IZO-based Thin-film Transistors Research Articles

Negative Bias Instability of InZnO-Based Thin-Film Transistors Under Illumination Stress.

In this study, we investigated the threshold voltage (Vth) instability of solution-processed indium zinc oxide (IZO) thin film transistors (TFTs) prior to and after negative bias illumination stress (NBIS) with varying carrier suppressors (Ga, Al, Hf, and Zr). Variations in electrical properties of the IZO-based TFTs as a function of carrier suppressors were attributed to the differences in metal-oxygen bonding energy of the materials, which was numerically verified by calculating the relative oxygen deficient ratio from the X-ray photoelectron spectroscopy analysis. Furthermore, the values of Vth shift (ΔVth) of the devices subjected to negative gate bias stress under 635 nm (red), 530 nm (green), and 480 nm (blue) wavelength light irradiation increased as the incident photon energy increased. IZO TFTs doped with Ga atoms demonstrated weaker metal-oxygen bonding energy compared to the others and exhibited the largest ΔVth. This result was attributed to the suppressor-dependent distribution of neutral oxygen vacancies which determine the degrees of photon energy absorption in the IZO films. Then, the ΔVth instability of IZO-based TFTs under NBIS correlated well with a stretched exponential function.

Double in-plane-gate IZO-based thin-film transistors with pea protein gate dielectrics

Double in-plane-gate indium–zinc–oxide (IZO) thin-film transistors (TFTs) using pea protein as the gate dielectric films were fabricated on ITO glass substrates at room temperature. Pea protein, a natural biodegradable solid electrolyte, showed a very high specific gate capacitance of 2.0 μF cm−2 at 1.0 Hz due to the electric-double-layer effect. The field effect mobility, current ON/OFF ratio, and subthreshold swing of the IZO-based TFTs with bottom gate were estimated to be 27.6 cm2 V−1 s−1, 3 × 106, and 167 mV/decade, respectively. Then, a resistor-loaded inverter with a high voltage gain of 18 was investigated. At last, ‘NAND’ logic operation was demonstrated with two in-plane gates as the input terminals. Such double in-plane-gate IZO-based TFTs with pea protein gate dielectrics have potential applications in low-cost electronics.

Solution-processed indium–zinc oxide with carrier-suppressing additives

Metal oxide semiconductors were considered promising materials as backplanes of future displays. Moreover, the adoption of carrier-suppressing metal into indium–zinc oxide (IZO) has become one of the most important themes in the metal oxide research field. In this paper, efforts to realize and optimize IZO with diverse types of carrier suppressors are summarized. Properties such as the band gap of metal in the oxidized form and its electronegativity were examined to confirm their relationship with the metal's carrier-suppressing ability. It was concluded that those two properties could be used as indicators of the carrier-suppressing ability of a material. As predicted by the properties, the alkali earth metals and early transition metals used in the research effectively suppressed the carrier and optimized the electrical properties of the metal oxide semiconductors. With the carrier-suppressing metals, IZO-based thin-film transistors with high (above 1 cm2/V·s) mobility, a lower than 0.6 V/dec sub-threshold gate swing, and an over 3×106 on-to-off current ratio could be achieved.