Comparative study of wet and dry oxides on polycrystalline GaAs by AES, SIMS, and XPS

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Complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and x-ray photoelectron spectroscopy (XPS) are used to evaluate low-temperature wet and dry oxides and the oxide/semiconductor interfaces on polycrystalline GaAs. The dry oxides are found to be primarily Ga2O3 and are relatively uniform in composition. The wet oxides are less uniform and mixed, with a more abrupt transition region that the dry oxide/GaAs interface. XPS data confirm the presence of Ga2O3 in the dry oxide. In comparison, Ga2O3, As2O5 are detected in the wet oxide layer. SIMS shows higher trace impurity concentrations in the wet oxide with some buildup at the oxide/GaAs interface. The relative performance of solar cells fabricated from these structures is discussed.