Stability improvement of nitrogen doping on IgO TFTs under positive gate bias stress and hysteresis test

Thin-film transistors (TFTs) using indium-gallium-oxide (IGO) semiconductor materials as channel layers were fabricated. In this study, nitrogen was introduced in the process of channel deposition to investigate its effect on device performance. The experimental results showed that moderate nitrogen doping can significantly improve the device stability under positive gate bias stress owing to the reduction of oxygen vacancies. Furthermore, for the purpose of understanding the influence of different doping levels, the nitrogen doping ratio was modulated in ascending order from 0 sccm to 5 sccm. Among the fabricated c-IGO TFTs, the one with 2 sccm nitrogen doping exhibited the least threshold voltage shift. In addition, the hysteresis measurement further confirmed that the interface traps between the channel and the dielectric were significantly passivated in nitrogen-doped TFT. In this regard, the method of in-situ nitrogen doping was certified to serve an efficient way of fabricating a passivation-free TFT and improve the device stability simultaneously.