Optical excitation, with an energy of 1.16eV, was used to study defect-related photoluminescence in amorphous hydrogenated material. Light-induced electron spin resonance showed that both electrons and holes were generated in the band tails by defect absorption. The carriers appeared to be created in a 2-step process and to cluster around the defects. The photoluminescence spectra exhibited both the usual intrinsic band near to 1.3eV, and a defect-related band near to 0.8eV. It was suggested that the defect bands in undoped, P-doped or B-doped films originated from the tunnelling transitions of majority carriers from band-tail states and into the respective predominant dangling-bond state (D0, D- or D+, in the dark). The overall behavior suggested that the tunnelling transitions into defect states were generally non-radiative. However, depending upon the specific local configuration, this transition could also occur radiatively.

I.Ulber, R.Saleh, W.Fuhs, H.Mell: Journal of Non-Crystalline Solids, 1995, 190[1-2], 9-20