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The transport properties of vacuum evaporated films of “pure” selenium and selenium doped with small quantities of Cl (0–40 ppm) and As (∼12at.%) have been examined using a time-resolved drift technique. Addition of Cl alone acts as an electron trap, and addition of As alone acts as a hole trap while greatly increasing the electron free-carrier lifetime. When used in combination, controlled addition of these two impurities can be used to produce hole ranges greater than 7.5×10−6 cm2/V and electron ranges greater than 1.2×10−6 cm2/V in the same film. This hole range is approximately a factor of 3 greater and the electron range a factor of 5 greater than that observed in the best pure Se films.