Plasma passivation of gallium arsenide*

Abstract

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: H2, H2/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 H2/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.