Gallium nitride crystal, group 13 nitride crystal, group 13 nitride crystal substrate, and manufacturing method

Abstract

A gallium nitride crystal having a hexagonal crystal structure includes a first region located on an inner side of a cross section intersecting c-axis of the hexagonal crystal structure, and a second region surrounding at least a part of the outer periphery of the first region in the cross section. An emission spectrum of each of the first region and the second region with electron beam or ultraviolet light excitation has a first peak including a band edge emission of gallium nitride and a second peak located in a longer wavelength area than the first peak. A peak intensity of the first peak is smaller than a peak intensity of the second peak in the first region, and a peak intensity of the first peak is greater than a peak intensity of the second peak in the second region.

1 . A gallium nitride crystal having a hexagonal crystal structure comprising:
 a first region located on an inner side of a cross section intersecting c-axis of the hexagonal crystal structure; and   a second region surrounding at least a part of the outer periphery of the first region in the cross section, wherein   an emission spectrum of each of the first region and the second region with electron beam or ultraviolet light excitation has a first peak including a band edge emission of gallium nitride and a second peak located in a longer wavelength area than the first peak,   a peak intensity of the first peak is smaller than a peak intensity of the second peak in the first region, and   a peak intensity of the first peak is greater than a peak intensity of the second peak in the second region.   
     
     
         2 . The gallium nitride crystal according to  claim 1 , wherein
 the emission spectrum is measured at a room temperature, and   the second peak is located in a wavelength range of 450 nm to 650 nm.   
     
     
         3 . The gallium nitride crystal according to  claim 2 , wherein
 the second peak is located in a wavelength range of 590 nm to 650 nm.   
     
     
         4 . The gallium nitride crystal according to  claim 1 , wherein
 the second region surrounds an entire outer periphery of the first region in the cross section.   
     
     
         5 . The gallium nitride crystal according to  claim 1 , wherein
 a thickness of the second region is 100 nm or more in the cross section.   
     
     
         6 . The gallium nitride crystal according to  claim 1 , wherein
 a boron density of the first region is higher than the boron density of the second region.   
     
     
         7 . The gallium nitride crystal according to  claim 6 , wherein
 the boron density of the first region is 4×10 18  atms/cm 3  or more, and   the boron density of the second region is less than 4×10 18  atms/cm 3 .   
     
     
         8 . The gallium nitride crystal according to  claim 1 , wherein
 a length L in a c-axis direction is 9.7 mm or more, and a ratio L/d which is a ratio of the length L to a crystal diameter d in c-plane is larger than 0.813.   
     
     
         9 . The gallium nitride crystal according to  claim 8 , wherein
 the length L is 37.4 mm or more.   
     
     
         10 . A group 13 nitride crystal containing therein at least a part of the gallium nitride crystal according to  claim 1 . 
     
     
         11 . The group 13 nitride crystal according to  claim 10 , wherein
 a dislocation density of a region other than the gallium nitride crystal in c-plane of the group 13 nitride crystal is smaller than the dislocation density of the gallium nitride crystal contained in the c-plane on an inner side of the group 13 nitride crystal.   
     
     
         12 . A group 13 nitride crystal substrate containing at least a part of the gallium nitride crystal according to  claim 1 . 
     
     
         13 . The group 13 nitride crystal substrate according to  claim 12 , wherein
 a c-plane of the hexagonal crystal structure is a main surface.   
     
     
         14 . A method of manufacturing a gallium nitride crystal, the method comprising:
 a first process to grow a first region of the gallium nitride crystal containing boron; and   a second process to grow a second region of the gallium nitride crystal outside of the first region, the second region having a boron density lower than the boron density of the first region.   
     
     
         15 . A method of manufacturing a group 13 nitride crystal, wherein
 the gallium nitride crystal according to  claim 1  is used as a seed crystal to grow the group 13 nitride crystal.