WO2007037654A1 - Iii-nitride compound semiconductor light emitting device - Google Patents

Iii-nitride compound semiconductor light emitting device Download PDF

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Publication number
WO2007037654A1
WO2007037654A1 PCT/KR2006/003929 KR2006003929W WO2007037654A1 WO 2007037654 A1 WO2007037654 A1 WO 2007037654A1 KR 2006003929 W KR2006003929 W KR 2006003929W WO 2007037654 A1 WO2007037654 A1 WO 2007037654A1
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Prior art keywords
compound semiconductor
nitride compound
layer
light emitting
emitting device
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PCT/KR2006/003929
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French (fr)
Inventor
Eun-Hyun Park
Tae-Kyung Yoo
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Epivalley Co., Ltd.
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Publication of WO2007037654A1 publication Critical patent/WO2007037654A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
    • H01L33/22—Roughened surfaces, e.g. at the interface between epitaxial layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02455—Group 13/15 materials
    • H01L21/02458—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02538—Group 13/15 materials
    • H01L21/0254—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

Definitions

  • the present invention relates to a III- nitride compound semiconductor light emitting device, and more particularly, to a Ill-nitride compound semiconductor light emitting device in which a plurality of semiconductor layers include a rough surface region formed by removing part of the layer from the side portion between a substrate and an active layer to improve external quantum efficiency.
  • the Ill-nitride compound semiconductor light emitting device means a light emitting device such as a light emitting diode including a compound semiconductor layer composed of Al Ga
  • N In N (O ⁇ x ⁇ l, O ⁇ y ⁇ l, 0 ⁇ x+y ⁇ l), and may further include a material composed of other group elements, such as SiC, SiN, SiCN and CN, or a semiconductor layer made of such a material.
  • FIG. 1 is a cross-sectional view illustrating one example of a conventional semiconductor light emitting device.
  • the conventional semiconductor light emitting device includes a substrate 100, a buffer layer 200 epitaxially grown on the substrate 100, an n-type nitride compound semiconductor layer 300 epitaxially grown on the buffer layer 200, an active layer 400 epitaxially grown on the n-type nitride compound semiconductor layer 300, a p-type nitride compound semiconductor layer 500 epitaxially grown on the active layer 400, a p-side electrode 600 formed on the p-type nitride compound semiconductor layer 500, a p-side bonding pad 700 formed on the p-side electrode 600, and an n-side electrode 800 formed on the n-type nitride compound semiconductor layer 301 exposed by mesa-etching the p-type nitride compound semiconductor layer 500 and the active layer 400.
  • a GaN substrate can be used as a homo-substrate, and a sapphire substrate, an SiC substrate or an Si substrate can be used as a hetero- substrate.
  • a sapphire substrate, an SiC substrate or an Si substrate can be used as a hetero- substrate.
  • any kinds of substrates on which the nitride compound semiconductor layers can be grown can be used.
  • MOCVD metal organic chemical vapor deposition
  • the buffer layer 200 serves to overcome differences in lattice parameter and thermal expansion coefficient between the hetero-substrate 100 and the nitride compound semiconductor.
  • USP 5,122,845 discloses a method for growing an AIN buffer layer having a thickness of 100 to 500 on a sapphire substrate at 380 to 800 C.
  • USP 5,290,393 diss a method for growing an Al (x) Ga (1-x) N (0 ⁇ x ⁇ l) buffer layer having a thickness of 10 to 5000 on a sapphire substrate at 200 to 900 C.
  • the international publication official gazette WO/2017053042 discloses a method for growing an SiC buffer layer (seed layer) at 600 to 990 C, and growing an In Ga N (0 ⁇ x ⁇ l) layer
  • n-type nitride compound semiconductor layer 300 At least a region where the n-side electrode 800 is formed (an n-type contact layer) is doped with a dopant.
  • the n-type contact layer is made of GaN and doped with Si.
  • USP 5,733,796 discloses a method for doping an n-type contact layer at a target doping concentration by controlling a mixture ratio of Si and other source material.
  • the active layer 400 generates light quantum (light) by recombination of an electron and a hole.
  • the active layer 400 is made of In Ga N (0 ⁇ x ⁇ l) and
  • (x) (1-x) comprises single quantum well layer or multi quantum well layers.
