Effect of indium doping on the properties of Ge[BOND]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. In0.3Ge15Sb85 alloy exhibits an amorphous–crystalline transition temperature (Tc) 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 In0.3Ge15Sb85 thin films is thermally activated with an activation energy of 0.32 eV. The optical transmission spectrum shows that the optical bandgap is Eg = 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 Tc. 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 In0.3Ge15Sb85 alloy for phase-change memory applications with low switching voltage.