Properties Of Field-effect Transistors Research Articles

Reduced interface effect of proton beam irradiation on the electrical properties of WSe2/hBN field effect transistors

Two-dimensional transition metal dichalcogenide (TMDC) semiconductors are emerging as strong contenders for electronic devices that can be used in highly radioactive environments such as outer space where conventional silicon-based devices exhibit nonideal characteristics for such applications. To address the radiation-induced interface effects of TMDC-based electronic devices, we studied high-energy proton beam irradiation effects on the electrical properties of field-effect transistors (FETs) made with tungsten diselenide (WSe2) channels and hexagonal boron-nitride (hBN)/SiO2 gate dielectrics. The electrical characteristics of WSe2 FETs were measured before and after the irradiation at various proton beam doses of 1013, 1014, and 1015 cm−2. In particular, we demonstrated the dependence of proton irradiation-induced effects on hBN layer thickness in WSe2 FETs. We observed that the hBN layer reduces the WSe2/dielectric interface effect which would shift the transfer curve of the FET toward the positive direction of the gate voltage. Also, this interface effect was significantly suppressed when a thicker hBN layer was used. This phenomenon can be explained by the fact that the physical separation of the WSe2 channel and SiO2 dielectric by the hBN interlayer prevents the interface effects originating from the irradiation-induced positive trapped charges in SiO2 reaching the interface. This work will help improve our understanding of the interface effect of high-energy irradiation on TMDC-based nanoelectronic devices.

ReS2-MoS2 heterojunction nanotube FET with superlattice structures for ultrasensitive detection of miRNA

Ultrasensitive detection of cancer biomarkers holds immense importance in facilitating the early diagnosis and treatment of cancer. Compared to conventional detection techniques, field-effect transistor (FET) biosensors have demonstrated substantial potential in achieving sensitive detection of cancer biomarkers. However, the ultrasensitive FET still remains great challenges due to the limited electron transport capacity and sensitivity of channel materials. Herein, we employed rhenium disulfide-molybdenum disulfide nanotube (ReS2-MoS2 NT) featuring superlattice structures as channel materials in FET biosensors for the highly sensitive detection of cancer biomarker miRNA-21. More concretely, ReS2-MoS2 NT featuring superlattice structures was synthesized using the anodic aluminum oxide (AAO) template sacrifice method and atomic layer deposition (ALD) method. The electrical properties of single ReS2-MoS2 NT FET were regulated by adjusting the total layers and number of heterojunction interfaces, and the optimal number of heterojunction interfaces of 7 was obtained. Finally, FET biosensors utilizing the network ReS2-MoS2 NT as the channel materials were fabricated and exhibited remarkable sensitivity in detecting miRNA-21 under an external light source. The linear range for detection spanned from 10 aM to 1 nM, with an exceptionally low detection limit of 2.1 aM. This study holds promise for replacing current channel materials and surpassing the detection threshold of cancer biomarkers in the future.

Design of Pentacene Thin-Film Transistor Based Hydrogen Gas Sensor with High-K Dielectric Materials for High Sensitivity

Electrical properties of an organic field-effect transistor were modelled in top gate top contact (TGTC) geometry and H2 gas sensors were designed for increased sensitivity based on the structure. Safety concerns related to hydrogen usage must be addressed; these hazardous characteristics include a wide flammable range (4%–75%) that results in a rapid burning velocity, a low minimum ignition energy (0.017 mJ), a high heat of combustion (143 kJ g−1), and the high diffusivity of hydrogen gas (0.61 cm2 s−1 in the air). These characteristics make it impossible to control hydrogen combustion after a specific time. All simulations were performed in the Silvaco TCAD ATLAS tool. We analysed the driving principle of gas sensors and introduced gas sensing properties in OFET using platinum metal at the gate electrode for H2 gas detection. IOFF, ION, and VTH are sensitivity parameters that alter when the metalwork function of the gate changes with respect to the gas present on it. The designed sensor was analysed for different dielectric materials. Results demonstrate that the increase in sensitivity for OFET-based H2 sensors is 73.4%, 80.7%, 90.5%, and 95.6% when the work function changes by 50, 100, 150, and 200 meV for Pt gate electrodes with an increase in dielectric value of insulating layer from SiO2 (3.9) to La2O3 (27). Results were compared with the In1-xGaxAs CGNWFET-based H2 sensor as the work function varies at 200 meV,the sensitivity enhancement with OFET-based H2 sensors is 8.09%.

