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Organic ferroelectric field-effect transistors (Fe-OFETs) exhibit exceptional capabilities in mimicking biological neural systems and represent one of the primary options for flexible artificial synaptic devices. Ferroelectric polymers, such as poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), given their strong ferroelectricity and facile solution processing, have emerged as the preferred choices for the ferroelectric dielectric layer of wearable devices. However, the solution processed P(VDF-TrFE) films can lead to high interface roughness, prone to cause excessive gate leakage. Meanwhile, the ferroelectric layer in neural computing and memory applications also faces a trade-off between storage time and energy for read/write operations. This study introduces a composite dielectric layer for Fe-OFETs, fabricated via a solution-based process. Different thicknesses of poly(N-vinylcarbazole) (PVK) are shown to significantly alter the ferroelectric hysteresis window and leakage current. The optimized devices exhibit synaptic plasticity with a transient current of 3.52 mA and a response time of approximately 50 ns. The Fe-OFETs with the composite dielectric were modeled and integrated into convolutional neural networks, achieving a 92.95% accuracy rate. This highlights the composite dielectric's advantage in neuromorphic computing. The introduction of PVK optimizes the interface and balances device performance of Fe-OFETs for neuromorphic computing. [ABSTRACT FROM AUTHOR]

The development of complementary metal-oxide-semiconductor field-effect transistor (CMOSFET) based on two-dimensional (2D) materials offers an important opportunity to reduce static power and increase the integration density of integrated circuits. One promising approach to realize these CMOSFETs is to employ ambipolar 2D materials as channel materials with designed device structure to control the carrier transport properties for CMOSFET characteristics. However, these devices always suffer from complex multi-gate electrode structure, and hence face challenges in complicated inter-connection design and excessive voltage source requirement for circuit implementation. Here, we develop a three-terminal CMOSFET using ambipolar 2D material based on the drain electric field-induced carrier injection self-blocking mechanism. The designed drain electrode can effectively suppress carrier injection from the drain to the channel material, while the gate voltage can only regulate carrier injection in the source region. As a result, we can configure the device as either N-field-effect transistors (FET) or P-FET with a high current on/off ratio of over 105 by adjusting the three voltages (gate, source, and drain). Furthermore, we utilize these devices to demonstrate multifunctional wave modulator, low-static-power logic inverter (<5 pW), and combinational logic computing in the form of a compact complementary circuit. Our work would explore an efficient approach for implementing complementary circuits using 2D materials. [ABSTRACT FROM AUTHOR]

Graphene provides a unique platform for hosting high quality 2D electron systems. Encapsulating graphene with hexagonal boron nitride (hBN) to shield it from noisy environments offers the potential to achieve ultrahigh performance nanodevices, such as photodiodes and transistors. However, the absence of a bandgap at the Dirac point presents challenges for using this system as a useful transistor. In this study, we investigated the functionality of hBN-aligned monolayer graphene as a field effect transistor (FET). By precisely aligning the hBN and graphene, bandgaps open at the first Dirac point and at the hole-doped induced Dirac point via an interfacial moiré potential. To characterize this as a submicrometer scale FET, we fabricated a global bottom gate to tune the density of a conducting channel and a local top gate to switch off this channel. This demonstrated that the system could be tuned to an optimal on/off ratio regime by separately controlling the gates. These findings provide a valuable reference point for the further development of FETs based on graphene heterostructures. [ABSTRACT FROM AUTHOR]

The imperative for continuous device miniaturization has heightened the need for logic reconfigurability due to its benefits in circuit design simplification and process optimization. Van der Waals ambipolar transistors, notable for their inherent reconfigurable characteristics, have garnered significant interest for their potential to revolutionize information electronics. Nevertheless, as the semiconductor thickness approaches the 3-nm mark, precise modulation of electrical polarity presents a considerable challenge as minor variations in thickness can lead to significant electrical disparities. Here, we introduce a silicon backend process-compatible approach by employing surface charge transfer doping to skillfully adjust the polarity in ambipolar transistors. This universal method can achieve a controllable p-type doping effect and good electrical symmetry in ambipolar semiconductors. Through careful calibration of the MoO3 dopant layer thickness, we significantly enhance the hole mobility in doped WSe2 field-effect transistors (FETs), increasing it from 8 to 100 cm2 V−1 s−1, surpassing the performance of most non-silicon p-type semiconductors. A thorough temperature-dependent doping characterization elucidates the deeper traps-induced Schottky barrier variation for hole transport, and a reduction in current fluctuation for electron transport in WSe2/MoO3 FETs. Leveraging the precision in electrical polarity control, we demonstrate a complementary logic inverter by integrating two doped ambipolar FETs on a single monolithic channel. This advancement paves the way for quasi-forksheet structures and underscores the benefits in evolving advanced processing technologies, steering toward scalable, cost-effective, and efficient electronic device fabrication. [ABSTRACT FROM AUTHOR]

Stochastic resonance (SR) is an intriguing phenomenon in which noise, typically considered a detrimental aspect of electronic communication systems, assumes a beneficial role in the detection of undetectable signals. The SR phenomenon for detecting low-intensity optical signals using PBTTT-C14-based organic field-effect transistors (OFETs) is being reported. In this discourse, we explicate the sensing of an undetectable periodic optical signal with a frequency of 5 Hz, using a PBTTT-C14-based OFETs in the presence of a finite and optimal quantity of Gaussian noise (noise bandwidth of 1 Hz and noise amplitude of 2.0, 4.0, 6.0, and 7.5 V). The detection of higher harmonics for optical signals using the SR phenomenon has not been hitherto explored for OFETs. This report presents a noteworthy finding elucidating the detection of the principal frequency and also higher harmonics of the optical signal. This simplistic methodology for examining the SR phenomenon holds great promise in identifying its robust utility in diverse real-world contexts. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) hold great potential in various applications, including biosensing and neural network computation. Traditional "all-in-one" OECT device architecture faces the problems of unclear amplification mechanisms and complex side reactions, to name a few. The reaction cell OECT (RC-OECT) device architecture, proposed by Ting et al. [Adv. Funct. Mater. 31(19), 2010868 (2021)], effectively resolves these problems. Furthermore, in many applications of OECTs, such as high throughput (bio)sensing, an OECT device array instead of a single OECT is needed. Therefore, the size (area) of the OECT device, which represents the amount of occupied chip real estate and the integration of the device, matters. In this paper, we developed a hydrogen peroxide sensor based on the RC-OECT. We utilized an RC cathode modified by the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate film and a Ag/AgCl OECT gate electrode for facilitating device integration, varied RC anode area, and achieved optimization of at least one of the two parameters, sensitivity and lower limit of detection (LLoD), in conjunction with the level of integration of the device. Multiple quantitative sensitivity metrics have been adopted in this work. We also evaluated the correlation between RC anode area and LLoD. In addition, a mechanistic analysis of the RC-OECT device structure, in terms of faradic and non-faradaic currents, was carried out to illustrate the interplay between sensing performance and the electrode area of the reaction cell. This mechanistic analysis provides insights for miniaturizing OECT devices with the RC-OECT architecture. [ABSTRACT FROM AUTHOR]

