The Influence of Oxygen High-Pressure Annealing on the Performance and Bias Instability of Amorphous Ge–In–Ga–O Thin-Film Transistors

The effects of oxygen high-pressure annealing (O
₂
HPA) on the performance and instability of amorphous Ge–In–Ga-O (a-GIGO) thin-film transistors (TFTs) were examined. The TFTs with HPA under 30 atm O
₂
ambient exhibited consistently better stability against the applied temperature stress and positive gate bias stress. We demonstrate that the superior stability of the HPA-treated device can be correlated with the evolution of electronic structure in a-GIGO thin films, as measured by spectroscopic ellipsometry, which reveals the significantly reduced band edge states below the conduction band by the O
₂
HPA treatment. Based on the Meyer–Neldel rule, the total density of subgap states energy distribution, including the interfacial and semiconductor bulk trap densities, was also extracted and compared, which can support the experimental observation.