Abstract
Transient currents induced by the random walk of particles in site percolation clusters have been investigated by the Monte Carlo technique. The features of the calculated transient currents could be fitted by a pair of hyperbolic decay functions and can describe dispersive transient currents observed in time-of-flight experiments on amorphous solids. The dispersion parameter αi calculated for the incipient percolation cluster was found to be given by T/d where d and d are fractal and fracton dimensions, respectively. We indicate the similarity between the dispersion parameters calculated and those obtained experimentally for amorphous solids and further show that the temperature evolution of the dispersion parameters of a-Si: H can be explained by a random walk in the percolation clusters.