Supriyo Bandyopadhyay

The field effect transistor is the most celebrated electron device and possibly the one most researched with the most investment in both academia and industry. While the original idea involved changing the concentration of charge carriers in the channel with a gate voltage to modulate the flow of current between the source and the drain contacts, later avatars explored more fanciful ways of changing the source to drain current with a gate voltage. Perhaps the most intriguing notion was to change the spin-polarization of electrons in the channel with a gate voltage instead of changing the concentration. The gate voltage induced Rashba-type spin-orbit interaction in the channel material (usually a narrow gap semiconductor) which modulated the current flowing between ferromagnetic source and drain contacts that acted as spin polarizers and analyzers. The presumed advantage was the lower switching energy dissipation accruing from the fact that the electron concentration did not have to change; only the spin polarization will change. This is the now celebrated Spin Field Effect Transistor (SPINFET) that was named as one of the most important scientific advances in this century by the journal Nature. Regardless of all the excitement and enthusiasm, the SPINFET has never been demonstrated unambiguously. This talk will chart out some of the reasons why this device has been so elusive. There are different types of SPINFETs based on different aspects of spin transport and different physical mechanisms. While they do not ultimately exhibit any feature that will eclipse the traditional FET in overall performance, they nevertheless sport certain features (e.g., oscillatory transfer characteristics with both positive and negative transconductance) that can have niche applications, such as single transistor frequency multipliers. 

Biography:

Supriyo Bandyopadhyay is Commonwealth Professor of Electrical and Computer Engineering at Virginia Commonwealth University where he directs the Quantum Device Laboratory. Research in the laboratory has been frequently featured in national and international media (newspapers, internet blogs, magazines, journals such as Nature and Nanotechnology, TV and radio, and internet news portals). Prof. Bandyopadhyay was named Virginia’s Outstanding Scientist by Virginia’s Governor Terence R. McAuliffe in 2016. His alma mater, the Indian Institute of Technology, Kharagpur, India named him a distinguished alumnus in 2016. His current employer Virginia Commonwealth University bestowed upon him the Distinguished Scholarship Award (given annually to one faculty member in the University) and the University Award of Excellence (the highest honor the University can bestow on a faculty member, one per year). His department gave him the Lifetime Achievement Award (one of two given in the department’s history). His earlier employer, University of Nebraska-Lincoln, conferred on him the College of Engineering Research Award (1998), the College of Engineering Service Award (2000) and the Interdisciplinary Research Award (2001). In 2018, he received the State Council of Higher Education for Virginia Outstanding Faculty Award. This is the highest award for educators in private and public universities in the State of Virginia. In 2020, Prof. Bandyopadhyay was named the winner of the “Pioneer in Nanotechnology” award of the Nanotechnology Council of IEEE, which is the highest award of that Council. That year, he served as a Jefferson Science Fellow of the US National Academies of Science, Engineering and Medicine, and was assigned as a Senior Adviser to the USAID Bureau of Europe and Eurasia, Division of Energy and Infrastructure. Prof. Bandyopadhyay has authored and co-authored over 400 research publications and presented over 150 invited talks and colloquia across six continents. He is a Fellow of IEEE, APS, IoP, ECS and AAAS. 

Address:Dept. of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, VA 23284, , United States