Search

In this study, we investigated the effects of high-energy electron beam irradiation (HEEBI) on the device properties of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at RT at an electron beam energy of 0.8 MeV and a dose of 1 × 1014 electrons/cm2. Without the HEEBI treatment, the devices operated in depletion mode with a threshold voltage (V th ) of −11.25 V, a field-effect mobility (µ FE ) of 8.71 cm2/Vs, an on-off ratio (I on/off ) of 1.3 × 108 and a sub-threshold slope (SS) of 0.3 V/decade. A huge positive-shifted V th of −1 V, a very high µ FE of 420 cm2/Vs, a high I on/off of 6.1 × 108, and a lower SS of 0.25 V/decade were achieved for the HEEBI-treated devices, suggesting that the device characteristics of the developed TTFTs were significantly improved by the HEEBI treatment. The best device characteristics, which include I on/off of 8.1 × 108, SS of 0.25 V/decade, V th of +1 V, µ FE of 8.8 cm2/Vs, and operation in the enhancement mode without aging, were obtained for the samples that had been annealed after HEEBI treatment. On the basis of the experimental results, we believe that HEEBI treatment can be crucial to develop IGZO-based TFTs with high performance and long-term reliability.

We explored the effects of high-energy electron beam irradiation (HEEBI) on the gate-bias and light stabilities of indium-gallium-zinc-oxide (IGZO)-based transparent thin film transistors (TTFTs). The developed TTFTs had a top gate structure, which used IGZO and Al2O3 films for the active layer and the gate dielectric, respectively. The developed TTFTs were treated with HEEBI in air at room temperature at an electron beam energy of 0.8 MeV and a dose of 1 × 1014 electrons/cm2. Without the gate bias and/or light stresses, the HEEBI-treated devices showed a positive threshold voltage (Vth) shift (+ΔVth), suggesting that acceptor defects might have been generated by HEEBI treatment near the valence band edge. The HEEBI-treated devices also exhibited a lower +ΔVth, a higher negative Vth shift (−ΔVth), and a much lower −ΔVth under positive gate bias, negative gate bias, and light stresses compared to those for the HEEBI-untreated devices, respectively. These Vth instabilities were observed without significant change in the sub-threshold slope, indicating that charge trapping in the gate dielectric and/or at the active layer/dielectric interface was the dominant mechanism of the device instability.

Zinc oxide (ZnO)-based thin-film transistors (TFTs) with top gate structures were produced. Radio-frequency-magnetron sputtering was used to deposit indium tin oxide for both the source and the drain electrodes and n-type undoped ZnO at high oxygen partial pressures for the active layer. Direct-current-magnetron sputtering and plasma enhanced chemical vapor deposition were used to deposit Al for the gate electrode and the SiN gate dielectric, respectively. The devices operated in the enhancement mode with a threshold voltage, mobility, on-off ratio and sub-threshold slope of 9 V, 0.05 cm2/Vs, ∼5 × 105, and 1.3 V/decade, respectively.