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 (T_c).