Luminescence gap in hydrogenated amorphous silicon

The “luminescence gap” is used instead of the thermalization gap and the hopping-gap because the gap is obtained from the luminescence measurement. The luminescence gaps in hydrogenated amorphous silicon (a-Si:H) are observed in the temperature range from 4.2 to 225 K for the films prepared at different substrate temperatures 170 to 300 °C by plasma CVD. It is shown from the temperature dependence of the luminescence gap that the luminescence edges are at the localized band tail states at which the waiting time for the hopping is equal to the life time of the luminescence. The excitation energy dependence of the luminescence peak energy similar to that of the porous Si has been observed.