Design and Optimization of Bilayer InGaSnO and Nitrogen-Doped InSnO Thin-Film Transistors for Enhanced Mobility and Reliability

In this study, high-performance indium gallium tin oxide (IGTO) and nitrogen (N) doped indium tin oxide (ITO) hetero structured bilayer thin-film transistors (TFTs) are prepared by incorporating an N-doped ITO intercalation layer in single-layer IGTO TFTs. The performance of the IGTO/ITO:N bilayer TFTs is significantly improved compared with single-layer IGTO TFTs, with specific indicators including a field-effect mobility of 32.6 cm2/V $\cdot $ s, a subthreshold swing of 201 mV/dec, a threshold voltage shifts of 0.21 V and −0.45 V under ±10 V gate-bias stress. The results show that the performance enhancement is due to the rational design of the bilayer structure, in which the ITO layer functions as a charge-accumulation layer, providing additional electrons. Meanwhile, N doping effectively reduces the oxygen vacancies, thereby decreasing the interfacial trap density, and ultimately enhancing the performance of single-layer IGTO TFTs. Through X-ray photoelectron spectroscopy and low-frequency noise analyses, we further confirmed the positive effects of N doping and bilayer structure on reducing the defective states and enhancing the stability of TFTs. Overall, the strategy presented here is effective for preparing high performance oxide TFTs for potential applications in future optoelectronic displays.