleviating the deformation does not necessarily need to be formed of a group III nitride semiconductor layer having a layer thickness of λ / 4n when forming the DBR layer. The superlattice structure is formed by causing the layer thickness of the Al-containing III-nitride semiconductor layers having an Al composition ratio of X ₂ and X ₃ to be fixed at a ratio of, for example, 1: 3. If the Al-containing group III nitride semiconductor layer having an Al composition ratio of X ₃ larger than X ₂ is of a larger layer thickness, the resulting superlattice structure is preferable for the purpose of alleviating the deformation.

When the superlattice structure is manufactured using the Al-containing group III nitride semiconductor layer having an Al composition ratio of X ₃ equal to or less than X ₁ , that is, the superlattice structure has a relationship of 0 <X ₂ <X ₃ ≤X ₁ . When manufactured using a group III nitride semiconductor layer having a satisfactory Al composition ratio of X ₂ and X ₃ , the resulting superlattice structure can be avoided from having cracks due to deformation.

When arranging a superlattice structure on an Al-containing III-nitride semiconductor layer (intervention layer) having an Al composition ratio of X ₁ , disposing a III-nitride semiconductor layer having an Al composition ratio of X ₄ therebetween as an intermediate layer and The procedure further comprising stacking the superlattice structure thereon results in enhancing the effect of making the superlattice structure more stable to avoid having cracks. It is confirmed that it is particularly preferable to form an intermediate layer of an Al-containing group III nitride semiconductor layer having an Al composition ratio of X ₄ (X ₂ <X ₄ ? X ₃ ) that exceeds X ₂ and is X ₃ or less.

The laminated construction contemplated by the present invention in order to stably produce a superlattice structure having no cracks is schematically illustrated in FIG. 1 with reference to the Al composition ratio (X ₁ to X ₄ ). The laminate structure 10 includes (a) a buffer layer 12 formed of γ-Al having a lattice constant close to (a) a group III nitride semiconductor such as, for example, AlN, on the surface of the silicon single crystal substrate 11, (c) a group III nitride semiconductor layer (intervention layer) 13 having an Al composition ratio of X ₁ (0 <X ₁ ≦ 1), (d) Al of X ₄ (0 <X ₂ <X ₄ ≦ X ₃ ) The intermediate layer 14 formed of the group III nitride semiconductor having the composition ratio, and (e) the Al composition ratios of X ₂ and X ₃ are different from each other without exceeding X ₁ (0 <X ₂ <X ₃ ≤ X ₁ ) It is comprised by laminating | stacking the superlattice structure 15 which consists of a group III nitride semiconductor layer.

For example, Ⅲ nitride semiconductor layer (interposed layer) 13 is formed of a AlN layer having the Al composition ratio of X ₁ 1, the intermediate layer 14 is Al _.50 Ga ₀ having the Al composition ratio of 0.50 X _{4 0} is formed in a _.50 N layer, the superlattice structure 15 is formed of a AlN layer having the Al composition ratio of Al _{0 .05 0 .95} Ga N layer, and a 1 X ₃ having the Al composition ratio X ₂ of 0.05. In addition, the present invention need not be limited to the configuration of FIG. 1, but the buffer layer 12 and the intermediate layer 14 may be combined as necessary.

The number of Al-containing III-nitride semiconductor layers having Al composition ratios of X ₂ or X ₃ which are alternately stacked to form the superlattice structure, that is, the number of cycles, is not specified. For example, in the case of a superlattice structure used in a DBR, the number of periods (pairs) is preferably such that light emission can be reflected with high efficiency. In this case, when the Al-containing III-nitride semiconductor layer exhibiting the largest refractive index as possible is used as the uppermost surface layer close to the light emitting portion in the formation of the superlattice structure, the DBR layer having high reflectance can be produced in a small number of cycles. . For example, alternating Al _{0 .05} Ga _{0 .95} N and the case of forming the super lattice structure by stacking AlN having a X ₃ of 1, ₀ Al _.05 Ga has a higher reflectance than AlN is arranged as a top surface layer procedures, including the formation of a _{0 .95} superlattice structure by carrying out a cross to those 20 cycles which N layers are with respect to light having a wavelength of 460nm enables the formation of the DBR layer having a reflectance greater than 90% .

