Negative-bias illumination stress (NBIS) of amorphous InGaZnO (IGZO) transistors can cause a large negative shift (>7.1 V) in threshold voltage, something frequently attributed to the trapping of photoinduced hole carriers. This work demonstrates that the deterioration of threshold voltage by NBIS can be strongly suppressed by high-pressure annealing under 10 atm O2 ambient. This improvement occurred through a reduction in oxygen vacancy defects in the IGZO film, indicating that a photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability.

This study examined the effect of the thickness of interfacial indium-tin oxide (ITO) on the performance and bias reliability of zinc-tin oxide (ZTO) thin film transistors (TFTs). The 3.5-nm-thick ITO-inserted ZTO TFTs exhibited superior mobility (43.2 cm2/V s) to that of the ZTO only TFTs (31.6 cm2/V s). Furthermore, the threshold voltage shifts for the ZTO/ITO bi-layer device decreased from 1.43 and −0.88 V (ZTO only device) to 0.46 V and −0.41 V under positive and negative bias stress, respectively. This improvement can be attributed to a decrease in the interfacial trap density for the ITO-inserted ZTO device.

Indium tin oxide (ITO) films are representative transparent conducting oxide media for organic light-emitting diodes, liquid crystal displays, and solar cell applications. Extending the utility of ITO films from passive electrodes to active channel layers in transparent field-effect transistors (FETs), however, has been largely limited because of the materials' high carrier density (>1 × 10(20) cm(-3)), wide band gap, and polycrystalline structure. Here, we demonstrate that control over the cation composition in ITO-based oxide films via solid doping of titanium (Ti) can optimize the carrier concentration and suppress film crystallization. On 120 nm thick SiO(2)/Mo (200 nm)/glass substrates, transparent n-type FETs prepared with 4 at % Ti-doped ITO films and fabricated via the cosputtering of ITO and TiO(2) exhibited high electron mobilities of 13.4 cm(2) V(-1) s(-1), a low subthreshold gate swing of 0.25 V decade(-1), and a high I(on/)I(off) ratio of >1 × 10(8).

The impact of a gate insulator ͑GI͒ material on the device instability of InGaZnO ͑IGZO͒ thin film transistors ͑TFTs͒ was investigated. The IGZO TFTs with SiO 2 GI showed consistently better stability against the applied temperature stress and positive/negative gate bias stress than their counterparts with SiN x GI. This superior stability of the SiO 2-gated device was attributed to the reduced total density of states ͑DOS͒ including the interfacial and semiconductor bulk trap densities. Based on the Meyer-Neldel rule, the total DOS energy distribution for both devices was extracted and compared, which can explain the experimental observation.

This study examined the effect of oxygen (O2) high pressure annealing (HPA) on tin-doped indium oxide (ITO) thin film transistors (TFTs). The HPA-treated TFT at 150 °C exhibited a high saturation mobility (μSAT), low subthreshold gate swing (SS), threshold voltage, and Ion/off of 25.8 cm2/Vs, 0.14 V/decade, 0.6 V, and 2 × 108, respectively. In contrast, the ambient-annealed device suffered from a lower μSAT and high SS value of 5.2 cm2/Vs and 0.58 V/decade, respectively. This improvement can be attributed to the decreased concentration of oxygen vacancy defects in the ITO channel layer during the effective O2 HPA treatment, which also resulted in smaller hysteresis and less degradation of the drain current under positive bias stress conditions.