Two-dimensional layered ReX2 (X = Se, S) has attracted researcher's great interest due to its unusual in-plane anisotropic optical and electrical properties and great potential in polarization-sensitive optoelectronic devices, while the clean, energy-saving, and ecological synthesis of highly crystalline ReSe2 with controlled domains remains challenging. Here, we develop a space-confined solid-phase approach for growing high-quality two-domain 1T′-ReSe2 with tunable optoelectronic properties by using pure Re powder as a Re precursor. The results show that ReSe2 can be grown at a temperature as low as 550 °C in a small-tube-assisted space-confined reactor, with its size and shape well-tailored via temperature control. A solid-phase two-domain ReSe2 growth mechanism is proposed, as evidenced by combining in situ optical monitoring, ex situ electron microscope, elemental mapping, and polarized optical imaging. Moreover, two-domain ReSe2 transistors are fabricated, which exhibit a switchable transport behavior between n-type and ambipolar character via grain boundary orientation control. This modulation phenomenon is attributed to the different doping levels between grain boundary and single domain. Furthermore, our two-domain ReSe2 photodetectors exhibit a highly gate-tunable current on–off ratio (with a maximum value of ∼8.2 × 103), a polarization-sensitive photo-response, and a high-speed response time (∼300 μs), exceeding most of the previously reported ReX2 photodetectors. Our work, thus, provides a low-consumption, energy-saving growth strategy toward high-quality, domain-controlled ReX2 for highly tunable and high-performance optoelectronics. [ABSTRACT FROM AUTHOR]

As transistor footprint scales down to the sub-10 nm regime, the process development for advancing to further technology nodes has encountered slowdowns. Achieving greater functionality within a single chip requires concurrent development at the device, circuit, and system levels. Reconfigurable transistors possess the capability to transform into both n-type and p-type transistors dynamically during operation. This transistor-level reconfigurability enables field-programmable logic circuits with fewer components compared to conventional circuits. However, the reconfigurability requires additional polarity control gates in the transistor and potentially impairs the gain from a smaller footprint. In this paper, we demonstrate a 2D control-gate-free reconfigurable transistor based on direct modulation of out-of-plane conduction in an ambipolar MoTe2 channel. Asymmetric electrostatic gating at the source and drain contacts is employed in the MoTe2 transistor resulting in different Schottky barrier widths at the two contacts. Consequently, the ambipolar conduction is reduced to unipolar conduction, where the current flow direction determines the preferred carrier type and the transistor polarity. Temperature dependence of the transfer characteristics reveals the Schottky barrier-controlled conduction and confirms that the Schottky barrier widths at the top contact are effectively tuned by electrostatic gating. Without the complexity overhead from polarity control gates, control-gate-free reconfigurable transistors promise higher logic density and lower cost in future integrated circuits. [ABSTRACT FROM AUTHOR]

SmB6, a topological Kondo insulator, possesses topologically protected surface states, in which carrier mobility is supposed to be high but is significantly varied in orders of magnitude dependent upon characterization methods. Herein, we performed magnetoresistance measurements on a Hall-bar device constructed on a highly uniform SmB6 nanoribbon with (001) surface grown by chemical vapor deposition. Unusual non-linear Hall resistance was observed at low temperature and explained with a two-carrier model. The two types of carriers were attributed to two types of Fermi pockets on the Brillouin zone of the SmB6 (001) surface. The Fermi pocket on Γ point provided high hole mobility up to 1.4 × 10 3 cm2/V s but low hole density at a temperature of 2.2 K. On the other hand, the Fermi pockets on X points supplied low electron mobility down to 1.8 cm2/V s but high electron density. The identification of the two types of pockets laid the foundation for the understanding of the transport via the topological surface states of the SmB6 (001) surface. [ABSTRACT FROM AUTHOR]

The light-induced synaptic transistors, with their large-scale and cost-effective benefits, hold significant promise for advancing neuromorphic electronics. In this work, we propose a hybrid phototransistor with a channel layer composed of C8-BTBT and PM6. This device exhibits an extended optical response range in comparison to pure C8-BTBT transistors. In addition, the device shows excellent synaptic plasticity under red, green, and blue light stimuli, with the potential for tuning through light dosage and pulse duration. The study further confirms consistent device performance and reliable operation. Moreover, we show that this type of device can be fabricated into array to write the letters "C", "S", and "U" and store red, green, and blue information. These experimental results show the excellent responsiveness and storage performance of our devices under red, green, and blue light stimuli, suggesting promising applications in artificial vision. [ABSTRACT FROM AUTHOR]

We demonstrated that the carrier polarity of MoTe2 transistors can be modulated by controlling the channel thickness with NiTe2 semimetal contacts. The multilayer MoTe2 transistors (thickness >7.1 nm) exhibit a symmetric ambipolar conduction, and a transition to unipolar p-type polarity occurs as the channel thickness decreased down to ∼2.3 nm. The position of the semimetal NiTe2 work function was verified to be located at the mid-gap of multilayer MoTe2, and the observed transition was interpreted by a synergistic effect of the channel thickness-dependent band alignment and charge transfer behavior with unique NiTe2 semimetal contacts. [ABSTRACT FROM AUTHOR]

Artificial intelligence technology has fueled the requirement for flexible hardware. Although flexible electronic devices have become promising candidates in recent years, they inevitably face problems like performance degradation caused by deformation. In this paper, we report a stable performance and flexible indium tin oxide synaptic transistor with an ultralow back-sweep subthreshold swing of 28.52 mV/dec, which is ascribed to the positive charge trapping/de-trapping effect introduced by a naturally oxidized Al2O3 layer. Even after bending 1 × 103 times, the flexible artificial synapse shows stable electrical performance without evident attenuation. Furthermore, the synaptic transistor exhibits good compatibility with an external thin-film pressure sensor, and their combination empowers the device to realize tactile sensing, which can achieve the function of Braille code recognition. Evidently, the reported flexible synaptic transistor demonstrates its potential for artificial perception processing. [ABSTRACT FROM AUTHOR]

