Patent ID: 8548021

Claim:
A III-nitride semiconductor laser, comprising: a semiconductor substrate comprising a hexagonal III-nitride semiconductor, the semiconductor substrate having a primary surface, the primary surface being inclined at an angle of inclination in a range of not less than 50 degrees and not more than 70 degrees toward either one of an a-axis direction and an m-axis direction of the III-nitride semiconductor with respect to a reference plane perpendicular to a reference axis, and the reference axis extending along a c-axis direction of the III-nitride semiconductor; a first cladding layer provided on the primary surface of the semiconductor substrate, the first cladding layer comprising a first conductivity type gallium nitride-based semiconductor; a second cladding layer provided on the primary surface of the semiconductor substrate, the second cladding layer comprising a second conductivity type gallium nitride-based semiconductor; an active layer provided between the first cladding layer and the second cladding layer, and an InGaN layer provided between the first cladding layer and the active layer, misfit dislocations being provided at an interface between the first cladding layer and the InGaN layer, wherein the misfit dislocations relax the InGaN layer and create variation in anisotropy of strain in the active layer, a waveguide direction in the active layer being directed along another of the a-axis direction and the m-axis direction, in an orthogonal coordinate system having an X1 axis direction along the waveguide direction, an X2 axis perpendicular to the X1 axis and an X3 axis perpendicular to the X1 axis and the X2 axis, the first cladding layer, the active layer, and the second cladding layer being arranged in a direction of the X3 axis, the active layer having a multiple quantum well structure, the multiple quantum well structure comprising well layers and barrier layers, the well layers and barrier layers being arranged alternately in the direction of the X3 axis, the well layers comprising InGaN, and the barrier layers comprising GaN, the multiple quantum well structure being provided such that at least either of thickness of the well layers and bandgap energy difference between the well layers and the barrier layers enables a polarization degree P in an LED mode of the III-nitride semiconductor laser to fall within a range of not less than −1 and not more than 0.1, and the polarization degree P being defined as follows: P=(|1−|1)/(|1+|2), where |1 indicates an electric field component of light in the LED mode in the X1 direction and |2 indicates an electric field component of light in the LED mode in the X2 direction, wherein the thickness of the well layers is not less than 2 nm and not more than 10 nm, and an indium composition of the well layers is not less than 0.1 and not more than 0.4.