Low-dislocation monocrystalline aln substrate

Abstract

A bulk AlN single crystal is grown on a monocrystalline AlN seed crystal having a central longitudinal mid-axis and disposed in a crystal growth region of a growing crucible. The bulk AlN single crystal grows parallel to the longitudinal mid-axis by deposition on the AlN seed crystal. The crucible has a lateral crucible inner wall extending in the growth direction. A free space is formed between the AlN crystals and the lateral crucible inner wall. Bulk AlN single crystals and monocrystalline AlN substrates produced therefrom are obtained with only few dislocations, which are substantially distributed homogeneously. Growing crucibles are provided with a crucible lid with a gap formed between an inner growing crucible and the crucible lid through which some of the AlN growth gas phase generated inside the crystal growth region escapes and is deposited on a bottom of an outer growing crucible opposite the lid.

1 . A monocrystalline AlN substrate, comprising:
 a) a main substrate surface with a diameter of at least 200 mm;   b) a global dislocation density, determined for an entire said main substrate surface, of at most 10 4  cm −2 ; and   c) a local dislocation density, determined for any 4 mm 2  subsurface of said main substrate surface, greater than said global dislocation density at most by a factor of two.   
     
     
         2 . The AlN substrate according to  claim 1 , wherein said local dislocation density is determined for a square subsurface. 
     
     
         3 . The AlN substrate according to  claim 1 , wherein said local dislocation density, which is at most a factor of two greater than said global dislocation density, applies for any 1 mm 2  large subsurface of said main substrate surface. 
     
     
         4 . The AlN substrate according to  claim 3 , wherein said local dislocation density is determined for a square subsurface. 
     
     
         5 . The AlN substrate according to  claim 1 , wherein said global and local dislocation densities respectively specify in a surface-referenced way how many dislocations of at least one dislocation type selected from the group consisting of step dislocation, screw dislocation, and basal plane dislocation, are present in a crystal structure of the AlN substrate and are detectable on said main substrate surface.