Showing papers on "Thin-film transistor published in 2018"

Recent Advances of Solution-Processed Metal Oxide Thin-Film Transistors.

Abstract: Solution-processed metal oxide thin-film transistors (TFTs) are considered as one of the most promising transistor technologies for future large-area flexible electronics. This work surveys the recent advances in solution-processed metal oxide TFTs, including n-type oxide semiconductors, oxide dielectrics, and p-type oxide semiconductors. We first deliver a review on the history and present status of metal oxide TFTs. Then, we present the recent progress in solution-processed n-type oxide semiconductors, with a special focus on low-temperature and large-area solution-based approaches as well as emerging nondisplay applications. Next, we give a detailed analysis of the state-of-the-art solution-processed oxide dielectrics for low-power electronics. We further discuss the recent advances in solution-based p-type oxide semiconductors, which will enable the highly desirable future low-cost large-area complementary circuits. Finally, we draw conclusions and outline the perspectives over the research field.

Flexible active-matrix organic light-emitting diode display enabled by MoS2 thin-film transistor

Abstract: Atomically thin molybdenum disulfide (MoS2) has been extensively investigated in semiconductor electronics but has not been applied in a backplane circuitry of organic light-emitting diode (OLED) display. Its applicability as an active drive element is hampered by the large contact resistance at the metal/MoS2 interface, which hinders the transport of carriers at the dielectric surface, which in turn considerably deteriorates the mobility. Modified switching device architecture is proposed for efficiently exploiting the high-k dielectric Al2O3 layer, which, when integrated in an active matrix, can drive the ultrathin OLED display even in dynamic folding states. The proposed architecture exhibits 28 times increase in mobility compared to a normal back-gated thin-film transistor, and its potential as a wearable display attached to a human wrist is demonstrated.

Solution Processed Metal Oxide High-κ Dielectrics for Emerging Transistors and Circuits.

Abstract: The electronic functionalities of metal oxides comprise conductors, semiconductors, and insulators. Metal oxides have attracted great interest for construction of large-area electronics, particularly thin-film transistors (TFTs), for their high optical transparency, excellent chemical and thermal stability, and mechanical tolerance. High-permittivity (κ) oxide dielectrics are a key component for achieving low-voltage and high-performance TFTs. With the expanding integration of complementary metal oxide semiconductor transistors, the replacement of SiO2 with high-κ oxide dielectrics has become urgently required, because their provided thicker layers suppress quantum mechanical tunneling. Toward low-cost devices, tremendous efforts have been devoted to vacuum-free, solution processable fabrication, such as spin coating, spray pyrolysis, and printing techniques. This review focuses on recent progress in solution processed high-κ oxide dielectrics and their applications to emerging TFTs. First, the history, basics, theories, and leakage current mechanisms of high-κ oxide dielectrics are presented, and the underlying mechanism for mobility enhancement over conventional SiO2 is outlined. Recent achievements of solution-processed high-κ oxide materials and their applications in TFTs are summarized and traditional coating methods and emerging printing techniques are introduced. Finally, low temperature approaches, e.g., ecofriendly water-induced, self-combustion reaction, and energy-assisted post treatments, for the realization of flexible electronics and circuits are discussed.

Room-Temperature Solution-Synthesized p-Type Copper(I) Iodide Semiconductors for Transparent Thin-Film Transistors and Complementary Electronics

Abstract: Here, room-temperature solution-processed inorganic p-type copper iodide (CuI) thin-film transistors (TFTs) are reported for the first time. The spin-coated 5 nm thick CuI film has average hole mobility (µFE ) of 0.44 cm2 V-1 s-1 and on/off current ratio of 5 × 102 . Furthermore, µFE increases to 1.93 cm2 V-1 s-1 and operating voltage significantly reduces from 60 to 5 V by using a high permittivity ZrO2 dielectric layer replacing traditional SiO2 . Transparent complementary inverters composed of p-type CuI and n-type indium gallium zinc oxide TFTs are demonstrated with clear inverting characteristics and voltage gain over 4. These outcomes provide effective approaches for solution-processed inorganic p-type semiconductor inks and related electronics.

