Transition from transient to steady-state dark currents in amorphous As2Se3

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Abstract
The time dependent evolution of the dark current following application of a voltage step to an amorphous As2Se3 gold contact sandwich cell has been studied as a function of field, temperature, sample thickness and surface photoexcitation The gold a-As2Se3 interface is demonstrated to form a finite injecting contact not an ohmic contact as is commonly presumed. The initial time dependent dark current shape following step excitation is found to exhibit a number of unique experimental features which reflect the interplay of a finite contact reservoir with the highly dispersive hole transport process known to be characteristic of a-As2Se3. These features are shown to follow naturally from a model which treats, in a small signal approximation, the evolving current for several transit times after excitation as the convolution of a time dependent surface source function with the stochastic description of the hole transits.