Search Results (13)

Indium oxide (In₂O₃) has recently emerged as a promising semiconductor for advanced electronics due to its high electron mobility and wide bandgap. In this article, the lateral scaling characteristics of top-gate In₂O₃ thin-film transistors (TFTs) featuring a 1.5 nm thick channel and a 7 nm thick HfO₂ gate dielectric are investigated by two-dimensional device simulation. The analysis covers short-channel effects, DC characteristics, transconductance behavior, and small-signal radio frequency (RF) metrics across a gate-length (L_G) range of 20 nm to 700 nm. Simulation results identify a critical gate length near 100 nm for the transition from long-channel to short-channel behavior. For L_G ≤ 100 nm, pronounced short-channel effects emerge, featuring a significant negative V_TH shift and a drain-induced barrier lowering (DIBL) coefficient up to ~130 mV/V. A non-classical gm scaling behavior is observed, where g_{m_max} initially increases with L_G, then remains within a narrow range and eventually evolves toward the conventional long-channel trend. Further analysis of the lateral electric field distribution, field-dependent mobility, and transconductance efficiency indicates that this behavior originates from a crossover between short-channel field-assisted transport and gate-controlled channel modulation. The devices show strong RF potential, with f_T and f_max reaching 124.32 GHz and 157.64 GHz, respectively, at L_G = 20 nm. The high-mobility In₂O₃ channel leads to a less distinct f_T scaling transition from the classical 1/L²_G dependence to the short-channel 1/L_G dependence, while f_max scaling evolves through different regimes governed by capacitance-related limitations, intrinsic transport enhancement, and short-channel non-idealities. This work provides physical insight into the lateral scaling behavior of ultrathin top-gate In₂O₃ TFTs and highlights their potential for high-frequency and power-dense applications. Full article

Ultrathin oxide semiconductors are promising channel materials for next-generation thin-film transistors (TFTs), but their performance is severely limited by bulk and interface defects as the channel thickness approaches a few nanometers. In this study, we show that high-pressure hydrogen annealing (HPHA) effectively mitigates these limitations in 3.6 nm thick ZnO TFTs. HPHA-treated devices exhibit a nearly four-fold increase in on-current, a steeper subthreshold swing, and a negative shift in threshold voltage compared to reference groups. X-ray photoelectron spectroscopy reveals a marked reduction in oxygen vacancies and hydroxyl groups, while capacitance–voltage measurements confirm more than a three-fold decrease in interface trap density. Low-frequency noise analysis further demonstrates noise suppression and a transition in the dominant noise mechanism from carrier number fluctuation to mobility fluctuation. These results establish HPHA as a robust strategy for defect passivation in ultrathin oxide semiconductor channels and provide critical insights for their integration into future low-power, high-density electronic systems. Full article

In this study, we investigated the density of states extraction method for atomic-deposited ZnO thin-film transistors (TFTs) by analyzing gate-dependent field-effect mobility. The atomic layer deposition (ALD) method offers ultra-thin and smooth ZnO films, but these films suffer from interface and semiconductor defects, which lead to disordered localized electronic structures. Hence, to investigate the unstable localized structure of ZnO TFTs, we tried to derive the electronic state relationship by assuming field-effect mobility can be expressed as a gate-dependent Arrhenius relation, and the activation energy in the relation is the required energy for hopping. Following this derived relationship, the DOS of the atomic-deposited ZnO transistor was extracted and found to be consistent with those using temperature-dependent measurements. Moreover, to ensure the proposed method is reliable, we applied methods for the extraction of DOSs of doped ZnO transistors, which show enhanced mobilities with shifted threshold voltages, and the results show that the extraction method is reliable. Thus, we can state that the mobility-based DOS extraction method offers practical benefits for estimating the density of states of disordered transistors using a single transfer characteristic of these devices. Full article

