Professor Weidong Zhang

Weidong Zhang is a professor of nano-electronics, leading the memory devices research at Liverpool John Moores University (LJMU), where the research in this field is ranked 11th and 26th in the last two UK government research assessments. He is the principal investigator and co-investigator of a number of research projects with a total value of more than £3 million, including five prestigious research grants from the Engineering and Physical Sciences Research Council (EPSRC), a leading UK government research funding council. He has led the LJMU’s collaboration with IMEC memory device group for the past 14 years, whose partners include Intel, Micron, Samsung, western Digital, SK Hynix and Toshiba. His current research interests include characterization and quality assessment of resistive switching and flash memory and selector devices, CMOS devices based on Si, Ge and III-V materials, and GaN HEMT devices. His work is predominantly published in international journals and premier conferences, including Applied Physics Letters, IEEE Electron Device Letters, IEEE Transactions on Electron Devices. He has co-authored 10 papers in the flagship IEEE International Electron Device Meeting (IEDM) and 7 papers in IEEE Symposium on VLSI Technology (VLSI) in the past 10 years.

Invited Talk Topic: Reliability and Characterization of GeSe OTS Selector Device

Selector device with high on-state current, high half-bias nonlinearity and excellent endurance is critical to suppress the sneak path in high-density cross-point resistive switching memory arrays. Based on novel characterization and supported by first-principles simulations, filamentary-type switching, Weibull distribution of time-to-switch-on/-off and Vth relaxation in GexSe1-x OTS selector device are demonstrated and associated with defect delocalization/localization. Its endurance degradation and recovery mechanisms are identified as delocalized slow defects accumulation and Ge-Se segregation/crystallization. An optimal refreshing scheme is designed that can improve the endurance by more than five orders. This work provides new insights to the OTS switching, relaxation and degradation mechanisms and guidance for performance improvement.