Enhanced low voltage nonlinearity in resonant tunneling metal–insulator–insulator–metal nanostructures

Graphical abstractDisplay Omitted Ta2O5/Al2O3 and Nb2O5/Al2O3 bi-layer MIM devices were studied.Obtained an asymmetry of 18 at 0.35V on Ta2O5/Al2O3 MIIM device.Peak responsivity of 9A/W at 0.2V achieved on Nb2O5/Al2O3 MIIM.Resonant tunnelling effect was observed near 2V. The electrical properties of bi-layer Ta2O5/Al2O3 and Nb2O5/Al2O3 metal-insulator-insulator-metal nanostructures as rectifiers have been investigated. The ultra-thin (1-6nm) insulator layers were deposited by atomic-layer deposition or rf magnetron sputtering with Al as metal contacts. Variable angle spectroscopic ellipsometry was performed to extract the optical properties and band gap of narrow band gap insulator layers while the surface roughness of the metal contacts was measured by atomic force microscopy. Superior low voltage large signal and small signal nonlinearities such as asymmetry of 18 at 0.35V, rate of change of non-linearity of 7.5V-1, and responsivity of 9A/W at 0.2V were observed from the current-voltage characteristics. A sharp increase in current at ~2V on Ta2O5/Al2O3 device can be ascribed to resonant tunneling.