Design of power efficient and reliable hybrid inverter approach based 11 T SRAM design using GNRFET technology

Designing a power efficient and high-speed static random-access memory (SRAM) cell with improved noise stability using traditional complementary metal oxide semiconductor (CMOS) devices is an arduous task. Owing to balanced electrical properties of graphene nanoribbon field-effect transistor (GNRFET), its capability to realize high performance SRAM cells need a keen exploration. This article proposes an 11-transistor GNRFET SRAM cell which deploys hybrid inverter scheme. The hybrid inverter scheme encompasses two distinct inverters, based on stacked transistors and Schmitt trigger (ST) techniques. The simulations conducted using 16 nm GNRFET model in HSPICE simulator show that proposed SRAM cell has write power, hold power, read power, write static noise margin, hold static noise margin, read static noise margin, write delay and read delay of 0.445 nW, 0.978 µW, 1.8 nW, 225 mV, 222.8 mV, 225.1 mV, 24 pS and 49.6 pS, respectively. The results obtained for proposed SRAM cell have been found to be encouraging in contrast to previously reported SRAM cells implemented using 16 nm GNRFET model. Besides this, the effect of variation in various parameters of GNRFET on performance of proposed SRAM cell has been investigated in this article. The outstanding performance results of SRAM makes its suitable for developing high performance memories devices for biomedical digital gadgets, internet of things (IoT), artificial intelligence (AI) and smart agricultural applications.

In-situ methyl red doped MoS2 field effect transistor made by atomically thin MoS2 channel

Here we present the effects of Methyl Red (MR) doping on the electrical properties of the MoS2 field effect transistor (FET) in in-situ experimental system where the doping and electrical measurement are carried out in a single ultra-high vacuum chamber. A single-layered MoS2 flake was used as channel material for the FET preparation. N-type doping by MR was confirmed by the left shift of threshold voltage (Vth) and the surface vibrational change measured by Raman spectroscopy. The n-doping by MR is implied by the Fermi level shift towards greater binding energy with MR coverage, as proven by an X-ray photoelectron spectroscopy (XPS) measurement. It is estimated from XPS that the MoS2-FET device may detect the doping effect from the sub-monolayer MR. MR was detected on the MoS2 surface by the Time-of-Flight Secondary Ionization Mass Spectroscopy (ToF-SIMS). The findings may pave the way for innovations in electronic device design, with potential implications for fields ranging from nanoelectronics to sensor technology.

High-Transconductance and Low-Leakage Current Single Aluminum Nitride Nanowire Field Effect Transistor

This study presents electrical transport properties of a catalyst-free grown single aluminum nitride nanowire field effect transistor (AlNNW-FET) exhibiting a very high transconductance of 26.9 pS, high on/off current ratio of 795.9, high conductivity of 9.8 x 10-4 Ω-1.cm-1, and a very low leakage current of 10 pA. The conductivity of AlN nanowire is two orders of magnitude higher than the reported studies. The AlNNW-FET reveals a dominant p-type conductivity. The p-type conductivity can be attributed to aluminum vacancies and complexes composed of Al vacancies and oxygen impurities. In consequence, the fabricated AlNNW-FET with high-performance, cost-effectiveness, and high-power efficiency is very well suited for use in low power and high temperature nanoelectronic and piezoelectric sensor applications, as well as integrated electro-optical devices including optomechanical devices and pyroelectric photodetectors.

The interfacial properties of 2D metal-monolayer blue phosphorene heterojunctions and transport properties of their field-effect transistors

Monolayer blue phosphorene (BlueP) has attracted much interest as a potential channel material in electronic devices. Searching for suitable two-dimensional (2D) metal materials to use as electrodes is critical to fabricating high-performance nanoscale channel BlueP-based field effect transistors (FETs). In this paper, we adopted first-principles calculations to explore binding energies, phonon calculations and electronic structures of 2D metal-BlueP heterojunctions, including Ti3C2-, NbTe2-, Ga(110)- and NbS2-BlueP, and thermal stability of Ti3C2-BlueP heterojunction at room temperature. We also used density functional theory coupled with the nonequilibrium Green function method to investigate the transport properties of sub-5 nm BlueP-based FETs with Ti3C2-BlueP electrodes. Our calculated results indicate that Ti3C2-BlueP has excellent thermal stability and may be used as a candidate electrode material for BlueP-based FETs. The double-gate can more effectively improve the device performance compared with the single-gate. The estimated source leakage current of sub-5 nm transistors reaches up to 369 µA µm−1, which is expected to meet the requirements of the international technology roadmap for semiconductors for LP (low-power) devices. Our results imply that 2D Ti3C2 may act as an appropriate electrode material for LP BlueP-based FETs, thus providing guidance for the design of future short-gate-length BlueP-based FETs.

