Determination of localized state distributions in amorphous semiconductors from excess charge carrier thermalization

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Abstract
Assuming a shape for the time-dependent trap occupancy function, a general relation between the number of free excess carriers n(t) and the density of trapping states G(E) is derived in the form of a Volterra integral equation of the second kind. An algorithm for solving this equation numerically using limited computer time is described. A simple program is applied to transient-current data for several trap distributions, obtained analytically or by means of computer-assisted Monte Carlo simulation. The calculated distributions are in good agreement with the original ones, especially where features in the density of states are wide or well separated. Effects of the use of incorrect system parameters are also considered.