Photoluminescence and Light-Induced ESR in a-Si:H Studied with Subgap Excitation

Abstract

We have studied the influence of the photon energy of the exciting light on the distribution of the carriers in the gap of a-Si:H by light-induced electron spin resonance (LESR) and photoluminescence (PL). In the LESR spectra the number of spins in the broad line (h) is larger than in the narrow line (e or e+db) by a factor of 2-3. For excitation in the bulk of the sample this asymmetry does not depend on the light intensity and photon energy, which suggests that it is not possible to relate the asymmetry to a specific defect structure. LESR and PL show that both bandtails can be populated by absorption of IR light (1060 nm) by optical transitions from occupied and into empty defect states. The recombination kinetics suggest that these absorption processes occur as a two-step process at the same defect