Characterisation of graphene nano-ribbon field effect transistor and design of high performance PPN 12T GNRFET Full adder

Owing to the balanced electrical properties of graphene nanoribbon field effect transistors (GNRFETs), they are suitable next-generation devices for designing high performance circuits. However, as the fabrication for GNRFETs is at premature stage the performance of GNRFET device need to be explored with variation in its parameters. This article comprehensively analyses the impact of variations in GNRFET parameters on its threshold voltage, subthreshold swing and I ON /I OFF ratio. As an application example high performance PPN 12 T full adder is proposed using GNRFET device. The proposed full adder circuit shows dynamic power, propagation delay, low power-delay product and unity noise gain of 43.3 nW, 0.47 pS, 0.02 × 10−18 J and 0.46 respectively using supply voltage of 0.7 V. The performance of proposed full adder is compared with five previously proposed full adders using 16 nm GNRFET model in HSPICE simulation tool. Further, the impact of the GNRFET parameters on performance of proposed FA is investigated. A study of this nature is expected to improve performance of computing systems used in internet of things (IoT)-based infrastructure and health industry which demand for high performance next generation devices-based circuits.

Interfacial Engineering of Quantum Dots–Metal–Organic Framework Composite Toward Efficient Charge Transport for a Short‐Wave Infrared Photodetector

AbstractShort‐wave infrared (SWIR) quantum dot (QD)‐converted photodetectors are one of the promising devices used in artificial intelligence and automatic navigation systems. However, compared to semi‐conductor‐type photodetectors, they suffer from poor chemical stability and weak electronic conductivity. In this study, a PbS QD and conductive metal–organic framework (MOF) hybrid composite is designed with SWIR detection capability. The Fourier‐transform infrared spectroscopy confirms the surface modification of PbS QDs with MOF. X‐ray absorption near‐edge structures spectra reveal the chemical bonding between MOF and PbS QDs. Furthermore, 2D grazing‐incidence small‐ and wide‐angle X‐ray scattering is utilized to unveil the particle stacking and the preferred orientation of the PbS@MOF thin film. By integrating the PbS@MOF thin film directly on top of the graphene field effect transistor (FET) device, the chemical stability and photoelectric properties of graphene FET are enhanced, and these are investigated using a focus ion beam with a high‐resolution transmission electron microscope. This study offers a strategy to simultaneously improve the chemical stability and the photoelectronic properties of the nanomaterials as well as contribute to the advancement of a QD‐converted SWIR photodetector.

Self-Assembled Monolayer Doping for MoTe2 Field-Effect Transistors: Overcoming PN Doping Challenges in Transition Metal Dichalcogenides.

Transition metal dichalcogenides (TMDs) have gained significant attention as next-generation semiconductor materials that could potentially overcome the integration limits of silicon-based electronic devices. However, a challenge in utilizing TMDs as semiconductors is the lack of an established PN doping method to effectively control their electrical properties, unlike those of silicon-based semiconductors. Conventional PN doping methods, such as ion implantation, can induce lattice damage in TMDs. Thus, chemical doping methods that can control the Schottky barrier while minimizing lattice damage are desirable. Here, we focus on the molybdenum ditelluride (2H-MoTe2), which has a hexagonal phase and exhibits ambipolar field-effect transistor (FET) properties due to its direct band gap of 1.1 eV, enabling concurrent transport of electrons and holes. We demonstrate the fabrication of p- or n-type unipolar FETs in ambipolar MoTe2 FETs using self-assembled monolayers (SAMs) as chemical dopants. Specifically, we employ 1H,1H,2H,2H perfluorooctyltriethoxysilane and (3-aminopropyl)triethoxysilane as SAMs for chemical doping. The selective SAMs effectively increase the hole and electron charge transport capabilities in MoTe2 FETs by 18.4- and 4.6-fold, respectively, due to the dipole effect of the SAMs. Furthermore, the Raman shift of MoTe2 by SAM coating confirms the successful p- and n-type doping. Finally, we demonstrate the fabrication of complementary inverters using SAMs-doped MoTe2 FETs, which exhibit clear full-swing capability compared to undoped complementary inverters.

