Effect of initial growth on the quality of GaN on patterned sapphire substrate with ex situ physical vapor deposition AlN seed layer

Abstract

GaN epitaxy was explored on a cone-patterned sapphire substrate with an ex situ AlN seed layer prepared by physical vapor deposition (PVD). The effect of initial growth on the quality of the GaN epilayer was investigated using both ex situ PVD-AlN seed layers with various thicknesses and various deposition parameters such as temperature and reactor pressure in metal–organic vapor-phase epitaxy (MOVPE). It was found that the quality of GaN is insensitive to both the thickness of the ex situ PVD-AlN seed layer and the MOVPE growth conditions. A high-quality GaN film was realized, as indicated by room-temperature CL mapping (dark spot density of 1.6 × 108 cm−2), on a patterned sapphire substrate with a wide growth condition window by simply employing an ex situ PVD-AlN seed layer.