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

• Published in: Nano research 2016-05, Vol.9 (5), p.1290-1299
• Main Authors: Yang, Xuhui, Gu, Yousong, Migliorato, Max A., Zhang, Yue
• Format: Article
• Language: English
• Subjects: Atomic/Molecular Structure and Spectra; Barriers; Biomedicine; Biotechnology; Chemistry and Materials Science; Computer simulation; Condensed Matter Physics; Conduction; Conduction bands; Design optimization; Diodes; Electric contacts; Electron density; Electrostatic properties; Electrostatics; Light emitting diodes; Magnesium oxide; Materials Science; Metals; MIS (semiconductors); Nanostructure; Nanotechnology; Nanotechnology devices; Nanowires; Organic light emitting diodes; Research Article; Schottky diodes; Schrodinger equation; Thickness; Tunneling; Ultraviolet radiation; Zinc oxide; 性能; 氧化锌纳米线; 管理信息系统; 绝缘层厚度; 金属-半导体-金属; 金属-绝缘体; 金属氧化锌; 隧穿二极管
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-016-1024-y

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 Schr6dinger 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.