Preparation and basic electrical properties of CdTe thick films

Results of I-U characteristics, C-U dependences, impedance and phase angle measurements, and microscopic measurements on n-and p-type CdTe films allow to construct the following model of the film. The film is composed of conductive grains separated by more resistive intergranular (IG) regions with barriers on interfaces. The space charge regions are formed in grains and in IG regions. The barriers are formed in consequence of localized states on grain-IG regions interfaces and the diffusion across the barriers is the dominating mechanism for transport of charge in the film at 2 to 5 V. The equivalent circuit of the film represents a series chain composed from elements containing parallel (RC) circuits with series resistances R0. R0's correspond to the resistance of neutral bulk of grains and IG regions, parallel RC terms correspond to space charge regions. The frequency dependence of capacity of these regions is caused probably by inertial charge accomodation by localized states on grain-IG regions interfaces, or inside the IG regions. Also the form of Cole-Cole plots can be explained by presence of these states and corresponds to a symmetrical distribution of relaxation times of the interface states. (author)