Doping level-dependent dry-etch damage in n-type GaN

The electrical effects of dry-etch on n-type GaN by an inductively coupled Cl₂/CH₄/H₂/Ar plasma were investigated as a function of ion energy, by means of ohmic and Schottky metallization methods. The specific contact resistivity (ρ_c) of the ohmic contact was decreased, while the leakage current in the Schottky diode was increased with increasing ion energy due to the preferential sputtering of nitrogen. At a higher rf power, an additional effect of damage was found on the etched sample, which was sensitive to dopant concentration in terms of the ρ_c of the ohmic contact. This can be attributed to effects such as the formation of deep acceptors as well as the electron-enriched surface layer within the depletion layer. Furthermore, the thermal annealing process enhanced the ohmic and Schottky properties of the heavily damaged surface.