Stable organic thin-film transistors

Abstract: Organic thin-film transistors (OTFTs) can be fabricated at moderate temperatures and through cost-effective solution-based processes on a wide range of low-cost flexible and deformable substrates. Although the charge mobility of state-of-the-art OTFTs is superior to that of amorphous silicon and approaches that of amorphous oxide thin-film transistors (TFTs), their operational stability generally remains inferior and a point of concern for their commercial deployment. We report on an exhaustive characterization of OTFTs with an ultrathin bilayer gate dielectric comprising the amorphous fluoropolymer CYTOP and an Al 2 O 3 :HfO 2 nanolaminate. Threshold voltage shifts measured at room temperature over time periods up to 5.9 × 10 5 s do not vary monotonically and remain below 0.2 V in microcrystalline OTFTs (μc-OTFTs) with field-effect carrier mobility values up to 1.6 cm 2 V −1 s −1 . Modeling of these shifts as a function of time with a double stretched-exponential (DSE) function suggests that two compensating aging mechanisms are at play and responsible for this high stability. The measured threshold voltage shifts at temperatures up to 75°C represent at least a one-order-of-magnitude improvement in the operational stability over previous reports, bringing OTFT technologies to a performance level comparable to that reported in the scientific literature for other commercial TFTs technologies.

High-Performance Visible-Blind Ultraviolet Photodetector Based on IGZO TFT Coupled with p–n Heterojunction

Abstract: A visible-blind ultraviolet (UV) photodetector was designed based on a three-terminal electronic device of thin-film transistor (TFT) coupled with two-terminal p–n junction optoelectronic device, in hope of combining the beauties of both of the devices together. Upon the uncovered back-channel surface of amorphous indium–gallium–zinc-oxide (IGZO) TFT, we fabricated PEDOT:PSS/SnOx/IGZO heterojunction structure, through which the formation of a p–n junction and directional carrier transfer of photogenerated carriers were experimentally validated. As expected, the photoresponse characteristics of the newly designed photodetector, with a photoresponsivity of 984 A/W at a wavelength of 320 nm, a UV–visible rejection ratio up to 3.5 × 107, and a specific detectivity up to 3.3 × 1014 Jones, are not only competitive compared to the previous reports but also better than those of the pristine IGZO phototransistor. The hybrid photodetector could be operated in the off-current region with low supply voltages (<0.1 V)...

Imide-Functionalized Thiazole-Based Polymer Semiconductors: Synthesis, Structure–Property Correlations, Charge Carrier Polarity, and Thin-Film Transistor Performance

Abstract: Imide-functionalized arenes, exemplified by naphthalene diimides (NDIs), perylene diimides (PDIs), and bithiophene imides (BTIs), are the most promising building blocks for constructing high-perfor...

Low-temperature fabrication of sputtered high-k HfO2 gate dielectric for flexible a-IGZO thin film transistors

Abstract: In this work, low temperature fabrication of a sputtered high-k HfO2 gate dielectric for flexible a-IGZO thin film transistors (TFTs) on polyimide substrates was investigated. The effects of Ar-pressure during the sputtering process and then especially the post-annealing treatments at low temperature (≤200 °C) for HfO2 on reducing the density of defects in the bulk and on the surface were systematically studied. X-ray reflectivity, UV-vis and X-ray photoelectron spectroscopy, and micro-wave photoconductivity decay measurements were carried out and indicated that the high quality of optimized HfO2 film and its high dielectric properties contributed to the low concentration of structural defects and shallow localized defects such as oxygen vacancies. As a result, the well-structured HfO2 gate dielectric exhibited a high density of 9.7 g/cm3, a high dielectric constant of 28.5, a wide optical bandgap of 4.75 eV, and relatively low leakage current. The corresponding flexible a-IGZO TFT on polyimide exhibited an optimal device performance with a saturation mobility of 10.3 cm2 V−1 s−1, an Ion/Ioff ratio of 4.3 × 107, a SS value of 0.28 V dec−1, and a threshold voltage (Vth) of 1.1 V, as well as favorable stability under NBS/PBS gate bias and bending stress.

High-Performance, Ultrathin, Ultraflexible Organic Thin-Film Transistor Array Via Solution Process.

Abstract: Ultrathin organic thin-film transistors (OTFTs) have received extensive attention due to their outstanding advantages, such as extreme flexibility, good conformability, ultralight weight, and compatibility with low-cost and large-area solution-processed techniques. However, compared with the rigid substrates, it still remains a challenge to fabricate high-performance ultrathin OTFTs. In this study, a high-performance ultrathin 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) OTFT array is demonstrated via a simple spin-coating method, with mobility as high as 11 cm2 V-1 s-1 (average mobility: 7.22 cm2 V-1 s-1 ), on/off current ratio of over 106 , switching current of >1 mA, and a good yield ratio as high as 100%. The ultrathin thickness at ≈380 nm and the ultralight weight at ≈0.89 g m-2 enable the free-standing OTFTs to imperceptibly adhere onto human skin, and even a damselfly wing without affecting its flying. More importantly, the OTFTs show good electrical characteristics and mechanical stability when conformed onto the curved surfaces and even folded in a book after 100 folding cycles. These results illustrate the broad application potential of this simply fabricated ultrathin OTFT in next-generation electronics such as foldable displays and wearable devices.

