Inclusion-free uniform semi-insulating group III nitride substrates and methods for making same

摘要

In a method for making an inclusion-free uniformly semi-insulating GaN crystal, an epitaxial nitride layer is deposited on a substrate. A 3D nucleation GaN layer is grown on the epitaxial nitride layer by HVPE under a substantially 3D growth mode, wherein a surface of the nucleation layer is substantially covered with pits and the aspect ratio of the pits is essentially the same. A GaN transitional layer is grown on the nucleation layer by HVPE under a condition that changes the growth mode from the substantially 3D growth mode to a substantially 2D growth mode. After growing the transitional layer, a surface of the transitional layer is substantially pit-free. A bulk GaN layer is grown on the transitional layer by HVPE. After growing the bulk layer, a surface of the bulk layer is smooth and substantially pit-free. The GaN is doped with a transition metal during at least one of the foregoing GaN growth steps.