Capacitance–voltage characteristics of In0.3Ge2Sb2Te5 thin films

The influence of indium doping on the capacitance variation with temperature and applied bias voltage of Ge2Sb2Te5 is investigated. The capacitance–voltage (C–V) measurements of In0.3Ge2Sb2Te5 and Ge2Sb2Te5 thin films were performed for a sweep of voltages from −20 to +20 V at different temperatures. The results show different capacitance behavior of In0.3Ge2Sb2Te5 and Ge2Sb2Te5 films. As the temperature increases the capacitance of the indium-doped sample decreases and becomes negative. The negative capacitance effect might be attributed to a significant increase of the film’s conductivity due to temperature and applied bias voltage. The nonlinearity in the capacitance and conductivity could be related to the nucleation mechanism as the temperature becomes close to the amorphous–crystalline transition temperature.