Electrical and stoichiometric characteristics of CdTe films deposited by the hot-wall flash-evaporation technique

The electrical and stoichiometric characteristics of polycrystalline CdTe films deposited by the hot-wall flash-evaporation technique are reported for different deposition parameters. The crystallites in these films grow in a columnar type of grain. The stoichiometry of the films is largely dependent on substrate (T_s) and wall temperatures (T_w) during deposition. At low values of T_s and T_w (∼92 and 425 °C, respectively) a large excess of Te is present (∼30 at. %). At T _s≅192 °C and T_w≅560 °C, nearly stoichiometric films were obtained. The electrical characteristics were strongly dependent on the amount of excess Te present in the samples. A change in the resistivity of up to seven orders of magnitude was measured between the samples with ∼30 at. % of excess Te and those with a stoichiometry close to 1:1. Also a large difference in the resistivity measurements was observed on the surface and across the samples for the different deposition conditions studied. The behavior of the resistivity with temperature in the 100-500 K range is also discussed.