Electron transport in selenium-based amorphous xerographic photoreceptors

Abstract

The present paper is the sequel to a previous report. In this paper, electron transport in various selenium-based amorphous xerographic photoreceptors is described. As before, measurements were carried out using xerographic time-of-flight (XTOF) and conventional time-of-flight (TOF) experiments. From the observed flight time the electron drift mobilityμ _e was deduced. Transient photocurrent signals were also recorded at low fields to determine the decay time constant. For a given composition, the sample thickness, light intensity, substrate material and top contacts (in TOF) were varied to investigate whether the observed decay time constantτ _e is a meaningful bulk parameter as in the case of hole transport. Detailed results will be presented to show that the interpretation ofτ _e is complicated. The more plausible explanation for the observed decay is the presence of a uniform distribution of positive space charge in the bulk.μ _e andτ _e were also measured as a function of composition and applied field. Experimental data suggest that electron transport is shallow trap-controlled. Light doping of selenium with arsenic or tellurium creates shallow traps and hence reducedμ _e. The field dependence of electron mobility is in the formμ _e ∝E ⁿ whereE is the applied field andn is a constant less than unity. No electron response can be detected in chlorine-doped Se-As or Se-Te alloys.