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

摘要

Phase-change random access memory cells with superlattice-like (SLL) GeTe/Sb_2Te_3 were demonstrated to have excellent scaling performance in terms of switching speed and operating voltage. In this study, the correlations between the cell size, switching speed and operating voltage of the SLL cells were identified and investigated. We found that small SLL cells can achieve faster switching speed and lower operating voltage compared to the large SLL cells. Fast amorphization and crystallization of 300ps and 1ns were achieved in the 40nm SLL cells, respectively, both significantly faster than those observed in the Ge_2Sb_2Te_5 (GST) cells of the same cell size. 40nm SLL cells were found to switch with low amorphization voltage of 0.9V when pulse-widths of 5ns were employed, which is much lower than the 1.6V required by the GST cells of the same cell size. These effects can be attributed to the fast heterogeneous crystallization, low thermal conductivity and high resistivity of the SLL structures. Nanoscale PCRAM with SLL structure promises applications in high speed and low power memory devices.