Silicon surface states and subsurface hydrogen

The n-Si|fluoride electrolyte interface exhibits a small interface-state density, as shown by the presence of a weak capacitance peak in the capacitance-potential curves. After in situ chemical dissolution of an anodically formed oxide, a quasi ideal interface with a very low interface-state density was obtained. At open-circuit potential, a slow increase in the interface-state density was observed. These interface states result from the penetration of hydrogen into the silicon subsurface region. The inward diffusion of hydrogen produced by electrochemical etching of silicon accounts for the large time constant observed.