| Summary: | 碩士 === 國立交通大學 === 光電工程學系 === 101 === Recently, a-IGZO is the high-potential material for active layer of thin film transistor. With a high mobility (>10 cm2/Vs) than conventional amorphous silicon semiconductor and a low operating voltage (< 5 V) and small sub-threshold voltage swing, amorphous In-Ga-Zn-O thin-film transistors (a-IGZO TFTs) draw a lot of attentions. When a-IGZO TFTs are developed for a low-power high-frequency circuit, good electron performances, such as high field-effect mobility (μFE) and low sub-threshold swing (S.S.) are required. Dual gate (DG) is one of the techniques to enhance the performance of a-IGZO TFTs by connecting top gate (TG) and bottom gate (BG) together to enhance the channel accumulation. In our previous work, we have demonstrated that the effective mobility of a-IGZO TFT can be greatly improved by utilizing nano-meter dot-like doping (NDD) in a-IGZO channel region. We proposed that the NDD structure lowers the potential barrier in the intrinsic a-IGZO by the neighboring high conductive regions and hence increase the field-effect mobility of TG a-IGZO TFTs from 4 to 79 cm2V−1s−1. In this work, we employ NDD in DG a-IGZO TFTs. By connecting TG and BG together, we expect to reduce the vertical field in a-IGZO film and to further enhance the mobility. We successfully obtain a 1.5-times enhanced output current in DG NDD a-IGZO TFT. Taking the gate capacitance of TG NDD as the reference, the effective mobility for TG NDD a-IGZO TFT and for DG NDD IGZO TFT are 102 cm2V−1s−1 and 272 cm2V−1s−1, respectively.
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