Semiconductor laser device and manufacturing method thereof
View Patent ↗The present invention aims to provide a long-lived semiconductor laser device with low threshold current and available for high-output operation in a blue-violet semiconductor laser device using a nitride semiconductor layer. In the semiconductor laser device, the following layers are sequentially formed on a GaN substrate 1 : an n-type GaN layer 2 ; an n-type AlGaN cladding layer 3 , a first n-type GaN guiding layer 4 ; and a p-type AlGaN blocking layer 6 (current-blocking layer), further a striped opening is formed on a portion of the p-type AlGaN blocking layer 6 , a second n-type GaN guiding layer 5 is formed to cover the opening, and the following layers are sequentially formed on the second n-type GaN guiding layer 5 : an InGaN multiple quantum well active layer 7 ; an undoped GaN guiding layer 8 ; a p-type AlGaN electron overflow suppression layer 9 , a p-type AlGaN cladding layer 10 , and a p-type GaN contact layer 11.
1. A semiconductor laser device comprising:
a substrate;
a current-blocking layer which has an opening and is formed above said substrate, said current-blocking layer being one of a p-type layer and a semi-insulating layer;
an n-type semiconductor layer formed at least in the opening; and
a light-emitting layer formed above said current-blocking layer,
wherein the top surface of said semiconductor layer is substantially flat, and
said light-emitting layer is formed on said semiconductor layer, contacting with said semiconductor layer.
2. The semiconductor laser device according to claim 1 ,
wherein the top surface of said semiconductor layer is planar, and
said light-emitting layer is formed on said semiconductor layer, contacting with said semiconductor layer.
3. The semiconductor laser device according to claim 2 ,
wherein said current-blocking layer has a smaller refractive index than said semiconductor layer.
4. The semiconductor laser device according to claim 3 ,
wherein said current-blocking layer has an area into which two or more types of impurities are doped.
5. The semiconductor laser device according to claim 4 ,
wherein said current-blocking layer is made up of layers which have compositions that are different from each other.
6. The semiconductor laser device according to claim 5 ,
wherein said semiconductor layer includes:
a first semiconductor layer; and
a second semiconductor layer formed on said first semiconductor layer, contacting with said first semiconductor layer,
said first semiconductor layer is formed between said current-blocking layer and said substrate,
said second semiconductor layer is formed between said current-blocking layer and said light-emitting layer, and is formed inside the opening, and
said first semiconductor layer has a higher impurity concentration on a side of said light-emitting layer than on a side of said substrate.
7. The semiconductor laser device according to claim 6 ,
wherein a composition of said first semiconductor layer is different from a composition of said second semiconductor layer.
8. The semiconductor laser device according to claim 7 ,
wherein impurity concentrations of said first semiconductor layer and said second semiconductor layer reach a peak at an interface between said first and second semiconductor layers.
9. The semiconductor laser device according to claim 8 ,
wherein said light-emitting layer and said semiconductor layer are made of a compound semiconductor including nitrogen.
10. The semiconductor laser device according to claim 9 ,
wherein said current-blocking layer is doped with magnesium.
11. The semiconductor laser device according to claim 10 ,
wherein a concentration of the magnesium in said current-blocking layer is 1×10 19 cm −3 or less.
12. The semiconductor laser device according to claim 11 ,
wherein said semiconductor layer is made of GaN.
13. The semiconductor laser device according to claim 12 ,
wherein said light-emitting layer is made of InGaAlN, and
said light-emitting layer has a larger Al composition in an area positioned above said current-blocking layer than in an area positioned above the opening.
14. The semiconductor laser device according to claim 13 ,
wherein said light-emitting layer has a smaller In composition in the area positioned above said current-blocking layer than in the area positioned above the opening.
15. The semiconductor laser device according to claim 8 ,
wherein said first semiconductor layer is made of In x Ga 1-x N, where 0≦x≦1, and
said second semiconductor layer is made of GaN.
16. The semiconductor laser device according to claim 5 ,
wherein said current-blocking layer is made up of a first Al x Ga 1-x N layer and a second Al y Ga 1-y N layer formed on the first Al x Ga 1-x N layer, where 0≦x≦1, 0≦y≦1 and x<y.
17. The semiconductor laser device according to claim 4 ,
wherein said current-blocking layer is made of Al x Ga 1-x N layer, where 0≦x≦1.
18. The semiconductor laser device according to claim 1 , wherein said semiconductor layer functions as a cladding layer, and said semiconductor laser device further comprises
a light-guiding layer formed between said light-emitting layer and said cladding layer, said light-guiding layer being made of In x Ga 1-x N, where 0≦x≦1.
19. The semiconductor laser device according to claim 18 ,
wherein said light-guiding layer has a periodic structure in which InGaN and GaN are periodically arranged.
20. The semiconductor laser device according to claim 1 ,
wherein the top surface of said semiconductor layer is free of steps and asperities.
21. A semiconductor laser device comprising:
a substrate;
a current-blocking layer which has an opening and is formed above said substrate, said current-blocking layer being one of a p-type layer and a semi-insulating layer;
an n-type semiconductor layer formed at least in the opening; and
a light-emitting layer formed above said current-blocking layer,
wherein said semiconductor layer comprises:
a first semiconductor layer; and
a second semiconductor layer formed on said first semiconductor layer, contacting with said first semiconductor layer,
said first semiconductor layer is formed between said current-blocking layer and said substrate,
said semiconductor layer is formed between said current-blocking layer and said light-emitting layer, and is formed inside the opening, and
said first semiconductor layer has a higher impurity concentration on a side of said light-emitting layer than on a side of said substrate.