The structure obtained by disposing a light emitting portion on a super lattice structure functioning as a DBR layer showing a function of efficiently reflecting light emission becomes superior to the manufacture of high-brightness LEDs.

Example 1:

The subject matter of the present invention will be described in detail below with reference to the case of constructing an LED by using a superlattice structure formed on a (001) Si single crystal substrate which is intended to be used as a DBR and has a (001) crystal plane as its surface. will be.

FIG. 2 schematically shows a planar structure of the LED 20 according to the first embodiment below, and FIG. 3 is a schematic cross-sectional view of the LED 20 along the broken line III-III of FIG. 2.

The laminate structure 200 intended to manufacture the LED 20 was formed by using n-type silicon (Si) single crystal (silicon) having a (001) crystal plane as a surface as the substrate 201. By using a general MBE apparatus, the substrate 201 was heat-treated at 800 ° C. in a high vacuum to generate a (2 × 1) rearrangement structure on the surface of the substrate 201. Then, a cubic SiC buffer layer 202 having a layer thickness of about 2 nm was formed on the surface of the Si substrate 201. Observation of a lattice image by high-resolution TEM (HR-TEM) shows that at the junction boundary between the substrate 201 and the buffer layer 202, six (001) crystal faces of SiC are domain matched with five (001) crystal faces of Si. It was shown.

On the surface of the SiC buffer layer 202, an interlayer 203 of n-type AlN doped with silicon (Si) (Al-containing Group III nitride semiconductor layer having an Al composition ratio of X ₁ as described above, except that In the examples X ₁ is 1). The intervening layer 203 had a layer thickness of about 40 nm.

On the via layer 203, formed by alternately laminated by a Si doped with an n-type Al _{0 .05} Ga _{0 .95} N and n-type AlN in a typical MBE method in super lattice structure 204 is obtained as a DBR layer It became. That is, the superlattice structure 204 formed of AlN having a composition ratio of Al of the Al _{0 .05} Ga _{0 .95} N 1 and X ₃ having the Al composition ratio X ₂ of 0.05. Said superlattice structure (204) for use as DBR is AlN (refractive index: about 2.16), the intervening Al _{0 .05} Ga ₀ has a larger refractive index than the adjacent layer and the AlN layer (203) _.95 N (refractive index formed by: 2.43). From the viewpoint of efficiently reflecting light having a wavelength of 460nm, the AlN layer and the Al _{0 .05} Ga _{0 .95} N layer forming the superlattice structure (204) has been given to the layer thicknesses of 53nm and 47nm . The AlN layer and was the Al _{0 .05} Ga _{0 .95} stacked number of cycles N layer 20.

Since the second AlN layer and the N layer and the Al _{0 .05 0 .95} Ga to form a lattice structure 204 is disposed through the Ⅲ nitride semiconductor layer having a high Al composition ratio of X ₁ 1, the configuration of a semiconductor layer finally obtained Has always been excellent in continuity. When the light having a wavelength of 460nm is incident vertically on the surface of the Al _{0 .05} Ga _{0 .95} N layer constituting the top layer of the superlattice structure (204), for use as DBR on the same wavelength of light The reflectivity of the superlattice structure 204 was about 97%.

The superlattice structure 204, the Al _{0 .05} Ga _{0 .95} N on the surface of the layer, n-type Al _{0 .01} Ga _{0 .99} lower clad layer 205 formed of the N layer constituting the uppermost layer of a, n type GaN layer and the n-type Ga _0.85 in _0.15 N layer to a pair of 5 cycles repeatedly multiple quantum well light emitting layer 206 is formed of a (MQW) structure obtained by laminating, and the p-type Al _{0 .15} Ga _{0 .85} N layer The upper clad layer 207 formed as described above was sequentially stacked by the general MBE method in order to form a light emitting part having a pn junction double hetero (DH) structure. The n-type Al _{0 .01} Ga _{0 .99} constituting the lower clad layer (205) N layer has been given a thickness of 250nm, the upper p-type Al _{0 .15} to configure a cladding layer (207) Ga _{0 .85} The N layer was given a thickness of 90 nm. A barrier layer formed of n-type GaN layer constituting the light-emitting layer 206 having an MQW structure is been given to a thickness of 10nm, the well layer formed of n-type Ga _{0 .85} In _{0 .15} N layer was given a thickness of 3nm .

