| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 100 === In this dissertation, amorphous zinc indium tin oxide (a-ZITO) thin film transistors (TFTs) with different kinds of dielectric layers were fabricated and analysis of deep UV phototransistor investigated.
First, we apply a-ZITO thin film as channel layer to the fabrication of TFT with SiO2 gate dielectric. it was found that the field-effect mobility were 7.7 cm2/Vs, threshold voltage of 1 V, subthreshold swing of 0.5 V/decade and Ion/Ioff of 105 for a-ZITO TFT with SiO2 gate dielectric. Additionally, we report the effect of cation composition on the device performance of a-ZITO TFTs was investigated. Then, the exact origin of the improvement of electrical characteristics, and optimize the effects of the In, Zn, and Sn fractions in ZITO thin films, in order to improve the performance of a device.
In the second part of our experiment, The fabrication of a-ZITO thin-film transistor with a Ta2O5 dielectric on a glass substrate was demonstrated. The room-temperature-deposited a-ZITO channel with Ta2O5 exhibits threshold voltage of 0.75 V, drain-source current on/off ratio of 105, subthreshold swing of 0.45 V/decade, and field-effect mobility of 72.3 cm2/Vs under a low operation voltage (i.e.,2V). Compared with various high k material and conventional gate dielectric, it was found that we can achieve higher mobility, low threshold voltage and operation voltage. These results could be contributed to the high k material for the increased higher gate capacitance.
On the part of a-ZITO phototransistor, A deep-UV and near-UV sensitive a-ZITO phototransistor with Ta2O5 gate dielectric was fabricated. It was also found that measured current increased from 2.3×10-9 A to 7.97×10-5 A as we illuminated the sample with λ= 250 nm UV light when VG was biased at 0 V. With an incident light wavelength of 250 nm and an applied gate bias of 0 V, it was found that measured responsivity of the device was 3.9 A/W. Then, with an incident light wavelength of 380 nm and an applied gate bias of 0 V, it was found that measured responsivity of the device was 2.13×10-4 A/W. It was also found that we could achieve the photosensitivity of 2.3×105 when the device was biased at 0 V. These results suggest that the a-ZITO thin film transistors have the low power consumption, high responsivity and rejection ratio when used in UV detection.
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