Towards an optimal MIIM diode for rectennas at 10.6 μm

We investigate, for the first time, optimization of the responsivity of metal-insulator-insulator-metal (MIIM) diodes by carefully considering materials' properties. The diode's resistance is fixed at 100 Ω in order to match the nano antenna's impedance and to increase the total efficiency of the rectifying antenna (rectenna). The optimization is performed at zero-bias responsivity and resistance to ensure zero-bias operation. The diode's resistance and responsivity are calculated from the simulated current-voltage characteristics using Airy functions-based transfer matrix method (TMM) that was verified using experimental results. The design parameters of barrier heights for each insulator and metals, their dielectric constants, and the difference in the metals' work functions, are optimized to enhance the overall diode's performance. Optimal results are presented showing the beneficial effect of simultaneously varying these design parameters. Suggestions for implementing these optimal values with real materials are proposed and presented. Finally, the MIIM capacitance effect on the rectenna cut-off frequency is investigated to ensure that proposed MIIM diodes allow the rectenna to operate efficiently in the IR regime.