To fabricate oxide thin-film transistors (TFTs) with high performance and excellent stability, preparing high-quality semiconductor films in the channel bulk region and minimizing the defect states in the gate dielectric/channel interfaces and back-channel regions is necessary. However, even if an oxide transistor is composed of the same semiconductor film, gate dielectric/channel interface, and back channel, its electrical performance and operational stability are significantly affected by the thickness of the oxide semiconductor. In this study, solution process-based nanometer-scale thickness engineering of InZnO semiconductors was easily performed via repeated solution coating and annealing. The thickness-controlled InZnO films were then applied as channel regions, which were fabricated with almost identical film quality, gate dielectric/channel interface, and back-channel conditions. However, excellent operational stability and electrical performance suitable for oxide TFT backplane was only achieved using an 8 nm thick InZnO film. In contrast, the ultrathin and thicker films exhibited electrical performances that were either very resistive (high positive V_Th and low on-current) or excessively conductive (high negative V_Th and high off-current). This investigation confirmed that the quality of semiconductor materials, solution process design, and structural parameters, including the dimensions of the channel layer, must be carefully designed to realize high-performance and high-stability oxide TFTs. Full article

We report water-induced nanometer-thin crystalline indium praseodymium oxide (In-Pr-O) thin-film transistors (TFTs) for the first time. This aqueous route enables the formation of dense ultrathin (~6 nm) In-Pr-O thin films with near-atomic smoothness (~0.2 nm). The role of Pr doping is investigated by a battery of experimental techniques. It is revealed that as the Pr doping ratio increases from 0 to 10%, the oxygen vacancy-related defects could be greatly suppressed, leading to the improvement of TFT device characteristics and durability. The optimized In-Pr-O TFT demonstrates state-of-the-art electrical performance with mobility of 17.03 ± 1.19 cm²/Vs and on/off current ratio of ~10⁶ based on Si/SiO₂ substrate. This achievement is due to the low electronegativity and standard electrode potential of Pr, the high bond strength of Pr-O, same bixbyite structure of Pr₂O₃ and In₂O₃, and In-Pr-O channel’s nanometer-thin and ultrasmooth nature. Therefore, the designed In-Pr-O channel holds great promise for next-generation transistors. Full article

We demonstrate the growth of ultra-thin (~5 nm) indium ytterbium oxide (In-Yb-O) thin film using a simple vacuum-free aqueous solution approach for the first time. The influences of Yb addition on the microstructural, chemical, optical, and electrical properties of In₂O₃ are well investigated. The analyses indicate that Yb dopant could suppress oxygen vacancy defects effectively owing to the lower standard electrode potential, lower electronegativity, and stronger metal-oxide bond strength than that of In. The optimized In-Yb-O thin-film transistors (TFTs) exhibit excellent electrical performance (mobility of 8 cm²/Vs and on/off ratio of ~10⁸) and enhanced stability. The triumph of In-Yb-O TFTs is owing to the high quality In₂O₃ matrix, the remarkable suppressor of Yb, and the nanometer-thin and atomically smooth nature (RMS: ~0.26 nm) of channel layer. Therefore, the eco-friendly water-induced ultra-thin In-Yb-O channel provides an excellent opportunity for future large-scale and cost-effective electronic applications. Full article

Thin-film transistors (TFTs) made of solution-processable transparent metal oxide semiconductors show great potential for use in emerging large-scale optoelectronics. However, current solution-processed metal oxide TFTs still suffer from relatively poor device performance, hindering their further advancement. In this work, we create a novel ultrathin crystalline indium–boron–oxide (In-B-O) channel layer for high-performance TFTs. We show that high-quality ultrathin (~10 nm) crystalline In-B-O with an atomically smooth nature (RMS: ~0.15 nm) could be grown from an aqueous solution via facile one-step spin-coating. The impacts of B doping on the physical, chemical and electrical properties of the In₂O₃ film are systematically investigated. The results show that B has large metal–oxide bond dissociation energy and high Lewis acid strength, which can suppress oxygen vacancy-/hydroxyl-related defects and alleviate dopant-induced carrier scattering, resulting in electrical performance improvement. The optimized In-B-O (10% B) TFTs based on SiO₂/Si substrate demonstrate a mobility of ~8 cm²/(V s), an on/off current ratio of ~10⁶ and a subthreshold swing of 0.86 V/dec. Furthermore, by introducing the water-processed high-K ZrO₂ dielectric, the fully aqueous solution-grown In-B-O/ZrO₂ TFTs exhibit excellent device performance, with a mobility of ~11 cm²/(V s), an on/off current of ~10⁵, a subthreshold swing of 0.19 V/dec, a low operating voltage of 5 V and superior bias stress stability. Our research opens up new avenues for low-cost, large-area green oxide electronic devices with superior performance. Full article

