CN100358167C - GaN base LED high reflectance electrode - Google Patents
GaN base LED high reflectance electrode Download PDFInfo
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- CN100358167C CN100358167C CNB200410101245XA CN200410101245A CN100358167C CN 100358167 C CN100358167 C CN 100358167C CN B200410101245X A CNB200410101245X A CN B200410101245XA CN 200410101245 A CN200410101245 A CN 200410101245A CN 100358167 C CN100358167 C CN 100358167C
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Abstract
The present invention relates to a GaN base LED high reflectivity electrode, which belongs to the technical field of photoelectronic device manufacture. The electrode comprises a semiconductor GaN base course 1, an ohmic contact layer 6, a high reflectivity mirror 3 and a protecting layer 4 from bottom to top, wherein light emitted from the device admixed with Mg can be reflected from the semiconductor GaN base course to a high reflectivity electrode layer, and then, the light which is reflected by the electrode to return from the high reflectivity electrode layer to the inner side of the device. The present invention is characterized in that the ohmic contact layer 6 is metal Ni and Mg solid melt layer positioned between the base course 1 and the high reflectivity mirror 3 and directly contacted with the base course 1, and a metal Pa layer 7 is arranged between the metal Ni and Mg solid melt layer and the high reflectivity mirror; a connecting layer which is a Ti layer 8 is arranged between an electrode protecting layer and the high reflectivity mirror. The electrode of the present invention realizes low contact resistance, less light absorption, increased light output power and increased heat reliability, and simple fabrication.
Description
Technical field
The invention belongs to optoelectronic device manufacturing technology field, particularly relate to a kind of light-emitting diode (LED) electrode with high reflective mirror.
Background technology
GaN base LED is used widely at present.On high-power and high-luminance LED was used, it was that P type electrode is used as the high reflecting surface of light that people generally adopt inverted structure, and the device substrate face is the structure of light-emitting face.Also there are some difficulties at present in P type electrode technology, and its specific contact resistivity is bigger.Reducing the most effective way of specific contact resistivity is that P type GaN is mixed.But it is not very high that P-GaN mixes the concentration of Mg, is generally less than 1 * 10
18Cm
-3, and exist Mg to form the H-Mg key easily, and cause the dopant passivation phenomenon, be unfavorable for reducing specific contact resistivity (needing heating anneal to open the H-Mg key).And can not find the metal (metal work function is all low than P-GaN work function) that is complementary with P-GaN work function (greater than 6.5eV).This specific contact resistivity that just causes P type electrode than higher (generally greater than 10
-6Ω cm
2).The electrode specific contact resistivity is big more, and is unfavorable more to prolonging device lifetime.The heat of the low more generation of contact resistance is few more, and P type high reflectance electrode thermal reliability is high more, so contact resistance is low more good more.The metal electrode light absorption that contact resistance is low in addition is serious, and this mainly is because the extinction coefficient bigger (extinction coefficient K is greater than 1) of metal.The thick more extinction of contact layer is serious more.The ohmic contact layer of metal electrode is in order to obtain low contact resistance, high transmitance, and general thickness is all less than 10nm, nonetheless, the absorption of light still is higher than oxide conductive film far away.Because the light that absorbs changes heat energy into, heat energy rises device temperature, and temperature rises and causes the further absorption that increases light of device, forms positive feedback, causes descend even make device lifetime and burns device.When LED was operated in big electric current, the heat that the metal electrode absorbing light generates was to cause the principal element that descends device lifetime.Conductive oxide film extinction coefficient smaller (10
-4-10
