Space charge perturbed transient transport in a dispersive medium a-As 2Se 3

Abstract

Transport of an injected sheet of flash photoexcited holes is compared under small and large signal conditions in the same a-As 2Se 3 specimen films. Under small signal conditions the injected charge packet transits the specimen bulk in a uniform field. Under lage signal conditions nearly a CV of charge is injected and transport therefore proceeds under space charge perturbed conditions. Many experimental comparisons between transport under small and large signal conditions have been made in non-dispersive media. Features unique to transient transport under space charge perturbed conditions in nondispersive systems are theoretically predicted and typically observed. In a-As 2Se 3, a prototypical dispersive medium, no analogous distinction is observed between transient transport behavior under small and large signal conditions. Key characteristics of dispersive transport under small signal (pulse injection) conditions for example, the computed transit times, universality of the transient current pulse shape with respect to field and the correlation between current pulse shape and field dependence of the transit time are unchanged in the large photoexcitation limit. Temperature dependence of the dispersion parameter α is observed. It is also unaffected by photoexcitation intensity.