Fabrication And Performance Study Of Heterojunction Light Emitting Devices By Zno Microwire

Zinc Oxide is a direct band-gap semiconductor material; it has been recognizedas a high efficiency material for ultraviolet light-emitting device (UV-LEDs). BecauseZnO-based LEDs could be compatible with the silicon micro-electronic technology,ZnO microwire/Si heterostructure has great research value. In this paper, focusing onthe design, preparation light emitting devices of ZnO single microwire (SMW) tocarry out work, and the optical and electrical charateristics of the device were studied.Apply the optical microscopy and scanning electron microscopy to study themorphology, structure and size of sample and ZnO SMW. ZnO microwire has sixsurfaces, and each one is very smooth. Then, ZnO microwire sample is measured byX-ray diffraction (XRD) and photoluminescence (PL). We observe six diffractionpeaks through the XRD, therefore, ZnO microwire is hexagonal structure. By the PLspectra, one UV and visble emission can be detected.Study the experimental method of ZnO SMW-based device, a thin film of poly(methyl methacrylate)(PMMA) was spin-coated on the ZnO microwire to preventcontact between substrate and the top electrode. Analyze the influence of metalelectrode and the transparent conductive film on ZnO SMW-based devicesfabrication.The n-ZnO SMW/p-Si heterojunction LEDs are fabricated using thetransparent conductive ITO film as electrode. A distinct UV emission resulting fromfree exciton recombination in ZnO single microwire is observed in theelectroluminescence. Size difference of ZnO single microwire shows significant influence on emission efficiency. The EL spectra of ZnO single microwire exhibitedrelatively stronger UV emission which compared with n-ZnO single nanowire/p-Siheterostructure and n-ZnO film/p-Si heterostructure.The n-ZnO SMW-based high-purity ultraviolet light emitting diodes (UV-LEDs)with SiO2barrier layer has been fabricated on the p-Si substrate. Apply the transparentconductive AZO film to achieve reliable electrical injection, both UV and visibleemissions could be detected in the electroluminescence (EL) measurement. When theinjection current attained4.5mA, a sharp UV emission with peak around390nm,which originated from the n-ZnO SMW, was observed at room temperature. Theintense UV emission in the n-ZnO SMW/SiO2/p-Si heterojunction indicated that SiO2barrier layer can restrict the movement of electrons as expected and resulted ineffective electron-hole recombination in ZnO SMW.n-ZnO single microwire/p-Si heterojunction has been achieved the electricallypumped lasing at room temperature. Whether the device is applied forward bias orreverse bias, the device could electroluminescence, and when the injection currentreached a certain threshold, some sharp emission peak appears in theelectroluminescence spectra, this indicating that the device has achieved electricallypumped lasing under the positive and negative bias.