-6Magnitude), extinction hardly.But the oxide conductive film thermal diffusivity is very poor, forms thermal accumlation easily.The temperature of device rises along with the accumulation of heat, when acquiring a certain degree, can reduce the life-span of device, and thermal reliability is relatively poor.At present the conventional P type high reflectance electrode that exists Ni/Au/Ag is arranged, based on plate electrodes such as outer silver-plated high reflective mirror electrode of nesa coating (TCO) and Ni/Ag.Ni/Au/Ag electrode such as Fig. 1, the semiconductor-based end 1, Ni/Au contact layer 2, Ag high reflective mirror 3, protective layer 4.Its ohmic contact layer 2 is Ni/Au, and specific contact resistivity can be as small as 10
-6Ω cm
2Yet the contact layer of this electrode reaches 20%-30% (460nm wavelength) to light absorption very big (mainly being gold), and optical power loss is serious.If reduce the thickness of Ni/Au, appearance contacts not firm problem with substrate again.Based on the high reflectance electrode of the outer silver-plated high reflective mirror of TCO, its ohmic contact layer absorbs hardly to light absorption, but TCO is that the oxide heat radiation is bad, and thermal reliability is poor under big electric current.Ni/Ag electrode ohmic contact layer has only skim Ni, and luminous absorptance Ni/Au contact layer is few, so this luminous absorptance Ni/Au/Ag electrode is little, its specific contact resistivity is for can accomplish 10
-4Ω cm
2-10
-5Ω cm
2, remain further to be reduced.Traditional electrode cuts both ways on performances such as light absorption, contact resistance and heat radiation, all can not satisfy the requirement of low contact resistance, low light absorption simultaneously, and especially LED thermal reliability when high power work is poor.How finding a best joint that contact resistance can be satisfied at this Several Parameters aspect and to reduce light absorption again in our needs, to improve the reliability of LED work, is the subject matter that current P type high reflectance electrode faces.Appear at recently and mix Zn among the Ni and make contact layer, and then add the electrode of high reflective mirror, contact layer is thin, does not contain the serious Au layer of extinction.This sample is the LED of 300 μ m * 300 μ m, and its P-GaN substrate is thick to be 1.5 μ m, and Mg is doped to 5 * 10
17Cm
-3The Ni-Zn layer of kind electrode is that 2.5nm or 10nm are thick, and Ag is 200nm, and specific contact resistivity is 10
-4Ω cm
2-10
-5Ω cm
2, forward bias 3.25V (electric current 20mA), contact layer transmitance about 83%.The ionization energy of Zn is 9.394eV more greatly, is not fine for forming P type semiconductor doping (doping can reduce semiconductor and Metal Contact potential barrier, helps reducing contact resistance) effect, and its contact resistance needs further to reduce.For existing high reflectance electrode, have all that can't to satisfy contact layer thickness simultaneously little, contact resistance is low, and the shortcoming that light absorption is little all is further improved.
Summary of the invention
The P type electrode that the objective of the invention is to solve present GaN base LED can not satisfy and has lower contact resistance and the few problem of light absorption simultaneously, improves GaN base LED reliability and optical output power and thermal reliability.At technical problem to be solved, the present invention has designed the new structure high reflectance electrode on a kind of GaN of being used for base inverted structure LED.Its core is improved the high reflectance electrode ohmic contact layer, with nickel magnesium solid solution layer with add layer of metal thin layer Pd again after the GaN substrate contacts, and then add high reflective mirror.Because the nickel magnesium solid solution that the present invention contacts with the GaN substrate, and Mg is the dopant of p type GaN, (7.646eV) is littler than Zn for the ionization energy of Mg, so the specific contact resistivity rate is all lower with the Ni-Zn contact layer of mixing Zn than simple Ni contact layer, and metal Pd has the effect (palladium of 1 volume unit can dissolve the hydrogen of 700 volumes-800 volume unit) that absorbs hydrogen, and the specific contact resistivity rate reaches 10
-5Ω cm
2-10
-6Ω cm
2, light absorption is owing to contact layer can reduce 13% by attenuate 20%.In order to improve metallic gold and silver-colored adhesiveness, between gold and silver, plated layer of metal Ti again.
