GROUP III NITRIDE SEMICONDUCTOR LASER

• US 20100189148A1
• Filed: 02/17/2009
• Published: 07/29/2010
• Est. Priority Date: 02/25/2008
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Kyono, Takashi, Akita, Katsushi, Yoshizumi, Yusuke
• Granted Patent: US 7,949,026 B2
• Time in Patent Office: Days
• US Class Current: 372/45.10
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 2304/04 MOCVD or MOVPE
• CPC Class Codes: H01S 5/320275 semi-polar orientation
• CPC Class Codes: H01S 5/3211 characterised by special cladding layers, e.g. details on band-discontinuities
• CPC Class Codes: H01S 5/3215 graded composition cladding layers
• CPC Class Codes: H01S 5/3407 characterised by special barrier layers
• 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 group III nitride semiconductor laser is provided that has a good optical confinement property and includes an InGaN well layer having good crystal quality.

An active layer 19 is provided between a first optical guiding layer 21 and a second optical guiding layer 23. The active layer 19 can include well layers 27a, 27b, and 27c and further includes at least one first barrier layer 29a provided between the well layers. The first and second optical guiding layers 21 and 23 respectively include first and second InGaN regions 21a and 23a smaller than the band gap E₂₉ of the first barrier layer 29a, and hence the average refractive index n_GUIDE of the first and second optical guiding layers 21 and 23 can be made larger than the refractive index n₂₉ of the first barrier layer 29a. Thus, good optical confinement is achieved. The band gap E₂₉ of the first barrier layer 29a is larger than the band gaps E₂₁ and E₂₃ of the first and second InGaN regions 21a and 23a.

Claims

1. A group III nitride semiconductor laser comprising:

a substrate having a main surface;

an n-type cladding layer provided on the substrate and composed of a group III nitride semiconductor;

a p-type cladding layer provided on the substrate and composed of a group III nitride semiconductor;

an active layer provided between the n-type cladding layer and the p-type cladding layer;

a first optical guiding layer provided between the n-type cladding layer and the active layer; and

a second optical guiding layer provided between the p-type cladding layer and the active layer,

wherein the active layer includes a plurality of well layers and at least one first barrier layer provided between the well layers,

the first optical guiding layer includes a first InGaN region composed of InGaN that has a band gap smaller than a band gap of the first barrier layer and larger than a band gap of the well layers,

the second optical guiding layer includes a second InGaN region that is composed of InGaN,

among the well layers of the active layer, a well layer that is closest to the first optical guiding layer is a first well layer,

among the well layers of the active layer, a well layer that is closest to the second optical guiding layer is a second well layer, and

the active layer includes a second barrier layer provided between the first well layer and the first optical guiding layer, and a third barrier layer provided between the second well layer and the second optical guiding layer.

2. The group III nitride semiconductor laser according to claim 1, wherein

the second InGaN region is composed of InGaN that has a band gap smaller than the band gap of the first barrier layer and larger than the band gap of the well layers;

the second barrier layer includes a portion having a band gap larger than the band gap of the first InGaN region; and

the third barrier layer includes a portion having a band gap larger than a band gap of the second InGaN region.

3. The group III nitride semiconductor laser according to claim 1, wherein the first barrier layer is composed of a gallium nitride-based semiconductor, and the second and third barrier layers are composed of the gallium nitride-based semiconductor.

4. The group III nitride semiconductor laser according to claim 1, wherein

the second optical guiding layer further includes a third InGaN region provided between the third barrier layer and the second InGaN region, and

the third InGaN region has an indium composition that increases in a direction from the third barrier layer to the second InGaN region.

5. The group III nitride semiconductor laser according to claim 4, wherein

the third barrier layer includes an InGaN region, and

the InGaN region of the third barrier layer has an indium composition that increases in a direction from the second well layer to the second InGaN region.

6. The group III nitride semiconductor laser according to claim 1, wherein

the second optical guiding layer further includes a fourth InGaN region provided between the second InGaN region and the p-type cladding layer, and

the fourth InGaN region has an indium composition that decreases from the second InGaN region toward the p-type cladding layer.

