Charge Transport and Photoconductivity in Amorphous Arsenic Trisulfide Films

Abstract

Charge transport and photoconductivity in As2S3 amorphous films have been investigated at a temperature of 25°C. It is found that holes are the mobile carriers in As2S3 whereas electrons are quite immobile in the material. The photoconductivity is mainly governed by the product of the photogeneration efficiency and the schubweg of the generated holes. Both of these quantities are electric field dependent. Carrier transport is essentially dominated by bulk trapping. The traps are distributed in energies above the hole conduction states. The release rate of the trapped charges varies since the rate is an inverse function of the trap energy. A theoretical model describing the transport process is presented to account for the experimental results. The photogeneration efficiency as a function of electric field at high fields (greater than 105 V/cm) has been determined for incident photon energies of 2.5–3.1 eV. The generation efficiency is observed to decrease in the same manner as the absorption coefficient with decreasing photon energy in the light wavelength range 4000–5000 Å.