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This paper systematically studies the reliability of non-uniformly doped Double Gate Junctionless transistor using ATLAS TCAD simulation. The reliability analysis is mainly based on the understanding of Band-To-Band-Tunneling (BTBT) current, lattice temperature, drain conductance and gate leakage current. Presented results show that higher source/drain work-function is beneficial in reducing tunneling current (1 × 10−9 A to 4 × 10−11 A @ Vgs = −1 V) but eventually it will also degrade electrostatic current significantly (∼3 order). Source/Drain length has also been varied during optimization and it has been observed that, shorter source drain extension region degrades the device reliability (i.e. higher magnitude of tunneling current (7 × 10−9 A @ Vgs =−1 V for LS = LD = 5 nm)). Different doping profile considered for performance assessment are: uniform, step (i.e. low–low–high and high–high–low etc.) and different configurations of gaussian doping profile. Minimum variation in tunneling current with negative gate bias, i.e. ∼ 1 order has been seen from the device having uniform doping 1019 cm−3 but at the cost of significantly high off-state current (2 × 10−9 A @ Vgs = 0 V) and tunneling current (2 × 10−8 A @ Vgs = −1 V). Thus, instead of using uniform doping, step type profile (i.e. Case A) is the better choice which results in lower tunneling current (1 × 10−9 A @ Vgs = −1 V), moderate lattice temperature (326) and better Ion/Ioff ratio (243 × 108). Device lattice temperature has also been controlled by using step A doping profile even at the higher operating temperatures due to lower Self Heating Effect. [ABSTRACT FROM AUTHOR]

In this work, TCAD-based investigation of junctionLess (JL) architecture having double gate (DG) has been performed for visualizing the sensitivity of the device against light intensity. Comparison has been drawn between conventional DG MOSFET and DG-JL transistor (DG-JLT) under dark and light conditions. Effect of light intensity and wavelength has been modulated to optimize the device sensitivity. Higher shift in the drain current (in subthreshold region) has been observed at 0.35 μm of wavelength, i.e., more sensitive to ultraviolet (UV) light. The improved sensitivity of DG-JLT as compared to DG-MOSFET is due to the better subthreshold characteristics of the device (i.e., lower leakage current and subthreshold slope). From the results, it can be concluded that the DG-JLT with channel doping of 1019 cm−3, 10 nm of channel thickness, and having 1 nm of oxide thickness is the best possible choice for UV photodetector due to high sensitivity and responsivity. It has also been observed that more optimizing parameters are available with DG-JLT as the DG-MOSFET is immune toward the device parameter variation. [ABSTRACT FROM AUTHOR]

Amrasca biguttula biguttula (Ishida) commonly known as cotton leafhopper is a severe pest of cotton and okra. Not much is known on this insect at molecular level due to lack of genomic and transcriptomic data. To prepare for functional genomic studies in this insect, we evaluated 15 common housekeeping genes (Tub, B-Tub, EF alpha, GADPH, UbiCF, RP13, Ubiq, G3PD, VATPase, Actin, 18s, 28s, TATA, ETF, SOD and Cytolytic actin) during different developmental stages and under starvation stress. We selected early (1st and 2nd), late (3rd and 4th) stage nymphs and adults for identification of stable housekeeping genes using geNorm, NormFinder, BestKeeper and RefFinder software. Based on the different algorithms, RP13 and VATPase are identified as the most suitable reference genes for quantification of gene expression by reverse transcriptase quantitative PCR (RT-qPCR). Based on RefFinder which comprehended the results of three algorithms, RP13 in adults, Tubulin (Tub) in late nymphs, 28S in early nymph and UbiCF under starvation stress were identified as the most stable genes. We also developed methods for feeding double-stranded RNA (dsRNA) incorporated in the diet. Feeding dsRNA targeting Snf7, IAP, AQP1, and VATPase caused 56.17–77.12% knockdown of targeted genes compared to control and 16 to 48% mortality of treated insects when compared to control. [ABSTRACT FROM AUTHOR]

In this work, the sensitivity of two types gate underlap Junctionless Double Gate Metal-Oxide-Semiconductor Field-Effect Transistor (JL DG MOSFET) has been compared when the analytes bind in the underlap region. Gate underlap region considered at source end and drain end once at a time in the channel of JL DG MOSFET. Separate models have been derived for both types of gate underlap JL DG MOSFETs and verified through device simulation TCAD tool sprocess and sdevice. To detect the bio-molecules, Dielectric Modulation technique has been used. The shift in the threshold voltage has been pondered as the sensing parameter to detect the presence of biomolecules when they are bound in gate underlap channel region of the devices. [ABSTRACT FROM AUTHOR]

