Sol–Gel Solution-Deposited InGaZnO Thin Film Transistors

Abstract

Thin film transistors (TFTs) fabricated by solution processing of sol-gel oxide semiconductor precursors in the group In-Ga-Zn are described. The TFT mobility varies over a wide range depending on the precursor materials, the composition, and the processing variables, with the highest mobility being about 30 cm(2)/(V s) for IZO and 20 cm(2)/(V s) for IGZO. The positive dark bias stress effect decreases markedly as the mobility increases and the high mobility devices are quite stable. The negative bias illumination stress effect is also weaker in the higher mobility TFTs, and some different characteristic properties are observed. The TFT mobility, threshold voltage, and bias stress properties are discussed in terms of the formation of self-compensated donor and acceptor states, based on the chemistry and thermodynamics of the sol-gel process.

Enhanced Electrical Properties and Stability of Solution-processed Amorphous Oxide Thin Film Transistors with Multi-active Layers

“…V O is expecially known to be a deep donor [12] and can be ionized into or related to hole trapping [13]. Street et al reported that solution-processed TFTs with high mobility were stable under PBS [24]. The results in Table 2 indicate that the InZnO TFT exhibited high mobility and good stability under PBS compared to the InGaZnO TFT, which is consistent with the previous results [24].…”

“…Street et al reported that solution-processed TFTs with high mobility were stable under PBS [24]. The results in Table 2 indicate that the InZnO TFT exhibited high mobility and good stability under PBS compared to the InGaZnO TFT, which is consistent with the previous results [24]. In addition, the TFTs with low mobility have more acceptor states in the deep levels [25].…”

Control of electrical properties and gate bias stress stability in solution-processed a-IZO TFTs by Zr doping

“…Furthermore, the starting point of the ON state for TFTs can be controlled by Zr doping. Some non-doped IZO TFTs with very high mobility are [21]. From the perspective of device operation, an additional gate voltage is required separate the OFF state from the ON state.…”

“…Several reports explain the V th shift to the direction of the gate bias stress by assuming that the trapped charges screen the gate voltage [19] or an electric field from the trapped charges is produced that can be offset by gate voltage [20]. In case of trapped charges in the bulk active layer, the mechanism of the subgap density of state (DOS), such as the formation of accept-like or donor-like levels, has been reported [21]. If very small metal additive can control the subgap DOS, the amount of V th shift under the gate bias stress will be changed.…”

Effects of post-lift-off annealing conditions on contact oxidation of Ti–Au top-contacts in In-Sn–Zn–O TFT

“…Indium based solution processed metal oxide semiconductors have garnered a lot of interest in recent years due to their tremendous ability to retain high mobility even in amorphous solution processed forms, enabling printable roll-to-roll fabrication for display backplanes [1][2][3][4]. Mixed metal oxide semiconductors based on indium, like indium gallium zinc oxide (IGZO), have overcome one of the degradation problems of indium-only oxide semiconductors by careful selection of component metals that bind relatively strongly to the oxygen and thereby suppressing oxygen vacancies formation [2,5].…”