A Sustainable Approach to Flexible Electronics with Zinc‐Tin Oxide Thin‐Film Transistors

Abstract: N CO RR EC TE D P RO O F 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Flexible zinc-tin oxide (ZTO) thin-film transistors (TFTs) processed at only 180 °C are reported for the first time. Although no critical elements as In and Ga are used, device performance approaches the one of indium-gallium-zinc oxide TFTs. Hydrogen incorporation during ZTO sputtering and integration with a high-κ multilayer dielectric are explored to obtain Von ≈ 0 V, μFE ≈ 5 cm2 V-1 s-1, and S = 0.26 V dec-1. Inverters with railto-rail operation (VDD = 5 V) and a differential amplifier with positive feedback loop with gain of 17 dB and unity gain frequency of 40 kHz are demonstrated. Q3 C. Fernandes, A. Santa, Â. Santos, P. Bahubalindruni, J. Deuermeier, R. Martins, E. Fortunato, P. Barquinha* ........................... 1800032

Low voltage operation of IGZO thin film transistors enabled by ultrathin Al2O3 gate dielectric

Abstract: An ultrathin, 5 nm, Al2O3 film grown by atomic-layer deposition was used as a gate dielectric for amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The Al2O3 layer showed a low surface roughness of 0.15 nm, a low leakage current, and a high breakdown voltage of 6 V. In particular, a very high gate capacitance of 720 nF/cm2 was achieved, making it possible for the a-IGZO TFTs to not only operate at a low voltage of 1 V but also exhibit desirable properties including a low threshold voltage of 0.3 V, a small subthreshold swing of 100 mV/decade, and a high on/off current ratio of 1.2 × 107. Furthermore, even under an ultralow operation voltage of 0.6 V, well-behaved transistor characteristics were still observed with an on/off ratio as high as 3 × 106. The electron transport through the Al2O3 layer has also been analyzed, indicating the Fowler–Nordheim tunneling mechanism.

Review Article: Atomic layer deposition for oxide semiconductor thin film transistors: Advances in research and development

Abstract: This article is a review of recent research and development advances in oxide thin film transistors (TFTs) fabricated by atomic layer deposition (ALD) processes. The ALD process is remarkable as it offers accurate control of film thickness and composition as well as the ability to achieve excellent uniformity over large areas at relatively low temperatures. Firstly, an introduction to n-type oxide TFTs is provided with a focus on the development of active-layer material combinations from binary oxide active layers, like zinc oxide and indium oxide, to ternary and quaternary oxide active layers formed by doping with elements such as gallium or tin to achieve high mobility and high device stability for TFTs. Secondly, ALD p-type channel oxide TFTs are also introduced, which are required for the realization of many types of low-power circuits, such as complementary metal oxide semiconductor devices.

High-Mobility and Hysteresis-Free Flexible Oxide Thin-Film Transistors and Circuits by Using Bilayer Sol–Gel Gate Dielectrics

Abstract: In this paper, we demonstrate high-performance and hysteresis-free solution-processed indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) and high-frequency-operating seven-stage ring oscillators using a low-temperature photochemically activated Al2O3/ZrO2 bilayer gate dielectric. It was found that the IGZO TFTs with single-layer gate dielectrics such as Al2O3, ZrO2, or sodium-doped Al2O3 exhibited large hysteresis, low field-effect mobility, or unstable device operation owing to the interfacial/bulk trap states, insufficient band offset, or a substantial number of mobile ions present in the gate dielectric layer, respectively. To resolve these issues and to explain the underlying physical mechanisms, a series of electrical analyses for various single- and bilayer gate dielectrics was carried out. It is shown that compared to single-layer gate dielectrics, the Al2O3/ZrO2 gate dielectric exhibited a high dielectric constant of 8.53, low leakage current density (∼10–9 A cm–2 at 1 MV cm–1), and sta...