  • the international publication official gazette WO/02/021121 discloses a method for partially doping a plurality of quantum well layers and barrier layers.
  • the p-type nitride compound semiconductor layer 500 is doped with an appropriate dopant such as Mg, and provided with a p-type conductivity by activation process.
  • USP 5,247,533 discloses a method for activating a p-type nitride compound semiconductor layer by electron beam radiation.
  • USP 5,306,662 discloses a method for activating a p-type nitride compound semiconductor layer by annealing at 400 C and above.
  • the international publication official gazette WO/2017022655 discloses a method for preparing a p-type nitride compound semiconductor layer with a p-type conductivity without activation, by using ammonia and a hydrogen group source material as a nitrogen precursor for the growth of the p-type nitride compound semiconductor layer.
  • the p-side electrode 600 is provided to facilitate current supply to the whole p-type nitride compound semiconductor layer 500.
  • USP 5,563,422 discloses a light transmitting electrode formed over almost the whole surface of a p-type nitride compound semiconductor layer to ohmic-contact the p-type nitride compound semiconductor layer, and composed of Ni and Au.
  • USP 6,515,306 discloses a method for forming an n-type super lattice layer on a p-type nitride compound semiconductor layer, and forming a light transmitable electrode made of ITO thereon.
  • the p-side electrode 600 can be formed thick not to transmit light, namely, to reflect light to the substrate side.
  • a light emitting device using such p- side electrode 600 is called a flip chip.
  • USP 6,194,743 discloses an electrode structure including an Ag layer having a thickness over 20nm, a diffusion barrier layer for covering the Ag layer, and a bonding layer made of Au and Al for covering the diffusion barrier layer.
  • the p-side bonding pad 700 and the n-side electrode 800 are formed for current supply and external wire bonding.
  • USP 5,563,422 discloses a method for forming an n- side electrode with Ti and Al
  • USP 5,652,434 discloses a method for making a p- side bonding pad directly contact with a p-type nitride compound semiconductor layer by removing a part of a light transmitable electrode.
  • One of the disadvantages of the III- nitride compound semiconductor light emitting device is that a large amount of light generated by the active layer 400 is confined inside the device and the substrate 100 due to a refractive index difference between the device and the ambient air.
  • External quantum efficiency can be improved by mechanically processing a chip shape of the light emitting device, or roughening the surface of the semiconductor layer by chemical etching or dry etching. Recently, in the growth of the p-type nitride compound semiconductor layer 500, the surface is roughened by deteriorating quality of thin film by using the growth conditions such as pressure, temperature and gas flow.
  • the mechanical processing is suitable for the substrate having low hardness such as a SiC substrate.
  • the surface of the semiconductor layer is roughened by chemical etching or dry etching, the area able to be roughened is limited and reproducibility and uniformity are reduced.
  • An object of the present invention is to provide a Ill-nitride compound semiconductor light emitting device in which a plurality of semiconductor layers include a rough surface region formed by removing part of the layer from the side portion between a substrate and an active layer to improve external quantum efficiency.
  • Ill-nitride compound semiconductor light emitting device comprising a substrate, and a plurality of nitride compound semiconductor layers which are grown on the substrate and which include an active layer for generating light by recombination of an electron and a hole, wherein the plurality of nitride compound semiconductor layers includes a rough surface region between the substrate and the active layer, the rough surface region formed by removing the plurality of nitride compound semiconductor layers from a side thereof.
  • the plurality of nitride compound semiconductor layers include a first Al In Ga N x y z
  • the rough surface region is formed by photoelectrochemical etching.
  • the plurality of nitride compound semiconductor layers further include a p-type nitride compound semiconductor layer between the active layer and the rough surface region.
  • the plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the active layer and the rough surface region, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
  • the plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the p-type nitride compound semiconductor layer and the substrate, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
  • the n-type nitride compound semiconductor layer contains indium.
  • the plurality of nitride compound semiconductor layers further include an additional n-type nitride compound semiconductor layer contacting the n-type nitride compound semiconductor layer containing indium, and having a lower indium content than the n-type nitride compound semiconductor layer.
  • external quantum efficiency can be improved by forming the rough surface region between the substrate and the active layer.
