III-Nitride semiconductor laser device, and method of fabricating the III-Nitride semiconductor laser device

Abstract

In a III-nitride semiconductor laser device, a laser structure includes a support base with a semipolar primary surface comprised of a III-nitride semiconductor, and a semiconductor region provided on the semipolar primary surface of the support base. First and second dielectric multilayer films for an optical cavity of the nitride semiconductor laser device are provided on first and second end faces of the semiconductor region, respectively. The semiconductor region includes a first cladding layer of a first conductivity type gallium nitride-based semiconductor, a second cladding layer of a second conductivity type gallium nitride-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 are arranged in an axis normal to the semipolar primary surface. A c+ axis vector indicating a direction of the <0001> axis of the III-nitride semiconductor of the support base is inclined at an angle in the range of not less than 45 degrees and not more than 80 degrees or in the range of not less than 100 degrees and not more than 135 degrees toward a direction of any one crystal axis of the m- and a-axes of the III-nitride semiconductor with respect to a normal vector indicating a direction of the normal axis. The first and second end faces intersect with a reference plane defined by the normal axis and the one crystal axis of the hexagonal III-nitride semiconductor. The c+ axis vector makes an acute angle with a waveguide vector indicating a direction from the second end face to the first end face. A thickness of the second dielectric multilayer film is smaller than a thickness of the first dielectric multilayer film.

1 . A III-nitride semiconductor laser device comprising:
 a laser structure comprising a support base and a semiconductor region, the support base having a semipolar primary surface of a III-nitride semiconductor, and the semiconductor region being provided on the semipolar primary surface of the support base; and   first and second dielectric multilayer films for an optical cavity of the nitride semiconductor laser device, the first and second dielectric multilayer films being provided on first and second end faces of the semiconductor region, respectively,   the semiconductor region including a first cladding layer of a first conductivity type gallium nitride-based semiconductor, a second cladding layer of a second conductivity type gallium nitride-based semiconductor, and an active layer, and the an active layer being 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 in a normal axis to the semipolar primary surface,   the active layer comprising a gallium nitride-based semiconductor layer,   a c+ axis vector being inclined at an angle in a range of not less than 45 degrees and not more than 80 degrees and of not less than 100 degrees and not more than 135 degrees toward a direction of any one crystal axis of m- and a-axes of the III-nitride semiconductor with respect to a normal vector, the c+ axis vector indicating a direction of a <0001> axis of the III-nitride semiconductor of the support base, and the normal vector indicating a direction of the normal axis,   the first and second end faces intersecting with a reference plane, the reference plane being defined by the normal axis and the one crystal axis of the hexagonal III-nitride semiconductor,   the c+ axis vector making an acute angle with a waveguide vector, and the waveguide vector indicating a direction from the second end face to the first end face, and   a thickness of the second dielectric multilayer film being smaller than a thickness of the first dielectric multilayer film.   
     
     
         2 . The III-nitride semiconductor laser device according to  claim 1 , wherein the laser structure comprises first and second surfaces, and the first surface is opposite to the second surface,
 wherein the semiconductor region is located between the first surface and the support base, and   wherein each of the first and second end faces is included in a fractured face, and the fractured face extends from an edge of the first surface to an edge of the second surface.   
     
     
         3 . The III-nitride semiconductor laser device according to  claim 1 , wherein the c-axis of the III-nitride semiconductor is inclined toward the direction of the m-axis of the nitride semiconductor. 
     
     
         4 . The III-nitride semiconductor laser device according to  claim 1 , wherein the primary surface of the support base is inclined in the range of not less than −4 degrees and not more than +4 degrees with respect to any one of {10-11}, {20-21}, {20-2-1}, and {10-1-1} planes. 
     
     
         5 . The III-nitride semiconductor laser device according to  claim 1 , wherein the c-axis of the III-nitride semiconductor is inclined toward the direction of the a-axis of the nitride semiconductor. 
     
     
         6 . The III-nitride semiconductor laser device according to  claim 1 , wherein the primary surface of the support base is inclined in the range of not less than −4 degrees and not more than +4 degrees from any one of {11-22}, {11-21}, {11-2-1}, and {11-2-2} planes. 
     
     
         7 . The III-nitride semiconductor laser device according to  claim 1 , wherein the active layer comprises a well layer of a strained gallium nitride-based semiconductor, and the strained gallium nitride-based semiconductor containing indium as a constituent element. 
     
     
         8 . The III-nitride semiconductor laser device according to  claim 1 , wherein the active layer is provided to generate a laser beam having a wavelength in a range of 430 nm to 550 nm. 
     
     
         9 . The III-nitride semiconductor laser device according to  claim 1 , wherein the III-nitride semiconductor comprises GaN. 
     
     
         10 . The III-nitride semiconductor laser device according to  claim 1 , wherein the first dielectric multilayer film has a dielectric layer, and the dielectric layer in the first dielectric multilayer film is comprised of at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, titanium nitride, titanium oxynitride, zirconium oxide, zirconium nitride, zirconium oxynitride, zirconium fluoride, tantalum oxide, tantalum nitride, tantalum oxynitride, hafnium oxide, hafnium nitride, hafnium oxynitride, hafnium fluoride, aluminum oxide, aluminum nitride, aluminum oxynitride, magnesium fluoride, magnesium oxide, magnesium nitride, magnesium oxynitride, calcium fluoride, barium fluoride, cerium fluoride, antimony oxide, bismuth oxide, and gadolinium oxide, and
 wherein the second dielectric multilayer film has a dielectric layer, and the dielectric layer in the second dielectric multilayer film is comprised of at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, titanium nitride, titanium oxynitride, zirconium oxide, zirconium nitride, zirconium oxynitride, zirconium fluoride, tantalum oxide, tantalum nitride, tantalum oxynitride, hafnium oxide, hafnium nitride, hafnium oxynitride, hafnium fluoride, aluminum oxide, aluminum nitride, aluminum oxynitride, magnesium fluoride, magnesium oxide, magnesium nitride, magnesium oxynitride, calcium fluoride, barium fluoride, cerium fluoride, antimony oxide, bismuth oxide, and gadolinium oxide.   
     
