High temperature mmWave switches based on insulator-to-metal transition of Lanthanum Cobalt Oxide

On-wafer millimeter-wave (mmWave) switches are essential components in integrated circuits (ICs) for signal routing, power limiting, and multiplexing. Insulator-to-metal (IMT) phase transition oxides are alternatives to PIN diode and MEMs devices that offer advantages in insertion loss, bandwidth, and size. Most IMT switches use vanadium dioxide (VO2), which cannot operate above 50 C, limiting applications inside high-power and space-based ICs. Here, we show new lanthanum cobalt oxide (LaCoO3, LCO) millimeter-wave switches with IMT switching behavior up to 125 C. We grew epitaxial LCO by sputtering onto both sapphire and silicon carbide substrates. By applying DC current across the LCO, we observe a rapid decrease in resistance from kiloOhms to Ohms, starting around 0.5 mA bias current. Our best switch transitions fully to metal with an applied DC current bias of 50 mA at 125 C, showing a 9 dB change at 30 GHz between the on-state and off-state. This switch had a figure of merit in excess of 2 THz at 125 C.