Controlled aluminum oxide doping at an atomic level into binary indium/tin oxide thin-films allows control of crucial TFT parameters such as the mobility (μsat), the threshold-voltage (Vth) and on/off ratio (IOn/IOff). Moreover, it stabilizes TFT performance under optical stress.

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Electronic influence of ultrathin aluminum oxide on the transistor device performance of binary indium/tin oxide films

In this work, the effects of the atomic-layer deposition (ALD)-derived Al2O3 passivation layer with different growth cycles on the interfacial chemistry and electrical performance of sputtering-driven ErSmO/InP metal oxide semiconductor (MOS) capacitors have been comparatively investigated. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization have confirmed that the ALD-driven Al2O3 passivation layer with 20 growth cycles could form a flat dielectric layer and effectively suppress the diffusion of In and P elements at the InP interface. Meanwhile, the ErSmO/Al2O3/InP gate stack with 20 growth cycles exhibited optimal electrical properties, including a large dielectric constant of 37.42, a minimum interface state density (Dit) of 5.43 × 1011 eV–1 cm–2, and a low leakage current of 3.95 × 10–6 A/cm–2. The leakage current conduction mechanisms of InP-MOS capacitors measured at room temperature and low temperature have also been systematically analyzed. Particularly, low-frequency noise (LFN) is used to evaluate trap levels in InP-MOS capacitors. All experimental results have demonstrated that the ErSmO/Al2O3/InP gate stack has potential applications in future ultrahigh-speed and high-frequency microelectronic devices. 

Interface Chemistry and Defect State Optimization of the ErSmO/InP Heterojunction Modified by ALD-Driven Al2O3 Interlayers

We performed a quantitative study using a trap-limited conduction method to correlate the density of localized states with the performance of Sm2O3- and HfO2-gated metal-oxide thin-film transistors (TFTs) fabricated at room temperature. We found that TFT performance with a Sm2O3 gate dielectric exceeds that with a HfO2 gate dielectric. Sm2O3-gated TFTs with an In-Ga-Zn-O (In-Zn-O) channel show a saturation mobility of 57.1 (114.9) cm $^2$ V $^{-1}$ s $^{-1}$ , effective threshold voltage of 0.9 (1.6) V, and subthreshold swing of 0.116 (0.256) Vdec $^{-1}$ . Based on a trap-limited conduction model, the improved performance correlates with the lower density of localized states in the tail and deep regions. A lower density of tail states leads to higher mobility, and the lower density of deep states tends to reduce both the threshold voltage and the subthreshold swing. Using semi-empirical quantum chemistry simulations, we show that the decrease in the number of localized states is associated with the inherent characteristics of Sm cations, due to their lower electropositivity and larger ionic radius compared to Hf, which leads to less ionic distortion in the channel.

Correlating the Density of Trap-States and the Field-Effect Performance in Metal-Oxide Thin-Film Transistors With High- $\kappa$ Gate Dielectrics via a Trap-Limited Conduction Method

Chun-Wen Cheng

Papers

Correlating the Density of Trap-States and the Field-Effect Performance in Metal-Oxide Thin-Film Transistors With High- $\kappa$ Gate Dielectrics via a Trap-Limited Conduction Method