New feature of the photoconductivity in p-type a-Si : H: independence of photoconductivity of p-type a-Si : H films on doping level and defect concentration

Experimental results and results of numerical calculations of T-dependencie s of photoconductivity sigma (ph) in a-Si:H are reported. It was experiment ally observed that the photoconductivity in p-type a-Si:H films (in contras t to n-type ones) depends only slightly on the Fermi level position and def ect concentration at temperatures from 200 to 330 K. It is shown that such asymmetric E-F - E-V and N-D dependencies of sigma (ph) result from asymmet ry of states density distribution in tails. According to calculations, the activated behavior of photoconductivity in p-type a-Si:H is controlled by r ecombination of free carriers through dangling bonds. But occupation statis tic of dangling bonds in p-type a-Si:H under illumination differs essential ly from the one in the dark. (C) 2001 Elsevier Science B.V. All rights rese rved.