PLASMA PASSIVATION OF GALLIUM-ARSENIDE

Improved electrical properties of the SiO2-GaAs interface have been obtained using in situ plasma surface treatments prior to film deposition. We present a comparison of several hydrogen based plasma passivation schemes: H-2, H-2/N2, and H2S. Hydrogen plasmas remove native oxides, while nitrogen or sulfur form passivating surface layers. Samples were characterized using metal-insulator-semiconductor C-V analysis, x-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry. The H-2/N2 and H2S treated samples display improved C-V characteristics. XPS indicates the presence of nitrogen and sulfur respectively on the uncapped samples, although little evidence remains after SiO2 deposition. H2S plasmas offer the best results, providing a self-terminating process that prevents roughening of the GaAs surface by hydrogen plasma etching. However, surfaec doping effects were observed after exposure to high temperatures.