Ab initio study of impact of nitridation at amorphous-SiNx/GaN interface

Abstract

A set of amorphous-SiNx/GaN interfaces is studied by ab initio calculation to understand the effects of GaN surface nitridation on interface state distribution. This study reveals that for the Si-rich SiNx/GaN interface without nitridation, both shallow and deep traps exist in a wide energy range within the GaN bandgap. However, with proper surface nitridation prior to SiNx deposition, the interface exhibits a much cleaner bandgap structure with significantly suppressed interface state density (Dit). With the increase in the interfacial N-adatom coverage ratio, the shallow traps dramatically disappear while the deep traps merge into the GaN valence band, indicating a high-quality interface with low Dit after sufficient nitridation. The low Dit would eventually lead to enhanced Vth stability in GaN metal–insulator–semiconductor (MIS)-gate devices. The nitridation effects on Dit are further verified by capacitance–voltage (C–V) measurements in the GaN metal–insulator–semiconductor (MIS) diode with/without interface nitridation.