Ion electromigration in CdTe Schottky metal–semiconductor–metal structure
Abstract We measured current transients in metal–semiconductor– metal (M–S–M) structure with two Au Schottky contacts fabricated to low resistivity p-CdTe material and propose a new model considering the electromigration of ions in the depletion region formed at the reversed biased Au–CdTe interface. We assume that the electric field confined in the depletion region causes at elevated temperatures electromigration of donor defects in the semiconductor bulk. The drift of these ions changes with time the value of the electric field at the Au–CdTe interface and the value of resistance of the depletion region. The correlation between this field and the value of the reversed electric current is determined from the shape of current–voltage characteristics of the structure. We explain the change of the current with time as a result of changing electric field at the interface. The I R -V measurement on the studied sample reveals that the field dependence of barrier height due to the image force is the mechanism responsible for the non-saturated reverse current. We also determined the initial value of the charge density and extracted the diffusion coefficients of the donor ions. The behavior of resistance of the depletion region with time confirms the proposed model of electromigration of positive ions under the field in the depletion region. The stability and possible recovery of the resistivity of the sample were checked out, and we note that there was only very weak tendency of the resistivity to revert to initial conditions even after 14 days.