Methods for producing improved crystallinity group iii-nitride crystals from initial group iii-nitride seed by ammonothermal growth

Abstract

The present invention discloses methods to create higher quality group III-nitride wafers that then generate improvements in the crystalline properties of ingots produced by ammonothermal growth from an initial defective seed. By obtaining future seeds from carefully chosen regions of an ingot produced on a bowed seed crystal, future ingot crystalline properties can be improved. Specifically, the future seeds are optimized if chosen from an area of relieved stress on a cracked ingot or from a carefully chosen N-polar compressed area. When the seeds are sliced out, miscut of 3-10° helps to improve structural quality of successive growth. Additionally a method is proposed to improve crystal quality by using the ammonothermal method to produce a series of ingots, each using a specifically oriented seed from the previous ingot. When employed, these methods enhance the quality of Group III nitride wafers and thus improve the efficiency of any subsequent device.

What is claimed is: 
     
         1 . A method of fabricating a group III nitride wafer comprising:
 a. growing a first ingot of group III nitride on a first seed crystal of group III nitride by an ammonothermal method until
 i. a radius of curvature of a c-plane lattice of the first ingot becomes larger, and 
 ii. the radius of curvature of the c-plane lattice of the first ingot inverts from a bowing direction of the first seed crystal along the c-plane lattice of the first seed crystal; and 
   b. slicing a wafer out of the first ingot and from a nitrogen polar side of the first ingot.   
     
     
         2 . The method of  claim 1 , wherein the wafer has a lattice curvature that is convex toward the +c direction. 
     
     
         3 . The method of  claim 2 , wherein the act of slicing the wafer comprising slicing a c-plane oriented wafer with miscut angle within 10 degrees. 
     
     
         4 . The method of  claim 1 , wherein the first ingot has a N-polar face during growth, and the N-polar face of the first ingot grows under compression. 
     
     
         5 . The method of  claim 4 , wherein the compression provides continuous oriented growth. 
     
     
         6 . The method of  claim 4 , wherein the compression prevents cracking of the first ingot at the N-polar face during growth of the first ingot. 
     
     
         7 . The method of  claim 6 , wherein the group III nitride of the first ingot is GaN, and the group III nitride of the first seed crystal is GaN. 
     
     
         8 . The method of  claim 7 , wherein the wafer has a lattice curvature convex toward the +c direction. 
     
     
         9 . The method of  claim 8 , wherein the act of slicing the wafer comprising slicing a c-plane oriented wafer with miscut angle within 10 degrees. 
     
     
         10 . The method of  claim 1 , wherein the wafer is formed as a second seed crystal for growth of a second ingot of group III nitride. 
     
     
         11 . The method of  claim 10 , wherein the wafer has a lattice curvature that is convex toward the +c direction. 
     
     
         12 . The method of  claim 11 , wherein the act of slicing the wafer comprising slicing a c-plane oriented wafer with miscut angle within 10 degrees. 
     
     
         13 . The method of  claim 1 , wherein strain in the wafer is reduced from strain in the first seed crystal. 
     
     
         14 . The method of  claim 13 , wherein the wafer has a lattice curvature that is convex toward the +c direction. 
     
     
         15 . The method of  claim 14 , wherein the act of slicing the wafer comprising slicing a c-plane oriented wafer with miscut angle within 10 degrees. 
     
     
         16 . The method of  claim 1 , wherein the wafer has a thickness between about 0.1 mm and about 2 mm. 
     
     
         17 . The method of  claim 1 , wherein the act of slicing the wafer comprises slicing multiple wafers out of the first ingot. 
     
     
         18 . The method of  claim 17 , wherein at least one of said wafers has a lattice curvature that is convex toward the +c direction. 
     
     
         19 . The method of  claim 18 , wherein said multiple wafers are sliced from the ingot with miscut angle within 10 degrees. 
     
     
         20 . The method of  claim 1 , wherein the act of slicing the wafer comprising slicing a c-plane oriented wafer with miscut angle within 10 degrees. 
     
     
         21 . A wafer formed by the method of  claim 2 . 
     
     
         22 . A wafer formed by the method of  claim 3 . 
     
     
         23 . A wafer formed by the method of  claim 8 . 
     
     
         24 . A wafer formed by the method of  claim 9 . 
     
     
         25 . A wafer formed by the method of  claim 11 . 
     
     
         26 . A wafer formed by the method of  claim 12 . 
     
     
         27 . A wafer formed by the method of  claim 14 . 
     
     
         28 . A wafer formed by the method of  claim 15 . 
     
     
         29 . A plurality of wafers formed by the method of  claim 18 . 
     
     
         30 . A plurality of wafers formed by the method of  claim 19 .