Corrugated Heterojunction Metal-Oxide Thin-Film Transistors with High Electron Mobility via Vertical Interface Manipulation

Abstract: A new strategy is reported to achieve high-mobility, low-off-current, and operationally stable solution-processable metal-oxide thin-film transistors (TFTs) using a corrugated heterojunction channel structure. The corrugated heterojunction channel, having alternating thin-indium-tin-zinc-oxide (ITZO)/indium-gallium-zinc-oxide (IGZO) and thick-ITZO/IGZO film regions, enables the accumulated electron concentration to be tuned in the TFT off- and on-states via charge modulation at the vertical regions of the heterojunction. The ITZO/IGZO TFTs with optimized corrugated structure exhibit a maximum field-effect mobility >50 cm2 V-1 s-1 with an on/off current ratio of >108 and good operational stability (threshold voltage shift <1 V for a positive-gate-bias stress of 10 ks, without passivation). To exploit the underlying conduction mechanism of the corrugated heterojunction TFTs, a physical model is implemented by using a variety of chemical, structural, and electrical characterization tools and Technology Computer-Aided Design simulations. The physical model reveals that efficient charge manipulation is possible via the corrugated structure, by inducing an extremely high carrier concentration at the nanoscale vertical channel regions, enabling low off-currents and high on-currents depending on the applied gate bias.

Display device and method for manufacturing the same

Abstract: A display device and a method for manufacturing the same capable of preventing a defective drive of a gate-in-panel (GIP) driver by dissipating high heat generated in a large-sized thin film transistor of the GIP driver are disclosed. The display device includes a flexible substrate, a GIP driver and a display unit disposed on the flexible substrate, a protective member disposed under the flexible substrate, and a heat pad disposed between the flexible substrate and the protective member and overlapping the GIP driver.

Patterned Liquid Metal Contacts for Printed Carbon Nanotube Transistors

Abstract: Flexible and stretchable electronics are poised to enable many applications that cannot be realized with traditional, rigid devices. One of the most promising options for low-cost stretchable transistors are printed carbon nanotubes (CNTs). However, a major limiting factor in stretchable CNT devices is the lack of a stable and versatile contact material that forms both the interconnects and contact electrodes. In this work, we introduce the use of eutectic gallium–indium (EGaIn) liquid metal for electrical contacts to printed CNT channels. We analyze thin-film transistors (TFTs) fabricated using two different liquid metal deposition techniques—vacuum-filling polydimethylsiloxane (PDMS) microchannel structures and direct-writing liquid metals on the CNTs. The highest performing CNT–TFT was realized using vacuum-filled microchannel deposition with an in situ annealing temperature of 150 °C. This device exhibited an on/off ratio of more than 104 and on-currents as high as 150 μA/mm—metrics that are on par wi...

Effect of hydrogen diffusion in an In–Ga–Zn–O thin film transistor with an aluminum oxide gate insulator on its electrical properties

Abstract: We fabricated amorphous InGaZnO thin film transistors (a-IGZO TFTs) with aluminum oxide (Al2O3) as a gate insulator grown through atomic layer deposition (ALD) method at different deposition temperatures (Tdep). The Al2O3 gate insulator with a low Tdep exhibited a high amount of hydrogen in the film, and the relationship between the hydrogen content and the electrical properties of the TFTs was investigated. The device with the Al2O3 gate insulator having a high H content showed much better transfer parameters and reliabilities than the low H sample. This is attributed to the defect passivation effect of H in the active layer, which is diffused from the Al2O3 layer. In addition, according to the post-annealing temperature (Tpost-ann), a-IGZO TFTs exhibited two unique changes of properties; the degradation in low Tpost-ann and the enhancement in high Tpost-ann, as explained in terms of H diffusion from the gate insulator to an active layer.

Atomic-Layer-Deposition of Indium Oxide Nano-films for Thin-Film Transistors

Abstract: Atomic-layer-deposition (ALD) of In2O3 nano-films has been investigated using cyclopentadienyl indium (InCp) and hydrogen peroxide (H2O2) as precursors. The In2O3 films can be deposited preferentially at relatively low temperatures of 160–200 °C, exhibiting a stable growth rate of 1.4–1.5 A/cycle. The surface roughness of the deposited film increases gradually with deposition temperature, which is attributed to the enhanced crystallization of the film at a higher deposition temperature. As the deposition temperature increases from 150 to 200 °C, the optical band gap (Eg) of the deposited film rises from 3.42 to 3.75 eV. In addition, with the increase of deposition temperature, the atomic ratio of In to O in the as-deposited film gradually shifts towards that in the stoichiometric In2O3, and the carbon content also reduces by degrees. For 200 °C deposition temperature, the deposited film exhibits an In:O ratio of 1:1.36 and no carbon incorporation. Further, high-performance In2O3 thin-film transistors with an Al2O3 gate dielectric were achieved by post-annealing in air at 300 °C for appropriate time, demonstrating a field-effect mobility of 7.8 cm2/V⋅s, a subthreshold swing of 0.32 V/dec, and an on/off current ratio of 107. This was ascribed to passivation of oxygen vacancies in the device channel.