Although significant advances have been established in molecular biology of Oral squamous cell carcinoma (OSCC), innovative strategies are still required to further understand detailed molecular mechanisms. Using bioinformatic approach, we aim to explore the potential miRNA-mRNA pairs in cancer related inflammatory response and investigate their potential roles as signature miRNA and proteins in the signaling pathway. Firstly, the differentially expressed genes of OSCC were selected which then underwent gene ontology to identify genes engaged in inflammatory response and its regulation. Validated miRNAs were retrieved and miRNAs with complete complementarily with their targets were visualized for miRNA-mRNA regulatory network. Protein-protein interactions of inflammatory and its regulatory genes were analyzed for interacting genes involved in signaling pathway. Eight universal miRNAs were obtained for inflammation and its regulation. miRNA-19a/b showed significant influence in controlling inflammatory response in OSCC. Therefore, micronome on deregulated genes in inflammation identifies miRNA-mRNA pairs which have high potential to be targeted for diagnostic and treatment applications in OSCC. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a three port analysis for separate gate In0.52Al0.48As/In0.53Ga0.47As DG-HEMT and a small signal equivalent circuit is developed using charge control model. The various intrinsic short circuit admittance parameters (Y-parameters) are evaluated to extract scattering parameters, to determine the maximum transducer power gain of the device. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2796-2803, 2013 [ABSTRACT FROM AUTHOR]

In this paper, the effect of various device design engineerings such as channel engineering, i.e., graded channel (GC), gate stack (GS) engineering (high-\kappa), and dual-material gate (DMG) on double-gate MOSFET (DG MOSFET) have been analyzed using ATLAS device simulator. Furthermore, the combinations of these technologies i.e., GC, along with GS engineering, i.e., GCGSDG, and GS together with DMG, i.e., GS dual-material DG (GSDMDG), have been taken into consideration. The simulation results demonstrate that, out of the several design engineerings, the GCGSDG is the most suitable for high-speed switching applications. However, the GSDMDG provides superior performance as an amplifier. [ABSTRACT FROM PUBLISHER]

Abstract: A two-dimensional (2-D) analytical subthreshold model is developed for a graded channel double gate (DG) fully depleted SOI n-MOSFET incorporating a gate misalignment effect. The conformal mapping transformation (CMT) approach has been used to provide an accurate prediction of the surface potential, electric field, threshold voltage and subthreshold behavior of the device, considering the gate misalignment effect to be on both source and drain side. The model is applied to both uniformly doped (UD) and graded channel (GC) DG MOSFETs. The results of an analytical model agree well with 3-D simulated data obtained by ATLAS-3D device simulation software. [Copyright &y& Elsevier]

A new analytical threshold voltage model for InAlAs/InGaAs heterostructure, InP based HEMT has been developed considering the short-channel effect in subthreshold regime. The model is developed following the MESFET analysis, considering fully depleted InAlAs region as two isolated depletions––one due to metal–semiconductor contact and other due to transfer of carriers from InAlAs region to the 2DEG quantum well. Poisson’s equation is solved using Green’s Function technique and the solution is then verified by comparing it with Numerical technique. The 2D threshold voltage obtained from our analysis was found to be in good agreement with 1D threshold voltage for higher gate lengths, thus proving the validity of our model. [Copyright &y& Elsevier]

A new analytical model for InAlAs/InGaAs heterojunction, InP based high electron mobility transistor (HEMT) incorporating the depletion effect in the InAlAs region is developed and extended to predict sheet carrier density, the effect of parallel conduction through variation of depletion width, potential at the interface of depletions and ΔEc−Ef with gate voltage. The sheet carrier density obtained shows excellent agreement with the available results and gives a new solving procedure for HEMT from MESFET analysis. [Copyright &y& Elsevier]

A fringing field-effect-dependent MOSFET equivalent-circuit model for its microwave frequency applications has been developed. The thermal noise performance of the device has also been analyzed, including the distributed gate. The equivalent-current noise source takes into account the thermal noise generated by the resistive and inductive gate, and the results so obtained are compared with experimental/simulated data, and are in close agreement. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 97–105, 2001. [ABSTRACT FROM AUTHOR]

