Group-iii nitride semiconductor laser device, method of fabricating group-iii nitride semiconductor laser device, and epitaxial substrate

Abstract

A III-nitride semiconductor laser device is provided with a laser structure and an electrode. The laser structure includes a support base which comprises a hexagonal III-nitride semiconductor and has a semipolar primary surface, and a semiconductor region provided on the semipolar primary surface. The electrode is provided on the semiconductor region. The semiconductor region includes a first cladding layer of a first conductivity type GaN-based semiconductor, a second cladding layer of a second conductivity type GaN-based semiconductor, and an active layer provided between the first cladding layer and the second cladding layer. The laser structure includes first and second fractured faces intersecting with an m-n plane defined by the m-axis of the hexagonal III-nitride semiconductor and an axis normal to the semipolar primary surface. A laser cavity of the III-nitride semiconductor laser device includes the first and second fractured faces. An angle ALPHA between the normal axis and the c-axis of the hexagonal III-nitride semiconductor is 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. The laser structure includes a laser waveguide extending above the semipolar primary surface, and the laser waveguide extends in a direction of a waveguide vector directed from one to another of the first and second fractured faces. A c-axis vector indicating a direction of the c-axis of the hexagonal III-nitride semiconductor includes a projected component parallel to the semipolar primary surface and a vertical component parallel to the normal axis. An angle difference between the waveguide vector and the projected component is in the range of not less than −0.5 degrees and not more than +0.5 degrees.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a III-nitride semiconductor laser device, and a method of fabricating the III-nitride semiconductor laser device.[0003]2. Related Background Art[0004]Patent Literature 1 discloses a laser device. When a primary surface of a substrate is a face inclined at 28.1 degrees from a {0001} plane toward a direction equivalent to the [1-100] direction, secondary cleaved facets are {11-20} planes perpendicular to both of the primary surface and optical cavity faces, and the laser device is of a rectangular parallelepiped shape.[0005]Patent Literature 2 discloses a nitride semiconductor device. The back surface of the substrate for cleavage is polished to reduce the total thickness to about 100 μm. A dielectric multilayer film is deposited on cleaved facets.[0006]Patent Literature 3 discloses a nitride-based compound semiconductor device. The substrate used for the nitride-based compound semiconduct...

AI Technical Summary

Benefits of technology

[0020]It is an object of the present invention to provide a III-nitride semiconductor laser device with a laser cavity, enabling a low threshold current and a structure enabling improvement in lasing yield, on a semipolar plane of a support base inclined from the c-axis toward the m-axis of a hexagonal III-nitride, and to provide a method for fabricating the III-nitride semiconductor laser device. It is a further object of the present invention to provide an epitaxial substrate for the III-nitride semiconductor laser device.

[0062]By use of the slight slant surface from these typical semipolar planes, it is also feasible to provide the first and second end faces with flatness and perpendicularity enough to construct the laser cavity of the III-nitride semiconductor laser device, or without ion damage.

Problems solved by technology

However, this orientation of the laser waveguide does not allow use of the conventional cleaved facets such as c-planes, a-planes, or m-planes for the cavity mirrors.

It becomes a heavy burden to derive process conditions for obtaining good dry-etched facets in the current technical level.

However, when the laser waveguide extends in the inclination direction (off-axis direction) of the c-axis, it is not feasible to produce the cavity mirrors using the conventional cleaved facets.

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