GROUP-III NITRIDE SEMICONDUCTOR LASER DEVICE, AND METHOD OF FABRICATING GROUP-III NITRIDE SEMICONDUCTOR LASER DEVICE

• US 20110158275A1
• Filed: 07/15/2010
• Published: 06/30/2011
• Est. Priority Date: 12/25/2009
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: KATAYAMA, Koji, YOSHIZUMI, Yusuke, UENO, Masaki, IKEGAMI, Takatoshi, TAKAGI, Shimpei
• Granted Patent: US 8,265,113 B2
• Time in Patent Office: Days
• US Class Current: 372/44.011
• CPC Class Codes: H01S 2301/14 Semiconductor lasers with special structural design for lasing in a specific polarisation mode
• CPC Class Codes: H01S 5/0014 Measuring characteristics or properties thereof measuring techniques per se G01J, G01K, G01N, G01R
• CPC Class Codes: H01S 5/0202 Cleaving
• CPC Class Codes: H01S 5/028 Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
• CPC Class Codes: H01S 5/04254 characterised by the shape
• CPC Class Codes: H01S 5/1085 Oblique facets
• CPC Class Codes: H01S 5/16 Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface H01S5/14 takes precedence
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/2201 in a specific crystallographic orientation
• CPC Class Codes: H01S 5/320275 semi-polar orientation

Abstract

In a III-nitride semiconductor laser device, a laser structure includes a support base comprised of a hexagonal III-nitride semiconductor and having a semipolar primary surface, and a semiconductor region provided on the semipolar primary surface of the support base. An electrode is provided on the semiconductor region of the laser structure.

Claims

1. A III-nitride semiconductor laser device comprising:

a laser structure including a support base and a semiconductor region, the support base being comprised of a hexagonal III-nitride semiconductor and having a semipolar primary surface, and the semiconductor region being provided on the semipolar primary surface of the support base; and

an electrode provided on the semiconductor region of the laser structure,

the semiconductor region comprising a first cladding layer comprised of a first conductivity type GaN-based semiconductor, a second cladding layer being comprised of a second conductivity type GaN-based semiconductor, and an active layer provided between the first cladding layer and the second cladding layer,

the first cladding layer, the second cladding layer, and the active layer being arranged along an axis normal to the semipolar primary surface,

the active layer comprising a GaN-based semiconductor layer,

a c-axis of the hexagonal III-nitride semiconductor of the support base being inclined at an angle CALPHA with respect to the normal axis toward an m-axis of the hexagonal III-nitride semiconductor,

the laser structure comprising first and second fractured faces, the first and second fractured faces intersecting with an m-n plane defined by the normal axis and the m-axis of the hexagonal III-nitride semiconductor,

a laser cavity of the III-nitride semiconductor laser device comprising the first and second fractured faces,

the laser structure comprising first and second surfaces, and the first surface being opposite to the second surface,

each of the first and second fractured faces extending from an edge of the first surface to an edge of the second surface, and

the angle being in one of a range of not less than 45 degrees and not more than 80 degrees and a range of not less than 100 degrees and not more than 135 degrees,

the laser structure comprising a laser waveguide on the semipolar primary surface of the support base, the laser waveguide extending in a direction of a waveguide vector, and the waveguide vector extending in a direction from one of the first and second fractured faces to another of the first and second fractured faces,

the first fractured face making an angle β

with a reference plane perpendicular to the waveguide vector in a first plane, the first plane being perpendicular to the m-n plane, and the angle β

being defined on an end face of the support base in the first fractured face,

the first fractured face making an angle α

with a reference plane perpendicular to the waveguide vector in a second plane, the second plane being perpendicular to the m-n plane, and the angle α

being defined on an end face of the active layer in the first fractured face,

the angle α

being different from the angle β

, a sign of the angle α

being the same as that of the angle β

, and a difference between the angle α and

the angle β

being not less than 0.1 degrees.

2. The III-nitride semiconductor laser device according to claim 1, wherein the angle β

is greater than that of the angle α

.

3. The III-nitride semiconductor laser device according to claim 1, wherein the waveguide vector makes an angle of not less than 0.1 degrees with a normal vector of an a-n plane defined by the normal axis and an a-axis of the hexagonal III-nitride semiconductor.

4. The III-nitride semiconductor laser device according to claim 1, wherein the angle α

is not more than 0.5 degrees.

5. The III-nitride semiconductor laser device according to claim 1, wherein a thickness of the support base is not more than 400 μ

m.

6. The III-nitride semiconductor laser device according to claim 1, wherein a thickness of the support base is not less than 50 μ

m and not more than 100 μ

M.

7. The III-nitride semiconductor laser device according to claim 1, wherein laser light from the active layer is polarized in a direction of an a-axis of the hexagonal III-nitride semiconductor.

8. The III-nitride semiconductor laser device according to claim 1, wherein light in an LED mode of the III-nitride semiconductor laser device includes a polarization component I1 in a direction of an a-axis of the hexagonal III-nitride semiconductor, and a polarization component I2 in a direction of the c-axis projected onto the primary surface, and the polarization component I1 is greater than the polarization component I2.

9. The III-nitride semiconductor laser device according to claim 1, wherein the angle between the normal axis and the c-axis of the hexagonal III-nitride semiconductor is in one of a range of not less than 63 degrees and not more than 80 degrees and a range of not less than 100 degrees and not more than 117 degrees.

10. The III-nitride semiconductor laser device according to claim 1, wherein the semipolar primary surface is a surface with a slight slant in a range of not less than −

4 degrees and not more than +4 degrees with respect to any one semipolar plane of a {20-21} plane, a {10-11} plane, a {20-2-1} plane, and a {10-1-1} plane.

