Group III nitride semiconductor stacked structure and production method thereof
An object of the present invention is to provide a group III nitride semiconductor stacked structure having a high-quality A-plane group III nitride semiconductor layer on an R-plane sapphire substrate. The inventive group III nitride semiconductor stacked structure comprises a substrate composed of R-plane sapphire (α-Al 2 O 3 ), a buffer layer composed of aluminum gallium nitride (Al x Ga 1-x N: 0≦X≦1) formed on said substrate and an underlying layer composed of an A-plane group III nitride semiconductor (Al x Ga y In z N 1-a M a : 0≦X≦1, 0≦Y≦1, 0≦Z≦1, and X+Y+Z=1; wherein, M represents a group V element other than nitrogen (N), and 0≦a≦1) formed on said buffer layer, wherein the pit density of the surface of said underlying layer is 1×10 10 cm −2 or less.
1. A production method of a group III nitride semiconductor stacked structure comprising:
a first step wherein a buffer layer composed of aluminum gallium nitride (Al x Ga 1-x N: 0≦X≦1) is grown on a substrate composed of R-plane sapphire (α-Al 2 O 3 );
a second step wherein, an underlying layer composed of an A-plane undoped gallium nitride layer is grown on the buffer layer; and
a third step wherein an n-type contact layer, an n-type clad layer, a light-emitting layer, a p-type clad layer and a p-type contact layer are grown on the underlying layer in this order;
wherein, the substrate temperature of the second step is raised in three or more stages, and
wherein when the substrate temperature in the first stage of the second step is designated as T1, the substrate temperature in the second stage is designated as T2, and the substrate temperature in the third stage is designated as T3, then 700° C.<T1<1050° C., 1000° C.<T2<1100° C., 1100° C.<T3<1200° C., and T1<T2<T3, and
wherein the substrate temperature of the first step is higher than that of the second step.
2. The production method of a group III nitride semiconductor stacked structure according to claim 1 , wherein the ratio of the group V element (nitrogen) to the group III element in the first step (V/III ratio) is 200 or less (including the case of the V/III ratio being zero).
3. The production method of a group III nitride semiconductor stacked structure according to claim 1 , wherein the nitrogen raw material of the first step is a decomposition product of an adhered substance adhered inside a reactor.
4. The production method of a group III nitride semiconductor stacked structure according to claim 1 , wherein the nitrogen raw material of the second step is ammonia (NH 3 ).
5. A group III nitride semiconductor stacked structure produced according to the production method according to claim 1 .