High-performance p-type thin-film transistors (pTFTs) are crucial for realizing low-power display-on-panel and monolithic three-dimensional integrated circuits. Unfortunately, it is difficult to achieve a high hole mobility of greater than 10 cm²/V·s, even for SnO TFTs with a unique single-hole band and a small hole effective mass. In this paper, we demonstrate a high-performance GeSn pTFT with a high field-effect hole mobility (μ_FE), of 41.8 cm²/V·s; a sharp turn-on subthreshold slope (SS), of 311 mV/dec, for low-voltage operation; and a large on-current/off-current (I_ON/I_OFF) value, of 8.9 × 10⁶. This remarkably high I_ON/I_OFF is achieved using an ultra-thin nanosheet GeSn, with a thickness of only 7 nm. Although an even higher hole mobility (103.8 cm²/V·s) was obtained with a thicker GeSn channel, the I_OFF increased rapidly and the poor I_ON/I_OFF (75) was unsuitable for transistor applications. The high mobility is due to the small hole effective mass of GeSn, which is supported by first-principles electronic structure calculations. Full article

Metal-oxide thin-film transistors (TFTs) have been implanted for a display panel, but further mobility improvement is required for future applications. In this study, excellent performance was observed for top-gate coplanar binary SnO₂ TFTs, with a high field-effect mobility (μ_FE) of 136 cm²/Vs, a large on-current/off-current (I_ON/I_OFF) of 1.5 × 10⁸, and steep subthreshold slopes of 108 mV/dec. Here, μ_FE represents the maximum among the top-gate TFTs made on an amorphous SiO₂ substrate, with a maximum process temperature of ≤ 400 °C. In contrast to a bottom-gate device, a top-gate device is the standard structure for monolithic integrated circuits (ICs). Such a superb device integrity was achieved by using an ultra-thin SnO₂ channel layer of 4.5 nm and an HfO₂ gate dielectric with a 3 nm SiO₂ interfacial layer between the SnO₂ and HfO₂. The inserted SiO₂ layer is crucial for decreasing the charged defect scattering in the HfO₂ and HfO₂/SnO₂ interfaces to increase the mobility. Such high μ_FE, large I_ON, and low I_OFF top-gate SnO₂ devices with a coplanar structure are important for display, dynamic random-access memory, and monolithic three-dimensional ICs. Full article

Interest in laser crystallization (LC) of silicon (Si) thin films has been on the rise in fabrication of polycrystalline silicon (pc-Si) based thin/ultrathin photovoltaic solar cells and Si based thin film transistors (TFT). Laser based fabrication of device quality pc-Si thin films at room temperature is expected to be a key enabling technology because of its low energy, material and process time budget. Fabrication of high-quality pc-Si thin films without pre-/post-treatment at large is a disruptive technology which has the potential to revolutionize the Si thin film industry. We hereby describe in detail a multi-wavelength laser processing platform specially developed for crystallization of amorphous silicon (a-Si) thin films into pc-Si thin films. The platform has three main stages. The first stage consists of a nanosecond pulsed ytterbium (Yt³⁺) doped fibre-laser with a master oscillator power amplifier architecture, operating at a wavelength of 1064 nm with an adjustable repetition rate between 80 kHz–300 kHz. The output beam has a maximum power of 18 W with a pulse energy of 90 µJ. The pulse durations can be set to values between 15 ns–40 ns. The second stage has free-space optical elements for second harmonic generation (SHG) which produces an emission at a wavelength of 532 nm. Conversion efficiency of the SHG is 25% with an output pulse energy of 20 µJ. The platform provides two wavelengths at either 1064 nm or 532 nm in crystallization of a-Si films for different crystallization regimes. The last stage of the platform has a sample processing assembly with a line-focus, which has an x-y motorized stage on a vibration isolated table. Speed of the motorized stage can be set between 1 mm/s–100 mm/s. Stage speed and repetition rate adjustments help to adjust overlap of successive pulses between 97.22–99.99%. Our platform has variety of tune parameters that make it a uniquely flexible system for delicate Si thin film crystallization. A large selection of operational parameter combinations, the wavelength selection and simultaneous x-y scanning capability allow users to crystallize Si films on various substrates optimally. The operation wavelength choice can be done by considering optical absorption and thickness of a-Si films on different types of substrates. Hence, delivering precise amount of absorbed energy in the line-focus irradiation is useful in increasing the average size of crystalline domains; moreover, nucleation of crystallites can be initiated either from the top or bottom interface of the film. Continuous and simultaneous motion of the stage in two dimensions allows to process arbitrary continuous pc-Si geometries in a-Si film. In summary, our multi-wavelength laser processing platform offers all-in-one LC utility for intricate LC-Si processing. Full article

