These methods can increase the metal oxide bond and decrease V o by chemical oxidation but it requires a prolonged time (1–2 hours) and additional external energy source.
Thus, many studies regarding the reduction of V o without mobility deterioration, such as UV annealing 12 and high pressure oxygen annealing 13, are reported. To solve this issue, AOSs are deposited under the oxygen-rich condition in order to reduce oxygen vacancy, but it inevitably accompanies a decrease in mobility.
On the other hand, the instability problem related to V 0 is difficult to address because V 0 is involved in the intrinsic property of AOSs. The fundamental studies regarding first and second origins showed that the instability can be improved using a high quality gate dielectric and an appropriate passivation layer, respectively 10, 11. In general, the origin of the instability of AOSs comes from carrier trapping and injection, ambient gas interaction, and oxygen vacancy (V 0) 6, 7, 8, 9. However, the AOSs devices still suffer from instability issues such as illumination, bias, and temperature stress. Recently, these AOSs were used in various flexible devices 4 and a sensor array 5 as the active layer. Research on amorphous oxide-based semiconductors (AOSs) have attracted attentions as a leading candidate for flexibility, large scale, and transparent electrical devices due to high mobility, high optical transparency, and low temperature deposition compared to amorphous silicon 1, 2, 3. The mobility increased from 9.1 to 17.5 cm 2/Vs, on-off ratio increased from 8.9 × 10 7 to 7.96 × 10 9, and the threshold voltage shift of negative bias-illumination stress for 3600 secs under 5700 lux of white LED and negative bias-temperature stress at 50 ☌ decreased from 9.6 V to 4.6 V and from 2.4 V to 0.4 V, respectively. As a result, the SRD-treated amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) showed superior electrical performances compared with non-treated a-IGZO TFTs.
This SRD method, which uses UV irradiation and thermal hydrogen peroxide solution treatment, effectively decreased the amount of oxygen vacancies and facilitated self-passivation and doping effect by radical reaction with photo-activated oxygen defects. In this study, we propose a self-activated radical doping (SRD) method on the catalyzed surface of amorphous oxide film that can improve both the electrical characteristics and the stability of amorphous oxide films through oxidizing oxygen vacancy using hydroxyl radical which is a strong oxidizer.