Thermal excitation of carriers at tail states and recombination rate in hydrogenated amorphous silicon

Measurements of low-energy photoluminescence (PL) in hydrogenated amorphous silicon (a-Si:H) have been performed by means of frequency-resolved spectroscopy. Temperature variation of radiative recombination rate of electron–hole pairs and thermal excitation of carriers at the tail states are discussed. The results suggest that the tail electrons do not contribute to the PL of the energy lower than 1.0 eV. Experimental results are quantitatively explained by considering a two-level system instead of the tail states.