Ultrahigh Rectification Ratio in an Asymmetric Metal/Semiconductor/Metal Nanoscale Tunneling Junction: Implications for High-Frequency Rectifiers

The ultrafast quantum-based electron-transport mechanism with a typical tunneling time of femtoseconds is appealing to fabricate high-frequency rectifier diode devices for applications such as solar energy harvesting, THz mixers, and infrared detectors. Here, we demonstrate an ultrahigh rectification of more than 10⁴ and a large forward current density of 13.8 A/cm² at −2 V in the structure of a metal/semiconductor/metal (MSM, Pt/ZnO/TiN) nanoscale tunneling junction. Technology computer-aided design (TCAD) simulations demonstrate that high rectification originates from the switching of the electron-transport mechanism between direct tunneling (DT) and Fowler-Nordheim tunneling (FNT) under positive and negative voltage biases, respectively. The quantum-based FNT mechanism gives very slight temperature dependence of currents in a wide temperature range of 100-400 K. This work opens an avenue for high-frequency rectifier diodes based on MSM nanoscale tunneling junctions.