Impact of insulator layer thickness on the performance of metal–MgO–ZnO tunneling diodes

Xuhui Yang, Yousong Gu, Max A. Migliorato, Yue Zhang

    Research output: Contribution to journalArticlepeer-review


    The performance of metal–insulator–semiconductor (MIS) type tunneling diodes based on ZnO nanostructures is investigated through modeling. The framework used in this work is the Schrödinger equation with an effective-mass approximation. The working mechanism of the MIS type tunneling diode is investigated by examining the electron density, electric field, electrostatic potential, and conduction band edge of the device. We show that a valley in the electrostatic potential is formed at the ZnO/MgO interface, which induces an energy barrier at the ZnO side of this interface. Therefore, electrons need to overcome two barriers: the high and narrow MgO barrier, and the barrier from the depletion region induced at the ZnO side of the ZnO/MgO interface. As the MgO layer becomes thicker, the valley in electrostatic potential becomes deeper. At the same time, the barrier induced at the ZnO/MgO interface becomes higher and wider. This leads to a fast decrease in the current passing through the MIS diode. We optimize the thickness of the MgO insulating layer, sandwiched between a ZnO film (in this work we use a single ZnO nanowire) and a metal contact, to achieve maximum performance of the diode, in terms of rectification ratio. An optimal MgO layer thickness of 1.5 nm is found to yield the highest rectification ratio, of approximately 169 times that of a conventional metal–semiconductor–metal Schottky diode. These simulated results can be useful in the design and optimization of ZnO nanodevices, such as light emitting diodes and UV photodetectors. [Figure not available: see fulltext.]

    Original languageEnglish
    Pages (from-to)1290-1299
    Number of pages10
    JournalNano Research
    Issue number5
    Publication statusPublished - 1 May 2016


    • metal–insulator–semicon ductor (MIS) diode
    • MgO layer
    • tunneling mechanism
    • ZnO nanodevices


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