This study examines the low-frequency noise characteristics of the 2,7-dioctyl[1] benzothieno[3,2-b][1] benzothiophene organic thin-film transistor (OTFT) having a CYTOP dielectric layer. Specifically, the fabricated OTFT exhibits 1/f noise, and its behavior is explained via a carrier number fluctuation model. Additionally, the volume trap density (NT) of the gate dielectric is quantitatively evaluated and compared with its counterpart having SiO2 dielectric layer. The analysis of the results shows that the hydrophilic entities of the dielectric layer strongly influence the NT, while the CYTOP having hydrophobic properties provides less NT than that of SiO2. [ABSTRACT FROM AUTHOR]

It is shown that in bottom gate, bottom-contact sub micrometer organic thin-film transistors (TFTs) with Dinaphtho[2,3-b:2′,3′-f]thieno-[3,2-b]thiophene active semiconductors, the addition of a top gate results in substantial improvements in a whole range of electrical performance characteristics. These improvements are not due to additional charge induced by the top gate but originate from the spatial redistribution of the charge induced by the bottom gate by the top gate. In the TFTs described in this work, the bottom gate insulator consists of a bilayer of SiO2 and solution-deposited high-k ZrO2, while the top gate insulator is a relatively thick CYTOP® layer deposited from a solution by spin coating. The capacitances per unit area of the bottom gate insulator and top gate insulator are 87 and 8 nF/cm2, respectively. On account of this large difference, the top gate is referred to as "weak," as its ability to induce charges in the channel is very much limited. The use of a weak top gate is shown to result in large improvements in the on-state drain current, sub-threshold swing, threshold voltage, and contact resistance compared to single gate operation. Weak top gates are especially useful when processing constraints make it difficult to realize symmetric or close to symmetric dual gate designs. While this demonstration is for a specific materials system, the design principle is more general and is likely to benefit a range of short channel length TFTs including organic/polymer, amorphous metal oxide, and 2D semiconductor-based transistors. [ABSTRACT FROM AUTHOR]

To support the ever-growing demand for faster, energy-efficient computation, more aggressive scaling of the transistor is required. Two-dimensional (2D) transition metal dichalcogenides (TMDs), with their ultra-thin body, excellent electrostatic gate control, and absence of surface dangling bonds, allow for extreme scaling of the channel region without compromising the mobility. New device geometries, such as stacked nanosheets with multiple parallel channels for carrier flow, can facilitate higher drive currents to enable ultra-fast switches, and TMDs are an ideal candidate for that type of next generation front-end-of-line field effect transistor (FET). TMDs are also promising for monolithic 3D (M3D) integrated back-end-of-line FETs due to their ability to be grown at low temperature and with less regard to lattice matching through van der Waals (vdW) epitaxy. To achieve TMD FETs with superior performance, two important challenges must be addressed: (1) complementary n- and p-type FETs with small and reliable threshold voltages are required for the reduction of dynamic and static power consumption per logic operation, and (2) contact resistance must be reduced significantly. We present here the underlying strengths and weaknesses of the wide variety of methods under investigation to provide scalable, stable, and controllable doping. It is our Perspective that of all the available doping methods, substitutional doping offers the ultimate solution for TMD-based transistors. [ABSTRACT FROM AUTHOR]

N-type organic field-effect transistors have suffered from poor environmental instability. Here, we report that, by using nickel (Ni) instead of the commonly used gold (Au) as contact electrodes, n-type polymer transistors showed much improved stability upon annealing in nitrogen and exposure to air. In particular, Au-contacted devices exhibited pronounced ambipolar conduction whereas Ni-contacted devices retained fairly good unipolar properties. The results are important to build stable n-type polymer transistors at low cost. [ABSTRACT FROM AUTHOR]

High-k dielectrics are frequently used for organic thin-film transistors (OTFTs), which facilitate the reduction of the device's operating voltage and enhance the total electrical performance. Along these lines, in this work, the fabrication of high-k AlOx dielectrics with high capacitance and low leakage current is proposed. On top of that, low-voltage flexible OTFTs with a solution-processed 2,7-dioctyl benzothieno[3,2-b] benzothiophene channel layer were demonstrated. The AlOx dielectric film was deposited by employing the reactive magnetron sputtering technique from a metal Al target by using a gas mixture of Ar and O2 at room temperature. At the same time, the surface morphology of the semiconductor film was optimized by controlling the solid solubility of polystyrene and polymethyl methacrylate in the semiconductor solution, which is important for improving the device performance. In this way, the prepared flexible OTFTs showed a low operating voltage of 3 V, a high switch ratio of 4.2 × 107, a high mobility is 2.39 cm2/V s, and a steep subthreshold swing close to the theoretical limit of 68 mV/decade. It is, thus, expected that this method will be applicable to the development of high-performance OTFTs. [ABSTRACT FROM AUTHOR]

For field effect transistors (FETs) based on electrospun oxide nanofibers, the electrical stability can be deteriorated by high-temperature annealing treatment. In this work, the self-passivation of an In2O3 nanofiber FET is achieved by the consequent thermal treatment, water treatment, and deep ultraviolet (DUV) irradiation, and the FET is named as a TWD (thermal treatment-water treatment-DUV irradiation)-device. For comparison, the devices treated by thermal treatment and by thermal + water treatment were also fabricated and abbreviated as a T-device and a TW (thermal treatment-water treatment)-device, respectively. From the transfer characteristics of the T-, TW-, and TWD-devices, the electrical performance is first degraded by water treatment and then recovered after DUV irradiation. The positive bias stress test confirms the stability enhancement after TWD treatment, indicating the achievement of the self-passivated FET based on In2O3 nanofibers. The excellent electrical stability is owing to the structural relaxation and the removal of trap sites such as oxygen vacancy and hydroxide. Integrated with the high-k ZrO2 dielectric, the TWD-In2O3/ZrO2 FET exhibits further improved electrical performance, including a mobility of 3.35 cm2/V s and a high on/off current ratio of 107. [ABSTRACT FROM AUTHOR]

The unique degradability and excellent biocompatibility make silk fibroin an attractive material for flexible transient memristors. Materials functionalization from the mesoscopic reconstruction view is a promising route to expand functions and create new types of electronic devices. Here, the transformation of the abrupt-to-progressive switching behavior in fibroin-based memristors is achieved via annealing to adjust the mesoscopic structure. Through electrical test and scanning electron microscope analysis, we study the electrochemical dynamics of metal nanoparticles in switching medium with different mesoscopic structures and directly reveal the microscopic origin of the abrupt-to-progressive transformation in fibroin-based transient memristors. The device exhibits abrupt resistive switching behaviors when the mobility and redox rate are high and displays progressive resistive switching behaviors under the low mobility and low redox rate condition. These findings reveal the microscopic origins of abrupt-to-progressive conversion and provide general guidance for designing high-performance memory devices and artificial synapses. [ABSTRACT FROM AUTHOR]