Blade Coating Aligned, High-Performance, Semiconducting-Polymer Transistors

Abstract: Recent demonstration of mobilities in excess of 10 cm2 V–1 s–1 have energized research in solution deposition of polymers for thin film transistor applications. Due to the lamella motif of most soluble, semiconducting polymers, the local mobility is intrinsically anisotropic. Therefore, fabrication of aligned films is of interest for optimization of device performance. Many techniques have been developed to control film alignment, including solution deposition via directed flows and deposition on topologically structured substrates. We report device and detailed structural analysis (ultraviolet–visible absorption, IR absorption, near-edge X-ray absorption (NEXAFS), grazing incidence X-ray diffraction, and atomic force microscopy) results from blade coating two high performing semiconducting polymers on unpatterned and nanostructured substrates. Blade coating exhibits two distinct operational regimes: the Landau–Levich or horizontal dip coating regime and the evaporative regime. We find that in the evapora...

One-Volt IGZO Thin-Film Transistors With Ultra-Thin, Solution-Processed Al x O y Gate Dielectric

Abstract: Indium–gallium–zinc-oxide thin-film transistors (TFTs) with solution-processed, high-capacitance Al x O y gate dielectrics have been fabricated at room temperature. The morphology and electrical properties of the anodized, ultra-thin Al x O y film have been studied. Several anodization voltages were used to create the gate dielectrics and the results showed that the TFTs gated with aluminum oxide anodized at 2.3 V (~3 nm) exhibited the best performance. The TFTs operate at an ultra-low voltage of 1 V with a high current on/off ratio >105 and a subthreshold swing ( SS ) as low as 68 mV/dec, which is very close to the theoretical limit of SS at 300 K. As a result, the presented devices possess a great potential for low-power electronics.

Photo-Induced Room-Temperature Gas Sensing with a-IGZO Based Thin-Film Transistors Fabricated on Flexible Plastic Foil

Abstract: We present a gas sensitive thin-film transistor (TFT) based on an amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) semiconductor as the sensing layer, which is fabricated on a free-standing flexible polyimide foil. The photo-induced sensor response to NO₂ gas at room temperature and the cross-sensitivity to humidity are investigated. We combine the advantages of a transistor based sensor with flexible electronics technology to demonstrate the first flexible a-IGZO based gas sensitive TFT. Since flexible plastic substrates prohibit the use of high operating temperatures, the charge generation is promoted with the help of UV-light absorption, which ultimately triggers the reversible chemical reaction with the trace gas. Furthermore, the device fabrication process flow can be directly implemented in standard TFT technology, allowing for the parallel integration of the sensor and analog or logical circuits.

Highly Sensitive Flexible Pressure Sensor by the Integration of Microstructured PDMS Film With a-IGZO TFTs

Abstract: The development of flexible and highly sensitive pressure sensors is critical for the realization of wearable health monitors and electronic skins. However, the sensitivity, flexibility, and large-area fabrication of pressure sensors remain the key challenges for their practical applications. In this letter, we present a novel pressure sensing system in an amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) configuration comprised of a microstructured polydimethylsiloxane (PDMS) capacitor fabricated on a 200 mm $\times200$ mm flexible substrate. The microstructured PDMS thin film shows the average sensitivity of 0.1 kPa−1 and response time of <190 ms for the pressure of 12 kPa. Through the amplification effect of the a-IGZO TFT, the device shows a high sensitivity in the subthreshold region for ultra-low-pressure regime (≤1.5 kPa) detection and good linearity in the linear region for low-pressure regime (≤7 kPa) detection. These results demonstrate a novel approach to pressure-sensing intelligent products.