7. The group III nitride semiconductor laser according to claim 1, wherein

the first optical guiding layer further includes a fifth InGaN region provided between the second barrier layer and the first InGaN region, and

the fifth InGaN region has an indium composition that increases in a direction from the second barrier layer to the first InGaN region.

8. The group III nitride semiconductor laser according to claim 7, wherein

the second barrier layer includes an InGaN region, and

the InGaN region of the second barrier layer has an indium composition that increases in a direction from the first well layer to the first InGaN region.

9. The group III nitride semiconductor laser according to claim 1, wherein

the first optical guiding layer further includes a sixth InGaN region provided between the first InGaN region and the n-type cladding layer, and

the sixth InGaN region has an indium composition that decreases in a direction from the first InGaN region to the n-type cladding layer.

10. The group III nitride semiconductor laser according to claim 1, wherein

the second barrier layer includes a portion having a band gap smaller than the band gap of the first InGaN region;

and

the third barrier layer includes a portion having a band gap smaller than a band gap of the second InGaN region.

11. The group III nitride semiconductor laser according to claim 10, wherein

the second optical guiding layer further includes a seventh InGaN region provided between the second InGaN region and the p-type cladding layer, and

the seventh InGaN region has an indium composition that decreases from the second InGaN region toward the p-type cladding layer.

12. The group III nitride semiconductor laser according to claim 10, wherein

the first optical guiding layer further includes an eighth InGaN region provided between the first InGaN region and the n-type cladding layer, and

the eighth InGaN region has an indium composition that decreases in a direction from the first InGaN region to the n-type cladding layer.

13. The group III nitride semiconductor laser according to claim 1, wherein the active layer includes a multiple quantum well structure provided such that the group III nitride semiconductor laser has a light-emitting wavelength in a wavelength region of 430 nm or more.

14. The group III nitride semiconductor laser according to claim 1, wherein

the first optical guiding layer has a thickness of 150 nm or less, and

the second optical guiding layer has a thickness of 150 nm or less.

15. The group III nitride semiconductor laser according to claim 1, wherein

the first InGaN region of the first optical guiding layer has an indium composition of 0.03 or more, and

the second InGaN region of the second optical guiding layer has an indium composition of 0.03 or more.

16. The group III nitride semiconductor laser according to claim 1, wherein

the first InGaN region of the first optical guiding layer has an indium composition of 0.12 or less, and

the second InGaN region of the second optical guiding layer has an indium composition of 0.12 or less.

17. The group III nitride semiconductor laser according to claim 1, wherein

the substrate is composed of a group III nitride semiconductor,

the main surface of the substrate is inclined at an angle of 1°

or more with respect to a c-plane of the group III nitride semiconductor, and

the main surface of the substrate is inclined at an angle of 50°

or less with respect to the c-plane of the group III nitride semiconductor.

18. The group III nitride semiconductor laser according to claim 17, wherein the main surface is inclined in a direction of an a-axis of the group III nitride semiconductor.

19. The group III nitride semiconductor laser according to claim 1, wherein the substrate is composed of GaN.

20. The group III nitride semiconductor laser according to claim 1, wherein the substrate is composed of InGaN.

21. A method for producing a group III nitride semiconductor laser, comprising:

a step of growing a first InGaN optical guiding layer on a first-conductivity-type cladding layer at a first temperature;

a step of growing a barrier layer after the first InGaN optical guiding layer is grown;

a step of growing an InGaN well layer after the barrier layer is grown;

a step of growing another barrier layer at a second temperature after the InGaN well layer is grown;

a step of growing another InGaN well layer after the another barrier layer is grown;

a step of growing still another barrier layer after the another InGaN well layer is grown; and

a step of growing a second InGaN optical guiding layer at a third temperature after the still another barrier layer is grown,

wherein the second temperature is higher than the first and third temperatures.