We propose a three-terminal variable-area capacitor integrated with a ferroelectric-gate field-effect transistor (FeFET) and a paraelectric thin-film capacitor. Owing to the large charge controllability and nonvolatile memory function of the ferroelectric Hf0.86Ce0.14O2 (14% Ce-HfO2) gate insulator, the variable-area capacitors exhibited high capacitance tuning ratios of up to 184 with steep modulation to gate voltage swing (440 mV/decade), a capacitance-switching speed of less than 10 ms, and capacitance-memory-retention characteristics of up to 105 s. An FeFET with an indium tin oxide (ITO) channel and a ferroelectric 14% Ce-HfO2 gate insulator was fabricated as a switching FET via chemical solution deposition, followed by stacking a sputtered Al2O3 film as a variable capacitor. The fabricated FeFETs exhibited a high on-current of ∼0.15 A/mm, a large on/off current ratio of 107, a field-effect mobility of 15.6 cm2/V s, and a memory window of ∼5 V. The high on-current, i.e., low on-resistance (84 Ω), and the large on/off current ratio allow the ITO channel to act as a wiring that connects and disconnects two capacitors with different electrode areas; therefore, the proposed variable capacitor can achieve wide and steep modulation by ferroelectric gating. This study provides prospects for the future integration of passive and active components for advanced high-efficiency and miniaturized electronics such as power devices and communication equipment. [ABSTRACT FROM AUTHOR]

Polymer semiconductor/gate dielectric interface is well known to influence the charge transport behaviors in organic field-effect transistors (OFETs). In the unidirectional floating-film transfer method (UFTM), thin floating films of uniaxially aligned π-conjugated polymers are solidified at the air/liquid interface before transferring them onto device substrates. Therefore, packing structures in the films prepared by UFTM are not affected by the strong interactions with the device substrate as usually seen in other film growth methods. Here, one question arises: will the difference in interactions between the liquid substrate and air impact the orientational structure of the polymer chain near the two surfaces or not? To answer this question, we have studied the charge-transport anisotropy in top- and bottom-gate OFETs by changing the film thickness. As a result, the field-effect carrier mobility and its anisotropy did not significantly differ for both surfaces and were constant against the film thickness. These results indicate that the UFTM can provide unidirectional alignment of polymer chains throughout the film thickness and gives a similar superior performance either for a bottom- or a top-gate OFET. [ABSTRACT FROM AUTHOR]

Photonic synapses provide fast response, high bandwidth, and less crosstalk in neuromorphic computation as well as simulation of visual perception systems. Herein, phototransistor-based photonic synapses that can be triggered by near-infrared light are reported. The artificial synapse is based on organic heterojunction phototransistors comprising the organic polymer semiconductor PDPPBTT and inorganic SnO2. The organic semiconducting polymer PDPPBTT serves as the near-infrared light absorbing materials and transistor channel, whereas SnO2 serves as the charge trapping materials. By adopting the heterojunction architecture, generation, separation, and transport of charge carriers are optimized under near-infrared illumination and electrical gating to yield photonic synaptic properties that can be readily modulated, including the excitatory postsynaptic current and paired-pulse facilitation. The results reveal a simple and effective concept for photonic synapses in the near-infrared region and provide insights into the development of advanced visual processing, neuromorphic computation, and biological nervous systems. [ABSTRACT FROM AUTHOR]

In this work, we report on the realization of SnO/β-Ga2O3 heterojunction vertical diodes and lateral field-effect transistors for power electronic applications. The p-type semiconductor SnO is grown by plasma-assisted molecular beam epitaxy on n-type (100) β-Ga2O3 with donor concentrations of 3 × 1017 cm−3 for the diode devices and 8.1 × 1017 cm−3 for the field-effect transistors. The deposited films show a predominant SnO (001) phase featuring a hole concentration and a mobility of 7.2 × 1018 cm−3 and 1.5 cm2/V s, respectively. The subsequent electrical characterization of the heterojunction diodes and field-effect transistors show stable switching properties with on/off current ratios >106 and specific on-resistances below 4 mΩ cm2. Furthermore, breakdown measurements in air of the non-field-plated heterojunction transistor with a gate-to-drain distance of 4 μm yield a breakdown voltage of 750 V, which equals an average breakdown strength of nearly 1.9 MV/cm. The resulting power figure of merit is calculated to 178 MW/cm2 demonstrating state-of-the-art properties. This emphasizes the high potential of this heterojunction approach. [ABSTRACT FROM AUTHOR]

A nonvolatile memory based on the floating-gate organic field-effect transistor was prepared by using the vacuum thermal evaporation taking small-molecule fullerenes (C60) as the floating-gate layer and long-chain alkane molecule tetratetracontane as the tunneling layer. Intrinsic correlations between microstructures of the floating gate and the memory performance, the physical mechanisms of the carrier injection, transfer, and storage, and the relationships between the charge-trapping capability of the floating-gate layers of different thicknesses made of small-molecule C60 and key parameters of the memory were investigated. The results show that the memory covers the charges stored in the manner of the opposite polarity during operation under the programming and erasing voltages. The bipolar charges (electrons and holes) are injected and captured in the floating gate. After optimization, the high-performance memory has an average memory window of 6.5 V, remains stable for more than one year, and is reliable for more than 220 programming/erasing cycles. Moreover, the memory also has excellent endurance to mechanical bending and retains favorable storage stability after being compressed or tensed 500 times to a bend-radius of 5 mm. [ABSTRACT FROM AUTHOR]

Due to their unique properties and potential applications, van der Waals (vdW) crystals with covalently bonded building blocks through vdW interactions have sparked widespread interest. In this article, we introduce a Ta2Ni3Se8 material as an example of an emerging one-dimensional (1D)-vdW-based material. Recently, it was demonstrated that bulk Ta2Ni3Se8 crystals may be effectively exfoliated into a few-chain-scale nanowires using simple mechanical and liquid-phase exfoliation. We performed density-functional theory calculations to get a better understanding of its electrical, magnetic, and transport properties. Theoretically, we expect that this Ta2Ni3Se8 is a semiconducting material, displaying the indirect-to-direct bandgap transition from bulk to single, as well as the band splitting and bandgap opening with the inclusion of Coulomb interaction. Based on deformation potential theory, the carrier mobility of bulk Ta2Ni3Se8 along the axis direction (a-axis) is as high as 264.00 cm2 V−1 s−1 for electrons and 119.62 cm2 V−1 s−1 for holes. The calculated carrier mobility of Ta2Ni3Se8, a 1D single nanowire, is 59.60 cm2 V−1 s−1 for electrons and 42.90 cm2 V−1 s−1 for holes, which is comparable to that of other 1D materials. This confirms that a recently developed field-effect transistor based on Ta2Ni3Se8 nanowires exhibits maximum experimental mobilities of 20.3 and 3.52 cm2 V−1 s−1 for electrons and holes, respectively. On the basis of the obtained intriguing properties of 1D vdW Ta2Ni3Se8 material, it is expected to be a potential candidate for additional 1D materials as channel materials. [ABSTRACT FROM AUTHOR]