An analytical model for the cutoff frequency and optimum noise figure of an optically controlled GaAs MESFET suitable for microwave integrated circuits and high-frequency optical communication systems is presented. The model calculates the cutoff frequency and optimum noise figure under dark and illuminated conditions. The significant feature is that, under optically controlled operation, the cutoff frequency increases, and a drastic reduction in the optimum noise figure is obtained. Some of the predicted results under dark conditions are compared with the data available in the literature to validate our proposed model. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 279–282, 2000. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Functional genomics in whitefly, Bemisia tabaci is gaining impetus due to its polyphagous nature, worldwide distribution and recently sequenced whole genome. These studies require an in-depth evaluation and validation of reference genes in different development stages and variable experimental setups. Normalization with reference genes is an essential step in the gene expression studies. Rather than selecting a reference gene empirically, the suitability of these genes must be validated for an individual organism, its specific stage or even for particular experimental conditions. The Quantitative real-time polymerase chain reaction (RT-qPCR) has evolved as an efficient and widely used technique for precise monitoring of gene expression. The prime focus of this study was to identify candidate reference genes in different developmental stages (adults, nymphs, eggs), sex (male and female), hosts (Gossypium hirsutum , G. arboreum), and under insecticidal and starvation stress. Expression stability of these genes in different experimental samples was evaluated by employing five different computational algorithms such as NormFinder, BestKeeper, Comparative delta-CT, geNorm and RefFinder. Our results identified a different set of reference genes under each experimental setup such as electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO), ubiquitin (UBIQ) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as best reference genes in adult whitefly. In addition, glutathione S-transferase (GST) in eggs, cyclophilin (CYCLOPH) in red eyed nymph, GAPDH in third instar, tubulin (Tub) in female, ubiquitin ribosomal protein S27 (UBIRPS2) in male, succinate dehydrogenase complex subunit B (SDHB) under insecticidal stress, ETF-QO under starvation stress, UBIRPS2 under host influence were the top most stable genes. Our studies report the importance of selection of specific reference genes for accurate gene expression studies under various experimental setups in B. tabaci. [ABSTRACT FROM AUTHOR]

Phenacoccus solenopsis is one of the major polyphagous crop pests in India. Inadequate genomic or transcriptomic resources have limited the molecular studies in this insect despite its huge economic importance. The existing molecular sequence resources of this insect were supplemented through RNA sequencing, de novo transcriptome assembly and analysis, which generated 12, 925 CDS from 23,643 contigs with an average size of 1077.5 bp per CDS and 85.1% positive BLAST hits with NCBI Non redundant (nr) database. Twenty three genes involved in RNAi machinery identified through BLASTx search against NCBI nr database suggested the existence of robust RNAi in mealybug. RNAi in P. solenopsis was demonstrated through knockdown of IAP (Inhibitor of Apoptosis), AQP (Aquaporin), CAL (Calcitonin), VATPase (V-type proton ATPase subunit F 1), bursicon, chitin synthase, SNF7 and α-amylase by injecting sequence specific dsRNA of respective genes in adult female. Additionally, feeding RNAi has been demonstrated in 2nd instar nymph through dsRNA uptake in plant. The knockdown of core RNAi machinery genes such as Dicer, Argonaute and Staufen significantly hampered RNAi efficiency in this insect. However, downregulation of dsRNases improved RNAi efficiency. Sequential studies for understanding RNAi in P. solenopsis using transcriptome sequences have also been reported. The present study provides a base for future research on developing RNAi as strategy for management of this pest. [ABSTRACT FROM AUTHOR]

ATLAS TCAD-based comparative investigation (mainly breakdown voltage, cut-off frequency and leakage current) has been presented in this work for different length of gate field plate and source field plate. 127 V of breakdown voltage has been achieved at 0.25 µm gate length having 0.8 µm gate field plate length and 1 µm source field plate length. By amalgamating source field plate, maximum cut-off frequency of 38 GHz was achieved at 0.25 µm channel length. Passivation layer permittivity and barrier thickness has also been used to optimize the device performance. The improvement in breakdown voltage is less prominent than the deterioration in cut-off frequency with the enhancement in passivation layer permittivity. Leakage current of source field plate HEMT has also been studied for different passivation layer permittivity. [ABSTRACT FROM AUTHOR]

