Nature of the band-edge electronic states in As-Te semiconducting glasses

Abstract

The validity of the commonly accepted concepts of mobility gap, optical gap and localized states is analysed by attempting a coherent interpretation of the optical absorption, spectral photoconductivity and transport measurements in the vitreous As-Te system. An essential feature of this work is that data are taken from well controlled bulk samples. The different types of experimental data can be coherently interpreted within the framework of the Mott model. Three independent experimental determinations are available for ΔE, the energy interval of the band-edge localized states. It is shown that the Dow and Redfield mechanism of broadening of excitonic states by random microfields is able to explain the absorption exponential tail as well as the spectral photoconduction over a domain of energy well below the gap. Finally, some properties of deep localized states are described.