3D Stackable and Scalable Binary Ovonic Threshold Switch Devices with Excellent Thermal Stability and Low Leakage Current for High‐Density Cross‐Point Memory Applications

• Published in: Advanced electronic materials Vol. 5; no. 7
• Main Authors: Yoo, Jongmyung, Kim, Seong Hun, Chekol, Solomon Amsalu, Park, Jaehyuk, Sung, Changhyuck, Song, Jeonghwan, Lee, Donghwa, Hwang, Hyunsang
• Format: Journal Article
• Language: English
• Published: 01.07.2019
• Subjects: first‐principles calculations; high thermal stability; high‐density cross‐point memory array; ovonic threshold switch
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.201900196

The development of selector devices is essential for the implementation of dense memory arrays. Ovonic threshold switch (OTS) devices have gained interest as high‐performance selectors, but their material complexity and low thermal stability remain concerns. The effect of element compositions and its types on binary telluride‐based OTS are investigated to develop selectors that meet the simple material composition and high thermal stability requirements while ensuring low OFF‐state leakage current (IOFF). Through a careful control of Te composition in binary tellurides, binary OTS devices with low IOFF (≈5 nA) and fast switching speed (<10 ns) are obtained. In addition, high endurance (108) and thermal stability (450 °C) are achieved by adopting tellurides including small elements. The high thermal stability of the developed OTS devices results from the strong covalent bonds between Te and small elements that prevent crystallization of the tellurides, which is revealed by performing first‐principles calculations. The binary OTS are also compatible with a 3D stacking technology, which is confirmed by fabricating a 3D B‐Te‐based device that shows good OTS characteristics. In addition, the OTS device successfully suppresses the leakage current in half‐selected cells when it is integrated with a resistive random access memory (ReRAM) device. An ovonic threshold switch (OTS) device with high thermal stability and low off‐state current is obtained by adopting a simple binary telluride system containing small elements and proper tellurium composition. The feasibility of the developed OTS device as a 3D stackable device and a selector is also confirmed, demonstrating its excellence as a promising switch device.