Enabling thin-film transistor technologies and the device metrics that matter

Abstract: The field-effect transistor kickstarted the digital revolution that propelled our society into the information age. One member of the now large family of field-effect devices is the thin-film transistor (TFT), best known for its enabling role in modern flat-panel displays. TFTs can be used in all sorts of innovative applications because of the broad variety of materials they can be made from, which give them diverse electrical and mechanical characteristics. To successfully utilize TFT technologies in a variety of rapidly emerging applications, such as flexible, stretchable and transparent large-area microelectronics, there are a number of metrics that matter.

Fully solution-induced high performance indium oxide thin film transistors with ZrOx high-k gate dielectrics

Abstract: Solution based deposition has been recently considered as a viable option for low-cost flexible electronics. In this context, research efforts have been increasingly focused on the development of suitable solution-processed materials for oxide based transistors. In this work, we report a fully solution synthesis route, using 2-methoxyethanol as solvent, for the preparation of In2O3 thin films and ZrOx gate dielectrics, as well as the fabrication of In2O3-based TFTs. To verify the possible applications of ZrOx thin films as the gate dielectric in complementary metal oxide semiconductor (CMOS) electronics, fully solution-induced In2O3 TFTs based on ZrO2 dielectrics have been integrated and investigated. The devices, with an optimized annealing temperature of 300 °C, have demonstrated high electrical performance and operational stability at a low voltage of 2 V, including a high μsat of 4.42 cm2 V−1 s−1, low threshold voltage of 0.31 V, threshold voltage shift of 0.15 V under positive bias stress for 7200 s, and large Ion/Ioff of 7.5 × 107, respectively. The as-fabricated In2O3/ZrOx TFTs enable fully solution-derived oxide TFTs for potential application in portable and low-power consumption electronics.

Silicon phthalocyanines as N-type semiconductors in organic thin film transistors

Abstract: Silicon phthalocyanines (SiPcs) represent a large class of molecules that have been studied as donors, acceptors and ternary additives in organic photovoltaics but not in organic thin-film transistors (OTFTs). We synthesized three novel SiPcs using axial substitution and examined their performance as the active layer in bottom-gate bottom-contact (BGBC) OTFTs. All three molecules exhibit N-type behaviour, with the dibenzoate substituted SiPc showing the greatest field-effect mobility of roughly 6 × 10−4 cm2 V−1 s−1 in vacuum. This performance improved to >0.01 cm2 V−1 s−1 when using a combination of dielectric modification with octadecyltrichlorosilane (ODTS) and a substrate temperature during deposition of 200 °C. These promising results point towards the possibility of high performance N-type SiPcs by exploring the wealth of available options in axial and peripheral substitution and careful process control during fabrication.

Solution-processed ternary p-type CuCrO2 semiconductor thin films and their application in transistors

Abstract: In this study, transparent p-type CuCrxOy semiconductor thin films were fabricated using spin coating and integrated as channel layers in thin-film transistors (TFTs). The structural, morphological components, and optical properties of CuCrxOy thin films, together with device performance, were systematically investigated. The phase conversion from a mixture of CuCr2O4 and CuO to pure CuCrO2 was achieved when the annealing temperature (Ta) was higher than 700 °C. The electrical performance of the CuCrxOy TFTs on SiO2 dielectric is improved with increasing Ta from 500 °C to 800 °C. The optimized CuCrO2 TFT exhibits an on/off current ratio of ∼105 and a hole mobility of 0.59 cm2 V−1 s−1, which is much better than those previous works on solution-processed binary CuxO TFTs. To our best knowledge, this work demonstrates the ternary p-type CuCrO2 TFTs fabricated via a low-cost solution process for the first time, which represents an important advancement towards the development of all-oxide, low-cost p–n junctions and CMOS logic circuits.

Remarkably High Hole Mobility Metal-Oxide Thin-Film Transistors.

Abstract: High performance p-type thin-film transistor (p-TFT) was realized by a simple process of reactive sputtering from a tin (Sn) target under oxygen ambient, where remarkably high field-effect mobility (μ FE ) of 7.6 cm2/Vs, 140 mV/dec subthreshold slope, and 3 × 104 on-current/off-current were measured. In sharp contrast, the SnO formed by direct sputtering from a SnO target showed much degraded μ FE , because of the limited low process temperature of SnO and sputtering damage. From the first principle quantum-mechanical calculation, the high hole μ FE of SnO p-TFT is due to its considerably unique merit of the small effective mass and single hole band without the heavy hole band. The high performance p-TFTs are the enabling technology for future ultra-low-power complementary-logic circuits on display and three-dimensional brain-mimicking integrated circuits.