Investigation of Indium-Gallium-Oxide (In-Ga-O) Thin Film Transistors and Optoelectronic Applications

• Main Authors: Chih-YuWei, 魏志諭
• Other Authors: Shoou-Jinn Chang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/kzm88p

碩士 === 國立成功大學 === 微電子工程研究所 === 103 === In this thesis, we use In-Ga-O thin film as active layer to fabricate and investigate thin film transistors and UV phototransistor. Firstly, we deposit and analyze In-Ga-O thin films, and In-Ga-O thin films show amorphous structure and smooth surface. And then we realize In-Ga-O MSM UV photodetectors. It is found that we could change the conductivity and cutoff wavelength of the fabricated photodetectors by changing the RF sputtering power for the In2O3 target. Secondly, we fabricate In-Ga-O TFTs. The performance of the TFTs is found to be strongly dependent on the element composition of channel layer. The optimized device, sample F, exhibites a good electrical property with a μFE of 6.5 cm2/Vs, a SS of 0.33 V/decade, and an on/off current ratio of 5.1×106. The cutoff wavelength of In-Ga-O phototransistors is red-shifted from 270 to 310 nm with increase in indium content. The UV-to-visible rejection ratio and photoresponsivity of the fabricated phototransistors are 4.8×103 and 0.24 A/W in sample F. Lastly, we fabricate dual channel In-Ga-O TFTs. We realize bilayer structure which can be deposited in-situ with same material, and the performance of TFTs can be improved through bandgap engineering. The fabricated device, sample L, exhibites good electrical properties with a μFE of 53.2 cm2/Vs, a SS of 0.19 V/decade, and an on/off current ratio of 3.2×107. Compared with the TFTs with single In-Ga-O layer, the photoresponsivity of dual channel TFTs are enhanced by the bilayer structure. The UV-to-visible rejection ratio and photoresponsivity of the fabricated phototransistors are 103 and 14.26 A/W in sample L. Degradation in UV-to-visible rejection ratio can be attributed to the relative high density of oxygen vacancies in front channel.