     
         11 . A method of fabricating a III-nitride semiconductor laser device, comprising the steps of:
 preparing a substrate with a semipolar primary surface, the semipolar primary surface comprising a hexagonal III-nitride semiconductor;   forming a substrate product having a laser structure, an anode electrode, and a cathode electrode, the laser structure comprising a substrate and a semiconductor region, and the semiconductor region being formed on the semipolar primary surface;   after forming the substrate product, forming first and second end faces; and   forming first and second dielectric multilayer films for an optical cavity of the nitride semiconductor laser device on the first and second end faces, respectively,   the first and second end faces intersecting with a reference plane, the reference plane being defined by a normal axis to the semipolar primary surface and any one crystal axis of a- and m-axes of the hexagonal III-nitride semiconductor,   the semiconductor region comprising a first cladding layer of a first conductivity type gallium nitride-based semiconductor, a second cladding layer of a second conductivity type gallium nitride-based semiconductor, and an active layer, and the active layer being 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 in a direction of the normal axis,   the active layer comprising a gallium nitride-based semiconductor layer,   the semipolar primary surface of the substrate being inclined at an angle in a range of not less than 45 degrees and not more than 80 degrees and of not less than 100 degrees and not more than 135 degrees with respect to a plane perpendicular to a c+ axis vector, and the c+ axis vector indicating a direction of the <0001> axis of the nitride semiconductor,   the c+ axis vector making an acute angle with a waveguide vector, and the waveguide vector indicating a direction from the second end face to the first end face, and   a thickness of the second dielectric multilayer film being smaller than a thickness of the first dielectric multilayer film.   
     
     
         12 . The method according to  claim 11 , further comprising a step of, prior to forming the first and second dielectric multilayer films, determining plane orientations of the first and second end faces. 
     
     
         13 . The method according to  claim 11 , wherein the step of forming the first and second end faces comprises the steps of:
 scribing a first surface of the substrate product; and   breaking the substrate product by press against a second surface of the substrate product to form a laser bar having the first and second end faces,   the first and second end faces of the laser bar being formed by the breaking,   the first surface being opposite to the second surface,   the semiconductor region being provided between the first surface and the substrate, and   each of the first and second end faces of the laser bar being included in a fractured face, and the fractured face extending from the first surface to the second surface and being formed by the breaking.   
     
     
         14 . The method according to  claim 11 , wherein a c-axis of the III-nitride semiconductor is inclined toward a direction of the m-axis of the nitride semiconductor. 
     
     
         15 . The method according to  claim 11 , wherein the primary surface of the substrate is inclined in a range of not less than −4 degrees and not more than +4 degrees with respect to any one of {10-11}, {20-21}, {20-2-1}, and {10-1-1} planes. 
     
     
         16 . The method according to  claim 11 , wherein a c-axis of the III-nitride semiconductor is inclined toward a direction of an a-axis of the nitride semiconductor. 
     
     
         17 . The method according to  claim 11 , wherein the primary surface of the substrate is inclined in the range of not less than −4 degrees and not more than +4 degrees from any one of {11-22}, {11-21}, {11-2-1}, and {11-2-2} planes. 
     
     
         18 . The method according to  claim 11 , wherein formation of the active layer comprises a step of growing a well layer of a strained gallium nitride-based semiconductor, and the strained gallium nitride-based semiconductor contains indium as a constituent element. 
     
     
         19 . The method according to  claim 11 , wherein the active layer is provided to generate light at a wavelength of 430-550 nm. 
     
     
         20 . The method according to  claim 11 , wherein the III-nitride semiconductor comprises GaN. 
     
     
         21 . The method according to  claim 11 , wherein the first dielectric multilayer film has a dielectric layer, and the a dielectric layer in the first dielectric multilayer film is formed using at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, titanium nitride, titanium oxynitride, zirconium oxide, zirconium nitride, zirconium oxynitride, zirconium fluoride, tantalum oxide, tantalum nitride, tantalum oxynitride, hafnium oxide, hafnium nitride, hafnium oxynitride, hafnium fluoride, aluminum oxide, aluminum nitride, aluminum oxynitride, magnesium fluoride, magnesium oxide, magnesium nitride, magnesium oxynitride, calcium fluoride, barium fluoride, cerium fluoride, antimony oxide, bismuth oxide, and gadolinium oxide, and
 wherein the second dielectric multilayer film has a dielectric layer, and the dielectric layer in the second dielectric multilayer film is formed using at least one selected from silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, titanium nitride, titanium oxynitride, zirconium oxide, zirconium nitride, zirconium oxynitride, zirconium fluoride, tantalum oxide, tantalum nitride, tantalum oxynitride, hafnium oxide, hafnium nitride, hafnium oxynitride, hafnium fluoride, aluminum oxide, aluminum nitride, aluminum oxynitride, magnesium fluoride, magnesium oxide, magnesium nitride, magnesium oxynitride, calcium fluoride, barium fluoride, cerium fluoride, antimony oxide, bismuth oxide, and gadolinium oxide.