Surface Oxidation of GaN(0001) Simulated by Charge-Transfer-Type Molecular Dynamics

In this study, the oxidation of Ga-polar GaN(0001) surface simulated by using originally developed charge-transfer-type interatomic potential is reported on. The adjusted potential parameters reproduce the cohesive energies in the range of 0.3 eV atom-1 and atomic forces with correlation coefficient as high as 0.9, compared to the results of first-principles calculations for more than 9000 structures associated with oxidation of GaN. The oxidation simulations reveal the formation of a periodic gallium oxide (GaOx) layer grown on GaN(0001) with O atoms replacing N atoms. The atomic distance between Ga-Ga in the GaOx layer along GaN[0001] direction is 3.05 angstrom, which is longer than wurtzite GaN (2.63 angstrom) and is quantitatively in agreement with the recent photoelectron holography measurement. The distances of the Ga atoms projected onto the GaN(11-20) plane are determined to be 3.19 angstrom for the GaOx layer and 2.79 angstrom for the interfacial GaN. These distances also align quantitatively with the scanning transmission electron microscopy imaging of the native oxide on GaN(0001). Further oxidation simulation in a larger model of 2304 atoms suggests the formation of the layered structure even in the subsequent layers away from the interface of GaN and gallium oxide. In this study, a new interatomic potential for Ga, N, and O tailored for GaN(0001) oxidation simulations is introduced. In this research, the formation of a periodic gallium oxide layer on GaN(0001) is validated in agreement with recent experiments. The results contribute to a better understanding of interfacial phenomena in GaN metal-oxide-semiconductor field-effect transistors for power-switching devices.image (c) 2024 WILEY-VCH GmbH