Hole generation in amorphous selenium

Hole generation by photons and high electric fields is investigated experimentally in quenched selenium. An essentially different dependence of generation on the applied electric field and temperature is found for the holes generated in the bulk and in the several micron thick high-resistivity surface layer of selenium. The surface layer is always present if selenium damage by air and short wavelength light is not avoided. The following regularities are determined: high electric fields generate holes only in the surface layer; the efficiency of photogeneration in the surface layer depends on field and temperature; no field and temperature activation is required for the uniform bulk photogeneration observed.