EFFECT OF GAP STATE DENSITY ON THE PHOTOCONDUCTIVITY AND PHOTO-LUMINESCENCE OF ALPHA-SI-H

This paper discusses experimental evidence that a fixed amount of hydrogen introduced into amorphous silicon at different hydrogen partial pressures during sputtering may have quite different results for the total density and distribution in energy of states in the pseudogap. Whereas the expected effect is the removal of gap states through the formation of strong Si-H bonds, we show evidence that the gap state densities in some films increase by an order of magnitude over other similar hydrogen content samples. Moreover, such material has much increased photoconductivity response and additional photoluminescence features. We speculate briefly on the possible origin of this higher density of gap states in terms of either natural defects of a-Si or states associated with the Si-H complex. © 1979.