Temperature dependence of photoluminescence in hydrogenated amorphous silicon.

Abstract

The temperature dependence of the photoluminescence (PL) intensity in hydrogenated amorphous silicon (a-Si:H) has been studied. At temperatures below 100 K the nonradiative probability has a power-law behavior with a temperature dependence ${T}^{\ensuremath{\gamma}}$, where \ensuremath{\gamma} is in the range 4 to 1.5, which is quite different from that above \ensuremath{\approxeq}100 K. After prolonged illumination at room temperature, a considerable change of the temperature dependence of the photoluminescence in undoped a-Si:H has been observed below about 100 K. The PL quenching begins at temperatures below 50 K for samples with a high defect density, while the quenching occurs at temperatures above 50 K for undoped a-Si:H with a low defect density. We propose a model assuming shallow radiative hole trap centers to explain our results. The temperature dependence of the photoluminescence below 100 K is probably due to the power-law temperature dependence of the capture cross sections for these radiative hole trap centers.