Effect of UV Irradiation on Ar-Plasma Etching Characteristics of GaN

We have investigated Ar-plasma etching characteristics of n-GaN with and without additional UV irradiation with an optical power of ∼400 mW/cm2 from the outside, employing X-ray photoelectron, X-ray absorption, and photoluminescence spectroscopy techniques. The conventional etching without the UV irradiation produces numerous N deficits and non-radiative point defects in the top surface (∼5 nm) and bulk (∼70 nm) regions of the etched GaN, respectively. More interestingly, the strong UV irradiation to GaN during the etching process is found to reduce the etching damage and to enhance the etching rate probably due to complex UV-absorption effects at the GaN surfaces and/or the Ar plasma.