Ultrafast switching in nanoscale phase-change random access memory with superlattice-likestructures

Abstract

Phase-change random access memory cells with superlattice-like (SLL)GeTe/Sb2Te3 were demonstrated to have excellent scaling performance in terms of switching speed andoperating voltage. In this study, the correlations between the cell size, switching speed andoperating voltage of the SLL cells were identified and investigated. We found that smallSLL cells can achieve faster switching speed and lower operating voltage compared to thelarge SLL cells. Fast amorphization and crystallization of 300 ps and 1 ns were achieved inthe 40 nm SLL cells, respectively, both significantly faster than those observed in theGe2Sb2Te5 (GST) cells of the same cell size. 40 nm SLL cells were found to switch with lowamorphization voltage of 0.9 V when pulse-widths of 5 ns were employed, which ismuch lower than the 1.6 V required by the GST cells of the same cell size. Theseeffects can be attributed to the fast heterogeneous crystallization, low thermalconductivity and high resistivity of the SLL structures. Nanoscale PCRAM with SLLstructure promises applications in high speed and low power memory devices.