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Low-Temperature Fluorination of GaAs Surface by CF4 Plasma

The GaAs surface was fluorinated at low temperatures in CF4 plasma. The constitution and the composition of the formed films as functions of the substrate temperature and exposure time were analyzed by X-ray photoelectron spectroscopy. The fluoride films whose thickness increased with the substrate temperature consisted of gallium oxyfluoride and free As. We have also examined the influence of the surface treatment of GaAs substrates as well as the capping layer on the fluoride films. The sulfur treatment delayed the initiation of fluorination, and a-Si:H capping layer prevented free As from evaporating out.