In this work, an MgIn2O4 (MIO) thin film transistor (TFT) with a bottom gate structure was fabricated. The MIO channel layer was deposited by RF sputtering using a single MgIn2O4 target. The performance of MIO TFT was highly related to oxygen vacancies. As-deposited MIO TFT showed a low field-effect mobility due to doping of Mg. An MgO buffer layer was introduced to enhance the mobility of MIO TFT due to improvement of the interface with the channel layer. In addition, oxygen vacancies in the MIO channel were suppressed because of oxygen diffusion from the buffer layer. MIO TFT with a 5 nm MgO buffer layer showed an on/off current ratio of 9.68 × 103, a field-effect mobility of 4.81 cm2/V?s, which was increased more than an order of magnitude compared with the device without a buffer layer, a threshold voltage of 2.01 V, and a subthreshold swing of 0.76 V/decade, which was improved more than 20% compared with the as-deposited one.
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