Ag/Ti/GeS/Ag Bidirectional\nConductive-Bridge Selector\nwith Low Turn-Off Latency, High Endurance, and Enhanced Switching\nUniformity

To fulfill the demands of three-dimensional (3D) cross-point\narray\narchitectures in embedded memories, selectors with low voltage and\nlow off current with high selectivity are imperative. Selector devices\nwith reliable pulsed switching performance at a logic-compatible voltage\nare crucial for achieving the ultimate goal of embedded 3D universal\ncross-point memory. While resistive ReRAM systems offer high density\nand ultralow power consumption, the 3D cross-point array introduces\nchallenges such as sneak path currents during read and write operations.\nTo overcome these problems, the selectors must be integrated into\neach cross-point cell. Although selector devices have been extensively\nstudied, no singular material system has currently fulfilled all the\nvital needs for integration with nonvolatile memory. Here, we demonstrate\nan Ag-gated GeS-based bidirectional threshold switching selector device\n(Ag/Ti/GeS/Ag) with a highly uniform cycle-to-cycle and device-to-device\nswitching performance. The device demonstrates highly uniform bidirectional\nthreshold switching with promising attributes, including low threshold\nvoltages (∼±0.22 V), low off current (∼pA), large\nselectivity window (∼3 × 108), an endurance of more than\n109 cycles, and an on/off switching latency of 50 ns at 1 V pulsed\noperations. The simple material configuration of the selector device\n(Ag/Ti/GeS/Ag) facilitates easy fabrication, and its uniform switching\nperformance makes it suitable for 3D cross-point integration with\nnonvolatile memory cells in a one-selector–one-resistor array\nconfiguration.