Growth and Characteristics Analysis of the Thermal Oxide Grown on Gallium Nitride

The thermal oxidation process at 900°C in dry oxygen O2 on gallium nitride (GaN) and the physical characteristics of the oxide thin films are investigated by spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS). XPS spectra of Ga3d and O1s core levels indicates that the thermal oxide is gallium oxide (Ga2O3), and the existence of much O loss on the surface induces the ratio of Ga to O is more than 1. SE metrical results indicate the average grown rate is ~25nm/h. The refractive index of Ga2O3 is 1.8~2.1 in the wavelength range of 300~800nm, which agrees with the prevenient study results. However, anomalous refractive phenomenon appeares at 300~400nm, the reason is probably interrelated with the strong absorbance of GaN in this wavelength range and needs deeper study later. Such stable and controllable Ga2O3 thermal growth process is significant for GaN gate dielectric applications in the future.