This study examines the extraction of small-signal equivalent circuit parameters, linearity and intermodulation metrics, and capacitance–voltage characteristics for both AlGaN and GaN channel HEMTs. Compared to GaN channel HEMTs, AlGaN channel HEMTs have better linearity and intermodulation distortion. In the instance of AlGaN channel HEMTs, the device parasitics are decreased. Additionally, the effect of graded AlGaN buffer layer thickness on breakdown characteristics and linearity is examined. For breakdown characteristics, the 200 nm-graded AlGaN buffer layer thickness yields superior results with VBOff 157 V for a thickness of 200 nm (147 V in the case of 500 nm). At 200 nm thickness, the linearity and intermodulation distortion FOMs are also reasonably good, and the remaining device properties are essentially unchanged. Hence, the graded AlGaN buffer thickness can be reduced for high-voltage applications. For higher-voltage applications, the graded AlGaN buffer thickness can, therefore, be decreased. [ABSTRACT FROM AUTHOR]

In this communication, various planar multiple resonators stacked microstrip antennas with differential inputs/outputs for wireless energy harvesting are presented. The antennas are designed for GSM 900 band using thick substrate on low‐dielectric constant. The developed antennas are fabricated on two different substrates to study and compare the efficiency of complete differential RF energy harvesting system. Gain of 9.03, 10.5, 10.62, and 12.05 is achieved for a broad bandwidth of 12, 17.5, 17.9, and 20.2% respectively for various antenna prototypes. Measured results show a peak efficiency of 70.85, 72.49, 75.68, and 86.33% for a load of 2, 1.2, 0.98, and 0.52 kΩ respectively. Finally, wireless power transmission is estimated using link budget analysis. [ABSTRACT FROM AUTHOR]

TCAD-based numerical investigation of RingFET has been presented in this paper for the detection of gas molecules. Sensitivity of the device has been assessed by calculating the change in off-state current with the change in gate work-function (which changes due to the presence of gas molecule). The behavior of the device has also been compared with the equivalent bulk MOSFET and it was observed that RingFET architecture shows 23% higher sensitivity against gas molecules than equivalent bulk MOSFET. Also, the degradation in device sensitivity with applied drain bias is higher in bulk MOSFET. Optimization in the sensitivity parameter has been done by using different channel materials like GaN, InGaN, and GaAs. Compared to GaAs and silicon, GaN-based RingFET is more sensitive towards gas molecules in the sub-threshold region (due to the wider band gap) besides having lower drain current than GaAs and silicon-based RingFET. [ABSTRACT FROM AUTHOR]

This paper presents three configurations of broadband differentially fed microstrip antenna for GSM1800, 1900 and 2100 MHz. The antennas are designed and fabricated using two different substrates for bottom and upper layer. The three antennas designed and tested have gain of 9.88, 9.66, and 11.14 dBi, respectively, at the center frequency. The proposed antennas also find its implementation in areas where, differential inputs/outputs wireless communication circuits are needed. Later, a differentially driven RF power harvesting system with maximum efficiency of 71%, 67% and 78% for a load of 520 Ω is also designed and developed. [ABSTRACT FROM AUTHOR]

Background: Thrips tabaci is a severe pest of onion and cotton. Due to lack of information on its genome or transcriptome, not much is known about this insect at the molecular level. To initiate molecular studies in this insect, RNA was sequenced; de novo transcriptome assembly and analysis were performed. The RNAseq data was used to identify reference and RNAi pathway genes in this insect. Additionally, feeding RNAi was demonstrated in T. tabaci for the first time. Results: From the assembled transcriptome, 27,836 coding sequence (CDS) with an average size of 1236 bp per CDS were identified. About 85.4% of CDS identified showed positive Blast hits. The homologs of most of the core RNAi machinery genes were identified in this transcriptome. To select reference genes for reverse-transcriptase real-time quantitative PCR (RT-qPCR) experiments, 14 housekeeping genes were identified in the transcriptome and their expression was analyzed by (RT-qPCR). UbiCE in adult, 28s in nymphs and SOD under starvation stress were identified as the most stable reference genes for RT-qPCR. Feeding dsSNF7 and dsAQP caused 16.4- and 14.47-fold reduction in SNF7 and AQP mRNA levels respectively, when compared to their levels in dsGFP fed control insects. Feeding dsSNF7 or dsAQP also caused 62 and 72% mortality in T. tabaci. Interestingly, simultaneous feeding of dsRNAs targeting SNF7 or AQP and one of the RNAi pathway genes (Dicer-2/Aubergine/Staufen) resulted in a significant reduction in RNAi of target genes. These data suggest the existence of robust RNAi machinery in T. tabaci. Conclusion: The current research is the first report of the assembled, analyzed and annotated RNAseq resource for T. tabaci, which may be used for future molecular studies in this insect. Reference genes validated across stages and starvation stress provides first-hand information on stable genes in T. tabaci. The information on RNAi machinery genes and significant knockdown of the target gene through dsRNA feeding in synthetic diet confirms the presence of efficient RNAi in this insect. These data provide a solid foundation for further research on developing RNAi as a method to manage this pest. [ABSTRACT FROM AUTHOR]

