Low-Interface-Trap-Density and High-Breakdown-Electric-Field SiN Films on GaN Formed by Plasma Pretreatment Using Microwave-Excited Plasma-Enhanced Chemical Vapor Deposition

We investigated the SiN/GaN interface properties formed by the microwave-excited plasma-enhanced chemical vapor deposition (PECVD) withSiH₄/ N₂/ H₂gases. The interface and insulating properties of SiN films on GaN, formed by the microwave-excited PECVD, strongly depend onSiH₄flow rate. Although the interface trap density is lower than10¹¹~ cm⁻²~ eV⁻¹at the relatively highSiH₄flow rate of 1.0 standardcm³/min(sccm), the breakdown electric field is very low (approximately 1 MV/cm). Using theSiH₄plasma pretreatment before the stoichiometric SiN deposition, both low interface trap density and high breakdown voltage greater than 2 MV/cm were obtained. In this case, the clearly ordered Ga bonding near the SiN/GaN interface was estimated by electron energy loss spectroscopy. The formation of SiN film on GaN using the microwave-excited PECVD is a very useful technique for the high-quality interface properties.