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Highlights • The light illumination stability of a-IGZO TFTs in O- 2 or H 2 O was characterized. • When the O 2 or H 2 O content increased, the devices showed better stability. • A qualitative model was proposed to explain the related physical mechanism. Abstract The light-illumination stability of amorphous InGaZnO Thin Film Transistors (a-IGZO TFTs) in oxygen and moisture ambience was in-depth characterized by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. With the illuminated light wavelength decreasing, both I-V and C-V curves shifted negatively. When the ambient oxygen content or moisture level increased, the a-IGZO TFTs exhibited more stable properties under light illumination. A qualitative model was proposed to explain the related physical mechanism. The higher oxygen content or moisture level benefited the light-illumination-induced oxygen adsorption at back channels of a-IGZO TFTs and prevented the formation of oxygen vacancies (V O) in channel layers; the V O variation with the light illumination became more difficult and hence led to better light-illumination stability of the corresponding TFT devices. [ABSTRACT FROM AUTHOR]

The nitrogen-doped (N-doped) amorphous InGaZnO thin film transistors ( a -IGZO TFTs) were investigated against the undoped and oxygen doped (O-doped) devices. The N-doped a-IGZO TFTs exhibited better electrical performance and bias stress stability, and especially more stable thermal properties. The X-ray photoemission spectroscopy (XPS) measurements were carried out at different temperatures (298 K and 393 K) to examine the physical essence of the thermal instability of undoped, O-doped, and N-doped a-IGZO TFTs. The XPS characterization results indicated that nitrogen doping caused lesser oxygen vacancy variation with the temperature (0.6%) compared with undoping (7.2%) and oxygen doping (11.8%). Hence, the a-IGZO TFTs with N-doped active layers had much better stability than those with undoped and O-doped active layers. [ABSTRACT FROM AUTHOR]

The thermal stability of amorphous InGaZnO thin film transistors (a-IGZO TFTs) with various ambient gases was investigated. The a-IGZO TFTs in air were more thermally stable than the devices in the ambient argon. Oxygen, rather than nitrogen and moisture, was responsible for this improvement. Furthermore, the thermal stability of the a-IGZO TFTs improved with the increasing oxygen content in the surrounding atmosphere. The related physical mechanism was examined, indicating that the higher ambient oxygen content induced more combinations of the oxygen vacancies and adsorbed oxygen ions in the a-IGZO, which resulted in the larger defect formation energy. This larger defect formation energy led to the smaller variation in the threshold voltage for the corresponding TFT devices. [ABSTRACT FROM AUTHOR]

The amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) with sputtered silver source/drain (S/D) and gate electrodes were investigated and developed. The sputtered single-film Ag was confirmed to be unfit for the electrodes of a-IGZO TFTs because of its bad contact with a-IGZO and atom diffusion into insulators. Accordingly the sputtered Mo films were proposed to serve as the capping layers, indicating that the 20-nm-thick Mo could effectively form ohmic contact with the a-IGZO, prevent the Ag diffusion into the SiO x , and make good adhesion to the glass substrates. The devices with multi-layer S/D and gate electrodes (Mo/Ag/Mo) were successfully fabricated, exhibiting the reasonably good performance and thus proving the application of the sputtered silver electrodes into a-IGZO TFTs was possible. [ABSTRACT FROM AUTHOR]