Investigation of the GaN/Al2O3 Interface by First Principles Calculations

Abstract

Metal–oxide–semiconductor field effect transistors (MOSFETs) based on GaN have been studied for high‐power performance because of the wide bandgap of GaN. Although Al2O3 is a promising dielectric film for GaN power devices, the interface structure of GaN/Al2O3 has not been revealed microscopically. We prepared two interface models with Ga–O bonds and Ga–Al bonds at the interface. Because the Ga–O bond is stronger than the Ga–Al bond, the Ga–O bonds are preferentially formed at the interface. When the Ga–Al bonds appear at the interface, they introduce defect levels in the bandgap of GaN. On the other hand, when the interface consists of Ga–O bonds, some defect structures can appear depending on the oxygen density. In oxygen‐rich conditions, dangling bonds appear at the N atoms and their states appear around the valence band maximum.