Nonvolatile resistive switching based memristor and memtransistor devices have emerged as a leading platform in neuromorphic computing. In this work, we have fabricated a multifunctional synaptic transistor (ST) using a conjugated polymer P3HT channel and a superionic rubidium silver iodide (RbAg4I5) thin film coated over a polyethylene oxide (PEO) layer as the gate dielectric. Large hysteresis in the transfer curve represents the memristive behavior with at least 105 current On/Off ratio. Enormously large specific capacitance induced by the electrical double layers at the interfaces of PEO/RbAg4I5 dielectric induces polaron (P3HT+) generation in the channel through bound states formation by the electrons with Ag+ ions and consequent movement of iodine ( I − ) counter ions toward the P3HT channel under a negative gate bias stress. This is strongly supported by the blue shift of the Raman peak from 1444.2 to 1447.9 cm−1 and the appearance of a new peak at 1464.6 cm−1. Interestingly, the proposed ST device exhibits various synaptic actions, which include an excitatory postsynaptic current, paired-pulse facilitation, and short-term potentiation to long-term potentiation after repeated rehearsal on top of standard nonvolatile data storage capability. Our ST also depicts an enhanced retention to 103 s and more than 103 discrete On- and Off-states during potentiation and depression function modulation, respectively, just by consuming a very low energy of about 2.0 pJ per synaptic event. These results are very significant to make this organic synaptic transistor as a potential candidate in terms of the desired metrics for neuromorphic computation at low cost and improved accuracy in the future. [ABSTRACT FROM AUTHOR]

Investigating lateral electrical transport in p-type thin film chalcogenides is important to evaluate their potential for field-effect transistors (FETs) and phase-change memory applications. For instance, p-type FETs with materials sputtered at low temperature (≤ 250 °C) could play a role in flexible electronics or back-end-of-line silicon-compatible processes. Here, we explore lateral transport in chalcogenide films (Sb2Te3, Ge2Sb2Te5, and Ge4Sb6Te7) and multilayers, with Hall measurements (in ≤ 50 nm thin films) and with p-type transistors (in ≤ 5 nm ultrathin films). The highest Hall mobilities are measured for Sb2Te3/GeTe superlattices (∼18 cm2 V−1 s−1 at room temperature), over 2–3× higher than the other films. In ultrathin p-type FETs with Ge2Sb2Te5, we achieve field-effect mobility up to ∼5.5 cm2 V−1 s−1 with on/off current ratio of ∼104, the highest for Ge2Sb2Te5 transistors to date. We also explore process optimizations (e.g., the AlOx capping layer, type of developer for lithography) and uncover their tradeoffs toward the realization of p-type transistors with acceptable mobility and on/off current ratio. Our study provides essential insights into the optimization of electronic devices based on p-type chalcogenides. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors with ionic liquids have attracted much attention, since the ionic liquids induce an intense electric field at a semiconductor interface, resulting in a high concentration of charge carriers. It is expected that such strong electric fields and highly doped charges induce nontrivial effects on the electronic band structures. Recently, the blue shift of the peak wavelength in photo-absorption spectra for a DNBDT-monolayer transistor was experimentally observed by increasing an ionic-liquid gate voltage, although the origin of the shift is still under debate. Therefore, we investigate the hole-doping and external electric-field effects on the electronic states of the organic semiconducting monolayer within the framework of the density functional theory. The calculated results show that the photo-absorption energy is increased by hole doping while an external field decreases the photo-absorption energy. We demonstrated that the calculations give useful information to understand the origin of the experimentally observed wavelength shift of photo-absorption spectra. [ABSTRACT FROM AUTHOR]

Electronic devices comprising low-temperature processed 2D materials can be utilized in back-end-of-line nonvolatile memory and logic applications, to augment conventional silicon technology. A promising structure for a low-temperature processed digital nonvolatile flash memory device and/or logic device is the double-gate MoS2 FET with a graphene floating gate and a thin h-BN gate dielectric serving as a tunneling dielectric. In this work, we show that experimental hysteretic current–voltage characteristics of this digital flash memory device can be well fit by a simple and effective physics-based model using a WKB approximation to calculate the tunneling current to the graphene floating gate and a capacitive network with 2D density-of-states to calculate the channel current flowing in the MoS2 channel. Accordingly, the model allows a device designer to predict and/or tune characteristics for this memory device, e.g., the width and center-position of the hysteresis loop as well as the value of source–drain current, as a function of both the bottom (control) gate and top (FET) gate voltages. It is noted that shifting of the center-position of the hysteresis loop enables improved reliability and functionality of the memory device in circuit applications and is a unique feature of this double-gated MoS2 FET. Overall, the demonstrated ability to well model this memory device lends further credence that 2D devices could augment silicon technology. [ABSTRACT FROM AUTHOR]

Increasing optical confinement is critical to lowering laser thresholds and increasing modal gain in semiconductor lasers. Here, mode-solver calculations are used to demonstrate that improvements to optical confinement are possible in organic field-effect transistor geometries by using high refractive index cladding layers. Optical experiments show that the proposed structure increases the efficiency of amplified spontaneous emission (ASE) and lowers ASE thresholds without incurring additional losses. The results suggest that the structure can be used to improve optical confinement for both optically pumped and electrical injection organic lasers where thin, low refractive index active materials are required. [ABSTRACT FROM AUTHOR]

Nanoelectronic devices emulating neuro-synaptic functionalities through their intrinsic physics at low operating energies are imperative toward the realization of brain-like neuromorphic computers. In this work, we leverage the non-linear voltage dependent partial polarization switching of a ferroelectric field effect transistor to mimic plasticity characteristics of biological synapses. We provide experimental measurements of the synaptic characteristics for a 28 nm high-k metal gate technology based device and develop an experimentally calibrated device model for large-scale system performance prediction. Decoupled read-write paths, ultra-low programming energies, and the possibility of arranging such devices in a cross-point architecture demonstrate the synaptic efficacy of the device. Our hardware-algorithm co-design analysis reveals that the intrinsic plasticity of the ferroelectric devices has potential to enable unsupervised local learning in edge devices with limited training data. [ABSTRACT FROM AUTHOR]

