EFFECT OF PROLONGED ILLUMINATION ON THE PROPERTIES OF COMPENSATED HYDROGENATED SILICON A-SI-H

The kinetics of the change produced in the conductivity [sigma(E)(t)], photoconductivity, and absorption in the defect region of compensated , hydrogenated amorphous silicon (a-Si:H) by prolonged illumination ar e investigated. The dependences sigma(E)(t) obtained are nonmonotonic, indicating the existence of two processes, one of which increases sig ma(E) at the initial stage of illumination and the other subsequently decreases sigma(E). The effect of the phosphorus and boron concentrati on on each of the two processes is investigated. The possible microsco pic mechanisms responsible for the increase and decrease of sigma(E) a re examined. The results obtained are explained by the formation of da ngling bonds as a result of prolonged illumination. These dangling bon ds are located next to the electrically active boron and phosphorus at oms, whose energy states lie, respectively, in the top and bottom halv es of the mobility gap. (C) 1996 American Institute of Physics.