This paper presents an extensive Victory TCAD based assessment to evaluate the device performance under heavy ion particle strike induced single event effects (SEEs). The impact of SEEs on π-shaped AlGaN/GaN HEMT architecture has been compared with conventional AlGaN/GaN HEMT. For validation of simulation, models have been calibrated against the experimental data of in-house fabricated GaN HEMTs on SiC wafers, after which π-shaped architecture is realized using Silvaco's Victory Process simulation tools. Comparisons demonstrate that π-Gate HEMT architecture is a SEE hardened device under different heavy ion particle strike conditions. Further, due to the step modification in the electric field itself, the π-Gate HEMT also exhibits SEE hardened operation under different ambient temperatures. The effect of angled heavy ion particle strike has also been studied for evaluating the device performance with regards to SEE. [ABSTRACT FROM AUTHOR]

This study investigates the electrical characteristics observed in n-channel and p-channel ferroelectric field effect transistor (FeFET) devices fabricated through a similar process flow with 10 nm of ferroelectric hafnium zirconium oxide (HZO) as the gate dielectric. The n-FeFETs demonstrate a faster complete polarization switching compared to the p-channel counterparts. Detailed and systematic investigations using TCAD simulations reveal the role of fixed charges and interface traps at the HZO-interfacial layer (HZO/IL) interface in modulating the subthreshold characteristics of the devices. A characteristic crossover point observed in the transfer characteristics of n-channel devices is attributed with the temporary switching between ferroelectric-based operation to charge-based operation, caused by the pinning effect due to the presence of different traps. This experimental study helps understand the role of charge trapping effects in switching characteristics of n- and p-channel ferroelectric FETs. [ABSTRACT FROM AUTHOR]

In this paper, the reliability issues due to localized charges on Double Gate Junctionless Nanowire Transistor (DG-JNT) based circuits are investigated. The localized/fixed charges come into existence at the interface of substrate and oxide in the device during the manufacturing due to radiation, stress, process and hot carriers damage which significantly alters various characteristics of the device. The damage due to different profiles of localized charges on several parameters of DG-JNT based P-MOSFET is analyzed. Also, for analog circuit application, this work explicitly reports the comprehensive analysis of localized charge profiles on DG- JNT based CMOS inverter and three Stage Ring Oscillator circuit at 20 nm Gate length. The simulated results are obtained using Silvaco Atlas, TCAD device simulator. [ABSTRACT FROM AUTHOR]

A study based on the numerical simulation of Double Gate JunctionLess Transistor DG-JLT has been presented under the influence of Trap Charges (TC) inside the oxide or at the oxide/channel interface using ATLAS TCAD software. These trap charges may be generated due to various effects like aging and exposure to radiation and chemical environment etc. and thus leading to variability in the device behavior. To evaluate the impact of TC, the forward and reverse threshold voltage were calculated by altering the gate voltage from zero to positive and subsequently returning to zero, while employing various gate bias durations. Asymmetric doping has also been employed to study the variability in DG-JLT with TC as compared to Uniformly Doped DG-JLT (UD-DG-JLT). Furthermore, the investigation is expanded to evaluate how the performance of AD-DG-JLT is affected by the Dual Material Gate (DMG) in the presence of generated TC. To explore the robustness of the device, breakdown voltage (BV) has been examined with varying TC and device specifications. The impact of the trap energy level (E C -E T) on the BV of the devices has also been explored. Extensive numerical simulations have also been performed to showcase the results regarding the change in drain current caused by Single Event Upset (SEU). • The influence of TC on the AD-DG-JLT is computed due to the applied gate bias stress. • The AD-DG-JLT (72 %) provides higher BV as compared to UD-DG-JLT. • DMG architecture further increases the device BV (35 %) and variability with TC. • The observed change in DMG-AD-DG-JLT architecture due to SEU is higher. [ABSTRACT FROM AUTHOR]

