HYDROGEN-INDUCED QUANTUM CONFINEMENT IN AMORPHOUS-SILICON

We study how hydrogen-induced quantum confinement in hydrogenated amor phous silicon influences the distribution of tail states. To do this, the potential structure of this semiconductor is treated as being comp rised of an ensemble of potential wells, these wells corresponding to unhydrogenated regions enveloped by hydrogenated regions. To evaluate the distribution of states, we determine the ground state associated w ith each well, and then average over the distribution of wells. We fin d that our calculated distribution of tail states exhibits an essentia lly exponential functional dependence, over several decades, and that this tail of states shifts toward the band edge as the hydrogen conten t is increased. This shift toward the band edge is suggested to be one of the factors responsible for the observed increase in energy gap wi th higher hydrogen content. (C) 1995 American Institute of Physics.