Reducing structural change in the phase transition of Ge-doped Bi0.5Sb1.5Te3 to enable high-speed and low-energy memory switching

Abstract

The improving efficiency in obtaining renewable energy has promoted the deployment of electronic systems in the area of limited wired power-supply, whereas the use of devices with reduced threshold-voltage and power-consumption is essential for guaranteeing continuous working capability. Herein, Bi_0.5Sb_1.5Te₃ was optimized by introducing Ge for high-speed and low-energy phase change memory (PCM) application. The high speed of 10 ns and the low threshold voltage of 1.6 V have been achieved, originating from the crystal-like octahedral motifs in the amorphous phase, in which crystallization can be accomplished by the shifting or rotation of these motifs. The good endurance of 10⁵ cycles is due to the small volume change of 4.6% and the formation of a homogenous phase during crystallization, which reduces the risk of stress- and segregation-induced device failure. The nucleation-dominated crystallization behavior of Ge_1.3Bi_0.5Sb_1.5Te₃ is observed, where the Ge atoms with lowest electronegativity are preferred to occupy the center cation layers in the nonuple-layer block, whereas the less metallic Bi and Sb atoms sit on the edged cation layers. The high-speed, low threshold voltage, and low power consumption have made the Ge_1.3Bi_0.5Sb_1.5Te₃ PCM film a promising candidate for application in self-powered electronic systems, i.e. Internet of Things systems with solar energy supply.