INFLUENCE OF DOPING ON THE PHOTOCONDUCTIVITY OF A-SI-H

An analysis is made of the influence of the nature and concentration o f a dopant on the photoconductivity of a-Si:H films at room temperatur es. The observed difference between the dependences of the photoconduc tivity of n- and p-type a-Si:H films on the dopant and defect concentr ations is due to the different lengths of the conduction- and valence- band tails of the density of states. The long valence-band tail result s in a strongly nonequilibrium occupancy of the states of defects duri ng illumination. Consequently, the concentration of recombination cent ers in p-type a-Si:H films is practically independent of the dopant an d defect concentrations, but it is governed by the density of states i n the valence-band tail.