  • FIG. 1 is a cross-sectional view illustrating one example of a conventional semiconductor light emitting device
  • Fig. 2 is a cross-sectional view illustrating thin films of a Ill-nitride compound semiconductor light emitting device in accordance with the present invention
  • Fig. 3 is a cross-sectional view illustrating a state where a masking film and a metal film are formed to manufacture the Ill-nitride compound semiconductor light emitting device in accordance with the present invention
  • Fig. 4 is a schematic view illustrating a state where the Ill-nitride compound semiconductor light emitting device is put into an etching solution and radiated with ultraviolet rays in accordance with the present invention.
  • Fig. 5 is a cross-sectional view illustrating the Ill-nitride compound semiconductor light emitting device in accordance with the present invention. Mode for the Invention
  • Fig. 2 is a cross-sectional view illustrating thin films of the Ill-nitride compound semiconductor light emitting device in accordance with the present invention.
  • a buffer layer 11 grown at a low temperature, a non-doped GaN layer 12, a first Al In Ga N x y z
  • Fig. 3 is a cross-sectional view illustrating a state where a masking film and a metal film are formed to manufacture the Ill-nitride compound semiconductor light emitting device in accordance with the present invention.
  • the masking film 20 and the metal film 21 are formed after a primary etching process for forming the n- side electrode and a secondary etching process for forming the metal film 21.
  • the bias applied through the metal film 21 helps uniform etching and selective etching progressing faster.
  • the masking film 20 is made of metal, dielectric or organic substance, for preventing the etching solution from penetrating into the region including the active layer 18. If the light is radiated to the substrate side 10, the masking film 20 can be not light tramsmittable.
  • Fig. 4 is a schematic view illustrating a state where the Ill-nitride compound semiconductor light emitting device is put into an etching solution and radiated with ultraviolet rays in accordance with the present invention.
  • KOH or H PO is used as the etching solution 23, the bias is applied through the metal film 21, and the ultraviolet rays 22 are radiated by an ultraviolet lamp or ultraviolet laser.
  • the etched portion is bent e f g slightly upwardly, so that the etching solution 23 can easily penetrate into the device and facilitate etching.
  • Fig. 5 is a cross-sectional view illustrating the Ill-nitride compound semiconductor light emitting device in accordance with the present invention.
  • the rough surface region 24 can be wholly or partially etched as needed, according to variations of etching time or conditions.
  • the rough surface region 24 can be selectively formed by preventing etching of a specific portion of the device, by forming a masking film for intercepting light on the specific portion.
  • the optical path of the light generated by the active layer 18 can be arbitrarily changed by using the rough surface region 24, thereby increasing the amount of light externally emitted from the device. As a result, external quantum efficiency of the device can be improved.

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  • Manufacturing & Machinery (AREA)
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Abstract

The present invention discloses a Ill-nitride compound semiconductor light emitting device including a substrate, and a plurality of nitride compound semiconductor layers which are grown on the substrate and which include an active layer for generating light by recombination of an electron and a hole. Here, the plurality of nitride compound semiconductor layers include a rough surface region between the substrate and the active layer, the rough surface region formed by removing the plurality of nitride compound semiconductor layers from a side thereof.

Description

Description
III-NITRIDE COMPOUND SEMICONDUCTOR LIGHT
EMITTING DEVICE
Technical Field
[1] The present invention relates to a III- nitride compound semiconductor light emitting device, and more particularly, to a Ill-nitride compound semiconductor light emitting device in which a plurality of semiconductor layers include a rough surface region formed by removing part of the layer from the side portion between a substrate and an active layer to improve external quantum efficiency. Here, the Ill-nitride compound semiconductor light emitting device means a light emitting device such as a light emitting diode including a compound semiconductor layer composed of Al Ga
(x) (y)
In N (O≤x≤l, O≤y≤l, 0<x+y≤l), and may further include a material composed of other group elements, such as SiC, SiN, SiCN and CN, or a semiconductor layer made of such a material. Background Art
[2] Fig. 1 is a cross-sectional view illustrating one example of a conventional semiconductor light emitting device. The conventional semiconductor light emitting device includes a substrate 100, a buffer layer 200 epitaxially grown on the substrate 100, an n-type nitride compound semiconductor layer 300 epitaxially grown on the buffer layer 200, an active layer 400 epitaxially grown on the n-type nitride compound semiconductor layer 300, a p-type nitride compound semiconductor layer 500 epitaxially grown on the active layer 400, a p-side electrode 600 formed on the p-type nitride compound semiconductor layer 500, a p-side bonding pad 700 formed on the p-side electrode 600, and an n-side electrode 800 formed on the n-type nitride compound semiconductor layer 301 exposed by mesa-etching the p-type nitride compound semiconductor layer 500 and the active layer 400.
