CHEMICALLY ASSISTED ION-BEAM ETCHING OF GALLIUM NITRIDE

Chemically assisted ion beam etching of gallium nitride (GaN) grown by metalorganic chemical vapor deposition has been characterized using an Ar ion beam and Cl-2 gas. The etch rate of GaN was found to increase linearly with Ar ion beam current density, increase linearly then saturate with Ar ion beam energy, vary slightly with Cl-2 flow rate, and lastly, increase moderately with substrate temperature. Etch rates as high as 330 nm/min were obtained at high beam energies and 210 nm/min at a more nominal level of 500 eV. The anisotropy of etched profiles improved in the presence of Cl-2 in comparison to those etched by Ar ion milling only. Elevated substrate temperatures further enhanced the anisotropy to obtain near-vertical profiles for fairly deep-etched structures. Auger electron spectroscopy was used to investigate etch-induced surface changes. Oxygen contamination was observed on the as-etched surface but a dilute HCl treatment restored the stoichiometry of the material to its unetched state.