The Effect of a Vacuum Environment on the Electrical Properties of a MoS2 Back-Gate Field Effect Transistor

Adsorption of gas molecules on the surface of two-dimensional (2D) molybdenum disulfide (MoS2) can significantly affect its carrier transport properties. In this letter, we investigated the effect of a vacuum environment on the electrical properties of a back-gate MoS2 FET. Benefiting from the reduced scattering centers caused by the adsorbed oxygen and water molecules in a vacuum, the current Ion/Ioff ratio of back-gate MoS2 field effect transistor increased from 1.4 × 106 to 1.8 × 107. In addition, the values of field effect carrier mobility were increased by more than four times, from 1 cm2/Vs to 4.2 cm2/Vs. Furthermore, the values of subthreshold swing could be decreased by 30% compared with the sample in ambient air. We demonstrate that the vacuum process can effectively remove absorbates and improve device performances.

Improving the optoelectronic properties of monolayer MoS2 field effect transistor through dielectric engineering

The reduced dielectric screening in atomically thin two-dimensional materials makes them very sensitive to the surrounding environment, which can be modulated to tune their optoelectronic properties. In this study, we significantly improved the optoelectronic properties of monolayer MoS2 by varying the surrounding environment using different liquid dielectrics, each with a specific dielectric constant ranging from 1.89 to 18. Liquid mediums offer the possibility of environment tunability on the same device. For a back-gated field effect transistor, the field effect mobility exhibited more than two-order enhancement when exposed to a high dielectric constant medium. Further investigation into the effect of the dielectric environment on the optoelectronic properties demonstrated a variation in photoresponse relaxation time with the dielectric medium. The rise and decay times were observed to increase and decrease, respectively, with an increase in the dielectric constant of the medium. These results can be attributed to the dielectric screening provided by the surrounding medium, which strongly modifies the charged impurity scattering, the band gap, and defect levels of monolayer MoS2. These findings have important implications for the design of biological and chemical sensors, particularly those operating in a liquid environment. By leveraging the tunability of the dielectric medium, we can optimize the performance of such sensors and enhance their detection capabilities.

Electrical Properties of Double-Gate Field-Effect Transistor Based on MA2N4 (M = Ti, Zr, and Hf; A = Si, Ge, and Sn) Monolayers

Electrical Properties of Double-Gate Field-Effect Transistor Based on MA₂N₄ (M = Ti, Zr, and Hf; A = Si, Ge, and Sn) Monolayers

Quantum Transport Properties of InAs NWFET with Surface Traps

The quantum transport properties of InAs nanowire field effect transistor (NWFET) have been calculated and analyzed depending on the surface trap concentrations. Surface traps can be either impurity atoms, dangling bonds or structural deformations. Here, we have left some In and As atoms unsaturated to obtain surface traps. Our calculations show that the on-state voltage increases as the surface trap concentration increases. Within an equivalent circuit model, we have found that the effective field mobility is as low as 250 cm2/V.s following with small transconductance value of 2.4 nS for our simulated device. This shows that surface traps significantly effect the benchmarking properties of InAs NWFET.

Probing the Electronic and Opto-Electronic Properties of Multilayer MoS2 Field-Effect Transistors at Low Temperatures.

Transition metal dichalcogenides (TMDs)-based field-effect transistors (FETs) are being investigated vigorously for their promising applications in optoelectronics. Despite the high optical response reported in the literature, most of them are studied at room temperature. To extend the application of these materials in a photodetector, particularly at a low temperature, detailed understanding of the photo response behavior of these materials at low temperatures is crucial. Here we present a systematic investigation of temperature-dependent electronic and optoelectronic properties of few-layers MoS2 FETs, synthesized using the mechanical exfoliation of bulk MoS2 crystal, on the Si/SiO2 substrate. Our MoS2 FET show a room-temperature field-effect mobility μFE ~40 cm2·V-1·s-1, which increases with decreasing temperature, stabilizing at 80 cm2·V-1·s-1 below 100 K. The temperature-dependent (50 K < T < 300 K) photoconductivity measurements were investigated using a continuous laser source λ = 658 nm (E = 1.88 eV) over a broad range of effective illuminating laser intensity, Peff (0.02 μW < Peff < 0.6 μW). Photoconductivity measurements indicate a fractional power dependence of the steady-state photocurrent. The room-temperature photoresponsivity (R) obtained in these samples was found to be ~2 AW-1, and it increases as a function of decreasing temperature, reaching a maximum at T = 75 K. The optoelectronic properties of MoS2 at a low temperature give an insight into photocurrent generation mechanisms, which will help in altering/improving the performance of TMD-based devices for various applications.

Synergistic Use of All-Acceptor Strategies for the Preparation of an Organic Semiconductor and the Realization of High Electron Transport Properties in Organic Field-Effect Transistors.

