Capacitance characteristics in PbSrSe thin films

We report bias- and frequency-dependent capacitance characteristics in Pb1−xSrxSe thin films with Sr composition from 0.066 to 0.276 grown by molecular beam epitaxy on BaF2 substrates. A grain boundary barrier model has been presented, which can well explain the experimental observation of the capacitance in relation with the bias, frequency, as well as the Sr composition. Negative capacitance phenomenon has been observed for samples with different Sr compositions under different bias and frequency conditions. The origin of this negative capacitance effect is believed to be due to the accumulation of minority carriers at the grain boundaries, which produces an additional dynamic capacitance with an opposite sign. In addition, the success in explaining the Sr composition dependent dark current characteristics gives further evidence for the model.