Recently, rutile germanium dioxide (r-GeO2) has emerged as a novel ultra-wide bandgap semiconductor due to its theoretical excellent properties, that is, high thermal conductivity, ambipolar dopability, and high carrier mobility, in addition to its wide bandgap (4.44–4.68 eV). In this study, r-GeO2 thin films were grown on (001) r-TiO2 substrates by mist chemical vapor deposition. To optimize the growth conditions, we analyzed the decomposition processes of the Ge source (C6H10Ge2O7) by thermogravimetry-differential thermal analysis. It is found that GeO2 was synthesized from C6H10Ge2O7 at 553–783 °C in aqueous vapor. We accomplished fabrication of (001)-oriented r-GeO2 on r-TiO2 with a growth rate of 1.2–1.7 μm/h. On the other hand, under lower growth rate conditions (50 nm/h), the full width at half maximum of the r-GeO2 002 peak remarked a relatively small value of 560 arc sec. In addition, clear diffraction spots of r-GeO2 and r-TiO2 were observed at the r-GeO2/r-TiO2 interface, and the film was found to be significantly strained along the in-plane direction (∼2.3%) by cross-sectional transmission electron microscopy. The growth rate of ≧1 μm/h must contribute to the fabrication of thick r-GeO2 films, which can be utilized as power electronics devices with high breakdown voltage. [ABSTRACT FROM AUTHOR]

Molecular engineering of organic semiconductors through different synthetic routes has remarkably improved the understanding of the structure–property relationship and charge transport physics, particularly in organic field-effect transistors (OFETs). Emerging OFETs with reliable charge-carrier mobilities exceeding >1 cm2 V−1 s−1 have been demonstrated. However, the field-effect mobilities of amorphous conjugated polymer semiconductors have still showed the values below 10−2 cm2 V−1 s−1 over the past two decades. Here, we report on highly reproducible amorphous organic PTB7 transistors with an exceptional mobility of 0.80 cm2 V−1 s−1 (μavg ≈ 0.51 ± 0.16 cm2 V−1 s−1) operating at 2 V comparable to that of inorganic amorphous silicon semiconductor devices (0.5–1 cm2 V−1 s−1). This remarkable performance is enabled by the use of high-capacitance electrolyte dielectric (Ci = 48.42 μF cm−2), allowing easily attainable lower contact resistance of < 400 Ω cm and improved charge carrier density in the transistor channel, compared to those fabricated using low-k poly(methyl methacrylate) (Ci = 6.2 nF cm−2) and high-k poly(vinylidene fluoride-co-hexafluoropropylene) (Ci = 49.8 nF cm−2) gate dielectrics. This work contributes an opportunity for understanding and improving device performances of amorphous conjugated polymer semiconductors. [ABSTRACT FROM AUTHOR]

Organic semiconductor crystals (OSCs) present better charge transport characteristics than organic semiconductor films. OSCs have captured worldwide attention because they show great potential for optoelectronic devices, including organic field-effect transistors, active-matrix organic light-emitting diodes, radio frequency identification tags, and sensors. Well-patterned OSCs minimize crosstalk between neighboring devices and decrease leakage current. Therefore, patterning OSCs offers more opportunities for advanced optoelectronic applications. In this work, OSC patterning strategies, advances in applications based on well-patterned OSCs, and challenges and outlooks in the field are discussed. [ABSTRACT FROM AUTHOR]

We demonstrate an enhanced electrical conductivity and power factor for pentacene based small-molecule organic thermoelectric (OTE) materials by constructing a PbI2/pentacene/PbI2 sandwich structure where the PbI2 serves as the surface transfer p-type dopant. The electronic structure evolution at interfaces between pentacene and PbI2 are investigated via in situ ultraviolet and x-ray photoelectron spectroscopy analysis. Significant charge transfer between pentacene and PbI2 is observed due to a high work function of PbI2 and a low ionization potential of pentacene. Such an interfacial charge transfer behavior results in efficient hole doping of pentacene from both sides. The increased hole density inside pentacene leads to the improvement in the thermoelectric performance, achieving a maximum power factor of 33.75 μW m−1 K−2 with an optimized pentacene interlayer thickness. This study opens a way to improve the OTE materials with the dopant/organic semiconductor/dopant sandwich structure. [ABSTRACT FROM AUTHOR]

Piezoelectricity of two-dimensional layered materials is of great significance for electromechanical coupling applications in nanoelectromechanical systems. The nanoscale devices based on graphene have attracted intense interest due to its excellent electronic and mechanical properties. However, the centrosymmetric crystal structure in intrinsic graphene severely restricts its applications in mechanical sensors, transducers, and energy harvesters. In this paper, a self-powered vibration sensing element based on rolled-up single-layer graphene is proposed and demonstrated, which realizes the conversion from mechanical vibrations into electrical signals. In contrast to previous pioneering works requiring silica cavities or Si/SiO2 calibration grating substrate to support the graphene, a three-dimensional (3D) non-closed tubular structure is adopted to develop the piezoelectricity in single-layer graphene, where the inversion symmetry of single-layer graphene is broken via self-rolled-up process induced strain. Hence, apparent piezoresponse from the 3D non-closed tubular graphene field effect transistor is observed. Moreover, a peak-to-peak amplitude for the piezoelectric current up to 4.2 is achieved, corresponding to the periodicity of mechanical vibration, and the value can increase to 10.8 nA by applying a small source–drain voltage of 6 mV. The device is also sensitive to mechanical vibration with different frequencies and shows similar currents. The electromechanical coupling in rolled-up graphene provides a basis for the applications in sensing, actuating, and energy harvesting. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the degradation mechanism in quantum dot light-emitting diodes (QLEDs) to improve the device lifetime. We measured the hole mobility using the delay time of transient electroluminescence for three types of hole transport layer (HTL) materials. In addition, we estimated the degradation of luminance efficiency and hole mobility under constant current drive. As a result, the HTL material with a higher hole mobility yielded longer QLED device lifetimes. Through substitution of the HTL material from poly (9-vinylcarbazole) (PVK) to poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), the hole mobility and the 95% luminance lifetime from initial luminance improved from 0.5 × 10−5 cm2/V⋅s and 2.90 h at J = 10 mA/cm2 to 1.1 × 10−5 cm2/V⋅s and 179 h, respectively. Moreover, we clarified that the degradation of the luminescent efficiency is correlated with the hole mobility. [ABSTRACT FROM AUTHOR]

