Bow-Tie Antenna Integrated with an HfO2-Based MIM Diode for Millimetre Wave Harvesting

In this paper, we present a millimetre wave harvester consisting of a bow-tie antenna integrated with a hafnium dioxide (HfO2)-based metal-insulator-metal (MIM) diode, capable to rectify the incoming electromagnetic radiation in the V band (i.e. 40–75 GHz). We reduced significantly the diode resistance, thus improving antenna-diode matching, which is a major issue when using a MIM diode with a differential resistance in the order of hundreds or thousands of $\mathrm{k}\Omega$. In detail, we designed, fabricated and tested on a standard 4-inch silicon wafer a 61.6-GHz rectenna in which the vertical Au-HfO2-Pt MIM structure is integrated between antenna arms. The 6-nm-thick HfO2 single-layer guarantees a much higher DC current density of almost $\mathbf{3}\times \mathbf{10}^{\mathbf{4}}\mathbf{A}/\mathbf{cm}^{2}$, in comparison with state-of-the-art single-layer MIM diodes. This way, the proposed rectenna efficiently harvests up to $\mathbf{250} \mu \mathbf{V}$ with −20 dBm of incoming power, with a promising voltage responsivity of over 5 V/W. The results are very encouraging for their practical exploitation in future low-power solutions for energetically-autonomous 5G terminal equipment.