Capacitance characterization of Ge₁₅Sb₈₅ phase-change thin films

The capacitance variation as a function of temperature and electric field for tellurium free Ge₁₅Sb₈₅ thin films deposited by the DC sputtering technique is investigated. The capacitance measurements were performed for a sweep voltage from -20 to +20V at different temperatures, and at a frequency of 100kHz. The results show a slight increase in the capacitance with temperature and it reaches a maximum value around 80°C. As the temperature increases, the capacitance decreases and eventually becomes negative at temperatures close to the amorphous-crystalline transition temperature (T_C). The sharp decrease in the capacitance can be attributed to the thermally activated conduction process with activation energy of 0.28eV. Nonlinearity in the variation of capacitance with the applied bias voltage is observed at high temperatures close to T_C. The phenomenon is explained in terms of the nucleation and growth process.