[3] In the case of the substrate 100, a GaN substrate can be used as a homo-substrate, and a sapphire substrate, an SiC substrate or an Si substrate can be used as a hetero- substrate. However, any kinds of substrates on which the nitride compound semiconductor layers can be grown can be used.
[4] The nitride compound semiconductor layers epitaxially grown over the substrate
100 are mostly grown by the metal organic chemical vapor deposition (MOCVD).
[5] The buffer layer 200 serves to overcome differences in lattice parameter and thermal expansion coefficient between the hetero-substrate 100 and the nitride compound semiconductor. USP 5,122,845 discloses a method for growing an AIN buffer layer having a thickness of 100 to 500 on a sapphire substrate at 380 to 800 C. USP 5,290,393 diss a method for growing an Al (x) Ga (1-x) N (0<x<l) buffer layer having a thickness of 10 to 5000 on a sapphire substrate at 200 to 900 C. The international publication official gazette WO/05/053042 discloses a method for growing an SiC buffer layer (seed layer) at 600 to 990 C, and growing an In Ga N (0<x≤l) layer
(x) (1-x) thereon. [6] In the n-type nitride compound semiconductor layer 300, at least a region where the n-side electrode 800 is formed (an n-type contact layer) is doped with a dopant.
Preferably, the n-type contact layer is made of GaN and doped with Si. USP 5,733,796 discloses a method for doping an n-type contact layer at a target doping concentration by controlling a mixture ratio of Si and other source material. [7] The active layer 400 generates light quantum (light) by recombination of an electron and a hole. Normally, the active layer 400 is made of In Ga N (0<x≤l) and
(x) (1-x) comprises single quantum well layer or multi quantum well layers. The international publication official gazette WO/02/021121 discloses a method for partially doping a plurality of quantum well layers and barrier layers.
[8] The p-type nitride compound semiconductor layer 500 is doped with an appropriate dopant such as Mg, and provided with a p-type conductivity by activation process. USP 5,247,533 discloses a method for activating a p-type nitride compound semiconductor layer by electron beam radiation. USP 5,306,662 discloses a method for activating a p-type nitride compound semiconductor layer by annealing at 400 C and above. Also, the international publication official gazette WO/05/022655 discloses a method for preparing a p-type nitride compound semiconductor layer with a p-type conductivity without activation, by using ammonia and a hydrogen group source material as a nitrogen precursor for the growth of the p-type nitride compound semiconductor layer.
[9] The p-side electrode 600 is provided to facilitate current supply to the whole p-type nitride compound semiconductor layer 500. USP 5,563,422 discloses a light transmitting electrode formed over almost the whole surface of a p-type nitride compound semiconductor layer to ohmic-contact the p-type nitride compound semiconductor layer, and composed of Ni and Au. USP 6,515,306 discloses a method for forming an n-type super lattice layer on a p-type nitride compound semiconductor layer, and forming a light transmitable electrode made of ITO thereon.
[10] On the other hand, the p-side electrode 600 can be formed thick not to transmit light, namely, to reflect light to the substrate side. A light emitting device using such p- side electrode 600 is called a flip chip. USP 6,194,743 discloses an electrode structure including an Ag layer having a thickness over 20nm, a diffusion barrier layer for covering the Ag layer, and a bonding layer made of Au and Al for covering the diffusion barrier layer. [11] The p-side bonding pad 700 and the n-side electrode 800 are formed for current supply and external wire bonding. USP 5,563,422 discloses a method for forming an n- side electrode with Ti and Al, and USP 5,652,434 discloses a method for making a p- side bonding pad directly contact with a p-type nitride compound semiconductor layer by removing a part of a light transmitable electrode.
[12] One of the disadvantages of the III- nitride compound semiconductor light emitting device is that a large amount of light generated by the active layer 400 is confined inside the device and the substrate 100 due to a refractive index difference between the device and the ambient air.