The development of n-type organic semiconductor materials for transporting electrons as part of logic circuits is equally important to the development of p-type materials for transporting holes. Currently, progress in research on n-type materials is relatively backward, and the number of polymers with high electron mobility is limited. As the core component of the organic field-effect transistor (OFET), the rational design and judicious selection of the structure of organic semiconductor materials are crucial to enhance the performance of devices. A novel conjugated copolymer with an all-acceptor structure was synthesized based on an effective chemical structure modification and design strategy. PDPPTT-2Tz was obtained by the Stille coupling of the DPPTT monomer with 2Tz-SnMe3, which features high molecular weight and thermal stability. The low-lying lowest unoccupied molecular orbital (LUMO) energy level of the copolymer was attributed to the introduction of electron-deficient bithiazole. DFT calculations revealed that this material is highly planar. The effect of modulation from a donor-acceptor to acceptor-acceptor structure on the improvement of electron mobility was significant, which showed a maximum value of 1.29 cm2 V-1 s-1 and an average value of 0.81 cm2 V-1 s-1 for electron mobility in BGBC-based OFET devices. Our results demonstrate that DPP-based polymers can be used not only as excellent p-type materials but also as promising n-type materials.

MoRe Electrodes with 10 nm Nanogaps for Electrical Contact to Atomically Precise Graphene Nanoribbons.

Atomically precise graphene nanoribbons (GNRs) are predicted to exhibit exceptional edge-related properties, such as localized edge states, spin polarization, and half-metallicity. However, the absence of low-resistance nanoscale electrical contacts to the GNRs hinders harnessing their properties in field-effect transistors. In this paper, we make electrical contact with nine-atom-wide armchair GNRs using superconducting alloy MoRe as well as Pd (as a reference), which are two of the metals providing low-resistance contacts to carbon nanotubes. We take a step toward contacting a single GNR by fabricating electrodes with needlelike geometry, with about 20 nm tip diameter and 10 nm separation. To preserve the nanoscale geometry of the contacts, we develop a PMMA-assisted technique to transfer the GNRs onto the prepatterned electrodes. Our device characterizations as a function of bias voltage and temperature show thermally activated gate-tunable conductance in GNR-MoRe-based transistors.

Electrical and Electronic Properties of Magnesium/Molybdenum Disulfide Heterojunction Field Effect Transistors: A Theoretical Study

The present article designs two-dimensional heterojunction duplex material FETs based on binary monolayer material, Mg and molybdenum disulfide. Despite having a hexagonal crystal structure, the monolayer Mg and molybdenum disulfide have good lattice matching ability, with a mismatch degree of approximately 5%. The electrostatic characteristics of Mg/molybdenum disulfide field effect transistors (FETs) are well suited for compact fabrication. Electronic structure of first-principles investigations, optical, mechanical, and electrochemical properties of MODES field-effect transistors based on density functional theory are mastered in order to master the electrostatic doping associated features of FETs. Based on the Silvaco TCAD platform, this simulation study was performed. There is theoretical value in engineering practice, both in terms of design and application.

Modeling the Impact of Phonon Scattering with Strain Effects on the Electrical Properties of MoS2 Field-Effect Transistors.

Molybdenum disulfide (MoS2) has distinctive electronic and mechanical properties which make it a highly prospective material for use as a channel in upcoming nanoelectronic devices. An analytical modeling framework was used to investigate the I-V characteristics of field-effect transistors based on MoS2. The study begins by developing a ballistic current equation using a circuit model with two contacts. The transmission probability, which considers both the acoustic and optical mean free path, is then derived. Next, the effect of phonon scattering on the device was examined by including transmission probabilities into the ballistic current equation. According to the findings, the presence of phonon scattering caused a decrease of 43.7% in the ballistic current of the device at room temperature when L = 10 nm. The influence of phonon scattering became more prominent as the temperature increased. In addition, this study also considers the impact of strain on the device. It is reported that applying compressive strain could increase the phonon scattering current by 13.3% at L = 10 nm at room temperature, as evaluated in terms of the electrons' effective masses. However, the phonon scattering current decreased by 13.3% under the same condition due to the existence of tensile strain. Moreover, incorporating a high-k dielectric to mitigate the impact of scattering resulted in an even greater improvement in device performance. Specifically, at L = 6 nm, the ballistic current was surpassed by 58.4%. Furthermore, the study achieved SS = 68.2 mV/dec using Al2O3 and an on-off ratio of 7.75 × 104 using HfO2. Finally, the analytical results were validated with previous works, showing comparable agreement with the existing literature.

Recovering the Intrinsic Electrical Property of a Graphene Field-Effect Transistor by Interface Cleaning Technology

Recovering the Intrinsic Electrical Property of a Graphene Field-Effect Transistor by Interface Cleaning Technology