GROUP III NITRIDE SEMICONDUCTOR SUBSTRATE AND MANUFACTURING METHOD OF THE SAME
A Group III nitride semiconductor substrate is provided, with diameter of 25 mm or more and thickness of 250 μm or more, wherein in at least an outer edge side part of an outer edge part within 5 mm from an outer edge of the group III nitride semiconductor substrate, stress within a main surface of the group III nitride semiconductor substrate works as a tensile stress, with the tensile stress becoming relatively greater compared to that of a center side part from the outer edge side part of the group III nitride semiconductor substrate.
1 . A Group III nitride semiconductor substrate with diameter of 25 mm or more and thickness of 250 μm or more, wherein in at least an outer edge side part of an outer edge part within 5 mm from an outer edge of the group III nitride semiconductor substrate, stress within a main surface of the group III nitride semiconductor substrate works as a tensile stress, with the tensile stress becoming relatively greater compared to that of a center side part from the outer edge side part of the group III nitride semiconductor substrate.
2 . The group III nitride semiconductor substrate according to claim 1 , wherein magnitude of the tensile stress of the outer edge side part is 30 MPa or more and 150 MPa or less.
3 . The group III nitride semiconductor substrate according to claim 1 , wherein the main surface is c-plane or an inclined surface inclined from the C-plane.
4 . The group III nitride semiconductor substrate according to claim 2 , wherein the main surface is c-plane or an inclined surface inclined from the c-plane.
5 . The group III nitride semiconductor substrate according to claim 1 , wherein the group III nitride semiconductor substrate is a GaN substrate.
6 . The group III nitride semiconductor substrate according to claim 2 , wherein the group III nitride semiconductor substrate is a GaN substrate.
7 . The group III nitride semiconductor substrate according to claim 3 , wherein the inclined surface is a surface inclined from the c-plane in an angle range of 10°.
8 . The group III nitride semiconductor substrate according to claim 1 , wherein thickness of the group III nitride semiconductor substrate is 1 mm or less.
9 . A manufacturing method of a group III nitride semiconductor substrate, comprising the steps of:
preparing a seed crystal substrate; and
supplying a raw material to the seed crystal substrate and crystal-growing thereon a group III nitride semiconductor layer,
wherein in the step of crystal-growing the group III nitride semiconductor layer on the seed crystal substrate, the group III nitride semiconductor layer crystal-grows on an outer peripheral part thereof while growth planes are formed so as to be inclined to a main surface of the seed crystal substrate at an angle larger than 0° and smaller than 90°, with a doping concentration of the group III nitride semiconductor layer of the outer peripheral part having the inclined growth planes, set to be higher than the doping concentration of the group III nitride semiconductor layer of a center side from the outer peripheral part.
10 . The manufacturing method of the group III nitride semiconductor substrate according to claim 9 , wherein Hydride Vapor Phase Epitaxy is used in crystal growth of the group III nitride semiconductor layer, and the crystal growth is carried out in an atmosphere where oxygen gas or oxygen compound gas exits.
11 . The manufacturing method of the group III nitride semiconductor substrate according to claim 10 , wherein the oxygen gas or the oxygen compound gas is supplied from outside of a growth furnace in which the crystal growth is carried out, or is generated by a reaction between a quartz member constituting the growth furnace and atmosphere gas in the growth furnace.
12 . The manufacturing method of the group III nitride semiconductor substrate according to claim 10 , wherein oxygen concentration added to the group III nitride semiconductor substrate of the outer peripheral part having the inclined growth planes, is 1×10 18 cm −3 or more and 5×10 20 cm −3 or less.
13 . The manufacturing method of the group III nitride semiconductor substrate according to claim 9 , comprising the step of grinding the outer peripheral part of the group III nitride semiconductor layer, after the step of crystal-growing the group III nitride semiconductor layer.
14 . The manufacturing method of the group III nitride semiconductor substrate according to claim 10 , comprising the step of grinding the outer peripheral part of the group III nitride semiconductor layer, after the step of crystal-growing the group III nitride semiconductor layer.
15 . The manufacturing method of the group III nitride semiconductor substrate according to claim 9 , wherein the group III nitride semiconductor layer is a GaN layer.
16 . The manufacturing method of the group III nitride semiconductor substrate according to claim 10 , wherein the group III nitride semiconductor layer is a GaN layer.
17 . The manufacturing method of the group III nitride semiconductor substrate according to claim 9 , wherein in the step of crystal-growing the group III nitride semiconductor layer, the outer peripheral part of the surface of the seed crystal substrate is covered with a mask, and the group III nitride semiconductor layer is crystal-grown on the seed crystal substrate inside of the mask.
18 . The manufacturing method of the group III nitride semiconductor substrate according to claim 9 , wherein a main surface of the seed crystal substrate is a c-plane or an inclined surface inclined from the c-plane.
19 . The manufacturing method of the group III nitride semiconductor substrate according to claim 10 , wherein the main surface of the seed crystal substrate is a c-plane or an inclined surface inclined from the c-plane.
20 . The manufacturing method of the group III nitride semiconductor substrate according to claim 19 , wherein the inclined growth planes are {10-11} planes and {11-22} planes.