Effects of N₂O plasma surface treatment on the electrical and ohmic contact properties of n-type GaN

An N₂O plasma surface treatment was introduced to improve the electrical and ohmic contact properties of the n-GaN surface. Hall measurements indicate that the sheet carrier concentration and sheet resistance of the N₂O treated n-GaN is considerably improved compared to as-grown samples. In addition, it is shown that the Ti/Al contact on the N₂O plasma surface-treated GaN results in a significant reduction in the specific contact resistance by about one order of magnitude, compared to that for a conventionally treated GaN. Based on the Hall measurement and Auger electron spectroscopy data, the observed improvements in the electrical and contact properties are due to the formation of a layer of highly conductive gallium oxynitride (GaO_xN_1-x) at the surface.