Drift Mobilities of Electrons and Holes and Space-Charge-Limited Currents in Amorphous Selenium Films

The band model has been applied to semiconducting amorphous selenium. Drift mobilities in pure films agreed well with previous results of Spear, and some evidence was obtained that the shallow electron and hole traps were caused by imperfections, with further considerations suggesting that the traps were distributed continuously in energy. Electron drift mobilities were reduced when arsenic was added to the films but their temperature dependence was unchanged, suggesting that arsenic increased the concentrations of imperfections which produce shallow electron traps. Hole ranges were (2-4)×${10}^{-8\mathrm{}}$ ${\mathrm{cm}}^2$/v and exhibited no observable temperature dependence, while electron ranges were (1-2)×${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^2$/v at 300°K and decreased with decreasing temperature.