Growth of Al oxide layers on GaAs (100) by reaction with condensed molecular oxygen

An Al oxide-GaAs (100) interface fabricated by the reactive deposition of Al into a molecular oxygen overlayer on a gallium terminated GaAs (100) surface at T=49 K is studied by synchrotron radiation photoemission. Al forms a stable oxide layer by reaction with O2 until all the oxygen is consumed. Limited oxidation of surface As atoms (≊20%) is observed during the initial deposition of Al, but further Al deposition reduces the AsO bond. The well-known exchange reaction between Al and Ga when Al is directly deposited on GaAs (100) is not observed.