Barrier height estimation of asymmetric metal-insulator-metal tunneling diodes

A method is developed to estimate barrier heights of an asymmetric metal-insulator-metal (MIM) diode exhibiting Fowler-Nordheim tunneling. The method requires determination of slopes and intercepts of a log(|I(V+Δϕ)2|) versus 1V+Δϕ plot rather than a log(|I(V)2|) versus 1V plot (i.e., a conventional Fowler-Nordheim plot), where I, V, and Δϕ refer to tunneling current, applied voltage, and the difference in barrier heights, respectively. As the value of Δϕ directly impacts the applied electric field magnitude, it is a critical component in barrier height determination from a current-voltage measurement. Conventional Fowler-Nordheim plot analysis does not employ Δϕ, which compromises the accuracy of barrier height estimation when Δϕ≠0. Using the described method, the barrier heights of a ZrCuNiAl/Al2O3/Al MIM diode are estimated to be 1.75 V and 1.07 V, respectively, and the Al2O3 tunneling effective mass is estimated to be 0.47. Additional MIM diodes are analyzed to show that the accuracy of MIM diode barrier height and effective mass estimates is highly sensitive to contamination and/or energy imparted during the deposition of the upper electrode.