In this work, a high-performance thin film transistor with an neodymium-doped indium zinc oxide (Nd:IZO) semiconductor via a room temperature approach and adopting the Nd:IZO/Al₂O₃ nanolaminate structure was investigated. The effects of the ultrathin Al₂O₃ layer and the thickness of Nd:IZO layer in the nanolaminate structure on the improvement of electrical performance and stability of thin film transistors (TFTs) were systematically studied. Besides the carrier movement confined along the near-channel region, driven by the Al₂O₃ layer under an electrical field, the high performance of the TFT is also attributed to the high quality of the 8-nm-thick Nd:IZO layer and the corresponding optimal Nd:IZO/Al₂O₃ interface, which reduce the scattering effect and charge trapping with strong M–O bonds in bulk and the back-channel surface of Nd:IZO, according to the X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), and micro-wave photo conductivity decay (μ-PCD) results. As a result, the Nd:IZO/Al₂O₃ TFT exhibits an outstanding performance, with a high μ_sat of 32.7 cm²·V⁻¹·s⁻¹, an I_on/I_off of 1.9 × 10⁸, and a low subthreshold swing (SS) value of 0.33 V·dec⁻¹, which shows great potential for the room temperature fabrication of TFTs in high-resolution or high-frame-rate displays by a scalable, simple, and feasible approach. Full article

We present a complete biosensing system that comprises a Thin Film Transistor (TFT)-based nanoribbon biosensor and a low noise, high-performance bioinstrumentation platform, capable of detecting sub-30 mpH unit changes, validated by an enzymatic biochemical reaction. The nanoribbon biosensor was fabricated top-down with an ultra-thin (15 nm) polysilicon semiconducting channel that offers excellent sensitivity to surface potential changes. The sensor is coupled to an integrated circuit (IC), which combines dual switched-capacitor integrators with high precision analog-to-digital converters (ADCs). Throughout this work, we employed both conventional pH buffer measurements as well as urea-urease enzymatic reactions for benchmarking the overall performance of the system. The measured results from the urea-urease reaction demonstrate that the system can detect urea in concentrations as low as 25 μM, which translates to a change of 27 mpH, according to our initial pH characterisation measurements. The attained accuracy and resolution of our system as well as its low-cost manufacturability, high processing speed and portability make it a competitive solution for applications requiring rapid and accurate results at remote locations; a necessity for Point-of-Care (POC) diagnostic platforms. Full article

A low-temperature solution-processed high-k gate dielectric layer for use in a high-performance solution-processed semiconducting polymer organic thin-film transistor (OTFT) was demonstrated. Photochemical activation of sol-gel-derived AlOx films under 150 °C permitted the formation of a dense film with low leakage and relatively high dielectric-permittivity characteristics, which are almost comparable to the results yielded by the conventionally used vacuum deposition and high temperature annealing method. Octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM) treatment of the AlO_x was employed in order to realize high-performance (>0.4 cm²/Vs saturation mobility) and low-operation-voltage (<5 V) diketopyrrolopyrrole (DPP)-based OTFTs on an ultra-thin polyimide film (3-μm thick). Thus, low-temperature photochemically-annealed solution-processed AlO_x film with SAM layer is an attractive candidate as a dielectric-layer for use in high-performance organic TFTs operated at low voltages. Full article