Semiconductor light-emitting device

• US 20040113166A1
• Filed: 12/09/2003
• Published: 06/17/2004
• Est. Priority Date: 03/21/2001
• Status: Active Grant

• Current Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Original Assignee: Mitsubishi Cable Industries Limited (Mitsubishi Materials Corporation)
• Inventors: Tsunekawa, Takashi, Okagawa, Hiroaki, Ouchi, Yoichiro, Tadatomo, Kazuyuki
• Granted Patent: US 7,053,420 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/12 with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

Concaves and convexes 1a are formed by processing the surface layer of a first layer 1, and second layer 2 having a different refractive index from the first layer is grown while burying the concaves and convexes (or first crystal 10 is grown as concaves and convexes on crystal layer S to be the base of the growth, and second crystal 20 is grown, which has a different refractive index from the first crystal). After forming these concavo-convex refractive index interfaces 1a (10a), an element structure, wherein semiconductor crystal layers containing a light-emitting layer A are laminated, is formed. As a result, the light in the lateral direction, which is generated in the light-emitting layer changes its direction by an influence of the concavo-convex refractive index interface and heads toward the outside. Particularly, when an ultraviolet light is to be emitted using InGaN as a material of a light-emitting layer, a quantum well structure is employed and all the layers between the quantum well structure and the low temperature buffer layer are formed of a GaN crystal, removing AlGaN. The quantum well structure preferably consists of a well layer made of InGaN and a barrier layer made of GaN, and the thickness of the barrier layer is preferably 6 nm-30 nm.

Claims

1. A semiconductor light-emitting element having an element structure comprising a first crystal layer processed to have concaves and convexes on its surface, a second crystal layer directly formed thereon or formed via a buffer layer, burying the concaves and convexes, said second crystal layer being made from a semiconductor material having a different refractive index from the aforementioned crystal layer, and a semiconductor crystal layer comprising a light-emitting layer laminated thereon.

2. The semiconductor light-emitting element of claim 1, wherein the second crystal layer and the semiconductor crystal layer thereon are made of a GaN group semiconductor crystal.

3. The semiconductor light-emitting element of claim 2, wherein the first crystal layer is a crystal substrate and the second crystal layer has grown while substantially forming-a facet structure from the concaves and convexes processed on the surface of the crystal substrate.

4. The semiconductor light-emitting element of claim 3, wherein the concaves and convexes processed on the surface of the crystal substrate have a stripe pattern, and the longitudinal direction of the stripe is a <

11-20>

direction or a <

1-100>

direction of a GaN group semiconductor grown while burying them.

5. The semiconductor light-emitting element of claim 1 or 4, wherein the concaves and convexes have a cross sectional shape of a rectangular wave, a triangular wave or a sine curve.

6. The semiconductor light-emitting element of claim 1, wherein the difference between the refractive index of the first crystal layer and that of the second crystal layer at the wavelength of a light emitted from the light-emitting layer is not less than 0.05.

7. The semiconductor light-emitting element of claim 1, wherein the light-emitting layer is made of an InGaN crystal having a composition capable of generating an ultraviolet light.

8. The semiconductor light-emitting element of claim 1, wherein the light-emitting layer is a quantum well structure comprising a well layer made of InGaN and a barrier layer made of GaN.

9. The semiconductor light-emitting element of claim 1, wherein the first crystal layer is a crystal substrate, the second crystal layer is grown, via a low temperature buffer layer, on the concaves and convexes processed on the surface of the crystal substrate while burying the concaves and convexes, the light-emitting layer is a quantum well structure comprising a well layer made of InGaN and a barrier layer made of GaN, and all the layers between the quantum well structure and the low temperature buffer layer are made of a GaN crystal.

10. The semiconductor light-emitting element of claim 8 or 9, wherein the barrier layer has a thickness of 6 nm-30 nm.

11. A semiconductor light-emitting element having an element structure comprising a crystal layer surface to be a base for crystal growth, a first GaN group semiconductor crystal grown on said surface to form concaves and convexes, a second GaN group semiconductor crystal having a different refractive index from the first GaN group semiconductor crystal, which is grown while covering at least a part of said concaves and convexes, a third GaN group semiconductor crystal grown until it flattens said concaves and convexes, and a semiconductor crystal layer having a light-emitting layer laminated thereon.

12. The semiconductor light-emitting element of claim 11, wherein the crystal layer surface to be a base for crystal growth has a structure or has been subjected to a surface treatment, which dimensionally limits a crystal growth area, and said limitation causes growth of the first GaN group semiconductor crystal into concaves and convexes, while forming substantial facet structure or a pseudo-facet structure.

13. The semiconductor light-emitting element of claim 12, wherein the structure or surface treatment limiting the crystal growth area is concaves and convexes processed on the crystal layer surface to be a base for crystal growth, or a mask pattern capable of causing a lateral growth, which is formed on the surface of the crystal layer to be a base for crystal growth, or a surface treatment capable of suppressing GaN group crystal growth, which is applied to a specific area of the surface of the crystal layer to be a base for crystal growth.

14. The semiconductor light-emitting element of claim 11, having an element structure wherein the second GaN group semiconductor crystal is grown covering, in a membrane, at least a convex part of the concaves and convexes made of the first GaN group semiconductor crystal, the third GaN group semiconductor crystal covering same is grown until it flattens said concaves and convexes, and the semiconductor crystal layer having the light-emitting layer is laminated thereon, and wherein the second GaN group semiconductor crystal has a multilayer membrane structure.

15. The semiconductor light-emitting element of claim 11, wherein the light-emitting layer is made of an InGaN crystal having a composition capable of generating an ultraviolet light.

16. The semiconductor light-emitting element of claim 11, wherein the light-emitting layer is a quantum well structure comprising a well layer made of InGaN and a barrier layer made of GaN.

17. The semiconductor light-emitting element of claim 16, wherein the barrier layer has a thickness of 6 nm-30 nm.

18. The semiconductor light-emitting element of claim 11, wherein said concaves and convexes have a stripe pattern, and the longitudinal direction of the stripe is a <

11-20>

direction or a <

1-100>

direction of the first GaN group semiconductor crystal.