A contact layer 208 formed of a p-type GaN layer (layer thickness = 80 nm) is laminated on the surface of the upper clad layer 207 constituting the light emitting part having a DH structure and intended for use in the LED 20. Formation of the laminated structure 200 was finished.

In some regions of the p-type contact layer 208, a p-type ohmic electrode 209 made of a gold (Au) -nickel oxide (NiO) alloy was formed. On the other hand, the n-type ohmic electrode 210 is a part of the contact layer 208, the upper clad layer 207 and the light emitting layer 206 present in the region selected for the formation of the electrode 210 by a dry etching technique. Was formed on the surface of the lower clad layer 205 exposed. Then, the LED 20 was manufactured by cutting the finished structure into chips.

The light emission characteristics were tested by causing the LED 20 to flow in the forward direction between the p-type and n-type ohmic electrodes 209 and 210 of the LED 20 by causing a device driving current of 20 mA. The main light emission from the LED 20 had a wavelength of about 460 nm. Since the superlattice structure formed of the Al-containing III-nitride semiconductor layer was disposed on the Al-containing III-nitride semiconductor layer (intervention layer) as a DBR layer, the intensity of the light emission reached a high value of about 1.9 cd. Since the light emitting portion having the pn junction DH structure was disposed on the superlattice structure formed of the Al-containing III group nitride semiconductor layer having excellent continuity, the light emitting portion could be formed of the group III nitride semiconductor layer having excellent continuity, and thus, The LED 20 could be provided which exhibits uniform intensity of light emission without producing non-uniform light emission.

Example 2:

The contents of the present invention will be described in detail below with reference to the case of constructing an LED by using a superlattice structure formed on a (111) Si single crystal substrate which has a (111) crystal plane as its surface and is intended to be used as a DBR. will be.

In a typical MBE apparatus, an n-type silicon substrate having a (111) crystal plane as its surface was heat-treated at high vacuum at 850 ° C. to generate a (7 × 7) rearrangement structure on the surface of the substrate. Then, an ultrathin film of γ-aluminum (γ-Al) having a thickness approximately equal to that of one atomic layer was formed as a buffer layer on the surface of the Si substrate.

On the surface of the γ-Al buffer layer, as described in Example 1, the same intervening layer formed of n-type AlN and doped with silicon was formed by a general MBE method. On such interposed layers, by laminating a Si doped n-type Al _{0 .10} Ga _{0 .90} N and n-type AlN in turn by the general MBE method was formed with a super lattice structure obtained as a DBR layer. The superlattice structure was formed in the AlN layer is formed of a (refractive index = 2.16), the uppermost surface layer is Al _{0 .10} Ga _{0 .90} N (refractive index = 2.41, higher than the AlN) adjacent to the intervening layer. From the viewpoint of efficiently reflecting light having a wavelength of 460nm, the second embodiment is the AlN layer that forms the superlattice structure and the thickness of Al _{0 .10 0 .90} Ga N layer was 53nm and 48nm respectively. It was the AlN layer and the Al _{0 .10} number of cycles of laminating Ga _{0 .90} N 30.

It has been arranged through the AlN layer and the Al _{0 .10} Ga _{0 .90} N layer Ⅲ nitride semiconductor layer (interposed layer) having a high Al composition ratio X ₁ of the first forming the super lattice structure, composition finally obtained The semiconductor layer has always been excellent in continuity. When the light having a wavelength of 460nm with a 30 constituting the top layer of the super lattice structure made by alternately performing a cycle to normal incidence on the surface of the Al _{0 .10} Ga _{0 .90} N layer, the same wavelength of light The reflectance of the superlattice structure for use as the DBR for the was about 95%.

