Nitride semiconductor laser device

• US 7,015,053 B2
• Filed: 11/04/2003
• Issued: 03/21/2006
• Est. Priority Date: 03/04/1999
• Status: Expired due to Term

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Nakamura, Shuji, Sano, Masahiko, Nagahama, Shinichi, Kozaki, Tokuya
• Primary Examiner(s): Le, Thao P.
• Application Number:
  US10/700,270
• Publication Number:
  US 20040101986A1
• Time in Patent Office: 868 Days
• Field of Search: 438/22
• US Class Current: 438/22
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 2304/00 Special growth methods for semiconductor lasers
• CPC Class Codes: H01S 5/04252 characterised by the material
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/0655 Single transverse or lateral mode emission
• CPC Class Codes: H01S 5/2004 Confining in the direction perpendicular to the layer structure
• CPC Class Codes: H01S 5/2031 characterized by special waveguide layers, e.g. asymmetric waveguide layers or defined bandgap discontinuities
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/2214 based on oxides or nitrides
• CPC Class Codes: H01S 5/2216 nitrides
• CPC Class Codes: H01S 5/223 Buried stripe structure H01S5/227 takes precedence
• CPC Class Codes: H01S 5/2231 with inner confining structure only between the active layer and the upper electrode
• CPC Class Codes: H01S 5/3213 asymmetric clading layers
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A nitride semiconductor laser device has an improved stability of the lateral mode under high output power and a longer lifetime, so that the device can be applied to write and read light sources for recording media with high capacity. The nitride semiconductor laser device includes an active layer, a p-side cladding layer, and a p-side contact layer laminated in turn. The device further includes a waveguide region of a stripe structure formed by etching from the p-side contact layer. The stripe width provided by etching is within the stripe range of 1 to 3 μm and the etching depth is below the thickness of the p-side cladding layer of 0.1 μm and above the active layer. Particularly, when a p-side optical waveguide layer includes a projection part of the stripe structure and a p-type nitride semiconductor layer on the projection part and the projection part of the p-side optical waveguide layer has a thickness of not more than 1 μm, an aspect ratio is improved in far field image. Moreover, the thickness of the p-side optical waveguide layer is greater than that of an n-side optical waveguide layer.

Claims

1. A method for manufacturing a nitride semiconductor light emitting device, the nitride semiconductor light emitting device including:

an n-type cladding layer made of an n-type nitride semiconductor;

a p-type cladding layer made of a p-type nitride semiconductor; and

an active layer provided between the n-type and p-type cladding layers, being made of an nitride semiconductor containing In;

the method comprising steps of;

forming a first p-type nitride semiconductor layer made of Al_aGa<sub>1−

a</sub>N (0<

a<

1) using metal organic chemical vapor deposition with nitrogen atmosphere, after formation of the active layer;

forming a second p-type nitride semiconductor layer made of Al_aGa<sub>1−

b</sub>N (0<

b<

1) using metal organic chemical vapor deposition with hydrogen atmosphere, after formation of the first p-type nitride semiconductor layer; and

forming the p-type cladding layer, after formation of the second p-type nitride semiconductor layer.

2. The method according to claim 1, further comprising a step of:

forming the active layer using metal organic chemical vapor deposition with the same atmosphere as that for the first p-type nitride semiconductor layer.

3. The method according to claim 1, further comprising a step of:

forming a p-type guide layer between the second p-type nitride semiconductor layer and the p-type cladding layer.

4. The method according to claim 1, wherein a total thickness of the first and second p-type nitride semiconductor layers is set in a range from 10 to 1000 Å

inclusive.

5. The method according to claim 1, wherein a total thickness of the first and second p-type nitride semiconductor layers is set in a range from 20 to 400 Å

inclusive.

6. The method according to claim 1, wherein a thickness of the first p-type nitride semiconductor layer is set in a range from 10 to 100 Å

inclusive.

7. The method according to claim 1, wherein a thickness of the second p-type nitride semiconductor layer is set in a range from 10 to 300 Å

inclusive.

8. The method according to claim 1, wherein an Al mixture ratio (a) of the first p-type nitride semiconductor layer is set in a range from 0.1 to 0.5 inclusive.

9. The method according to claim 1, wherein an Al mixture ratio (a) of the first p-type nitride semiconductor layer is set in a range from 0.1 to 0.35 inclusive.

10. The method according to claim 1, wherein an Al mixture ratio (b) of the second p-type nitride semiconductor layer is set in a range from 0.1 to 0.5 inclusive.

11. The method according to claim 1, wherein an Al mixture ratio (b) of the second p-type nitride semiconductor layer is set in a range from 0.1 to 0.35 inclusive.

12. The method according to claim 1, wherein the p-type cladding layer is made of Al_xGa₁₋

xN (0<

x<

1), whose Al ratio (x) satisfies both x≦

a and x≦

b.

13. The method according to claim 3, further comprising steps of:

forming a p-type contact layer, after formation of the p-type cladding layer; and

forming a stripe-shaped ridge waveguide by etching an upper portion above the active layer from the p-type contact layer side so that the p-type guide layer has a protruding portion, after formation of the p-type contact layer.

14. The method according to claim 13, further comprising a step of:

forming an insulating film on an etched surface of the p-type guide layer.

15. The method according to claim 1, further comprising steps of:

forming a p-type contact layer, after formation of the p-type cladding layer; and

forming a stripe-shaped ridge waveguide by etching an upper portion above the active layer from the p-type contact layer side so that the p-type cladding layer has a protruding portion, after formation of the p-type contact layer.

16. The method according to claim 15, further comprising a step of:

forming an insulating film on an etched surface of the p-type cladding layer.

17. The method according to claim 3, further comprising a step of:

forming the p-type guide layer by diffusion of Mg included in the first p-type nitride semiconductor layer into an undoped layer.

18. The method according to claim 1, wherein the p-type cladding layer has a super lattice structure formed by laminating GaN and AlGaN.

19. The method according to claim 1, wherein the active layer has a quantum well structure including a well layer made of In_cGa₁₋

cN (0≦

c≦

1).

20. The method according to claim 19, wherein the active layer has a single quantum well structure formed by laminating a well layer and a barrier layer made of AlInGaN.

21. The method according to claim 19, wherein the active layer has a multi quantum well structure formed by laminating a well layer and a barrier layer made of AlInGaN.

22. The method according to claim 20, wherein the active layer has a middle layer made of Al_uGa₁₋

uN (0≦

u≦

1) on the well layer.

23. The method according to claim 21, wherein the active layer has a middle layer made of Al_uGa₁₋

uN (0≦

u≦

1) on the well layer.