TRAPPING AND RECOMBINATION OF PHOTOGENERATED CARRIERS IN AS-GROWN HIGH-TEMPERATURE-ANNEALED AND LIGHT-SOAKED A-SIH

Our previous results of light-induced electron spin resonance (LESR) i ndicate that, in hydrogenated amorphous silicon (a-Si:H), light-induce d defects differ from those formed during deposition or high-temperatu re annealing. The concept of demarcation was used to interpret these d ifferences in terms of higher energy levels for light-induced defects. In this study, the constant photocurrent method (CPM), dark conductiv ity and transient-LESR are used to supply new evidence for the differe nces and to conduct two tests on our hypothesis. The demarcation energ ies for electrons and holes are shifted by varying the temperature or bias-light intensity for transient-LESR. In striking agreement with ou r hypothesis, we find that the light-induced changes in the LESR line shape (an increase in the broad component relative to the narrow one u pon light exposure) become indeed more dramatic as the demarcation ene rgies move closer to the midgap.