GALLIUM NITRIDE-BASED COMPOUND SEMICONDUCTOR LIGHT-EMITTING DEVICE AND LIGHT SOURCE APPARATUS USING THE DEVICE
A gallium nitride-based compound semiconductor light-emitting device formed of nitride semiconductor expressed by a general expression Al x In y Ga z N, where 0≦x<1, 0<y<1, 0<z<1, and x+y+z=1. The device includes a light-emitting layer having a growth surface of a non-polar plane or a semi-polar plane. A growth surface of the nitride semiconductor has two anisotropic axes. An In composition of the nitride semiconductor has distribution changing along a first axis of the two axes. An interface between a region with a low In composition and a region with a high In composition is inclined from a plane perpendicular to the first axis toward the growth surface of the nitride semiconductor.
1 . A gallium nitride-based compound semiconductor light-emitting device formed of nitride semiconductor expressed by a general expression Al x In y Ga z N, where 0≦x<1, 0<y<1, 0<z<1, and x+y+z=1, the device comprising:
a light-emitting layer having a growth surface of a non-polar plane or a semi-polar plane, wherein
a growth surface of the nitride semiconductor has two anisotropic axes,
an In composition of the nitride semiconductor has distribution changing along a first axis of the two axes,
an interface between a region with a low In composition and a region with a high In composition is inclined from a plane perpendicular to the first axis toward the growth surface of the nitride semiconductor, and
the region with the low In composition is formed along a slip plane to include the slip plane.
2 . The device of claim 1 , wherein
the In composition of the nitride semiconductor is uniform along a second axis of the two axes.
3 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor has a plurality of steps along an m-plane.
4 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor is an m-plane,
the first axis is along an a-axis direction, and
the second axis is along a c-axis direction.
5 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor is the semi-polar plane, and
the first axis is along one of the two axes, which has a component of a c-axis direction.
6 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor is a (11-22) plane,
the first axis is along a [-1-123] axis direction, and
the second axis is along an m-axis direction.
7 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor is a (20-21) plane,
the first axis is along a [10-1-4] axis direction, and
the second axis is along an a-axis direction.
8 . The device of claim 1 , wherein
the growth surface of the nitride semiconductor is a (1-102) plane,
the first axis is along a [1-101] axis direction, and
the second axis is along an a-axis direction.
9 . A gallium nitride-based compound semiconductor light-emitting device formed of nitride semiconductor expressed by a general expression Al x In y Ga z N, where 0≦x<1, 0<y<1, 0<z<1, and x+y+z=1, the device comprising:
a light-emitting layer having a growth surface of a non-polar plane or a semi-polar plane, wherein
the growth surface of the nitride semiconductor is an m-plane, and has two anisotropic axes,
a first axis of the two axes is along an a-axis direction,
a second axis of the two axes is along a c-axis direction,
an In composition of the nitride semiconductor has distribution changing along the first axis of the two axes, and
an interface between a region with a low In composition and a region with a high In composition is inclined from a plane perpendicular to the first axis toward the growth surface of the nitride semiconductor.
10 . A gallium nitride-based compound semiconductor light-emitting device formed of nitride semiconductor expressed by a general expression Al x In y Ga z N, where 0≦x<1, 0<y<1, 0<z<1, and x+y+z=1, the device comprising:
a light-emitting layer having a growth surface of a non-polar plane or a semi-polar plane, wherein
the growth surface of the nitride semiconductor is an m-plane, and has two anisotropic axes,
a first axis of the two axes is along an a-axis direction,
a second axis of the two axes is along a c-axis direction,
the nitride semiconductor includes a low In concentration region having an In concentration lower than a high In concentration region contributing to light emission, and
the low In concentration region is inclined along the first axis, and is in a band-like shape extending along the second axis.
11 . The device of claim 1 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not higher than 80% of the In composition of the region with the high In composition.
12 . The device of claim 10 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not higher than 80% of the In composition of the region with the high In composition.
13 . The device of claim 11 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not higher than 80% of the In composition of the region with the high In composition.
14 . The device of claim 1 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not less than 50% and not more than 80% of the In composition of the region with the high In composition.
15 . The device of claim 10 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not less than 50% and not more than 80% of the In composition of the region with the high In composition.
16 . The device of claim 11 , wherein
the In composition of the region with the low In concentration of the nitride semiconductor is not less than 50% and not more than 80% of the In composition of the region with the high In composition.
17 . The device of claim 1 , wherein
the light-emitting layer is at least one quantum well layer.
18 . The device of claim 10 , wherein
the light-emitting layer is at least one quantum well layer.
19 . The device of claim 11 , wherein
the light-emitting layer is at least one quantum well layer.
20 . The device of claim 18 , wherein
the quantum well layer has a thickness not less than 2 nm and not more than 20 nm.
21 . The device of claim 18 , wherein
the quantum well layer has a thickness not less than 6 nm and not more than 16 nm.
22 . The device of claim 1 , wherein
the region with the low In composition includes a plurality of regions each having the low In composition,
the low In concentration region includes a plurality of low In concentration regions,
a distance between a pair of the regions with the low In composition or between a pair of the low In concentration regions is not less than 10 nm and not more than 100 nm, and
a width of the region with the low In composition or a width of the low In concentration region is not less than 1 nm and not more than 20 nm.
23 . The device of claim 10 , wherein
the region with the low In composition includes a plurality of regions with the low In composition,
the low In concentration region includes a plurality of low In concentration regions,
a distance between a pair of the regions with the low In composition or between a pair of the low In concentration regions is not less than 10 nm and not more than 100 nm, and
a width of the region with the low In composition or a width of the low In concentration region is not less than 1 nm and not more than 20 nm.
24 . The device of claim 11 , wherein
the region with the low In composition includes a plurality of regions with the low In composition,
the low In concentration region includes a plurality of low In concentration regions,
a distance between a pair of the regions with the low In composition or between a pair of the low In concentration regions is not less than 10 nm and not more than 100 nm, and
a width of the region with the low In composition or a width of the low In concentration region is not less than 1 nm and not more than 20 nm.
25 . A light source apparatus comprising:
the gallium nitride-based compound semiconductor light-emitting device of claim 1 ; and
a wavelength converter including a fluorescent member converting a wavelength of light irradiated from the gallium nitride-based compound semiconductor light-emitting device.
26 . A light source apparatus comprising:
the gallium nitride-based compound semiconductor light-emitting device of claim 10 ; and
a wavelength converter including a fluorescent member converting a wavelength of light irradiated from the gallium nitride-based compound semiconductor light-emitting device.
27 . A light source apparatus comprising:
the gallium nitride-based compound semiconductor light-emitting device of claim 11 ; and
a wavelength converter including a fluorescent member converting a wavelength of light irradiated from the gallium nitride-based compound semiconductor light-emitting device.
28 . The device of claim 1 , wherein the region with the low In composition or the region with the high In composition has a fine line structure extending along the second axis of the two axes in a cross-section parallel to the second axis.