Enhanced low voltage nonlinearity in resonant tunneling metal-insulator-insulator-metal nanostructures (Microelectronic Engineering 2015)

The ultra-thin (1-6 nm) 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 0.35 V, rate of change of non-linearity of 7.5 V-1, and responsivity of 9 A/W at 0.2 V were observed from the current-voltage characteristics. A sharp increase in current at ~2 V on Ta2O5/Al2O3 device can be ascribed to resonant tunneling.