This work investigates the impact of barrier layer thickness on DC and RF performance of a GaN HEMT device, targeting the low noise high gain application. An optimisation workflow based on the barrier layer thickness and Al mole fraction is presented for improving the RF metrics of a GaN HEMT. AlGaN/GaN HEMTs with a gate length of 400 nm were fabricated with 22% Al content and a barrier layer thickness of 23 and 20 nm, respectively. TCAD simulation studies were carried out for different barrier thickness and Al mole fraction in accordance with the fabricated devices. Increasing the barrier thickness increases the 2-DEG density which increases the maximum drain current and results in a negative shift in the threshold voltage. With a thin barrier layer, the AlGaN/GaN HEMTs exhibit a higher transconductance due to improved gate action. The fabricated devices were investigated with the help of small-signal equivalent circuit, which demonstrate higher capacitances associated with a thin barrier layer. Apart from DC characteristics and small-signal performance, the intrinsic gain (gm/gd ratio), noise performance, and large-signal performance of the device has been investigated which provides a great contribution in creating a design subspace for a specific application (depending on the performance requirement). A thin barrier layer improves the intrinsic gain of the GaN HEMT device by 74% due to a higher transconductance and comparatively lower output conductance values. An increase in Al mole fraction increases the transconductance but is dominated by an increase in the output conductance, which in turn reduces the intrinsic gain of the device. An in-depth analysis is presented by investigating and optimising the trade-offs with barrier layer thickness and Al mole fraction towards the noise performance of the devices at microwave C- and X-band. [ABSTRACT FROM AUTHOR]

An explicit surface potential and subthreshold current model for novel Dual Metal Gate (DMG) Asymmetric Vacuum (AV) as gate dielectric Schottky Barrier (SB) Cylindrical Gate All Around (CGAA) MOSFET with the incorporation of localized charges (N f ) is developed to provide excellent immunity against threshold voltage (V th ) degradation due to hot carriers. Hot carrier induced Localized Charges (LC) either positive or negative leads to degrade the threshold of the device. The major advantage of the proposed DMG-AV-SB-CGAA MOSFET is that it mitigates the ambipolar behavior thus offering very good on current to off current ratio; and also reduces the electron temperature which leads to less hot carrier generation thus lesser degradation in V th and improved Hot Carrier reliability. The surface potential is determined for three different regions by solving 1-D Poisson’s and 2-D Laplace equation through separation of variable method to facilitate an optimal model for calculating the subthreshold drain current from Si-SiO 2 interface boundary. The developed model results are in good agreement with that of ATLAS-TCAD simulation. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model has been developed for junctionless silicon on insulator ion-sensitive FET for pH sensing applications. The pH sensors detect the change of the hydrogen ion concentration in the aqueous solution. The modeled results show good agreement with the simulation results obtained by using Sentaurus. The electrolyte region has been considered by changing appropriate intrinsic semiconductor material in which the electron and hole charges represent the mobile ions in the aqueous solution. The effect of pH on surface potential, threshold voltage, and drain current has been investigated through model and simulations. In addition, the impact of different gate oxide materials, which act as adhesion layer, has been investigated. The pH response is defined as the amount of threshold voltage shift when the pH (in the injected solution) is varied from lower to higher values. Effect of the electrolyte region thickness on the pH sensitivity has also been discussed in this paper. [ABSTRACT FROM AUTHOR]