For achieving the above object, electrode of the present invention adopts following technical scheme (referring to Fig. 3): electrode of the present invention comprises that from top to bottom light doped with Mg, that device sends is from this layer arrival high reflectance electrode layer, return the semiconductor GaN basalis 1 of device inside then again from this layer through the electrode reflection, ohmic contact layer 6, high reflective mirror 3, protective layer and thickening layer 4; Wherein said basalis 1, the light that device sends is from this layer arrival high reflectance electrode layer, return device inside from this layer again through the electrode reflection then, it is characterized in that: described ohmic contact layer 6 is the Ni and the Mg metal solid solution layers that directly contact with substrate between basalis and high reflective mirror, is metal Pd layer 7 between metal solid solution layer and high reflective mirror.
Described a kind of GaN base LED high reflectance electrode is characterized in that: the weight ratio that Mg accounts in Ni and the Mg metal solid solution layer is 7～10%, and the thickness of Ni and Mg metal solid solution layer is 0.7-2nm.The thickness of metal Pd layer is 0.6nm～1nm.
Described a kind of GaN base LED high reflectance electrode is characterized in that: articulamentum Ti layer 8 is arranged between electrode protecting layer and high reflective mirror.
Because the present invention adopted more optimized electrode structure and material, have lower specific contact resistivity and light absorption still less with the LED sample of same structure and size in the past, improved the power output and the thermal reliability of light, and made simply.
Description of drawings
Accompanying drawing 1 is traditional Ni/Au/Ag high reflectance electrode profile
1. mix Mg semiconductor P-GaN, 2.Ni/Au ohmic contact layer, 3. high reflective mirror, 4. diaphragm;
Accompanying drawing 2 is traditional Ni-Zn/Ag high reflectance electrode profile
1. mix Mg semiconductor P-GaN, 5.Ni-Zn ohmic contact layer, 3. high reflective mirror, 4. diaphragm;
Accompanying drawing 3 is high reflectance electrode profile of the present invention
1. mix Mg semiconductor P-GaN, 6. contain the ohmic contact layer of nickel magnesium solid solution, 7. metal Pd layer,
3. high reflective mirror, 8. metal Ti layer, 4. protective layer;
Embodiment
Embodiment 1:
1) prepare the LED sample of 300 μ m * 300 μ m with common metal organic chemistry vapour phase deposit (MOCVD) method, its P-GaN substrate is thick to be 1.5 μ m, and Mg is doped to 5 * 10
17Cm
-3
2) this sample is for to clean with general chemical cleaning method: HCl: H
2O after 1: 1 solution cleans 5 minutes to GaN surface, P district, washes 5 times with deionized water rinsing again.Clean the back with doing N
2Air-blowing is done;
3) sample is put into rapidly in the Denton Discovery550 sputtering unit reative cell, reative cell is extracted into 10
-5The vacuum that Pa is following;
4) the metal solid solutions that the speed of 1 /s is plated layer of Ni and Mg under 70 ℃ on semiconductor surface are as contact layer, and thickness is 0.7nm, and the weight ratio that Mg accounts for is 10%; The purity of Ni is 4N (99.99%);
5) metal Pds of the speed of 1 /s plating one deck 0.6nm under 60 ℃ on Ni-Mg solid solution;
6) Hitachi's spectrophotometer 4100 records the contact layer transmitance and reaches 96.4%;
7) and then unannealed, again with the speed of 10 /s at 70 ℃ of silver-colored Ag of plating one deck 200nm down, as high reflective mirror;
8) the Ti metal film of plating one deck 30nm on the Ag mirror;
9) on the Ti metal film with the speed of 4 /s at 60 ℃ of Au of plating one deck 500nm down, as protective layer with add thick electrode;
10) final sample 450 ℃ of alloys 5 minutes in general high temperature furnace obtain electrode of the present invention;
11) record its specific contact resistivity rate with traditional endless Transmission line method (CTLM) and reach 5 * 10
-6Ω cm
2, forward bias 3.14V (electric current 20mA);
Embodiment 2:
1) prepare the LED sample of 300 μ m * 300 μ m with common metal organic chemistry vapour phase deposit (MOCVD) method, its P-GaN substrate is thick to be 1.5 μ m, and Mg is doped to 5 * 10
17Cm
-3
2) this sample is for to clean with general chemical cleaning method: HCl: H
2O after 1: 1 solution cleans 5 minutes to GaN surface, P district, washes 5 times with deionized water rinsing again.Clean the back with doing N
2Air-blowing is done;
3) sample is put into rapidly in the Denton Discovery550 sputtering unit reative cell, reative cell is extracted into 10
-5The vacuum that Pa is following;
4) the metal solid solutions that plate layer of Ni and Mg with the speed of 1 /s under 70 ℃ on semiconductor surface are as contact layer, and thickness is 1nm, and the weight ratio that Mg accounts for is 8%; The purity of Ni is 4N (99.99%);
5) metal Pds of the speed of 1 /s plating one deck 0.6nm under 60 ℃ on Ni-Mg solid solution;
6) Hitachi's spectrophotometer 4100 records the contact layer transmitance and reaches 95.3%.
