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

The thermal oxidation process at 900degC in dry oxygen 02 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 Ga_3d and O_1s 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 ~25 nm/h. The refractive index of Ga₂O₃ is 1.8~2.1 in the wavelength range of 300~800 nm, which agrees with the prevenient study results. However, anomalous refractive phenomenon appeares at 300~400 nm, 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.