Effect of high-energy electron beam irradiation on the gate-bias stability of IGZO TFTs

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.