TFET Research Articles

Raised Ge-Source with n+ pocket and recessed drain line TFET: A proposal for biosensing applications

In this paper, we present a novel raised Ge-source with an n+ pocket and recessed drain line Tunnel Field-Effect Transistor (TFET). It offers enhanced performance for potential biosensing applications. The proposed device comprises a Ge source with a low bandgap, an n+ pocket, and a larger tunneling area. This results in improved performance characteristics: an ON current of 54.27 μA/μm, an ON-current to OFF-current ratio of 1.5 × 1012, and an average subthreshold swing of 21.3 mV/dec. The recessed drain design eliminates ambipolarity, further enhancing performance. The study thoroughly investigates biosensing capabilities, including DC and transient analyses, evaluating charged and neutral biomolecules (uricase, biotin, 3-aminopropyltriethoxysilane, DNA, keratin, and gelatin). The proposed biosensor, with a higher drain current sensitivity of 1.2 × 109 for gelatin (k = 12) and 3.05 × 108 for keratin (k = 8), outperforms existing approaches, making our proposed biosensor a compelling choice for future low-power biomedical applications.

Electrolyte gated based pH sensing vertical TFET biosensor: Design, simulation and noise analysis

In this manuscript, a pH-based stepped oxide gate underlap vertical tunnel field-effect transistor (hetero-pHVTFET) biosensor with GaSb-doped layers is explored. A novel feature of the proposed device involves the use of stepped oxides with underlapped cavity gates. During the fabrication of devices, several challenges have emerged. A vertical tunnel field-effect transistor (VTFET) is proposed in this study for the detection of biological molecules such as proteins, enzymes, deoxyribonucleic acids, and others using label-based electrical recognition through the Stern layer. The simulation model provides a generalized solution for biological molecule detection, featuring the effects of pH sensing. Surface potential and device current (IDS) are investigated in relation to pH changes. Moreover, pH sensors have also been used to measure changes in hydrogen ion concentration within electrolyte solutions and to examine the sensitivity of proposed biological sensors based on alterations in the density of states. A 40 nm cavity length of the proposed hetero-pHVTFET biosensor is estimated to have a drain current sensitivity of 9.2 × 105.

Steep Slope Field Effect Transistors Based on 2D Materials

AbstractWith field effect transistor (FET) sustained to downscale to sub‐10 nm nodes, performance degradation originates from short channel effects (SCEs) degradation and power consumption increment attributed to inhibition of supply voltage (VDD) scaling down proportionally caused by thermionic limit subthreshold swing (SS) (60 mV dec−1) pose substantial challenges for today's semiconductor industry. To further sustain the Moore's law life, incorporation of new device concepts or new materials are imperative. 2D materials are predicted to be able to combat SCEs by virtue of high carrier mobility maintainability regardless of thickness thinning down, dangling bonds free surface and atomic thickness, which contributes to super gate electrostatic controllability. To overcome increasing power dissipation problem, new device structures including negative capacitance FET (NCFET), tunnel FET (TFET), dirac source FET (DSFET) and the like, which show superiority in decreasing VDD by lowering SS below thermionic limit of 60 mV dec−1 have been brought out. The combination of 2D materials and ultralow steep slope device structures holds great promise for low power‐dissipation electronics, which encompass both suppressed SCEs and reduced VDD simultaneously, leading to improved device performance and lowered power dissipation.

Heavy ions and alpha particles irradiation impact on III-V broken-gap gate-all-around TFET

This report deals with the impact of radiation on III-V and Si gate-all-around tunnel field effect transistors (GAA TFET). The highly energetic particles (HEPs) such as heavy ions and alpha particles are allowed to strike the device at several locations along the channel to determine the sensitive location of the device. Once the sensitive location is determined, then the device is irradiated to different energies of heavy ions and alpha particles. Further, to get a proximate match as a practically exposed device, the device has been irradiated to several incident angles. Before analyzing the device's behaviour, the models used for the analysis are calibrated with the transfer characteristics of an experimentally published report on III-V GAA TFET. Thereafter, analysis of charge collection, transient current, hole generation in the channel, and different incident angles are analyzed. Finally, it is concluded that III-V GAA TFET shows better immunity towards different incident angles under a radiation environment when compared to Si GAA TFET.

