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

Abstract

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

Date of Award	2015 Jul 7
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)