11. The III-nitride semiconductor laser device according to claim 1, wherein the semipolar primary surface is one of a {20-21} plane, a {10-11} plane, a {20-2-1} plane, and a {10-1-1} plane.

12. The III-nitride semiconductor laser device according to claim 1, wherein a stacking fault density of the support base is not more than 1×

10⁴ cm<sup>−

1</sup>.

13. The III-nitride semiconductor laser device according to claim 1, wherein the support base can be comprised of any one of GaN, AlGaN, AlN, InGaN, and InAlGaN.

14. The III-nitride semiconductor laser device according to claim 1, further comprising a dielectric multilayer film provided on at least one of the first and second fractured faces.

15. The III-nitride semiconductor laser device according to claim 1, wherein the active layer includes a light emitting region provided so as to generate light at a wavelength of not less than 360 nm and not more than 600 nm.

16. The III-nitride semiconductor laser device according to claim 1, wherein the active layer includes a quantum well structure provided so as to generate light at a wavelength of not less than 430 nm and not more than 550 nm.

17. The III-nitride semiconductor laser device according to claim 1,

wherein an end face of the support base and an end face of the semiconductor region are exposed in each of the first and second fractured faces, and

wherein an angle between an end face of the active layer in the semiconductor region and a reference plane perpendicular to the m-axis of the support base of the hexagonal nitride semiconductor is in a range of not less than (CALPHA−

5) degrees and not more than (CALPHA+5) degrees on a first plane defined by the c-axis and the m-axis of the group-III nitride semiconductor.

18. The III-nitride semiconductor laser device according to claim 1, wherein the laser structure has a ridge structure.

19. A method of fabricating a III-nitride semiconductor laser device, the method comprising the steps of:

preparing a substrate comprised of a hexagonal III-nitride semiconductor and having a semipolar primary surface;

forming a substrate product having a laser structure, an anode electrode and a cathode electrode, the laser structure including a substrate and a semiconductor region formed on the semipolar primary surface;

scribing a first surface of the substrate product in part in a direction of an a-axis of the hexagonal III-nitride semiconductor; and

carrying out breakup of the substrate product by press against a second surface of the substrate product, to form another substrate product and a laser bar,

the first surface being opposite to the second surface,

the semiconductor region being located between the second surface and the substrate,

the laser bar having first and second end faces, the first and second end faces extending from the first surface to the second surface, and the first and second end faces being made by the breakup,

the first and second end faces constituting a laser cavity of the III-nitride semiconductor laser device,

the anode electrode and the cathode electrode being formed on the laser structure,

the semiconductor region comprising a first cladding layer comprised of a first conductivity type GaN-based semiconductor, a second cladding layer comprised of a second conductivity type GaN-based semiconductor, and an active layer provided between the first cladding layer and the second cladding layer,

the first cladding layer, the second cladding layer, and the active layer being arranged along an axis normal to the semipolar primary surface,

the active layer comprising a GaN-based semiconductor layer,

a c-axis of the hexagonal III-nitride semiconductor of the substrate being inclined at an angle CALPHA with respect to the normal axis toward an m-axis of the hexagonal III-nitride semiconductor,

the first and second end faces intersecting with an m-n plane defined by the normal axis and the m-axis of the hexagonal III-nitride semiconductor,

the angle being in one of a range of not less than 45 degrees and not more than 80 degrees and a range of not less than 100 degrees and not more than 135 degrees,

the laser structure comprising a laser waveguide on the semipolar primary surface of the support base, the laser waveguide extending in a direction of a waveguide vector, and the waveguide vector extending in a direction from one of the first and second end faces to another of the first and second end faces,

the first end face making an angle β

with a reference plane perpendicular to the waveguide vector in a first plane, the first plane being perpendicular to the m-n plane, and the angle β

being defined on an end face of the support base in the first end face,

the first end face making an angle α

with the reference plane in a second plane, the second plane being perpendicular to the m-n plane, and the angle α

being defined on an end face of the active layer in the first end face,

the angle α

being different from the angle β

, a sign of the angle α

being the same as that of the angle β

, and a difference between the angle α and

the angle β

, being not less than 0.1 degrees.

20. The method according to claim 19, wherein the angle β

is greater than that of the angle α

.

21. The method according to claim 19, wherein the waveguide vector makes an angle of not less than 0.1 degrees with a normal vector of an a-n plane defined by the normal axis and an a-axis of the hexagonal III-nitride semiconductor.

22. The method according to claim 19, wherein the angle CALPHA is in one of a range of not less than 63 degrees and not more than 80 degrees and a range of not less than 100 degrees and not more than 117 degrees.

23. The method according to claim 19, wherein in the step of forming the substrate product, processing, such as slicing or grinding of the substrate, is performed such that a thickness of the substrate becomes not more than 400 μ

m, and the second surface is composed of one of a processed surface made by the processing and a surface including an electrode formed on the processed surface.

24. The method according to claim 19, wherein in the step of forming the substrate product, the substrate is polished such that the substrate has a thickness of not less than 50 μ

m and not more than 100 μ

m, and the second surface is composed of one of a polished surface made by the polishing and a surface including an electrode formed on the polished surface.

25. The method according to claim 19, wherein an end face of the active layer in each of the first and second end faces makes an angle in a range of not less than (CALPHA−

5) degrees and not more than (CALPHA+5) degrees with respect to a reference plane perpendicular to the m-axis of the substrate of the hexagonal nitride semiconductor, and the angle is defined on a plane defined by the c-axis and the m-axis of the hexagonal III-nitride semiconductor.

26. The method according to claim 19, wherein the substrate is comprised of any one of GaN, AlGaN, AlN, InGaN and InAlGaN.