Comparative analysis of heavy ions and alpha particles impact on gate-all-around TFETs and gate-all-around MOSFETs

The single-event-transient (SET) effect due to heavy ions and alpha particles irradiation on n-type gate-all-around tunnel field effect transistor (GAA TFET) and n-type gate-all-around MOSFET (GAA MOSFET) has been carried out. Due to differences in carrier injection mechanisms, the generated electron-hole pairs (EHPs) due to high-energy particles (HEPs) act differently on the device. In addition, the impact of HEPs (i.e., heavy ions and alpha particles) on several locations along the channel are analyzed followed by the analysis of different energies of heavy ions and alpha particles irradiation on the device. Further, the impact of varying striking angles of HEPs on the device is also analyzed to get a close match as practically exposed device characteristic. Finally, the bipolar gain of the device has been analyzed which shows GAA TFET device has more immunity toward heavy ions strike and weak immunity toward alpha particle strikes when compared to the GAA MOSFET counterpart.

Realization of single MoTe2 crystal in-plane TFET by laser-induced doping technique

Significant recent progress has been achieved in the fabrication of tunnel field-effect transistors (TFETs) utilizing transition metal dichalcogenides (TMDCs) materials, particularly focusing on out-of-plane heterojunction structures. Due to the inherent limitations of doping technology for TMDCs, there have been limited investigations into the development of in-plane TFETs. In this study, we present the realization of an in-plane TFET based on a single crystal of multilayer MoTe2, utilizing a regioselective doping technique through laser irradiation. By constructing a p+/i/n++ homojunction structure, a band-to-band tunneling dominated performance with a minimum subthreshold swing value of 75 mV/dec and an on/off ratio of 105 was obtained at a low temperature. Furthermore, the “OFF” and “ON” state currents of the TFET operation were smaller than the gated diode operation in this structure, which is consistent with the tunneling mechanism.

Miller capacitance reduction in negative capacitance TFETs

ABSTRACT A dielectric stacked hetero-gate topology is proposed to reduce the Miller capacitance in a negative capacitance double gate TFET. An analytical charge-based model is introduced for the analysis of the terminal capacitance behaviour of the device. Charge and capacitance models are developed using the surface potential modelling approach by solving the Poisson Equation. The proposed closed-form charge model is SPICE-compatible and can be used for circuit simulations. The model accuracy is validated by combining one-dimensional Landau–Khalatnikov equation with the two-dimensional simulations of the double gate stacked-hetero-gate tunnel field effect transistor. The model shows excellent agreement with device simulations. The proposed topology exhibits Miller capacitance reduction of 30% which results in the gain band width product improvement of 43% more than the stacked homo-gate counterpart.

Two-Dimensional Tunneling Memtransistor with Thin-Film Heterostructure for Low-Power Logic-in-Memory Complementary Metal-Oxide Semiconductor.

With the demand for high-performance and miniaturized semiconductor devices continuously rising, the development of innovative tunneling transistors via efficient stacking methods using two-dimensional (2D) building blocks has paramount importance in the electronic industry. Hence, 2D semiconductors with atomically thin geometries hold significant promise for advancements in electronics. In this study, we introduced tunneling memtransistors with a thin-film heterostructure composed of 2D semiconducting MoS2 and WSe2. Devices with the dual function of tuning and memory operation were realized by the gate-regulated modulation of the barrier height at the heterojunction and manipulation of intrinsic defects within the exfoliated nanoflakes using solution processes. Further, our investigation revealed extensive edge defects and four distinct defect types, namely monoselenium vacancies, diselenium vacancies, tungsten vacancies, and tungsten adatoms, in the interior of electrochemically exfoliated WSe2 nanoflakes. Additionally, we constructed complementary metal-oxide semiconductor-based logic-in-memory devices with a small static power in the range of picowatts using the developed tunneling memtransistors, demonstrating a promising approach for next-generation low-power nanoelectronics.

