Investigation of slow surface states on a real germanium surface by the optical excitation technique

The slow states (SS) charging ΔQ_s under the action of light quanta of different energy (2 ? hv ? 4.6 eV) has been investigated on a real germanium surface. The considerable influence on the optical SS charging of the preparation method as well as of adsorption-desorption processes has been revealed. On the basis of the spectral dependencies ΔQ_s(hv) the conclusion has been made about the existence of the adsorption-sensitive system of “fluctuation” electron states near the edges of energy bands of the oxide layer. The photocharging method has been shown the construction of the whole energy scheme of the semiconductor-dielectric heterojunction (including the band gap of the dielectric layer). The possible origin of the deep traps in oxide layer which are responsible for the optical charging of a real germanium surface, has been discussed.