Electrical and crystallization properties of indium doped Ge-Sb-Se films

Rapid advances in information technology rely on large capacity, high speed, and thermally stable phase-change nonvolatile materials. This work is investigating the capacitance-voltage characteristics of multinary chalcogenides (Ge15Sb80Se5 and Ge15Sb70Se10In5) to study their electrical properties and their reliant on frequency, bias voltage, and temperature. The results show different capacitance behavior for the two films, Ge15Sb80Se5 and Ge15Sb70Se10In5. Adding indium to Ge-Sb-Se alloy improved its thermal stability by increasing the crystallization temperature by almost 20 K, and shows a fast crystallization process. The results illustrate that the capacitance of Ge15Sb70Se10In5 film has a nonlinear-temperature behavior and becomes negative at high temperatures. The negative capacitance could be attributed to a significant increase in the conductivity of the film due to temperature and applied bias voltage. Moreover, during the phase change, the amorphous-crystalline interfaces might behave as a junction with a potential barrier where charge carriers accumulate. The nonlinearity in the capacitance and conductance is attributed to the nucleation-growth mechanism when the temperature becomes close to the amorphous-crystalline transition temperature (Tc).