Effect of copper and chlorine on the properties of SiO2 encapsulated polycrystalline CdSe films

The effects of different copper doping concentrations on the properties of SiO2 encapsulated CdSe films have been investigated. Two methods were used to dope the films with copper: ion implantation and diffusion from a surfac e layer. The room temperature dark resistivity of films annealed in oxygen at 450 degreesC was found to increase as the copper concentration was incre ased until a maximum resistivity of 10(8) ohm cm occurred at a copper conce ntration of 10(20) atoms cm(-3) The room temperature resistivity in the lig ht was found to be independent of the copper concentration and whether the films were annealed in argon or oxygen. During annealing the grains grew fr om 0.03 mum to 0.3 mum and this growth was independent of the doping or the annealing ambient. The energy levels, carrier mobilities, and microstructu re of the annealed films were dependent on the method of doping. The ion im planted films had an additional energy level at 0.33 eV and their mobility was a factor of 4 smaller than films doped by the surface diffusion method, whose mobilities were 20 to 35 cm(2)V(-1) s(-1). The addition of chlorine to copper doped films had no effect on either the resistivity or photosensi tivity but slowed the response times of the photocurrent by a factor of 10. No energy levels were observed which could be associated with the copper n or was the copper found to affect the density of the observed intrinsic lev els at 0.65 and 1.1 eV.