NON-POLAR OR SEMI-POLAR GaN WAFER

Abstract

A non-polar or semi-polar GaN wafer in which a lower-crystallinity band present on a main surface has a reduced width. The GaN wafer includes a first main surface and a second main surface on a side opposite to the first main surface. The first main surface is parallel to or tilted relative to the M-plane. When the tilt, if exists, is decomposed into the a-axis direction component and the c-axis direction component, the a-axis direction component has an absolute value of 5° or less while the c-axis direction component has an absolute value of 45° or less. The GaN wafer includes a lower-crystallinity band extending on the first main surface in a direction perpendicular to the c-axis, and the lower-crystallinity band has a width of less than 190 μm.

1 . A GaN wafer comprising:
 a first main surface;   a second main surface on a side opposite to the first main surface; and   a lower-crystallinity band extending on the first main surface in a direction perpendicular to a c-axis, wherein   the first main surface is parallel to or tilted relative to an M-plane, when the tilt, if exists, is decomposed into an a-axis direction component and a c-axis direction component, the a-axis direction component has an absolute value of 5° or less while the c-axis direction component has an absolute value of 45° or less, and   the lower-crystallinity band has a width of less than 190 μm.   
     
     
         2 . The GaN wafer according to  claim 1 , wherein
 the lower-crystallinity band has a width of less than 150 μm.   
     
     
         3 . The GaN wafer according to  claim 2 ,
 wherein the lower-crystallinity band has a width of less than 120 μm.   
     
     
         4 . The GaN wafer according to  claim 1 , wherein
 X-ray rocking curve full width at half maximums of a (100) plane measured in an area distant from an outer periphery by 3 mm or more on the first main surface are less than 0.01°, except in the lower-crystallinity band.   
     
     
         5 . The GaN wafer according to  claim 1 , wherein
 the GaN wafer is a { 10 - 10 } wafer, a { 10 - 11 } wafer, a { 10 - 1 - 1 } wafer, a { 20 - 21 } wafer, a { 20 - 2 - 1 } wafer, a { 30 - 31 } wafer or a { 30 - 3 - 1 } wafer.   
     
     
         6 . The GaN wafer according to  claim 1 , wherein
 the GaN wafer is a disk having a diameter of from 45 to 55 mm, and   the number of the lower-crystallinity band the GaN wafer has on the first main surface is one or greater and three or smaller.   
     
     
         7 . The GaN wafer according to  claim 1 , further comprising a lower-crystallinity band extending on the first main surface in a direction perpendicular to an a-axis. 
     
     
         8 . The GaN wafer according to  claim 7 , wherein the GaN wafer is a disk having a diameter of from 95 to 155 mm. 
     
     
         9 . A method for producing a nitride semiconductor device, comprising:
 preparing the GaN wafer according to  claim 1 ; and   growing one or more nitride semiconductors on the prepared GaN wafer by vapor phase epitaxy to form a device structure.