Scanning Microscopy


GaAs oxide layers resulting from an oxygen plasma etching have been studied by Auger in-depth profiles and angle-resolved XPS experiments. From the Auger profiles, using the sequential layer sputtering (SLS) treatment, a quantitative determination of thickness and composition of the oxide layers has been performed. A model with several layers has been deduced. From the angle-resolved X-ray photoelectron spectroscopy (XPS) experiments, another model with several layers of different chemical compounds has also been deduced. The oxide layer is non-uniform in thickness and composition. Two or three different oxide layers are formed depending on the probed area. The interface layer is made of a mixture of Ga2O3 and elemental arsenic. The intermediate layer consists of an equal mixture of Ga2O3 and As2O3 with a small amount of As2O5. From the Auger experiments, an upper layer of Ga2O3 is found in the central part of the wafer, corresponding to a more important loss of arsenic due to a thermal effect.

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