Enhancement of the Electrical Performance and Bias Stability of RF-Sputtered Indium Tin Zinc Oxide Thin-Film Transistors with Vertical Stoichiometric Oxygen Control

Abstract

Indium tin zinc oxide (ITZO) thin-film transistors (TFTs) with different channel structures are investigated. The electrical performance and bias stress stability of bilayer-channel ITZO TFTs are enhanced in comparison with those of single-channel ITZO TFTs. The bilayer channel consists of an oxygen-uncompensated channel layer and an oxygen-compensated capping layer, while the single channel is an oxygen-uncompensated channel layer. The electrical properties of the bilayer-channel films are fine-tuned by adjusting their oxygen stoichiometry using the oxygen-compensated capping layer. The X-ray photoelectron spectroscopy measurements reveal that the bilayer channel shows advantages over the single channel in terms of increased metal oxide concentration and decreased oxygen vacancy and hydroxyl concentration. As a result, the bilayer-channel ITZO TFT exhibits a saturation field-effect mobility of 17.31 cm2/Vs, a sub-threshold swing of 0.24 V/dec, and a good operational bias stress stability in comparison with the single-channel TFT. This work demonstrates that the bilayer-channel ITZO TFTs have great potential for next-generation display applications.

Low‐Voltage, High‐Performance, Indium‐Tin‐Zinc‐Oxide Thin‐Film Transistors Based on Dual‐Channel and Anodic‐Oxide

“…This is due to additional oxygen CCL layer in device B, which can effectively prevent the oxygen absorption. [ 18 ] We analyzed the NBS and PBS results further by fitting the stress time dependence of ∆ V TH with the following stretched‐exponential equation [ 25 ] $$\[ \begin{array}{*{20}{c}}{\Delta {V_{{\rm{TH}}}} = \Delta {V_{{\rm{TH0}}}}\left\{ {1 - \exp \left[ { - {{(t/\tau )}^\beta }} \right]} \right\}}\end{array} \]$$where ∆ V TH0 is the ∆ V TH at infinite stressing time, τ is the characteristic trapping time, and β is the stretched‐exponential exponent. The stress time dependence of ∆ V TH for both NBS and PBS is well fitted with Equation () as shown in Figure S3 (Supporting Information).…”

“…This is due to additional oxygen CCL layer in device B, which can effectively prevent the oxygen absorption. [18] We analyzed the NBS and PBS results further by fitting the stress time dependence of ∆V TH with the following stretched-exponential equation [25] τ { }…”

“…[ 23 ] Fewer defects, such as a lower concentration of V o and OH at the surface and at the interface, improve the electrical performance of device B. [ 18 ] In addition, this reduced concentration of defects can improve the bias stress stability of ITZO TFTs, which will be discussed later in this paper.…”

“…[1][2][3][4] In particular, thin-film transistors (TFTs) based on oxide semiconductor materials, such as indium-gallium-zinc-a surface passivation on the channel layer or a dual-channel layer is generally required to reduce defects/traps and enhance the stability of the devices. [16][17][18] Heterojunction (e.g., ITZO/ IGZO) or homojunction (e.g., ITZO/ITZO) dual-channel oxide semiconductor TFTs exhibit significant performance and stability advantages in comparison with single-channel oxide semiconductor TFTs. [18,19] Thus, the electrical performance and bias stability of oxide semiconductor TFTs depends on many factors, including device structure, dielectric material, and fabrication process.…”

Effects of High-Energy X-ray Irradiation on the Electrical and Chemical Properties of In–Ga–Sn–O Thin Films with Al2O3 Passivation Layer for Thin-Film Transistor Applications

“…Previously, amorphous silicon (a-Si) and low-temperature polycrystalline silicon (LTPS) TFTs have been used as a backplane of the flat-panel X-ray detector; however, the low carrier mobility of a-Si , and poor X-ray radiation tolerance of LTPS channel materials ascribed to the degraded crystalline structure induced by X-ray irradiation make them not suitable for the channel material of highly stable TFTs for the X-ray detector applications. Recently, oxide semiconductor TFTs have been of particular interest as promising candidates for the TFT panels of X-ray detectors owing to their excellent electrical characteristics such as high carrier mobility, low leakage current, and high on–off current ratio. − However, considering the degraded reliability of oxide semiconductor TFTs under light illumination stress, − it is necessary to investigate the effects of high energy X-ray radiation on the electrical performance of oxide semiconductor TFTs to verify their practical use under radiation-harsh environments. A few studies have reported the electrical characteristics of the oxide semiconductor TFTs such as amorphous In–Ga–Zn–O (a-IGZO) TFTs under X-ray irradiation or UV/visible light radiation, exhibiting the shifts of threshold voltage ( V TH ); ,− however, little effort has been made to improve the radiation hardness of the oxide semiconductor TFTs under high energy X-ray irradiation and investigate the mechanisms of radiation damage to the oxide semiconductor TFT in detail.…”