Nitride semiconductor laser device

• US 6,711,191 B1
• Filed: 03/03/2000
• Issued: 03/23/2004
• 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): Ip, Paul
• Assistant Examiner(s): Rodriguez, Armando
• Application Number:
  US09/519,440
• Time in Patent Office: 1,481 Days
• Field of Search: 372/43-50, 372/54
• US Class Current: 372/43.01
• 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. An effective refractive index type nitride semiconductor laser device comprising:

a. an active layer for recombining electrons and holes;

b. p-side contact layer for contacting a p-side electrode;

c. a p-side optical waveguide layer and a p-side cladding layer between said active layer and said p-side contact layer;

a stripe-ridge-waveguide provided by selectively etching said p-side contact layer, said p-side cladding layer and said p-side optical waveguide layer up to a vicinity of said active layer, and

another p-side cladding layer between said active layer and said p-side optical waveguide layer,

wherein said p-side optical waveguide layer has a thickness of 1.0 μ

m or less at a projection region of a stripe structure included in said stripe-ridge-waveguide, and said p-side optical waveguide layer has a thickness of 0.05 μ

m or more and 0.1 μ

m or less at a region other than the projection region, and

said another p-side cladding layer near the active layer is a carrier confinement layer including Al_yGa<sub>1−

y</sub>N(0<

y<

0.5) and said p-side cladding layer outside the p-side optical waveguide layer is a light confinement layer including Al_zGa<sub>1−

z</sub>N(0<

z<

0.5, y>

z).

2. The effective refractive index type nitride semiconductor laser device according to claim 1 further comprising:

an insulating film covering surfaces of said stripe-ridge-waveguide; and

an electrode formed on a surface of said p-side contact layer and said insulating film, the surface of said p-side contact layer being an upper surface of said stripe-ridge-waveguide, wherein said insulating film includes a material other than Si oxide.

3. The effective refractive index type nitride semiconductor laser device according to claim 1, wherein said stripe-ridge-waveguide has a width ranging from 1 μ

m to 3 μ

m.

4. The effective refractive index type nitride semiconductor laser device according to claim 2, wherein said insulating film includes an oxide containing at least one element selected from the group consisting of Ti, V, Zr, Nb, Hf and Ta, or at least one element selected from the group consisting of SiN, BN, SiC and AlN.

5. The effective refractive index type nitride semiconductor laser device according to claim 1, wherein said stripe-ridge-waveguide has a width ranging from 1.2 μ

m to 2 μ

m.

6. The effective refractive index type nitride semiconductor laser device according to claim 1, wherein said p-side optical waveguide layer has a thickness of 0.15 μ

m or more and 0.4 μ

m or less at the projection region.

7. The effective refractive index type nitride semiconductor laser device according to claim 1, wherein said p-side optical waveguide layer includes In_xGa₁₋

xN(0≦

x<

1).

8. The effective refractive index type nitride semiconductor laser device according to claim 1, wherein said another p-side first cladding layer includes Al_yGa₁₋

yN(0<

y<

0.35).

9. An effective refractive index type nitride semiconductor laser device comprising:

a. an active layer for recombining electrons and holes;

b. p-side contact layer for contacting a p-side electrode;

c. a p-side optical waveguide layer and a p-side cladding layer between said active layer and said p-side contact layer;

a stripe-ridge-waveguide provided by selectively etching said p-side contact layer, said p-side cladding layer and said p-side optical waveguide layer up to a vicinity of said active layer,

d. an n-side optical waveguide layer opposite to said a p-side optical waveguide layer with respect to said active layer; and

another p-side cladding layer between said active layer and said p-side optical waveguide layer,

wherein said p-side optical waveguide layer has a thickness of 1.0 μ

m or less at a projection region of a stripe structure included in said stripe-ridge-waveguide, and said p-side optical waveguide layer has a thickness of 0.05 μ

m or more and 0.1 μ

m or less at a region other than the projection region, and said p-side optical waveguide layer has a larger thickness than said n-side optical waveguide layer, and

said another p-side cladding layer near the active layer is a carrier confinement layer including Al_yGa<sub>1−

y</sub>N(0<

y<

0.5) and said p-side cladding layer outside the p-side optical waveguide layer is a light confinement layer including Al_zGa<sub>1−

z</sub>N(0<

z<

0.5, y>

z).

10. The effective refractive index type nitride semiconductor laser device according to claim 9 further comprising:

an insulating film covering surfaces of said stripe-ridge-waveguide; and

an electrode formed on a surface of said p-side contact layer and said insulating film, the surface of said p-side contact layer being an upper surface of said stripe-ridge-waveguide, wherein said insulating film includes a material other than Si oxide.

11. The effective refractive index type nitride semiconductor laser device according to claim 9, wherein said stripe-ridge-waveguide has a width ranging from 1 μ

m to 3 μ

m.

12. The effective refractive index type nitride semiconductor laser device according to claim 10, wherein said insulating film includes an oxide containing at least one element selected from the group consisting of Ti, V, Zr, Nb, Hf and Ta, or at least one element selected from the group consisting of SiN, BN, SiC and AlN.

13. The effective refractive index type nitride semiconductor laser device according to claim 9, wherein said stripe-ridge-waveguide has a width ranging from 1.2 μ

m to 2 μ

m.

14. The effective refractive index type nitride semiconductor laser device according to claim 9, wherein said p-side optical waveguide layer has a thickness of 0.15 μ

m or more and 0.4 μ

m or less at the projection region.

15. The effective refractive index type nitride semiconductor laser device according to claim 9, wherein said p-side optical waveguide layer includes In_xGa₁₋

xN(0≦

x<

1).

16. The effective refractive index type nitride semiconductor laser device according to claim 9, wherein said another p-side first cladding layer includes Al_yGa₁₋

yN(0<

y<

0.35).