Electrical Switching Studies of Amorphous Ge1Se1Te2 Thin Film for a High-Performance Nonvolatile Phase-Change Memory

Abstract

In the present work, we studied the changes in the electrical conductivity occurring in a new composition of amorphous Ge1Se1Te thin film for a high-performance nonvolatile phase-change memory. A phase-change random access memory (PRAM) device without an access transistor is successfully fabricated with the Ge1Se1Te2 phase-change resistor, which has a much higher electrical resistivity than that of conventional Ge2Sb2Te5, and its electric resistivity can be varied by the factor of 105, related to the degree of crystallization. Chalcogenide Ge1Se1Te2 thin film of 100 nm thickness was formed by vacuum deposition at 1.5×10-5 Torr. The static mode switching characteristics are tested for the 100 µm-sized Ge1Se1Te2 PRAM device. In the first sweep, the amorphous Ge1Se1Te2 thin film showed a high resistance state in the low voltage region. However, when it reached the threshold voltage, Vth, the electrical resistance of the device was drastically reduced through the formation of an electrically conducting path. The results of pulsed mode switching of the 20 µm-sized Ge1Se1Te2 PRAM devices show that the reset process of the device was accomplished with an 80 ns–8.6 V pulse and the set process of the device was accomplished with a 200 ns–4.3 V pulse.