Showing papers on "Thin-film transistor published in 2019"

Amorphous IGZO TFT with High Mobility of ∼70 cm2/(V s) via Vertical Dimension Control Using PEALD

Abstract: Amorphous InGaZnOx (a-IGZO) thin-film transistors (TFTs) are currently used in flat-panel displays due to their beneficial properties. However, the mobility of ∼10 cm2/(V s) for the a-IGZO TFTs used in commercial organic light-emitting diode TVs is not satisfactory for high-resolution display applications such as virtual and augmented reality applications. In general, the electrical properties of amorphous oxide semiconductors are strongly dependent on their chemical composition; the indium (In)-rich IGZO achieves a high mobility of 50 cm2/(V s). However, the In-rich IGZO TFTs possess another issue of negative threshold voltage owing to intrinsically high carrier density. Therefore, the development of an effective way of carrier density suppression in In-rich IGZO will be a key strategy to the realization of practical high-mobility a-IGZO TFTs. In this study, we report that In-rich IGZO TFTs with vertically stacked InOx, ZnOx, and GaOx atomic layers exhibit excellent performances such as saturation mobilities of ∼74 cm2/(V s), threshold voltage of -1.3 V, on/off ratio of 8.9 × 108, subthreshold swing of 0.26 V/decade, and hysteresis of 0.2 V, while keeping a reasonable carrier density of ∼1017 cm-3. We found that the vertical dimension control of IGZO active layers is critical to TFT performance parameters such as mobility and threshold voltage. This study illustrates the potential advantages of atomic layer deposition processes for fabricating ultrahigh-mobility oxide TFTs.

Low-voltage high-performance flexible digital and analog circuits based on ultrahigh-purity semiconducting carbon nanotubes.

Abstract: Carbon nanotube (CNT) thin-film transistor (TFT) is a promising candidate for flexible and wearable electronics. However, it usually suffers from low semiconducting tube purity, low device yield, and the mismatch between p- and n-type TFTs. Here, we report low-voltage and high-performance digital and analog CNT TFT circuits based on high-yield (19.9%) and ultrahigh purity (99.997%) polymer-sorted semiconducting CNTs. Using high-uniformity deposition and pseudo-CMOS design, we demonstrated CNT TFTs with good uniformity and high performance at low operation voltage of 3 V. We tested forty-four 2-µm channel 5-stage ring oscillators on the same flexible substrate (1,056 TFTs). All worked as expected with gate delays of 42.7 ± 13.1 ns. With these high-performance TFTs, we demonstrated 8-stage shift registers running at 50 kHz and the first tunable-gain amplifier with 1,000 gain at 20 kHz. These results show great potentials of using solution-processed CNT TFTs for large-scale flexible electronics. Carbon nanotube thin-film transistor is promising for solution-processed, large-scale flexible electronics, but the device yields remain poor to date. Lei et al. show low-voltage flexible digital and analog circuits based on high-purity and high-yield separation of semiconducting carbon nanotubes.

Perovskite and Conjugated Polymer Wrapped Semiconducting Carbon Nanotube Hybrid Films for High-Performance Transistors and Phototransistors

Abstract: Although organic–inorganic halide perovskites continue to generate considerable interest due to great potentials for various optoelectronic devices, there are some critical obstacles to practical applications, including lead toxicity, relatively low field-effect mobility, and strong hysteresis during operation. This paper proposes a universal approach to significantly improve mobility and operational stability with reduced dual-sweep hysteresis for perovskite-based thin film transistors (TFTs) by coupling low-dimensional lead-free perovskite material (C6H5C2H4NH3)2SnI4 (hereafter abbreviated as (PEA)2SnI4) with embedded conjugated polymer wrapped semiconducting carbon nanotubes (semi-CNTs). In (PEA)2SnI4/semi-CNT hybrid TFTs, semi-CNTs can provide highway-like transport paths, enabling smoother carrier transport with less trapping and scattering. We also demonstrate the performance of (PEA)2SnI4/semi-CNT hybrid phototransistors with ultrahigh photoresponsivity (R) of 6.3 × 104 A/W and detectivity (D*) of ...

Ultra-High Sensitive NO2 Gas Sensor Based on Tunable Polarity Transport in CVD-WS2/IGZO p-N Heterojunction.

Abstract: In this work, a thin-film transistor gas sensor based on the p-N heterojunction is fabricated by stacking chemical vapor deposition-grown tungsten disulfide (WS2) with a sputtered indium–gallium–zi...

