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/gallium nitride (GaN) interface properties formed by the microwave-excited plasma-enhanced chemical vapor deposition (PECVD) with SiH₄/N₂/H₂ gases. The interface and insulating properties of SiN films on GaN formed by the microwave-excited PECVD strongly depend on SiH₄ flow rate. Although the interface trap density is lower than 10¹¹ cm-2eV-1 at the relatively high SiH₄ flow rate of 1 sccm, the breakdown electric field is very low (∼ 1 MV/cm). Using the SiH₄ plasma pretreatment before the stoichiometric SiN deposition, both low interface trap density and high breakdown voltage greater than 2 MV/cm are obtained. In this case, the clearly ordered Ga bonding near the SiN/GaN interface is estimated by an 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.