Physics and technology of electronic insulator-to-metal transition (E-IMT) for record high on/off ratio and low voltage in device applications

New device concepts related to both computing and biological function emulation are emerging rapidly based upon the electronic insulator-to-metal transition (E-IMT) effect that some oxides, such as VO2, exhibit. However, the experimental E-IMT devices to-date are limited to an ON/OFF ratio of ∼10², resulting in a small and inadequate dynamic range in device operation. In addition, the voltage that drives the E-IMT is high, typically above 1 V. In this paper, we investigate the physics and technology toward realizing both high ON/OFF and low-voltage E-IMT devices. We show that, the ON/OFF ratio, critical E-IMT voltage, and device reliability are closely coupled. A predictive model is developed and shows that, for reliable operation, the maximum ON/OFF ratio of an E-IMT device should follow a square-root relation with the strength of the thermally driven insulator-to-metal transition (T-IMT). This new design rule is verified by systematic experiments using prototypical VO2 E-IMT devices. Through this study, we achieve a record value of reliable E-IMT with an ON/OFF ratio of 3.5×10³ at 1.2 V - greater than 10x improvement over the previous state-of-the-art. A record low voltage of IMT switching at 0.3 V (ON/OFF ratio = 20) is also demonstrated. The proposed universal design rule is widely applicable for a range of emerging applications based on E-IMT devices. As an experimental example, the E-IMT based transistors show an ultra-steep subthreshold swing (<1mV/dec) and ON/OFF ratio >10³.