Solution-processed metal-oxide thin-film transistors: a review of recent developments.

Abstract: Driven by the rapid development of novel active-matrix displays, thin-film transistors (TFTs) based on metal-oxide (MO) semiconductors have drawn great attention during recent years. N-type MO TFTs manufactured through vacuum-based processes have the advantages of higher mobility compared to the amorphous silicon TFTs, better uniformity and lower processing temperature compared to the polysilicon TFTs, and visible light transparency which is suitable for transparent electronic devices, etc. However, the fabrication cost is high owing to the expensive and complicated vacuum-based systems. In contrast, solution process has the advantages of low cost, high throughput, and easy chemical composition control. In the first part of this review, a brief introduction of solution-processed MO TFTs is given, and the main issues and challenges encountered in this field are discussed. The recent advances in channel layer engineering to obtain the state-of-the-art solution-processed MO TFTs are reviewed and summarized. Afterward, a detailed discussion of the direct patterning methods is presented, including the direct photopatterning and printing techniques. Next, the effect of gate dielectric materials and their interfaces on the performance of the resulting TFTs are surveyed. The last topic is the various applications of solution-processed MO TFTs, from novel displays to sensing, memory devices, etc. Finally, conclusions are drawn and future expectations for solution-processed MO TFTs and their applications are described.

Flexible, Print-in-Place 1D-2D Thin-Film Transistors Using Aerosol Jet Printing.

Abstract: Semiconducting carbon nanotubes (CNTs) printed into thin films offer high electrical performance, significant mechanical stability, and compatibility with low-temperature processing. Yet, the imple...

Ultra-wide bandgap amorphous oxide semiconductors for NBIS-free thin-film transistors

Abstract: The transparency of oxide semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous oxide semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We show that a-ZGO thin-film transistors exhibit no negative-bias illumination-stress instability with no passivation and no light-shielding layer.

A High-Gain Inverter With Low-Temperature Poly-Si Oxide Thin-Film Transistors

Abstract: We report a complementary metal oxide semiconductor (CMOS) inverter made of p-type low-temperature poly-Si (LTPS) thin-film transistor (TFT) using blue laser annealing of amorphous Si and an n-type amorphous indium-gallium-zinc oxide (a-IGZO) TFT. The LTPS TFT exhibits a field-effect mobility, threshold voltage, and subthreshold swing of 81.76 cm2/Vs, −1.1 V, and 0.65 V/dec, respectively, and the a-IGZO TFT exhibits 13.52 cm2/Vs, 1.2 V and 0.25 V/dec, respectively. The CMOS inverter shows a full swing and a high gain of 114.28 V/V and a wide noise margin with rising and falling times of 1.44 and $3.52~\mu \text{s}$ , respectively.

All inorganic solution processed three terminal charge trapping memory device

Abstract: We demonstrate charge trapping memory devices comprising aluminum oxide phosphate (ALPO) blocking/indium gallium zinc oxide charge-trapping/ALPO tunneling layers with a bottom-gated architecture fabricated by sol-gel process technique at temperatures as low as 300 °C. The memory device offers a large memory hysteresis of 13.5 V in the Id–Vg curve when the gate voltage is swept from −20 to +30 V and back. The true program-erase (P/E) window of 7 V is established for the P/E square pulse of ±20 V s−1. Good retention characteristic is confirmed within the experimental limit of 104 s. The P/E mechanism is illustrated by the complete band structure of the memory devices. We also demonstrate a control device without a charge trapping layer, which shows excellent thin film transistor characteristics.

Sub-ppm and high response organic thin-film transistor NO2 sensor based on nanofibrillar structured TIPS-pentacene

Abstract: We investigated the effect of off-center spin coating process on the characteristics of organic thin-film transistors (OTFTs) based nitrogen dioxide (NO2) sensors. Different nanofibrillar structured directions were obtained through off-center spin coating which significantly improved the sensing property compared to that fabricated by the conventional on-center spin coating process. A remarkable enhancement of gas responsivity from 31.9% to 221.5% under 30 ppm NO2 was achieved by orthogonal off-center spin coating. While, device by parallel off-center spin coating showed an excellent sensitivity of 44.3% under ppb-level NO2 (250 ppb), and the response under 1 ppm also exhibited 35-fold increase. After a comprehensive analysis on the morphology properties of the organic films and electrical properties of devices, it was revealed that the multiform performance improvement was largely related to the nanofibrillar structured organic semiconductor (OSC) films facilitated by off-center spin coating, leading to a well-regulated change of potential barriers at grain boundaries. Compared to the common strategies, this work develops a simple, efficient and reliable access to obtain high performance solution-processed OTFT based gas sensors.

