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Study on the synthesis and properties of MSM ultraviolet detector system

Author: YangLeChen
Tutor: ZhouXiuLi
School: University of Electronic Science and Technology
Course: Optics
Keywords: ultraviolet photodetector metal-semiconductor-metal GaN/AlGaN Ga-doped ZnO quantum efficiency
CLC: TN23
Type: Master's thesis
Year: 2012
Downloads: 87
Quote: 0
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Abstract


The development of ultraviolet (UV) photodetector has been driven by numerous applications in defense, commercial, and scientific arenas. These include, for example, covert space-to-space communications, early missile threat detection, UV spectroscopy, chemical and biological threat detection, flame detection and monitoring, power line monitoring, UV environmental monitoring, and UV astronomy. Schottky metal-semiconductor-metal (MSM) photodetectors are also relatively simple photodetector to realize, these devices are arguably simpler to fabricate because there is no need to highly dope the material and to achieve ohmic contacts. MSM detectors exhibit all of the desirable attributes of a practical photodetector, such as:high gain, low dark current, high speed, large bandwidth and high sensitivity. However, these devices require an applied bias to operate, and their performance characteristics are dependant on this applied bias, since it changes the volume of the depletion region.Ⅲ-Nitrides are uniquely suited to the detection of ultraviolet light. The AlGaN material system covers the bulk of the UV portion of the spectrum, allowing tunable cutoffs from200nm (6.2eV) to365nm (3.4eV). The addition of aluminum increases the range even further allowing Ⅲ-Nitrides to cover most of the UV, including the strategic solar-blind UV, and the entire visible portion of the spectrum. In this paper, we fabricated and tested dual-color GaN/AlGaN heterostructure MSM structure photodetector. The detector can work efficiently at two frequencies scope, the peak responsivities is0.36A/W at288nm and0.322A/W at366nm with5V bias voltages. Spectrum response characteristics of the photodetector are investigated by changing the frequency of incident light signals and different bias voltages. The quantum efficiency with increasing chopper frequency for AlGaN bulk (288nm) decreases faster than that from GaN bulk (366nm). However, the quantum efficiency with increasing voltages ranging for AlGaN bulk (288nm) increases faster than that from GaN bulk (366nm).Zinc oxide (ZnO) is an Ⅱ-Ⅵ oxide semiconductor that is being explored widely in recent years for UV optoelectronic applications because of its attractive and promising properties. The properties in ZnO is fueled and fanned by its prospects in optoelectronics applications owing to its direct wide band gap Eg=3.3eV at300K. However, ZnO has some advantages over GaN among which are the availability of fairly high-quality ZnO bulk single crystals and a large exciton binding energy～60meV. In this paper, Ga-doped ZnO films were grown by RF Magnetron Sputtering on R-plane sapphire substrates. Photoconductor devices for ultraviolet light detection were fabricated by depositing Au (200nm)/Ni (50nm) Schottky metal contacts. The influence of rapid thermal annealing on the properties of ZnO:Ga UV detecters have investigated. Spectrum response characteristics of the photodetector are investigated by changing the frequency of incident light signals and different bias voltages.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > UV technology and equipment
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