Surface preparation of non-polar single-crystalline AlN substrates.

A surface preparation technique has been developed for non-polar m-plane aluminum nitride (AlN) single crystalline substrates. Chemical surface treatments were conducted on chemomechanically polished m-plane oriented AlN substrate surfaces. X-ray photoelectron spectroscopy was used to characterize the surface chemistry after each processing step. A layer of mixed aluminum oxide-hydroxide was identified on ambient air-exposed surfaces. Analysis of the oxygen core level spectra showed oxygen in three bonding states, identified by the binding energies and relative separation of the fitted peaks as O2−, OH− and H2O. Molar ratios of different components showed the oxide to be dominantly bonded in the OH− state. Wet etching reduced the amount of surface oxides. Ammonia annealing at 1100 °C converted the aluminum oxide-hydroxide layer to AlN. Although the overall amount of the oxide on the surface was reduced by surface treatments, the nature of the oxide remained predominantly of the OH−character. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]