GaN substrates having a low dislocation density and a small off-angle variation prepared by hydride vapor phase epitaxy and maskless-3D

Abstract

To produce high-quality GaN (0001) substrates with a low threading dislocation density (TDD) and a small off-angle variation, we have developed a technique named the "maskless-3D method."This method, which is applied during GaN boule growth by hydride vapor phase epitaxy (HVPE), induces three-dimensional (3D) growth on a normal GaN (0001) seed substrate. We showed that by an appropriate choice of HVPE conditions, and without using a mask, the 3D growth shape was controlled to eliminate the c-plane and thereby suppress the propagation of dislocations from the seed. Subsequently, two-dimensional (2D) growth was carried out on the 3D structure. This 2D growth area was machined to produce a 2 inch GaN substrate with a TDD of about 4 × 105 cm-2 and an off-angle variation of 0.05°. We also confirmed that it was possible to insert the 3D growth area twice, thereby further reducing the TDD to 104 cm-2.