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 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 1.0 standard cm³ (sccm), the breakdown electric field is very low (approximately 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 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.