Multiple effects of hydrogen on InGaZnO thin-film transistor and the hydrogenation-resistibility enhancement

Abstract

As the most common external dopant of amorphous oxide semiconductors (AOSs), the hydrogen (H) exhibits great influences on the performance of AOS thin-film transistors (TFTs) and is almost inevitable during device fabrication. In this work, the multiple effects of H doping on the amorphous InGaZnO (IGZO) TFT were systematically investigated by experimental and theoretical calculation methods, and the hydrogenation-resistibility was further investigated. The electrical performances of the hydrogenated IGZO TFT were determined by the concentrations of H itself and oxygen vacancy (Vo). With increasing H content, it separately serves as defect suppressor, donor defect, donor/acceptor transition state and then acceptor defect, resulting in the improved subthreshold slope (SS), negative shift of threshold voltage (Vth), fluctuation of mobility (μFE), and limitation of on-state current (Ion), respectively. The Vo in IGZO is considered to provide the diffusion channel of H dopant, thus determining the H concentration and the electrical behaviors. Furthermore, the hydrogen-resistibility of IGZO was enhanced by using the fluorine (F) dopant to suppress the intrinsic Vo content and weaken the dissociation energy of H-related bonds. The F-IGZO TFT exhibits excellent stabilities even in the H-rich environment. The findings not only deepen the understanding and manipulation of H doping in AOS devices, but also broaden the application scopes.