The Urbach tail in amorphous semiconductors

Abstract

The exponential absorption edge in amorphous semiconductors is discussed in relation to the Mott-Street model (Phys. Rev. Lett., vol.35, p.1293 (1975)) for chalcogenide glasses. It is shown that the absorption of a photon leads to neutralization of a donor-acceptor pair. The concentration of such pairs is exponentially dependent on the creation energy. The temperature, frequency and pressure dependence of the absorption and electroabsorption in amorphous materials are discussed.