| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 92 === In this thesis, the property and characteristics of transparency contact, a thin Ni/Au (3nm/6nm) bi-layer metal film, deposited on the glass substrate was discussed. With proper annealed in oxygen by the photo-CVD systems, the transmittance of the Ni/Au alloyed layer can beimproved from 65％ to 85％ in the wavelength around 520nm. The Ni/Au un-doped GaN Schottky contact was manufactured and the I-V curve and Schottky barrier height were also measured. The Ni/Au deposited on un-doped GaN annealed in oxygen for 3min at 600℃ had the lower dark-current and the Schottky barrier height was up to 0.94 eV.
Then, u-GaN and AlGaN/GaN heterojunction MSM photodetectors with semi-transparent NiO/Au Schottky barrier contact electrodes were fabricated. By photo-CVD annealing these photodetectors in O2, it was found that we can achieve a larger Ni/Au transmittance, higher Schottky barrier heights and larger photocurrent to dark current contrast ratios. The maximum quantum efficiencies were 13% and 57% for the photo-CVD annealed u-GaN and AlGaN/GaN heterojunction photodetectors, respectively. Furthermore, we can achieve a larger responsivity, a lower noise level and a larger detectivity by using the AlGaN/GaN
heterojunction structure.
Moreover, the p-InGaN/GaN(MQW)-n double functions devices was fabricated by AIXTRON 2600 G3HT MOCVD system. It exhibited the photodetector properties in reverse bias and preserved the distinct identities of LED in forward bias at the same time. The bigger size of devices showed the higher current density in photo-current and dark
current. The contrast ratio of the big size device was more rapid than the small one.
InGaN/GaN MQW MIS and MSM photodetectors with and without photo-CVD SiO2 layers were fabricated successfully. It was indicated that we could significantly reduce the dark current, while still maintain a reasonably large photo current by inserting a photo-CVD SiO2 layer between metal electrodes and the underneath InGaN/GaN MQW structure. With a 53nm-thick SiO2 layer, it was also found that we could achieve a high 1.53×103 photo current to dark current contrast ratio.
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