Integrating phase-change memory cell with Ge nanowire diode for crosspoint memory-experimental demonstration and analysis

In this paper, we demonstrate a novel phase-change memory cell utilizing a low-temperature in situ doped single crystalline germanium nanowire diode as a bottom electrode as well as a memory-cell selection device. The integrated memory cell shows promising characteristics such as low programming current, large set/reset resistance ratio, and rectifying behavior, which is required for high-density 3-D crosspoint memory. The small contact area determined by the diameter of nanowires enables low programming current below 200 mu A for reset and 50 mu A for set. The average resistance ratio of set/reset state programmed by repetitive pulse programming is 82, which is large enough for large-array operation. The heterojunction formed between in situ doped Ge nanowires and Si substrate provides 100x isolation for crosspoint-memory operation.