Electric Field Effects in Trapping Processes

Abstract

The effects of moderate electric fields (≤3×103 V/cm) on the trapping processes in photosensitive CdS‐CdSe single crystals have been investigated using photoelectronic techniques. Possible mechanisms such as injection of electrons, extraction of holes, dielectric polarization due to inhomogeneities, Joule heating, electrochemical effects, impact ionization, field‐assisted tunneling, and field‐associated changes in the capture cross sections and/or thermal emission probabilities of traps are considered. Evidence is presented for the reality of field‐associated changes in trapping parameters in the absence of all the other possible effects. Results are consistent with a field emptying of Coulomb‐attractive traps by a decrease in the trap depth and a decrease in the capture cross section of traps. The conclusions may be relevant to the interpretation of space‐charge‐limited current data and to mechanisms capable of leading to improved photoconductor speed for low intensity excitation.