[13] In the device showing serious light confinement, namely, the device having low external quantum efficiency, a large amount of light is confined and vanished as heat. Accordingly, a temperature of the device rises, which has detrimental effects on the lifespan and property of the device.
[14] External quantum efficiency can be improved by mechanically processing a chip shape of the light emitting device, or roughening the surface of the semiconductor layer by chemical etching or dry etching. Recently, in the growth of the p-type nitride compound semiconductor layer 500, the surface is roughened by deteriorating quality of thin film by using the growth conditions such as pressure, temperature and gas flow.
[15] The mechanical processing is suitable for the substrate having low hardness such as a SiC substrate. However, it is difficult to mechanically process the substrate having high hardness such as a sapphire substrate. In addition, when the surface of the semiconductor layer is roughened by chemical etching or dry etching, the area able to be roughened is limited and reproducibility and uniformity are reduced.
[16] In the case that the surface of the p-type nitride compound semiconductor layer 500 is roughened by changing the growth conditions, external quantum efficiency of the device is improved, but reliability thereof is seriously reduced. Disclosure of Invention Technical Problem
[17] The present invention is achieved to solve the above problems. An object of the present invention is to provide a Ill-nitride compound semiconductor light emitting device in which a plurality of semiconductor layers include a rough surface region formed by removing part of the layer from the side portion between a substrate and an active layer to improve external quantum efficiency.s Technical Solution
[18] In order to achieve the above-described object of the invention, there is provided a
Ill-nitride compound semiconductor light emitting device comprising a substrate, and a plurality of nitride compound semiconductor layers which are grown on the substrate and which include an active layer for generating light by recombination of an electron and a hole, wherein the plurality of nitride compound semiconductor layers includes a rough surface region between the substrate and the active layer, the rough surface region formed by removing the plurality of nitride compound semiconductor layers from a side thereof. [19] The plurality of nitride compound semiconductor layers include a first Al In Ga N x y z
(x+y+z=l) layer, a second Al In Ga N (a+b+c=l) layer and a third Al In Ga N a b c e f g
(e+f+g=l) layer which are sequentially stacked, and the rough surface region is formed by removing the second Al In Ga N (a+b+c=l) layer. a b c
[20] The second Al In Ga N (a+b+c=l) layer has a higher indium content than the first a b c
Al In Ga N (x+y+z=l) layer and the third Al In Ga N (e+f+g=l) layer (b»y, f). x y z e f g
[21] The first Al In Ga N (x+y+z=l) layer and the second Al In Ga N (a+b+c=l) layer x y z a b c have an n-type conductivity.
[22] The rough surface region is formed by photoelectrochemical etching.
[23] The second Al a In b Ga c N (a+b+c=l) layer is etched by photoelectrochemical etching.
[24] The third Al e In f Ga g N (e+f+g=l) layer has an n-type conductivity, and the plurality of nitride compound semiconductor layers further include a p-type Al In GaN h i J
(h+i+j=l) layer on the third Al e In f Ga g N (e+f+g=l) layer.
[25] The plurality of nitride compound semiconductor layers further include a p-type nitride compound semiconductor layer between the active layer and the rough surface region.
[26] The plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the active layer and the rough surface region, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
[27] The plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the p-type nitride compound semiconductor layer and the substrate, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
[28] The n-type nitride compound semiconductor layer contains indium.
[29] The plurality of nitride compound semiconductor layers further include an additional n-type nitride compound semiconductor layer contacting the n-type nitride compound semiconductor layer containing indium, and having a lower indium content than the n-type nitride compound semiconductor layer.
Advantageous Effects
[30] In accordance with the present invention, external quantum efficiency can be improved by forming the rough surface region between the substrate and the active layer.
