Thermoelectric and photothermoelectric effects in semiconductors: Cadmium sulfide films

Abstract

Techniques of thermoelectric and photothermoelectric analysis have been applied to investigate the electrical transport properties of both solution-sprayed and evaporated polycrystalline CdS films. Dark electron densities are independent of temperature between 200 and 330°K because of shallow donors; dark electron mobilities are thermally activated with energies between 0.09 and 0.23 eV. Photoconductivity of solution-sprayed films is caused primarily by an increase in electron mobility. Other effects investigated are the adsorption and desorption of oxygen, the diffusion of Cu acceptors, and field-assisted drift of Cu impurities in the film at a slightly elevated temperature (100°C). The structure and characteristics of intergrain boundaries dominate the transport processes in these polycrystalline films.