The constituting the top layer of the super lattice structure Al _{0 .10} Ga _{0 .90} on the surface of the N layer, n-type Al _0.05 Ga _0.95 N layer formed of the lower clad layer, n-type GaN layer and the n-type Ga _{0 .85} sequentially laminated by a typical MBE method a pair of in _{0 .15} N layer 5 light-emitting layer formed of an MQW structure obtained by repeatedly stacking up a cycle, and a p-type Al _0.10 Ga _0.90 N layer in the order mentioned upper clad layer formed As a result, a light emitting part having a pn junction DH structure was formed. The n-type Al _{0 .05} Ga _{0 .95} N layer constituting the lower clad layer has been given a thickness of 200nm, a p-type Al _{0 .10} constituting the upper clad layer Ga _{0 .90} N layer of 80nm Given by thickness. Example 1, a barrier layer formed of n-type GaN layer of the same, constituting the light emitting layer having an MQW structure is been given to a thickness of 10nm, the well layer formed of n-type Ga _{0 .85} In _{0 .15} N layer of 3nm Given by thickness.

The contact layer formed of the p-type boron phosphide (BP) layer (layer thickness = 190 nm) was further laminated on the surface of the upper clad layer constituting the light emitting part having the DH structure to terminate the formation of the laminated structure intended for use in the LED. It was. The BP layer constituting the contact layer was formed by a general MOCVD method.

In some regions of the p-type contact layer, a p-type ohmic electrode made of an Au—Zn alloy was formed. On the other hand, an n-type ohmic electrode was formed on the surface of the lower clad layer exposed by removing a portion of the upper clad layer and the light emitting layer which existed in a region selected for forming such an electrode by a dry etching technique. Thereafter, the same LED as the LED shown in FIGS. 2 and 3 was produced by cutting the finished structure into chips.

These LEDs were tested for their luminescence properties by causing a device drive current of 20 mA to flow in the forward direction between the p-type and n-type ohmic electrodes of the LEDs. The main light emission from the LED had a wavelength of about 460 nm. Since the superlattice structure formed of an Al-containing III-nitride semiconductor layer was disposed on an Al-containing III-nitride semiconductor layer (intervention layer) laminated on the γ-Al buffer layer as a DBR layer, the intensity of light emission was about 2.0 cd. High value reached. Since the light emitting part having the pn junction DH structure was disposed on the superlattice structure formed of an Al-containing group III nitride semiconductor layer having excellent continuity, the light emitting part could be formed of a group III nitride semiconductor layer having excellent continuity, and thus The LED can be provided which exhibits uniform intensity of light emission without producing uneven light emission.

Example 3:

The contents of the present invention are described below with reference to the case of configuring an LED by using a metal Al layer formed on a (111) Si single crystal substrate having a (111) crystal plane and a superlattice structure formed on the Al layer as its surface. It will be described in detail.

4 schematically shows the planar structure of the LED 30 according to the third embodiment.

On the surface of the (111) crystal surface of the silicon substrate 301, a buffer layer 302 formed of an γ-Al ultra thin film (thickness: about 1 atomic layer) was formed as described in Example 2.

On the buffer layer 302, an intervening layer 303 was formed of n-type AlN and doped with Si (i.e., an Al-containing group III nitride semiconductor layer having an Al composition ratio of X ₁ as described above, except Examples) 3 in X ₁ is 1).

On said intervening layer (302), Al _{0 .60} having a composition ratio of Al 0.60 Ga _{0 .40} N layer (corresponding to Ⅲ nitride semiconductor layer having Al bath ratio of X _4, stage, X in Example 3 _An intermediate layer 304 formed of ₄ is 0.60) was formed by a general MBE method. The intermediate layer 304 was formed of an n-type Si-doped conductive layer having a thickness of about 200 nm.

In the intermediate layer 304, as described in Example 2, a superlattice structure 305 obtained by alternately stacking n-type Si-doped Al _0.10 Ga _0.90 N and n-type AlN up to 30 cycles was formed. Wherein the second AlN layer and the Al _{0 .10} Ga _{0 .90} constituting the lattice structure (305) N layer was given a thickness of 53nm, and 48nm, respectively, as in the case of the second embodiment.

