Amorphous selenium as an X-ray photoconductor

Abstract

We report on electron and hole drift mobility, lifetime and range measurements on vacuum coated stabilized a-Se (a-Se alloyed with As and doped with Cl) X-ray photoconductor type layers as a function of the substrate temperature Tsubstrate during deposition; Tsubstrate has been varied from 6 to 66°C covering the glass transition temperature of a-Se (about 40°C). We find the electron mobility, lifetime and range show essentially no dependence on Tsubstrate, whereas for holes, although the drift mobility is not significantly affected, the lifetime deteriorates rapidly with decreasing Tsubstrate. We also re-examine and discuss the charge conversion efficiency of a-Se X-ray photoconductors by reanalyzing the electron–hole pair creation energy (W±) vs. field data, and evaluating the saturated (minimum) W± from the W± vs. reciprocal field plot.