Enhanced rectification performance of MIM tunnel diode applying an oxide semiconductor electrode*

MIM DIODE using F-N tunneling-based conduction mechanism is the most promising diode device as ultra-high frequency rectifier because the electron tunneling process takes only femtoseconds. However, in spite of the ultra-fast operation of the MIM, it is difficult to increase the On / Off ratio which is the most important property of diode. Here we propose a solution to apply an oxide semiconductor film as an electrode in MIM structure in order to increase a rectification ratio of electrical currents. An IGZO thin-film, which is a well-known-type semiconductor, was formed on a HfO₂ insulator with a thickness under 20 nm. Depending on the depleted surface charge state at the IGZO / HfO₂ interface under negative voltages, the current is rectified, therefore, the rectification ratio is highly enhanced to 10⁵ at 3 V. Furthermore, the conduction of electron maintains the F-N tunneling, which means our device can be operated at high frequency. We believe that the F-N tunneling-based MIS DIODE for ultra-high frequency diodes will be used in future electronic devices and wireless power transfers.