The top layer of a second lattice structure 305 to the Al _{0 .10} Ga _{0 .90} on the surface of the N layer, Example 2 n-type Al _{0 .05} Ga _{0 .95} of the same description as in the N layer constituting the lower cladding layer 306 is formed, the n-type GaN and an n-type Ga _{0 .85 0 .15} in the light-emitting layer 307 is formed of a pair of the N layer to the MQW structure obtained by repeatedly stacking a period up to 5, and a p-type Al _{0. 10} Ga _{0 .90} is sequentially laminated by a typical MBE method as an upper cladding layer 308 formed in the mentioned order N layer to form a light emitting portion having a pn-junction DH junction structure.

The contact layer 309 formed of the p-type BP layer described in Example 2 was laminated on the surface of the upper cladding layer 308 constituting the light emitting portion having a DH structure and intended for use in the LED 30. Formation of the laminated structure was completed.

In some regions of the p-type contact layer 309, a p-type ohmic electrode 310 made of Au-Zn alloy was formed as described in the second embodiment. On the other hand, the n-type ohmic electrode 311 is the contact layer 309, the upper clad layer 308 and the light emitting layer 307 present in the region selected for the formation of the electrode 311 by a dry etching technique. It was formed on the surface of the lower clad layer 305 exposed by removing a portion of it. Then, the LED 30 was manufactured by cutting the completed structure into chips.

The light emission characteristics were tested by causing the LED 30 to flow in the forward direction between the p-type and n-type ohmic electrodes of the LED 30 by causing a device driving current of 20 mA. The main light emission from the LED 30 had a wavelength of about 460 nm. The superlattice structure 305 is formed as a DBR layer from an Al-containing III-nitride semiconductor layer having excellent continuity, and as a result, on the Al-containing III-nitride semiconductor layer (intervention layer) 303 and the γ-Al buffer layer 302. Since the reflectance can be increased due to the arrangement of the superlattice structure 305 through the intermediate layer 304 formed in the above, the intensity of the light emission reaches a high value of about 2.0 cd.

Also, due to the placement of the superlattice structure 305 on the interlayer 304 as an underlayer, the superlattice structure 305 has its [2.-1.-1.0.] Crystal orientation in the interlayer ( 304) of the Al _{0 .65} Ga _{0 .35} N crystal constituting the [2.-1.-1.0] could be formed of an Al-containing ⅲ nitride semiconductor layer of the unique oriented parallel to the crystalline orientation. As a result, the light emitting part having the pn junction DH structure disposed on the superlattice structure could also be formed of a group III nitride semiconductor layer having excellent continuity and an integrated orientation. Thus, the LED 30 could be provided that exhibits uniform intensity of light emission without generating light of uneven intensity.

Since the light from the light emitting layer is not absorbed by the substrate, the light can be efficiently extracted to the outside. Therefore, a high brightness LED can be provided.

Claims (5)

An interlayer formed of a silicon single crystal substrate, an aluminum-containing Group III nitride semiconductor and disposed between the silicon single crystal substrate and the superlattice structure, a light emitting portion formed of a pn junction heterojunction structure and stacked on the intervening layer, the interposition A superlattice structure disposed between the layer and the light emitting portion and formed of a plurality of group III nitride semiconductor layers containing aluminum and having different aluminum composition ratios, and And a gamma (?) Aluminum film disposed between the silicon single crystal substrate and the intervening layer. The method of claim 1, wherein the intervening layer has an aluminum composition ratio of X ₁ (0 <X ₁ ≤ 1), and the semiconductor layer of the superlattice structure has an aluminum composition ratio of X ₂ and X ₃ not exceeding X ₁ A semiconductor light emitting diode satisfying a difference (0 <X ₂ <X ₃ ≤ X ₁ ). The method of claim 2, wherein the aluminum-containing Ⅲ group comprising nitride is formed from a semiconductor further has a middle layer disposed between the intervening layer and the superlattice structure, and said intermediate layer is greater than X ₂ the aluminum composition ratio of less than or equal to X ₃ X ₄ (0 <X ₂ semiconductor light-emitting diode, characterized in that it has <X ₄ ≤X ₃₎ a. The semiconductor light emitting diode according to any one of claims 1 to 3, wherein the intervening layer, the semiconductor layer and the intermediate layer of the superlattice structure are each formed of aluminum gallium nitride. delete

Images