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 T substrate during deposition; T substrate 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 T substrate , whereas for holes, although the drift mobility is not significantly affected, the lifetime deteriorates rapidly with decreasing T substrate . 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.