Brief Description of the Drawings
[31] The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein:
[32] Fig. 1 is a cross-sectional view illustrating one example of a conventional semiconductor light emitting device;
[33] Fig. 2 is a cross-sectional view illustrating thin films of a Ill-nitride compound semiconductor light emitting device in accordance with the present invention;
[34] Fig. 3 is a cross-sectional view illustrating a state where a masking film and a metal film are formed to manufacture the Ill-nitride compound semiconductor light emitting device in accordance with the present invention;
[35] Fig. 4 is a schematic view illustrating a state where the Ill-nitride compound semiconductor light emitting device is put into an etching solution and radiated with ultraviolet rays in accordance with the present invention; and
[36] Fig. 5 is a cross-sectional view illustrating the Ill-nitride compound semiconductor light emitting device in accordance with the present invention. Mode for the Invention
[37] A Ill-nitride compound semiconductor light emitting device in accordance with preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[38] Fig. 2 is a cross-sectional view illustrating thin films of the Ill-nitride compound semiconductor light emitting device in accordance with the present invention. A buffer layer 11 grown at a low temperature, a non-doped GaN layer 12, a first Al In Ga N x y z
(x+y+z=l) layer 13 having an n-type conductivity, a second Al In Ga N (a+b+c=l) b layer 14 having an n-type conductivity, a third Al In Ga N (e+f+g=l) layer 15 having e f g an n-type conductivity, a p-type Al InGaN (h+i+j=l) layer 16, an n-type nitride h i J compound semiconductor layer 17 on which an n-side electrode is formed, an active layer 18, and a p-type nitride compound semiconductor layer 19 on which a p-side electrode is formed are sequentially stacked on a substrate 10, thereby forming the III- nitride compound semiconductor light emitting device. [39] The second Al In Ga N (a+b+c=l) layer 14 is selectively etched in photoelec- a b c trochemical etching. Therefore, the second Al a In b Ga c N (a+b+c=l) layer 14 is etched more fast in the transverse direction than the first Al x In y Ga z N (x+y+z=l) layer 13 and the third Al e In f Ga g N (e+f+g=l) layer 15, thereby forming a rough surface region.
[40] In the photoelectrochemical etching, a sample which is an etching object is put into an etching solution, current is supplied thereto with bias, and light is radiated to the sample. Accordingly, the light-radiated portion is etched. The selective etching etches a specific layer by using an etch rate difference between the nitride compound layers composed of different elements.
[41] In case of selective etching, when the indium content and the higher n-type doping concentration become higher, selective etching is progressed more faster. Therefore the present invention is easily applicable. However, an excessive indium content deteriorates quality of a thin film grown later. Especially, light generated by the active layer 18 is absorbed by the second Al In Ga N (a+b+c=l) layer 14 having a high a b c indium content, which may reduce light emitting efficiency of the device. [42] In addition, the first Al In Ga N (x+y+z=l) layer 13 uniformly supplies the x y z externally- applied bias, the third Al In Ga N (e+f+g=l) layer 15 forms the rough e f g surface region at the lower portion of the device, and the p-type Al In Ga N (h+i+j=l) h i J layer 16 is doped with Mg, for reliably preventing the active layer 18 from being etched.
[43] Fig. 3 is a cross-sectional view illustrating a state where a masking film and a metal film are formed to manufacture the Ill-nitride compound semiconductor light emitting device in accordance with the present invention. Referring to Fig. 3, the masking film 20 and the metal film 21 are formed after a primary etching process for forming the n- side electrode and a secondary etching process for forming the metal film 21. The secondary etching process etches at least to the first Al In Ga N (x+y+z=l) layer 13. The bias applied through the metal film 21 helps uniform etching and selective etching progressing faster. The masking film 20 is made of metal, dielectric or organic substance, for preventing the etching solution from penetrating into the region including the active layer 18. If the light is radiated to the substrate side 10, the masking film 20 can be not light tramsmittable.
[44] Fig. 4 is a schematic view illustrating a state where the Ill-nitride compound semiconductor light emitting device is put into an etching solution and radiated with ultraviolet rays in accordance with the present invention. KOH or H PO is used as the etching solution 23, the bias is applied through the metal film 21, and the ultraviolet rays 22 are radiated by an ultraviolet lamp or ultraviolet laser.
[45] Preferably, tensile strain is formed to the first Al In Ga N (x+y+z=l) layer 13 and x y z the third Al In Ga N (e+f+g=l) layer 15. During the etching, the etched portion is bent e f g slightly upwardly, so that the etching solution 23 can easily penetrate into the device and facilitate etching.
[46] Fig. 5 is a cross-sectional view illustrating the Ill-nitride compound semiconductor light emitting device in accordance with the present invention. Current supply to a region 25 including the active layer 18 is intercepted by the masking film 20 and the p- type Al InGaN (h+i+j=l) layer 16, so that the region 25 can be protected from the h i J etching. The second Al In Ga N (a+b+c=l) layer 14 is selectively etched and a rough a b c surface region 24 is formed.
