Effect of indium doping on the properties of Ge-Sb phase-change alloy

The crystallization, electrical, and optical properties of indium-modified Ge₁₅Sb₈₅ phase-change alloy have been investigated in this work. This alloy is used for solid-state memory applications. In _0.3Ge₁₅Sb₈₅ alloy exhibits an amorphous-crystalline transition temperature (T_c) that is slightly higher than that of Ge₁₅Sb₈₅ alloy, which may lead to an improvement in its data retention time and thermal stability. AC conductivity measurements demonstrate that the conductivity of In_0.3Ge ₁₅Sb₈₅ thin films is thermally activated with an activation energy of 0.32 eV. The optical transmission spectrum shows that the optical bandgap is E_g = 0.44 eV. The reported data reveals the presence of a Fermi level in the vicinity of the valance-band localized states. The capacitance-voltage measurements were performed for a sweep voltage from -20 to +20 V at different temperatures. At low temperatures, the capacitance is electric-field independent and the crystallization is growth limited while the capacitance is electric field dependent at temperatures close to T_c. The reported data show that modifying Ge₁₅Sb₈₅ alloy with indium causes a significant increase in the electrical conductivity of the film that makes the capacitance always negative. These results promote the possibility of using In_0.3Ge₁₅Sb₈₅ alloy for phase-change memory applications with low switching voltage.