Electrical switching dynamics and broadband microwave characteristics of VO2 RF devices

摘要

Vanadium dioxide is a correlated electron system that features ametal-insulator phase transition (MIT) above room temperature and is ofinterest in high speed switching devices. Here, we integrate VO2 intotwo-terminal coplanar waveguides and demonstrate a large resistance modulationof the same magnitude (>10^3) in both electrically (i.e. by bias voltage,referred to as E-MIT) and thermally (T-MIT) driven transitions. We examinetransient switching characteristics of the E-MIT and observe twodistinguishable time scales for switching. We find an abrupt jump inconductivity with a rise time of the order of 10 ns followed by an oscillatorydamping to steady state on the order of several {\mu}s. We characterize the RFpower response in the On state and find that high RF input power drives VO2further into the metallic phase, indicating that electromagneticradiation-switching of the phase transition may be possible. We measureS-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at2.95 dB across the frequency range in the On state and sufficient isolation ofover 25 dB is observed in the Off state. We are able to simulate the RFresponse accurately using both lumped element and 3D electromagnetic models.Extrapolation of our results suggests that optimizing device geometry canreduce insertion loss further and maintain broadband flatness up to 40 GHz.