Influence of various distributions of localized states upon transit pulse dispersion in amorphous semiconductors

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Abstract
Monte Carlo simulation techniques have been employed in the examination of anomalously-dispersive transport characteristics of specimens with various energy distributions of localized states. For each of the four distributions studied, the ‘initial slope’ dispersion parameter, α1, varies similarly with temperature, and exhibits an approximately linear variation in the low-temperature regime. This demonstrates that such behaviour does not constitute evidence for the presence of a particular (e.g. exponential) energy distribution of traps. The ‘final slope’ dispersion parameter, α2 is found to be appreciably more sensitive than α1 to changes in the energy distribution of localized states. A comparison of experimental behaviour with the simulation data suggests that various non-crystalline semiconductors possess a comparatively structured distribution of trapping centres, rather than the featureless tail of localized states which has been inferred from some recent studies.