7) and then unannealed, again with the speed of 10 /s at 70 ℃ of silver-colored Ag of plating one deck 200nm down, as high reflective mirror;
8) on the Ag mirror with the speed of 4 /s at 60 ℃ of Ti metal films of plating one deck 30nm down;
9) on the Ti metal film with the speed of 8 /s at 75 ℃ of Au of plating one deck 500nm down, as protective layer with add thick electrode;
10) final sample 450 ℃ of alloys 5 minutes in general high temperature furnace obtain electrode of the present invention;
11) record its specific contact resistivity rate with traditional endless Transmission line method (CTLM) and reach 3.8 * 10
-6Ω cm
2, forward bias is 3.11V (electric current 20mA).
Embodiment 3:
1) prepare the LED sample of 300 μ m * 300 μ m with common metal organic chemistry vapour phase deposit (MOCVD) method, its P-GaN substrate is thick to be 1.5 μ m, and Mg is doped to 5 * 10
17Cm
-3
2) this sample is for to clean with general chemical cleaning method: HCl: H
2O after 1: 1 solution cleans 5 minutes to GaN surface, P district, washes 5 times with deionized water rinsing again.Clean the back with doing N
2Air-blowing is done;
3) sample is put into rapidly in the Denton Discovery550 sputtering unit reative cell, reative cell is extracted into 10
-5The vacuum that Pa is following;
4) the metal solid solutions that plate layer of Ni and Mg with the speed of 2 /s under 70 ℃ on semiconductor surface are as contact layer, and thickness is 2nm, and the weight ratio that Mg accounts for is 7%; The metal solid solution of Ni and Mg is by buying on the market, and the purity of Ni is 4N (99.99%);
5) plate the metal Pds that plate one deck 0.6nm on the Ni-Mg solid solution in speed down at 60 ℃ with 1 /s;
6) Hitachi's spectrophotometer 4100 records the contact layer transmitance and reaches 93.4%;
7) and then unannealed, again with the speed of 10 /s at 70 ℃ of silver-colored Ag of plating plating one deck 200nm down, as high reflective mirror;
8) on the Ag mirror with the speed of 4 /s at 60 ℃ of Ti metal films of plating plating one deck 30nm down;
9) on the Ti metal film with the speed of 8 /s at 75 ℃ of Au of plating plating one deck 500nm down, as protective layer with add thick electrode;
10) final sample 450 ℃ of alloys 5 minutes in general high temperature furnace obtain electrode of the present invention;
11) record its specific contact resistivity rate with traditional endless Transmission line method (CTLM) and reach 2.9 * 10
-6Ω cm
2, forward bias is 2.97V.