Semiconductor device and manufacturing method thereof

Abstract: A semiconductor device including a first substrate and a thin film transistor disposed on the first substrate is provided The thin film transistor includes a gate, a semiconductor pattern, a first insulating layer, a source and a drain The first insulating layer is disposed between the gate and the semiconductor pattern The source and the drain are separated from each other and disposed corresponding to the semiconductor pattern At least one of the source and the drain has a first copper patterned layer and a first copper oxynitride patterned layer The first copper oxynitride patterned layer covers the first copper patterned layer The first copper patterned layer is disposed between the first copper oxynitride patterned layer and the first substrate Moreover, a manufacturing method of the semiconductor device is also provided

Research Progress on Flexible Oxide-Based Thin Film Transistors

Abstract: Oxide semiconductors have drawn much attention in recent years due to their outstanding electrical performance, such as relatively high carrier mobility, good uniformity, low process temperature, optical transparency, low cost and especially flexibility. Flexible oxide-based thin film transistors (TFTs) are one of the hottest research topics for next-generation displays, radiofrequency identification (RFID) tags, sensors, and integrated circuits in the wearable field. The carrier transport mechanism of oxide semiconductor materials and typical device configurations of TFTs are firstly described in this invited review. Then, we describe the research progress on flexible oxide-based TFTs, including representative TFTs fabricated on different kinds of flexible substrates, the mechanical stress effect on TFTs and optimized methods to reduce this effect. Finally, an outlook for the future development of oxide-based TFTs is given.

Phase Separation of P3HT/PMMA Blend Film for Forming Semiconducting and Dielectric Layers in Organic Thin-Film Transistors for High-Sensitivity NO2 Detection.

Abstract: Formation of the semiconductor/dielectric double-layered films via vertical phase separations from polymer blends is an effective method to fabricate organic thin-film transistors (OTFTs). Here, we introduce a simple one-step processing method for the vertical phase separation of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(methyl methacrylate) (PMMA) blends in OTFTs and their applications for high-performance nitrogen dioxide (NO2) sensors. Compared to the conventional two-step coated OTFT sensors, one-step processed devices exhibit a great enhancement of the responsivity from 116 to 1481% for 30 ppm NO2 concentration and a limit of detection of ∼0.7 ppb. Studies of the microstructures of the blend films and the electrical properties of the sensors reveal that the devices formed by the one-step vertical phase separation have better capability for the adsorption of NO2 molecules. Moreover, a careful adjustment of the blend ratio between P3HT and PMMA can further improve the performance of the NO2 sensors, ranging from sensitivity to selectivity and to the ability of recovery. This simple one-step processing method demonstrates a potential possibility for developing high-performance, low-cost, and large-area OTFT gas sensors.

Highly sensitive and selective room-temperature NO2 gas-sensing characteristics of SnOX-based p-type thin-film transistor

Abstract: The high-performance p-type metal-oxide-semiconductor (MOS)-based gas sensor is an important subject of research in the field of gas-sensing technology. In this work, we demonstrated a p-type MOS-based thin-film transistor (TFT) nitrogen dioxide (NO2) gas sensor that used tin oxide (SnOX) for both the channel and sensing layers. The crystalline status, surface morphology, and atomic-bonding configuration of the thin-film were examined using X-ray diffraction, field emission-scanning electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that the deposited thin-film was mainly composed of polycrystalline SnO with a tetragonal structure. The fabricated p-type SnOX TFT showed a maximum response value of 19.4-10 ppm NO2 at room temperature (RT, 25 °C) when operated in the subthreshold region, which was significantly higher than that of 2.8–10 ppm NO2 obtained from a p-type SnOX thin-film chemiresistor at RT. In addition, the SnOX TFT gas sensor showed significantly higher sensitivity to NO2 gas than to other target gases such as NH3, H2S, CO2, and CO at RT. To the best of our knowledge, this is the first study to a p-type MOS-based field-effect transistor-type gas sensor. Our experimental results demonstrate that the p-type SnOX TFT is a promising gas sensor that can operate at RT with high sensitivity and selectivity to NO2 gas.

Analysis of Ultrahigh Apparent Mobility in Oxide Field-Effect Transistors.

