Direct growth of GaN on sapphire substrate via polarity transition from N- to Ga-polar using only hydride vapor phase epitaxy

Abstract

We established a method for directly growing the GaN layer on a sapphire substrate using only hydride vapor phase epitaxy (HVPE). The important factors that affect the manufacture of high-quality, low-cost, and large-diameter GaN substrates require a growth method that does not utilize either a GaN template or processes other than HVPE. N2 carrier gas and a high temperature are important growth parameters required to achieve the direct growth of the GaN layer on the sapphire substrate. The mechanism of the direct growth of the GaN layer on the sapphire substrate reveals that the N-polar GaN layer grows during the initial growth stage via the nitridation of the sapphire substrate and Ga-polar GaN is subsequently produced via polarity inversion. Furthermore, the dislocation density of the GaN layer directly grown on the sapphire substrate is lower than that of the GaN layer grown on a GaN template using metal-organic vapor phase epitaxy.