Performance analysis of dual material control gate cavity on source electrically doped TFET biosensor for biomedical applications

The fabrication complexity, low sensitivity, detection speed, and costs associated with nanoscale devices have been significant concerns in the development of label-free biosensors. To address these issues, we report a novel dual material control gate cavity on source electrically doped tunnel field-effect transistor (DM-CG-CS-ED-TFET) for label-free biosensors. In this regard, the n+ drain and p+ source regions within the proposed device are induced by applying polarity gate (PG) bias voltages of PG-1 = +1.2 V and PG-2 = −1.2 V, respectively, across the respective polarity gate electrodes. This approach not only overcomes doping control issues but also avoids thermal budget constraints and minimizes fabrication complexity when compared to conventional TFET. For biomolecule sensing in the device, a nanogap cavity is created within the gate dielectric by selectively etching a portion of the polarity gate dielectric layer towards the source side. The performance of the proposed biosensor device is evaluated based on the variations in carrier concentration profile, energy band diagram, electric field, transfer (IDS - VGS) characteristics, drain current (IDS) sensitivity, ON-state current (ION) sensitivity, switching ratio (ION/IOFF) and subthreshold swing (SS) sensitivity. The sensitivity of the device is also investigated based on nano-cavity dimensions, practical challenges such as various filling factors, and the step profile generated from the steric hindrance. Moreover, the effect of temperature on sensitivity has also been investigated. For this, various biomolecules including Streptavidin (k = 2.1), APTES (k = 3.57), ferrocytochrome c (k = 4.7), keratin (k = 8) and Gelatin (k = 12), have been investigated for their performance using Silvaco ATLAS device simulator. The simulation results demonstrate that the proposed biosensor is a viable option for biosensing applications in biomedical engineering.

Utilizing Forward Characteristics of Pocket Doped SiGe Tunnel FET for Designing LIF Neuron Model

Utilizing Forward Characteristics of Pocket Doped SiGe Tunnel FET for Designing LIF Neuron Model

Energy efficient artificial gustatory system for in-sensor computing

In this work, a novel bio-inspired artificial gustatory system is proposed for in-sensor neuromorphic computing. The system is demonstrated using a novel material-engineered compound-semiconductor double-gate ferroelectric tunnel FET. The behaviour of the device as a biosensor and as a spiking neuron is verified individually. Using extensive simulation in Atlas TCAD, the biosensor functionality is validated with ION sensitivity of 108. Likewise, the device shows excellent neuronal behaviour with energy consumption of 37 aJ/spike, without using any external circuitry. It also exhibits control over the spiking frequency through amplitude, frequency, and duty cycle of input synaptic current. By cascading the biosensor and neuron, a complete bio-mimicked gustatory system is designed to identify a separate pattern for different tastes. The proposed gustatory system integrates both the devices, and simultaneously performs sensing and spike encoding. The biosensor transduces the pH and dielectric constant of the target biomolecule, corresponding to gustatory neurons present in the taste buds of a biological gustatory system. The neuron performs spike encoding and acts as an input neuron in a classifying network, which corresponds to gustatory cortex of its biological counterpart. The system consumes an average power of 49.58 pW which is ∼1000 × lesser than the state-of-the-art artificial gustatory system, eliminating the need for complex hardware and exorbitant energy consumption. Therefore, the proposed gustatory system provides a highly efficient and compact solution for neuromorphic gustatory sensing and classification, with potential applications in portable, wearable, and implantable devices.

Tunnel Field Effect Transistor (TFET): A Review

Tunnel Field Effect Transistor (TFET): A Review

CMOS Scaling for the 5 nm Node and Beyond: Device, Process and Technology.

After more than five decades, Moore's Law for transistors is approaching the end of the international technology roadmap of semiconductors (ITRS). The fate of complementary metal oxide semiconductor (CMOS) architecture has become increasingly unknown. In this era, 3D transistors in the form of gate-all-around (GAA) transistors are being considered as an excellent solution to scaling down beyond the 5 nm technology node, which solves the difficulties of carrier transport in the channel region which are mainly rooted in short channel effects (SCEs). In parallel to Moore, during the last two decades, transistors with a fully depleted SOI (FDSOI) design have also been processed for low-power electronics. Among all the possible designs, there are also tunneling field-effect transistors (TFETs), which offer very low power consumption and decent electrical characteristics. This review article presents new transistor designs, along with the integration of electronics and photonics, simulation methods, and continuation of CMOS process technology to the 5 nm technology node and beyond. The content highlights the innovative methods, challenges, and difficulties in device processing and design, as well as how to apply suitable metrology techniques as a tool to find out the imperfections and lattice distortions, strain status, and composition in the device structures.