Abstract: For newly developed semiconductors, obtaining high-performance transistors and identifying carrier mobility have been hot and important issues. Here, large-area fabrications and thorough analysis of InGaZnO transistors with enhanced current by simple encapsulations are reported. The enhancement in the drain current and on-off ratio is remarkable in the long-channel devices (e.g., 40 times in 200 µm long transistors) but becomes much less pronounced in short-channel devices (e.g., 2 times in 5 µm long transistors), which limits its application to the display industry. Combining gated four-probe measurements, scanning Kelvin-probe microscopy, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and device simulations, it is revealed that the enhanced apparent mobility up to several tens of times is attributed to the stabilized hydrogens in the middle area forming a degenerated channel area while that near the source-drain contacts are merely doped, which causes artifact in mobility extraction. The studies demonstrate the use of hydrogens to remarkably enhance performance of oxide transistors by inducing a new mode of device operation. Also, this study shows clearly that a thorough analysis is necessary to understand the origin of very high apparent mobilities in thin-film transistors or field-effect transistors with advanced semiconductors.

Polymer Doping Enables a Two-Dimensional Electron Gas for High-Performance Homojunction Oxide Thin-Film Transistors.

Abstract: High-performance solution-processed metal oxide (MO) thin-film transistors (TFTs) are realized by fabricating a homojunction of indium oxide (In2 O3 ) and polyethylenimine (PEI)-doped In2 O3 (In2 O3 :x% PEI, x = 0.5-4.0 wt%) as the channel layer. A two-dimensional electron gas (2DEG) is thereby achieved by creating a band offset between the In2 O3 and PEI-In2 O3 via work function tuning of the In2 O3 :x% PEI, from 4.00 to 3.62 eV as the PEI content is increased from 0.0 (pristine In2 O3 ) to 4.0 wt%, respectively. The resulting devices achieve electron mobilities greater than 10 cm2 V-1 s-1 on a 300 nm SiO2 gate dielectric. Importantly, these metrics exceed those of the devices composed of the pristine In2 O3 materials, which achieve a maximum mobility of ≈4 cm2 V-1 s-1 . Furthermore, a mobility as high as 30 cm2 V-1 s-1 is achieved on a high-k ZrO2 dielectric in the homojunction devices. This is the first demonstration of 2DEG-based homojunction oxide TFTs via band offset achieved by simple polymer doping of the same MO material.

Impact of cation compositions on the performance of thin-film transistors with amorphous indium gallium zinc oxide grown through atomic layer deposition

Abstract: This paper reports the effect of the cation composition on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) where atomic layer deposition (ALD)...

Tailoring IGZO Composition for Enhanced Fully Solution-Based Thin Film Transistors.

Abstract: Solution-processed metal oxides have been investigated as an alternative to vacuum-based oxides to implement low-cost, high-performance electronic devices on flexible transparent substrates. However, their electrical properties need to be enhanced to apply at industrial scale. Amorphous indium-gallium-zinc oxide (a-IGZO) is the most-used transparent semiconductor metal oxide as an active channel layer in thin-film transistors (TFTs), due to its superior electrical properties. The present work evaluates the influence of composition, thickness and ageing on the electrical properties of solution a-IGZO TFTs, using solution combustion synthesis method, with urea as fuel. After optimizing the semiconductor properties, low-voltage TFTs were obtained by implementing a back-surface passivated 3-layer In:Ga:Zn 3:1:1 with a solution-processed high-к dielectric; AlOx. The devices show saturation mobility of 3.2 cm2 V-1 s-1, IOn/IOff of 106, SS of 73 mV dec-1 and VOn of 0.18 V, thus demonstrating promising features for low-cost circuit applications.

Lightweight flexible indium-free oxide TFTs with AND logic function employing chitosan biopolymer as self-supporting layer

Abstract: Chitosan, a natural polysaccharide, is nontoxic, lightweight and biodegradable, which exhibits a great potential for the emerging flexible and “green” electronic applications. Here, lightweight flexible aluminum-zinc-oxide (AZO) thin-film transistors (TFTs) are fabricated using chitosan biopolymer as self-supporting layer. This kind of biopolymer electrolyte can provide a strong electric-double-layer effect, which leads to a large capacitance with lower energy consumption. With the low-cost indium-free AZO deposited onto the chitosan film as the coplanar gate and source/channel/drain electrodes, the transistor shows a moderate on/off ratio of ∼104, a relatively ideal field-effect mobility of 0.3 cm2/Vs and a moderate sub-threshold swing of 0.65 V/dec. Moreover, logic “AND” function is realized in the flexible device with two coplanar gates as the input terminals. Such chitosan-gated flexible TFT devices can provide promising candidates for the next generation wearable and “green” electronics.

