Improvement in performance of indium gallium oxide thin film transistor via oxygen mediated crystallization at a low temperature of 200 °C

We report the fabrication of high-performance polycrystalline indium gallium oxide (IGO) thin film transistors (TFTs) at a low temperature of 200 °C. Growth of a highly aligned cubic phase with a bixbyite structure was accelerated at a certain proportion of oxygen plasma density during deposition of the IGO thin film, which leads to outstanding electrical characteristics. The resulting polycrystalline IGO TFT exhibited a high field-effect mobility of 56.0 cm2/V, a threshold voltage (VTH) of 0.10 V, a low subthreshold gate swing of 0.10 V/decade, and a current modulation ratio of >108. Moreover, the crystalline IGO TFTs have highly stable behaviors with a small VTH shift of +0.8 and −1.0 V against a positive bias stress (VGS,ST −VTH = 20 V) and negative bias illumination stress (VGS,ST −VTH = −20 V) for 3,600 s, which is attributed to the high quality of the bixbyite crystalline structure.