Drain Source-Engineered Double-Gate Tunnel FET for Improved Performance

Drain Source-Engineered Double-Gate Tunnel FET for Improved Performance

A novel TFET based nanogap high-sensitive biosensor by boosted reliability- new metric for sensitivity definition

This is a detailed report about the proposal of an efficient nanogap dielectrically modulated tunnel field-effect transistor (TFET) biodevice granting a high sensitivity in the detection of the targeted biomolecules while keeping high performance in the realistic situations with boosting the reliability. Two attractive approaches in the cases of the bandgap engineering and charge plasma concept have been suggested for the band energy correction increasing the sensing current and the sensitivity without occurrence possibility of fabrication process related issues as compared to common TFET and PNPN TFET biosensors. The streptavidin, biotin and APTES samples have been selected as typical biomolecules for the sensing performance comparison of the biosensors under the study. Also, the proposed biosensor showed performance superiority for other biomolecules. For the first time, a new metric for measuring sensitivity is proposed to combine both maximum current sensitivity and well-defined average sensitivity in a unique relation named effective sensitivity. This prevents the possible noise impact on the sensitivity of the biosensors since the TFET based biosensors suffer from the low detection current. Defining the effective sensitivity, the proposed biosensor has been evaluated in more realistic conditions including partial hybridization of biomolecules inside the nanogap, trap-assisted-tunneling (TAT) component, neutral/charged biomolecules and biomolecules accumulation in different orientations showing the performance superiority of the proposed biosensor.

Performance and reliability assessment of source work function engineered charge plasma based Ti/HfO2/Al2O3/Ge, double gate TFET

The Tunnel Field Effect Transistor (TFET) often suffers from low ON current (I ON), charge traps, and thermal variability, which limits its performance and reliability. To address these issues, the source work function engineered Ge Charge Plasma Double Gate Tunnel Field Effect Transistor (CP-DGTFET) device structure with HfO2/Al2O3 bilayer gate dielectric is designed and investigated using numerical TCAD simulations. The proposed Ti/HfO2/Al2O3/Ge CP-DGTFET device structure showed excellent DC characteristics with exceptional I ON, I ON/I OFF ratio, and minimal sub-threshold swing (S) of ∼3.04 × 10−4 A μm−1, ∼1.2 × 1010, and ∼3.4 mV/dec, respectively. Furthermore, the device’s analog characteristics displayed good transconductance, cut-off frequency, and gain bandwidth product of ∼0.75 mS/μm, ∼0.97 THz, and ∼102 GHz, respectively. Moreover, the charge trap exploration divulges that positive ITCs can enhance device performance, whereas negative ITCs can adversely impact the electrical characteristics of CP-DGTFET. Additionally, the temperature-dependent analysis showed that the OFF-state leakage current increases from ∼1.7 × 10−15 A μm−1 to 2.4 × 10−10 A μm−1 with temperature fluctuations from 275 K to 375 K. Overall, the work function-engineered CP-based Ti/HfO2/Al2O3/Ge DGTFET device structure shows great potential for improving the performance and reliability of Ge TFET technology.

Sensitivity, linearity, and noise evaluation of L‐shaped dielectrically modulated label free tunnel field‐effect transistor biosensor

AbstractThis research article examines a L‐shaped dielectrically modulated label free TFET (L‐DM‐TFET) biosensor for the purpose of detecting different biomolecules using a label‐free biosensing detection technique. The proposed structure allows for the recognition of biomolecules by modulating various electrical properties, such as the drain current, transconductance, and linearity parameters. The source region of the proposed TFET incorporates a SiGe (source)/Si (channel) heterojunction, utilizing a low bandgap material of SiGe. This heterojunction is employed to enhance the ON‐state current of the devices. The materials used and the fabrication steps involved in our proposed device are compatible with complementary metal‐oxide‐semiconductor (CMOS) technology. This analysis is conducted using a calibrated Silvaco technology computer‐aided design (TCAD) simulator. Additionally, by considering a dielectric constant range of 1–12, we calculate various figure of merits (FOMs) parameters for the device. These include evaluation of linearity, sensitivity, and noise characteristics. Furthermore, we have conducted an analysis of linearity FOMs, such as VIP2, VIP3, IIP3, and IMD3 for the proposed device under study. Additionally, the linearity analysis of the presented tunneling FET (TFET) indicates the device's excellent performance in distortionless switching operations. Consequently, the L‐shaped dielectrically modulated biosensor holds potential suitability for high‐speed circuit designs.

