Effect of the grain boundaries on the conductivity and current transport in II-VI films

The paper presents an investigation of the effect of the grain boundaries on the conductivity and current transport in polycrystalline ZnTe, CdS and CdTe films. The temperature dependence of the conductivity of films in parallel σ_∥ and perpendicular σ_⊥ directions to the substrate was studied. It is shown that σ_⊥ slightly increases with increasing of the temperature for all temperature range considered. We have shown that σ_∥ linearly decreases with increasing of the reverse value of temperature 1/T, which indicates that the barrier height does not depend on temperature. We have found that diffusion theory of the conductivity for bicrystals can be applied only at low voltages not exceeding the net voltage on the grain boundaries. At higher voltages, theory of current transport for drift approximation can be used for large grain films. It is concluded that the influence of the intergrain energy barrier height on the electrical properties of II-VI films is negligible at room temperature.