Polycrystalline In–Ga–O Thin-Film Transistors Coupled With a Nitrogen Doping Technique for High-Performance UV Detectors

In this article, thin-film transistors (TFTs) with a polycrystalline indium-gallium-oxide (poly IGO) active layer were fabricated for ultraviolet (UV) detection. To achieve better sensing performance, an in situ nitrogen doping (N-doping) technique was employed to passivate the excessive defect states in the bandgap. Under UV illumination, it is evident that the N-doped IGO TFT exhibited superior photoresponsivity and UV-to-visible rejection ratio (17.4 A/W and 1.0 × 10
⁶
) as compared to the undoped one (13.1 A/W and 1.2×10
⁵
). More importantly, a sharper responsivity cutoff at 340 nm (Eg ~ 3.65 eV) was observed, suggesting that the N-doped phototransistor had better wavelength selectivity. Through X-ray photoelectron spectroscopy analysis, it was shown that N-doping reduced the subgap states and thus suppressed the visible light-induced ionization of oxygen vacancy. Furthermore, the nitrogen incorporation slightly reduced the effective bandgap, which enhanced the band-to-band electron transition and the UV responsivity.