Photoconductivity of a-Si:H and a-Ge:H: influence of potential fluctuations

Long-range potential fluctuations that modulate the band edges significantly affect the dc and ac photoconductivities in a-Si:H and a-Ge:H. The so-called μτ-product and the dielectric relaxation time in the temperature range between 20 and 300 K are obtained in the present materials. The magnitude of potential fluctuations estimated from the dc and ac conductivities is almost consistent with that from the thermoelectric power.