Investigations of the Origins of Metastable Light-Induced Changes in Hydrogenated Amorphous Silicon. Annual Report, 1 January 1985-31 January 1986

摘要

This report contains results of a study on the light-induced instability problem in hydrogenated amorphous silicon using junction capacitance techniques; i.e., capacitance-temperature mesurements and drive-level capacitance profiling. These were used to examine specific changes in the density and occupation of gap states for undoped a-Si:H samples after light saturation and for a series of partial-anneal ''states'' that culminate in the original dark annealed state (state A). The data are used to deduce the energy distribution of metastable gap states and to estimate separately the changes in occupied and unoccupied gap states near midgap. Changes in the metastable occupied and unoccupied defects are neither equal nor proportional. The data are consistent with ESR studies suggesting that the metastable spin increase is independent of the impurity content but may be correlated with film strain. The deduced increase in the spinless D sub 3- levels appears to be correlated with the impurity content of our samples. The metastable defect distribution near midgap in several cases had a different energy distribution than the stable deep state (dangling bond) distribution. In state A, a photo-CVD-grown, a-Si:H sample had a defect density well within the range observed for glow-discharge samples. (ERA citation 11:040152)