Electronic states of chemically treated SiC surfaces

Electronic states at chemically treated SiC surfaces have been studied by scanning tunneling spectroscopy. Charge accumulation on the surface is deduced through a voltage shift observed in the spectra. More charge is observed on electro-polished surfaces as compared to untreated (as-received) surfaces. This difference is interpreted in terms of the electro-polished SiC surfaces being more insulating than as-received ones, such that on the former the transport of charge is limited and surface charges cannot come into equilibrium with the bulk semiconductor. Observations of tunneling spectra on SiC prepared by various amounts of hydrogen-etching are used to support this interpretation.