In2O3:Ni/Ga2O3 Heterojunction Thin-Film Transistors for UV-C Photodetection

Wide bandgap metal oxide semiconductors (MOS), such as In2O3 and Ga2O3, are multifunctional materials that can be used as electron transport and photosensitive layers in various optoelectronic devices. However, either the excessive free electrons or low carrier mobility caused by intrinsic defects of MOSs restrict the performance of these devices. The current work demonstrates that acceptor doping and interface energy band engineering can be used to achieve a high-performance MOS thin-film transistor (TFT) that is suitable for UV-C photodetection. The Ni doping concentration in the In2O3 layer and the thickness of the Ga2O3 layer are optimized to control the performance of the In2O3:Ni/Ga2O3 heterojunction TFTs. As a result, a threshold voltage of 0.34 V, linear mobility of 47 cm2/Vs, on/off current ratio over $10^{{7}}$ , and small threshold voltage shift under gate bias stress are obtained, owing to the electron accumulation at the In2O3:Ni/Ga2O3 interface in response to the energy band alignment. Under UV-C illumination, the In2O3:Ni/Ga2O3 heterojunction TFT shows a large responsivity of 879 A/W, an UV-C/visible light rejection ratio ( $\text{R}_{{254} \text {nm}}/\text{R}_{{400} \text {nm}}$ ) of $9.5\times 10^{{3}}$ , and a detectivity of $4\times 10^{{16}}$ Jones.