Claims (5)
1, a kind of GaN base LED high reflectance electrode comprises semiconductor GaN basalis (1) from top to bottom, ohmic contact layer (6), high reflective mirror (3), protective layer (4); Wherein, semiconductor GaN basalis (1) doped with Mg, the light that device sends arrives the high reflectance electrode layer from semiconductor GaN basalis, return device inside from semiconductor GaN basalis again through the electrode reflection then, it is characterized in that: described ohmic contact layer (6) is to be positioned at Ni that directly contacts with substrate between basalis (1) and the high reflective mirror (3) and the metal solid solution layer of Mg, is metal Pd layer (7) between metal solid solution layer and high reflective mirror.
2, a kind of GaN base LED high reflectance electrode according to claim 1 is characterized in that: the weight ratio that Mg accounts in Ni and the Mg metal solid solution layer is 7%～10%.
3, a kind of GaN base LED high reflectance electrode according to claim 1 and 2 is characterized in that: the thickness of Ni and Mg metal solid solution layer is 0.7-2nm.
4, a kind of GaN base LED high reflectance electrode according to claim 1, it is characterized in that: the thickness of metal Pd layer (7) is 0.6nm～1nm.
5, a kind of GaN base LED high reflectance electrode according to claim 1 is characterized in that: articulamentum Ti layer (8) is arranged between electrode protecting layer (4) and high reflective mirror.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB200410101245XA CN100358167C (en) | 2004-12-17 | 2004-12-17 | GaN base LED high reflectance electrode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB200410101245XA CN100358167C (en) | 2004-12-17 | 2004-12-17 | GaN base LED high reflectance electrode |
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| Publication Number | Publication Date |
|---|---|
| CN1622352A CN1622352A (en) | 2005-06-01 |
| CN100358167C true CN100358167C (en) | 2007-12-26 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB200410101245XA Expired - Fee Related CN100358167C (en) | 2004-12-17 | 2004-12-17 | GaN base LED high reflectance electrode |
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| Country | Link |
|---|---|
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5888132B2 (en) * | 2012-06-08 | 2016-03-16 | 豊田合成株式会社 | Method for manufacturing light emitting device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11177134A (en) * | 1997-12-15 | 1999-07-02 | Sharp Corp | Manufacture of semiconductor element, semiconductor, manufacture of light emitting element, and light emitting element |
| US5990500A (en) * | 1998-03-25 | 1999-11-23 | Kabushiki Kaisha Toshiba | Nitride compound semiconductor light emitting element and its manufacturing method |
| CN1330416A (en) * | 2000-06-30 | 2002-01-09 | 株式会社东芝 | Semiconductor light-emitting component and its manufacturing mehtod and semiconductor luminescent device |
| JP2003017741A (en) * | 2001-03-21 | 2003-01-17 | Furukawa Electric Co Ltd:The | GaN-BASED LIGHT EMITTING ELEMENT |
-
2004
- 2004-12-17 CN CNB200410101245XA patent/CN100358167C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11177134A (en) * | 1997-12-15 | 1999-07-02 | Sharp Corp | Manufacture of semiconductor element, semiconductor, manufacture of light emitting element, and light emitting element |
| US5990500A (en) * | 1998-03-25 | 1999-11-23 | Kabushiki Kaisha Toshiba | Nitride compound semiconductor light emitting element and its manufacturing method |
| CN1330416A (en) * | 2000-06-30 | 2002-01-09 | 株式会社东芝 | Semiconductor light-emitting component and its manufacturing mehtod and semiconductor luminescent device |
| JP2003017741A (en) * | 2001-03-21 | 2003-01-17 | Furukawa Electric Co Ltd:The | GaN-BASED LIGHT EMITTING ELEMENT |
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| Publication number | Publication date |
|---|---|
| CN1622352A (en) | 2005-06-01 |
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Address after: No. 1 North Ze street, Beijing Economic Development Zone, Beijing Patentee after: Beijing TimesLED Technology Co.,Ltd. Address before: Branch of Beijing economic and Technological Development Zone two Beijing street, No. 4 Building 2 layer in the south of 1-4 Patentee before: Beijing TimesLED Technology Co.,Ltd. |
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