Design of InZnSnO Semiconductor Alloys Synthesized by Supercycle Atomic Layer Deposition and Their Rollable Applications.

Abstract: Amorphous InGaZnO semiconductors have been rapidly developed as active charge-transport materials in thin film transistors (TFTs) because of their cost effectiveness, flexibility, and homogeneous c...

P and N type copper phthalocyanines as effective semiconductors in organic thin-film transistor based DNA biosensors at elevated temperatures

Abstract: Many health-related diagnostics are expensive, time consuming and invasive. Organic thin film transistor (OTFT) based devices show promise to enable rapid, low cost diagnostics that are an important aspect to enabling increased access and availability to healthcare. Here, we describe OTFTs based upon two structurally similar P (copper phthalocyanine – CuPc) and N (hexdecafluoro copper phthalocyanine – F16-CuPc) type semiconductor materials, and demonstrate their potential for use as both temperature and DNA sensors. Bottom gate bottom contact (BGBC) OTFTs with either CuPc or F16-CuPc semiconducting layers were characterized within a temperature range of 25 °C to 90 °C in both air and under vacuum. CuPc devices showed small positive shifts in threshold voltage (VT) in air and significant linear increases in mobility with increasing temperature. F16-CuPc devices showed large negative shifts in VT in air and linear increases in mobility under the same conditions. Similar OTFTs were exposed to DNA in different hybridization states and both series of devices showed positive VT increases upon DNA exposure, with a larger response to single stranded DNA. The N-type F16-CuPc devices showed a much greater sensing response than the P-type CuPc. These findings illustrate the use of these materials, especially the N-type semiconductor, as both temperature and DNA sensors and further elucidate the mechanism of DNA sensing in OTFTs.

High-Performance Thin-Film Transistors of Quaternary Indium-Zinc-Tin Oxide Films Grown by Atomic Layer Deposition.

Abstract: A new deposition technique is required to grow the active oxide semiconductor layer for emerging oxide electronics beyond the conventional sputtering technique. Atomic layer deposition (ALD) has the benefits of versatile composition control, low defect density in films, and conformal growth over a complex structure, which can hardly be obtained with sputtering. This study demonstrates the feasibility of growing amorphous In–Zn–Sn–O (a-IZTO) through ALD for oxide thin-film transistor (TFT) applications. In the ALD of the a-IZTO film, the growth behavior indicates that there exists a growth correlation between the precursor molecules and the film surface where the ALD reaction occurs. This provides a detailed understanding of the ALD process that is required for precise composition control. The a-IZTO film with In/Zn/Sn = 10:70:20 was chosen for high-performance TFTs, among other compositions, regarding the field-effect mobility (μFE), turn-on voltage (Von), and subthreshold swing (SS) voltage. The optimize...

High-Performance 1-V ZnO Thin-Film Transistors With Ultrathin, ALD-Processed ZrO 2 Gate Dielectric

Abstract: The high-performance ZnO thin-film transistors (TFTs) were fabricated on indium tin oxide glass with high-capacitance atomic layer deposition (ALD)-processed ZrO2 as the gate dielectric. The 5-nm ultrathin ZrO2 film showed a very high areal capacitance of 820 nF/cm2 at 20 Hz, a relatively high breakdown field of 14 MV/cm, and low surface root-mean-square (rms) roughness of 0.22 nm, making it possible for ZnO/ZrO2 TFT to not only be operated by an ultralow operating voltage of 1 V but also present a near theoretical limit subthreshold swing of 69 mV/dec. Furthermore, the ZnO TFT with a 5-nm ZrO2 gate dielectric exhibited excellent performance, such as a high Ion/Ioff of 107, large field effect mobility of 36.8 cm2/Vs, low-density of trapping states ( ${N}_{{\text {trap}}}$ ) of $1.6\times 10^{{11}}$ eV−1cm−2, and negligible hysteresis. In addition, the electron transport mode was built to explain the high mobility of nanocrystalline ZnO TFT. As a result, the ultralow operating voltage TFTs exhibited great potential for low-powered electronics applications.

Array substrate, display panel and display device

Abstract: The present disclosure provides an array substrate, a display panel and a display device. The array substrate includes a base substrate and a thin film transistor. An orthographic projection of a drain of the thin film transistor on the base substrate does not go beyond an orthographic projection of a gate of the thin film transistor on the base substrate.