Metal–insulator–insulator–insulator–metal diode combining defect-enhanced direct tunneling and geometric field enhancement

Abstract A metal–insulator–insulator–insulator–metal (MIIIM) diode with electrodes of different metals (Au and Al) and a ZnO–SiO 2 –Al 2 O 3 three-layer tunnel barrier deposited by atomic layer deposition is developed. Defect-enhanced direct tunneling (DEDT) caused by multilayering is promoted at low bias by applying the geometric field enhancement (GFE), effect to improve the ON voltage, zero-bias sensitivity, differential resistance, and asymmetry. GSG probe measurements of the input impedance of the MIIIM diode with a coplanar waveguide (CPW) show that the impedance of the MIIIM diode itself can be ignored. This simplifies the integration of the diode into a rectenna and allows miniaturization. We developed a single-shunt type class-F rectifier circuit that includes MIIIM diodes and evaluated its RF-DC rectification characteristics at 28 GHz. As a result, a DC voltage of 19.0 mV and a DC power of 1.81 nW were obtained. The results presented here are relevant to infrared energy harvesting by nanosized rectennas incorporating such MIIIM diodes.