[47] The rough surface region 24 can be wholly or partially etched as needed, according to variations of etching time or conditions.
[48] Also, the rough surface region 24 can be selectively formed by preventing etching of a specific portion of the device, by forming a masking film for intercepting light on the specific portion.
[49] The optical path of the light generated by the active layer 18 can be arbitrarily changed by using the rough surface region 24, thereby increasing the amount of light externally emitted from the device. As a result, external quantum efficiency of the device can be improved.
[50] Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.

Claims

Claims
[1] A Ill-nitride compound semiconductor light emitting device, comprising: a substrate; and a plurality of nitride compound semiconductor layers which are grown on the substrate and which include an active layer for generating light by recombination of an electron and a hole; wherein the plurality of nitride compound semiconductor layers includes a rough surface region between the substrate and the active layer, the rough surface region formed by removing the plurality of nitride compound semiconductor layers from a side thereof.
[2] The III- nitride compound semiconductor light emitting device of claim 1, wherein the plurality of nitride compound semiconductor layers include a first Al In Ga N (x+y+z=l) layer, a second Al In Ga N (a+b+c=l) layer and a third Al x y z a b c e
In Ga N (e+f+g=l) layer which are sequentially stacked, and the rough surface f g region is formed by removing the second Al In Ga N (a+b+c=l) layer. a b c
[3] The Ill-nitride compound semiconductor light emitting device of claim 2, wherein the second Al In Ga N (a+b+c=l) layer has a higher indium content than a b c the first Al In Ga N (x+y+z=l) layer and the third Al In Ga N (e+f+g=l) layer (b x y z e f g
>y,f).
[4] The Ill-nitride compound semiconductor light emitting device of claim 2, wherein the first Al In Ga N (x+y+z=l) layer and the second Al In Ga N x y z a b c
(a+b+c=l) layer have an n-type conductivity.
[5] The III- nitride compound semiconductor light emitting device of claim 1, wherein the rough surface region is formed by photoelectrochemical etching.
[6] The Ill-nitride compound semiconductor light emitting device of claim 2, wherein the second Al a In b Ga c N (a+b+c=l) layer is etched by photoelec- trochemical etching.
[7] The Ill-nitride compound semiconductor light emitting device of claim 2, wherein the third Al e In f Ga g N (e+f+g=l) layer has an n-type conductivity, and the plurality of nitride compound semiconductor layers further include a p-type Al In h
GaN (h+i+j=l) layer on the third Al In Ga N (e+f+g=l) layer. l j e f g
[8] The III- nitride compound semiconductor light emitting device of claim 1, wherein the plurality of nitride compound semiconductor layers further include a p-type nitride compound semiconductor layer between the active layer and the rough surface region.
[9] The III- nitride compound semiconductor light emitting device of claim 1, wherein the plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the active layer and the substrate, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
[10] The Ill-nitride compound semiconductor light emitting device of claim 9, wherein the n-type nitride compound semiconductor layer contains indium.
[11] The III- nitride compound semiconductor light emitting device of claim 10, wherein the plurality of nitride compound semiconductor layers further include an additional n-type nitride compound semiconductor layer contacting the n-type nitride compound semiconductor layer containing indium, and having a lower indium content than the n-type nitride compound semiconductor layer.
[12] The III- nitride compound semiconductor light emitting device of claim 8, wherein the plurality of nitride compound semiconductor layers further include an n-type nitride compound semiconductor layer between the p-type nitride compound semiconductor layer and the substrate, and the rough surface region is formed by removing the n-type nitride compound semiconductor layer.
[13] The Ill-nitride compound semiconductor light emitting device of claim 12, wherein the n-type nitride compound semiconductor layer contains indium.
[14] The III- nitride compound semiconductor light emitting device of claim 13, wherein the plurality of nitride compound semiconductor layers further include an additional n-type nitride compound semiconductor layer contacting the n-type nitride compound semiconductor layer, and having a lower indiym content than the additional n-type nitride compound semiconductor layer.
PCT/KR2006/003929 2005-09-29 2006-09-29 Iii-nitride compound semiconductor light emitting device WO2007037654A1 (en)

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