Circuit Level Implementation of Negative Capacitance Source Pocket Double Gate Tunnel FET for Low Power Applications

This manuscript presents a pioneering study on enhancing analog and radio frequency performance through the implementation of negative capacitance source pocket double gate tunnel field-effect transistor. By integrating a ferroelectric material into the gate stack and introducing a fully depleted n-type pocket near the source/channel junction, we achieved significant enhancements in key metrics such as ON current (ION), switching ratio, subthreshold swing (SS), and various analog/RF parameters like transconductance (gm), cutoff frequency (fT) when compared to existing literature. Additionally, we extend our analysis to circuit-level applications such as inverter and 5-stage ring oscillator. Our findings reveal an impressive inverter delay of 1.09 ps with a gain of 104, as well as a ring oscillator operating at a frequency of 500 GHz. These results position the proposed device as an ideal candidate for high-speed, low-power applications.

Two-dimensional transition metal dichalcogenides van der Waals heterojunctions with broken-gap for tunnel field-effect transistors applications

The scaling down of transistors is nearing the limits dictated by Moore's Law, primarily due to the quantum tunneling effect. This challenge has spurred considerable interest in exploring novel materials characterized by broken-gap band alignment. Among these materials, two-dimensional (2D) materials-based van der Waals heterojunctions (vdWHs) have emerged as promising candidates, owing to their nanoscale dimensions, which render them suitable for transistor construction. Type-III vdWHs, in particular, have been investigated for their ability to facilitate rapid quantum Band-To-Band Tunneling (BTBT), thereby enabling low-power charge transport. In our study, we conducted a detailed analysis of four vdWHs comprised of HfSe2 and WXY (where X and Y represent Se or Te). Our findings indicate that 2D WSeTe (or WTe2)/HfSe2 vdWHs exhibit a broken-gap band alignment (type-Ⅲ) under the influence of an external electric field, thus showcasing potential for integration into future tunnel field-effect transistors (TFETs). Additionally, our investigation revealed that the band gap of two other vdWHs, WTeSe (or WSe2)/HfSe2, varies linearly with the external electric field, fluctuating between 0.4 eV and 1.0 eV. This characteristic makes them well-suited for application as infrared detectors. By unveiling the distinct properties of these vdWH configurations, our research not only anticipates the emergence of a notable type-III band alignment vdWH but also underscores the potential of 2D vdWHs in optical sensor applications.

Al2O3/ZrO2 dual-dielectric Gr/CNT nanoribbon vertical tunnel FET based biosensor for genomic classification and S-protein detection in SARS-CoV-2

The ongoing genetic mutation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) possesses the capacity to inadvertently lead to an increase in both the rates of transmission and mortality. In this study, we showcase the use of an Al2O3/ZrO2 Dual-Dielectric Gr/CNT Nanoribbon vertical tunnel field-effect transistor biosensor for the purpose of detecting spike proteins of SARS-CoV-2 in clinical samples. The proteins mentioned above are situated within the protein capsids of the virus. The effectiveness of the suggested detector has been assessed through measurements of the alteration in current drain. The present study utilizes the dielectric coefficient analogue of viral proteins as a substitute for biomolecules that exhibit internal hybridization nanogaps. The high sensitivity of the suggested detector, as evaluated on a scale ranging from 0 to 115, suggests its potential as a high-quality sensing instrument. The purpose of this study is to examine the sensitivity of DNA charge density with the aim of identifying any alterations in the virus that may impact its ability to spread and infect humans. The chromosomal composition of SARS-CoV-2 has been determined. The CMC Research Centre, situated in Vellore, Tamil Nadu, India, conducted an examination of SARS-CoV-2 samples. The scientists possess the capability to do genome sequencing on these specimens, so facilitating the examination of mutation patterns and the dispersion of different clades. A total of 250 different mutations were found out of the 600 sequences that were evaluated. The sequencing data consists of a complete collection of 250 distinct variants, including 150 missense mutations, 80 synonymous mutations, 15 mutations in noncoding regions, and 5 deletions. The comprehension of genetic variety is significantly dependent on these mutations. The proposed detector is connected to a variety of previously documented biosensors based on field-effect transistors (FETs), which are employed for the examination of genetic modifications.