Step tunneling enhanced asymmetry in metal-insulator-insulator-metal (MUM) diodes for rectenna applications

摘要

We combine nanolaminate bilayer insulator tunnel barriers (Al_2O_3/HfO_2, HfO_2/Al_2O_3, Al_2O_3/ZrO_2) deposited via atomic layer deposition (ALD) with asymmetric work function metal electrodes to produce MUM diodes with enhanced Ⅰ-Ⅴ asymmetry and non-linearity. We show that the improvements in MUM devices are due to step tunneling rather than resonant tunneling. We also investigate conduction processes as a function of temperature in MIM devices with Nb_2O_5 and Ta_2O_5 high electron affinity insulators. For both Nb_2O_5 and Ta_2O_5 insulators, the dominant conduction process is established as Schottky emission at small biases and Frenkel-Poole emission at large biases. The energy depth of the traps that dominate Frenkel-Poole emission in each material are estimated.