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) with
${\rm SiH}_{4}/{\rm N}_{2}/{\rm H}_{2}$
gases. The interface and insulating properties of SiN films on GaN, formed by the microwave-excited PECVD, strongly depend on
${\rm SiH}_{4}$
flow rate. Although the interface trap density is lower than
$10^{11}~{\rm cm}^{-2}~{\rm eV}^{-1}$
at the relatively high
${\rm SiH}_{4}$
flow rate of 1.0 standard
${\rm cm}^{3}/\min$
(sccm), the breakdown electric field is very low (approximately 1 MV/cm). Using the
${\rm SiH}_{4}$
plasma 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.