Evidence from photoluminescence studies for a low-energy absorption tail in chalcogenide glasses and crystals

Abstract

The photoluminescence excitation spectra in some arsenic chalcogenide semiconductors have been explored to low energies, from which absorption coefficients down to 10⁻¹ cm⁻¹ can be derived. New evidence is presented for a weak absorption tail in both crystals and glasses, and the data are discussed in terms of an optical transition involving a localized defect state. It is shown that the data support a recent model in which the photoluminescence recombination centre is a shallow state that has a strong electron-phonon coupling.