Controlling the hysteresis effect in organic field-effect transistors (OFETs) is imperative to attain reliable devices that can be applied to complicated circuits for practical applications. In this Letter, we compare two naphthalene tetracarboxylic diimide (NDI) derivatives, namely, N,N′-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) and N,N′-bis(hexyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-C6), which are comprised of different side chains and exhibit significant variations in the hysteresis of electronic transfer potential caused by the electronic traps. Among them, NDI-BOCF3 manifests negligible hysteresis in OFETs, while the counterparts based on NDI-C6 show notable hysteresis. This work presents insight into the hysteresis phenomenon of NDIs in OFETs, which depends on various critical factors, including interfacial trap density, molecular structure, thin film growth mode, and surface energy. Particularly, NDI-C6 demonstrates two orders of magnitude higher interfacial trap density than that of NDI-BOCF3. Moreover, NDI-BOCF3 thin film displays small surface energy and higher surface coverage on the substrate, but the results are diametrically opposite in the case of NDI-C6. Considering these observations, we propose that the introduction of OCF3 group in NDI not only endues a well-matched surface energy that promotes uniform distribution of the thin film on n-Octyltrichlorosilane-modified SiO2 substrate but also provides a water-spelling feature which leads to fewer H2O/O2 absorption in the resulting thin films. Our findings offer a fundamental guideline to rationally design n-type organic semiconductors for the development of efficient OFETs with negligible hysteresis. [ABSTRACT FROM AUTHOR]

The development of nonvolatile organic field-effect transistor (OFET) memories with a satisfactory solution processability is highly desirable to fabricate the data storage media for flexible and printed electronic devices. In this study, we fabricate top-gate/bottom-contact OFET memories having an organic floating-gate structure by a spin-coating process and investigate their memory characteristics. An ambipolar polymer semiconductor of poly(N-alkyldiketopyrrolo-pyrrole-dithienylthieno[3,2-b]thiophene) (DPP-DTT) was used to fabricate an organic semiconductor layer, on which an organic composite of polystyrene and 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) was deposited to form an organic floating-gate structure through vertical phase separation. The existence of a deep lowest unoccupied molecular orbital (LUMO) level and the excellent electron transport property of the DPP-DTT enables the injection of electrons from the Au source-drain electrodes to the DPP-DTT semiconductor layer and the storage of electrons in the LUMO level of the TIPS-pentacene floating gates by programming under dark conditions. A high work function metal oxide layer of MoO3 was inserted at the Al gate electrode/CYTOP gate insulator interface to tune the energy level difference between the Au source-drain and Al gate electrodes. The DPP-DTT FET memories with MoO3/Al gate electrodes exhibit satisfactory retention characteristics and, because of the ambipolar trapping characteristics, allow the storing of holes in the highest occupied molecular orbital level of the TIPS-pentacene floating gates in the erasing process. Furthermore, the molecular floating-gate OFET memories exhibit a high storage capacity for multi-level data, and four state levels can be recorded with stable retention characteristics. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have gained significant interest in recent years due to their ability to transduce and amplify biochemical signals into easily recorded electrical signals. The magnitude of the amplification offered by an OECT is proportional to its transconductance, gm, making gm an important figure of merit. Much attention has, therefore, been paid to the materials and device geometries, which can maximize an OECT's gm. However, less attention has been paid to the role of the applied potentials and various operational regimes. In this paper, we expand on the seminal Bernards and Malliaras model of the OECT function to include negative gate potentials, allowing prediction of gm and general biosensor performance over a broader application range. The expanded model results in five operational regimes, only two of which were covered by the original model. We find an optimal combination of drain and (negative) gate potentials yielding maximal gm. We also find that reducing the pinch-off potential well below the water-splitting limit can yield larger operational windows at the highest gm. Our expanded model presents a general set of guidelines for OECT operation, yielding the highest possible gm, and, therefore, optimal amplification and associated (bio)sensor performance. [ABSTRACT FROM AUTHOR]

Ferroelectric organic field-effect transistor nonvolatile memories (Fe-OFET-NVMs) offer attractive features for future memory applications, such as flexible and wearable electronics. Polymer semiconductor-based top-gate Fe-OFET-NVMs possess natural advantages in the device structure and processing manufacturing, compared to small-molecule semiconductor-based bottom-gate Fe-OFET-NVMs. However, their performances, such as mobility and operating voltages, should be further improved to be comparable to those of the latter. In this Letter, we develop a route to achieve high-performance top-gate Fe-OFET-NVMs, by employing a polymer semiconductor channel and self-organized ferroelectric/dielectric gate insulators, which were processed by a solution spin-coating technique. The optimal Fe-OFET-NVM exhibits a high mobility of 1.96 cm2/V s on average, a reliable endurance over 400 cycles, a stable retention capability over 6 × 104 s, and a life more than one year. Furthermore, the operating voltage of the Fe-OFET-NVM is reduced to ±20 V by scaling down the thickness of the ferroelectric/dielectric gate insulator. The whole performances of our memories are comparable to or better than those of the previous Fe-OFET-NVMs. [ABSTRACT FROM AUTHOR]

We report on the growth of β-Ga2O3 thin films using trimethylgallium (TMGa) as a source for gallium and pure O2 for oxidation. The growth rate of the films was found to linearly increase with the increase in the molar flow rate of TMGa and reach as high as ∼6 μm/h at a flow rate of 580 μmol/min. High purity, lightly Si-doped homoepitaxial β-Ga2O3 films with a good surface morphology, a record low temperature electron mobility exceeding 23 000 cm2/V s at 32 K, and an acceptor concentration of 2 × 1013 cm−3 were realized, showing an excellent purity film. Films with room temperature (RT) electron mobilities ranging from 71 cm2/V s to 138 cm2/V s with the corresponding free carrier densities between ∼1.1 × 1019 cm−3 and ∼1.5 × 1016 were demonstrated. For layers with the doping concentration in the range of high-1017 and low-1018 cm−3, the RT electron mobility values were consistently more than 100 cm2/V s, suggesting that TMGa is suitable to grow channel layers for lateral devices, such as field effect transistors. The results demonstrate excellent purity of the films produced and confirm the suitability of the TMGa precursor for the growth of device quality β-Ga2O3 films at a fast growth rate, meeting the demands for commercializing Ga2O3-based high voltage power devices by metalorganic chemical vapor deposition. [ABSTRACT FROM AUTHOR]

