Control of Ga-oxide interlayer growth and Ga diffusion in SiO₂/GaN stacks for high-quality GaN-based metal–oxide–semiconductor devices with improved gate dielectric reliability

Abstract

A simple and feasible method for fabricating high-quality and highly reliable GaN-based metal–oxide–semiconductor (MOS) devices was developed. The direct chemical vapor deposition of SiO2 films on GaN substrates forming Ga-oxide interlayers was carried out to fabricate SiO2/GaOx/GaN stacked structures. Although well-behaved hysteresis-free GaN-MOS capacitors with extremely low interface state densities below 1010 cm−2 eV−1 were obtained by postdeposition annealing, Ga diffusion into overlying SiO2 layers severely degraded the dielectric breakdown characteristics. However, this problem was found to be solved by rapid thermal processing, leading to the superior performance of the GaN-MOS devices in terms of interface quality, insulating property, and gate dielectric reliability.