A MODEL FOR LOW-FREQUENCY CAPACITANCE IN CADMIUM TELLURIDE THIN-FILMS

The dependence of capacitance on thickness has been measured at 1 kHz for CdTe thin films in the thickness range 0.1-1.0-mu-m. The results are shown to be inconsistent with a simple parallel plate capacitance model or with models which also include either a single parallel or series capacitance. A model has therefore been developed which is based on the assumption of additional parallel and series capacitances. The model provides an excellent fit to the data and yields a value of relative permittivity of 9.55 or 9.62 (depending on the details of the model used), which is consistent with other values from the literature. Values of the capacitances derived from the model are approximately 96 pF (parallel) and 27 nF (series). Derived permittivity values are relatively insensitive to the derived capacitance values, always showing a change of less than 1% for capacitance changes of 10%.