Rutile germanium dioxide (r-GeO2) is a recently predicted ultrawide-bandgap semiconductor with potential applications in high-power electronic devices, for which the carrier mobility is an important material parameter that controls the device efficiency. We apply first-principles calculations based on density functional and density functional perturbation theory to investigate carrier-phonon coupling in r-GeO2 and predict its phonon-limited electron and hole mobilities as a function of temperature and crystallographic orientation. The calculated carrier mobilities at 300 K are μ elec , ⊥ c → = 244 cm2 V−1 s−1, μ elec , ∥ c → = 377 cm2 V−1 s−1, μ hole , ⊥ c → = 27 cm2 V−1 s−1, and μ hole , ∥ c → = 29 cm2 V−1 s−1. At room temperature, carrier scattering is dominated by the low-frequency polar-optical phonon modes. The predicted Baliga figure of merit of n-type r-GeO2 surpasses several incumbent semiconductors such as Si, SiC, GaN, and β-Ga2O3, demonstrating its superior performance in high-power electronic devices. [ABSTRACT FROM AUTHOR]

Thin film transistors with high mobility and bias stability were fabricated using an In–Ga–Zn–O (IGZO)/zinc oxynitride (ZnON) tandem structure. In addition to increasing the saturation mobility from 13.44 cm2/V s to 24.75 cm2/V s, the hysteresis and device degradation under positive bias stress decreased more than five times as the ZnON semiconductor was added to the IGZO layer. These results were due to the reduced number of trapped electrons caused by the lower amount of relatively deep trap sites in the ZnON semiconductor and the existence of an energy barrier between ZnON and IGZO layers. [ABSTRACT FROM AUTHOR]

Threshold voltage analysis can help reveal the reliability of semiconductor transistors and its underlying mechanism. Herein, negative constant voltage stress (NCVS)-induced threshold voltage instability is studied in hydrogen-terminated diamond metal-oxide-semiconductor field-effect transistors (HD MOSFETs) with an Al2O3 dielectric layer deposited via atomic layer deposition at 90 °C. An unusual bidirectional shift in threshold voltage (Vth) can be observed with time. When a weak gate NCVS is applied, Vth gradually decreases during the first 500 s but increases in the next 500 s. A similar but opposite phenomenon is observed when the HD MOSFETs are in a recovery stage upon removing the NCVS, i.e., Vth increases in the first 500 s but decreases in the next 4500 s. A kinetic hydrogen motion model shows that this phenomenon can be attributed to the larger characteristic time constant of the unactuated oxygen-dangling bonds (UODBs) compared to that of the traps in the gate dielectric. Consequently, the trapping effect dominates and decreases Vth at the onset of NCVS. After 500 s, the UODB effects can be observed, increasing Vth. In the recovery stage, Vth is larger than the initial value. Further, modified hydrogen kinetic equations accounting for the dynamic effects of UODBs and traps are provided to quantitatively analyze the results. [ABSTRACT FROM AUTHOR]

In organic field-effect transistors, conductivity is achieved by electronically injected charges that form high-density accumulation layers. We report self-consistent calculations of Poisson's equation, carrier statistics, and the Drude permittivity of the carrier gas at the interface between semiconductors and insulators. The results show that the injected carriers efficiently screen local potentials. Additionally, the AC permittivity of the carriers reduces electrical fields particularly at frequencies of several THz. This dynamic screening may affect the formation of large polarons and the transient localization of carriers. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have shown great promise in a variety of applications ranging from digital logic circuits to biosensors and artificial synapses for neuromorphic computing. The working mechanism of OECTs relies on the mixed transport of ionic and electronic charge carriers, extending throughout the bulk of the organic channel. This attribute renders OECTs fundamentally different from conventional field effect transistors and endows them with unique features, including large gate-to-channel capacitance, low operating voltage, and high transconductance. Owing to the complexity of the mixed ion-electron coupling and transport processes, the OECT device physics is sophisticated and yet to be fully unraveled. Here, we give an account of the one- and two-dimensional drift-diffusion models that have been developed to describe the mixed transport of ions and electrons by finite-element methods and identify key device parameters to be tuned for the next developments in the field. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have been widely used as transducers in electrophysiology and other biosensing applications. Their identifying characteristic is a transconductance that increases with channel thickness, and this provides a facile mechanism to achieve high signal amplification. However, little is known about their noise behavior. Here, we investigate noise and extract metrics for the signal-to- noise ratio and limit of detection in OECTs with different channel thicknesses. These metrics are shown to improve as the channel thickness increases, demonstrating that OECTs can be easily optimized to show not only high amplification, but also low noise. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) have attracted great attention as key elements in Internet-of-Thing (IoT) devices due to their advantages of low cost and mass producibility made possible by printing technology. Such devices require organic semiconductors (OSCs) that intrinsically possess high carrier mobility and air stability. In addition, the demand for low-voltage operation and low power consumption has been increasing because the potential power sources for actual devices are implementable energy harvesters that supply low power and low voltages. Based on recently developed high-performance single-crystal p-type and n-type OSCs, this work demonstrated air-stable, high-mobility OFETs with low-voltage operation by using an insulating polymer-blend printing method. By comparing two acrylic polymers poly(methyl methacrylate) and poly(adamantyl methacrylate) (PADMA), having remarkably different thermal properties, we found that PADMA showing a high glass transition temperature >200 °C was suitable for device fabrication, enhancing the flexibility of OSC materials. Also, PADMA spontaneously produced good charge-transport interfaces with the OSC single crystals, leading to high carrier mobilities of 6.6 and 2.2 cm2 V−1 s−1 in p-channel and n-channel OFETs at ≤1.5 V, respectively. The current electron mobility was the highest among low voltage-operation OFETs reported so far. These high-mobility OFETs were integrated into a complementary inverter, for which a low static power consumption of 6.6 pW was confirmed. Therefore, this study reports an advantage of polymer-blend printing for OFETs with enhanced processability and performance suitable for IoT applications. [ABSTRACT FROM AUTHOR]

A recent thrust toward efficient modulated light emitters for use in Li-Fi communications has sparked renewed interest in visible III-N InGaN light-emitting diodes (LEDs). With their high external quantum efficiencies, blue InGaN LEDs are ideal components for such devices. We report a method for achieving voltage-controlled gate-modulated light emission using monolithic integration of fin- and nanowire-n–i–n vertical FETs with bottom-tunnel junction planar blue InGaN LEDs. This method takes advantage of the improved performance of bottom-tunnel junction LEDs over their top-tunnel junction counterparts, while allowing for strong gate control on a low-cross-sectional area fin or wire without sacrificing the LED active area as in lateral integration designs. Electrical modulation of five orders and an order of magnitude of optical modulation are achieved in the device. [ABSTRACT FROM AUTHOR]