Phonon interactions in the luminescence of amorphous silicon

Experimental data and a new model of luminescence in glow-discharge-deposited amorphous silicon are described. The shape of the luminescence excitation spectrum rules out the previous model based on zero-phonon transitions. Instead, phonon interactions give a Stokes shift of 0.4–0.5 eV and the recombination is due to self-trapping of excitons bound to band tail localized states. The model explains the luminescence peak position and line width, the Stokes shift, and the thermal quenching of the luminescence intensity.