Performance comparison of MIM and MIS diodes for energy harvesting applications

Scavenging energy from electromagnetic waves is one of the emerging areas for low-power energy harvesting. The wave is received by an antenna and is then rectified using nonlinear devices for generating required DC voltages. In addition to the traditional diodes other rectifying elements with different structures are exploited to get reduced turn-on voltage and enhanced operating frequency range. For example metal-insulator-metal (MIM) diodes, which work on the principles of the quantum mechanical tunneling, are able to rectify the signals. In this direction this paper presents fabrication and characterization of tunneling-based rectifying MIM, metal-insulator-semiconductor (MIS) and metal-semiconductor (MS) Schottky diodes. Presented MIM tunnel diodes are made using Ti-TiO₂-Al and Ti-TiO₂-Pt stacks, while MIS and MS diodes are fabricated using Si as well as Ge substrates. Measurement results show that Ge p⁺n and Si MIS provide higher output DC voltage as compared to Si pn diodes. MIM diodes operate at a wider frequency range as compared to other devices.