In this article, a semi-analytical model for germanium absorber-based SOI-tunnel field-effect phototransistor at 1550 nm has been proposed. The model works efficiently for a wide range of intensities i.e. 10−2 to 102 µW/µm2 under the application of a very low gate voltage of 0.54 V. Exhaustive simulations using numerical ATLAS 2D device simulation tool with LUMNINOUS optical module have been carried out to propose the merit of tunnel field-effect transistors (TFETs) over metal oxide semiconductor field effect transistors (MOSFETs) for optical applications. The proposed TFET design provides a way to assist the ultrasensitive optical interconnects at a very low gate bias of 0.54 V with a maximum sensitivity of 1.5 × 107, responsivity of 270 mA/W, and detectivity of 3.5 × 1012 Jones at low power density of 0.01 µW/µm2. The TFET performance has further been improved by introducing a heavily doped pocket in between source and channel, which serves as a potential alternative for photodetector applications. The proposed pocket-doped TFET design offers significant improvements in device optical response with optimized sensitivity of 4.1 × 107, a responsivity of 772 mA/W, and a detectivity of 9.9 × 1012 Jones at an optical intensity of 0.01 µW/µm2, gate bias of 0.45 V, and drain voltage of 0.6 V. Transient analysis has been carried out to optimize the response time of the phototransistor for both Ge-gated conventional TFET and pocket-doped architecture and the fall time of ∼0.22 ms has been achieved. [ABSTRACT FROM AUTHOR]

This investigation examines the performance of AlGaN/GaN MISHEMTs having single-gate and dual-gate with different biasing combinations to explore the linearity in terms of gmpeak, gate voltage swing (GVS) and higher-order coefficients for intermodulation distortion for low-noise amplifiers (LNAs). In addition, the influence of distinct gate biasing configurations of DG-MISHEMT on current collapse (CC) (in response to OFF-state stress in drain) has been studied using TCAD simulations. It has been observed that drop in drain current value after the gate–drain voltages return to quiescent voltages (VGSQ, VDSQ) reduces for DG-MISHEMT (when both the gates are shorted together) to 9.1% as compared with 19.4% for SG-MISHEMT. Besides, the CC phenomena for DG-MISHEMTs (for shorted gates) exhibit a slight increase from 9% to 11.8% when workfunction increases from 4.1 eV to 5.2 eV for gate G2. Further, linearity in terms of GVS is observed to be doubled for AlGaN/GaN DG-MISHEMTs with both the gates connected together as compared with device with screen gate G2 shorted to source. Additionally, radio frequency performance has been studied in terms of cut-off frequencies fT and fmax and minimum noise-figure NFmin for AlGaN/GaN SG-MISHEMT and DG-MISHEMTs for different gate to gate distance i.e., LGG =100 and 200 nm. It is observed that NFmin is minimum for AlGaN/GaN DG-MISHEMT (with gate G1 floating and gate G2 is biased and LGG =100 nm) i.e., 1.13 dB with corresponding power gain of 18.7 dB at 50 GHz. [ABSTRACT FROM AUTHOR]

A physics-based analytical model for Schottky Barrier (SB) Cylindrical Gate All Around (CGAA) MOSFET with high- k dielectric is presented with Evanescent Mode Analysis (EMA). The electrostatic potential is obtained using the Superposition method. An exact expression for threshold voltage and subthreshold slope is also obtained. The proposed model also includes the effect of Barrier height lowering at metal semiconductor interface along with the effect of high-k (HfO 2 ) gate stack. Diffusion current and tunneling currents are combined to evaluate the total subthreshold current. The analytical results so obtained are compared with simulated data and they are in good agreement. The proposed model of SB-CGAA device with high-k dielectric is very useful for the design and optimization for high current and improved performance. [ABSTRACT FROM AUTHOR]

• β-Gallium oxide gated junctionless phototransistor has been presented as a solar-blind UV photodetector (210–280 nm). • The β-Gallium oxide has been used as a photo absorber layer over the complete channel of the silicon based junctionless transistor. • The device performance has been analyzed using the optical figure of merits, including sensitivity, responsivity, and detectivity. • Dynamic characterization has also been performed for the time response analysis. • The maximum sensitivity obtained is 6.31 × 106 with responsivity of 4.38 × 104 and detectivity of 1.1 × 1012. In this study, a gallium oxide gated junctionless phototransistor has been proposed for the first time for deep ultraviolet (210–280 nm) solar blind radiation (UVC) detection. The inherent optical property of gallium oxide has been utilized here to absorb deep ultraviolet radiation. It is designed as a photo absorber layer over the complete channel of the junctionless field effect transistor. Here, the conduction material is silicon (source, channel, and drain), which is entirely separated by the photo absorber (gallium oxide) layer with an intermediate silicon dioxide insulation layer, resulting in MOS-based architecture. The design optimization has been done using the SILVACO ATLAS-2D TCAD simulations by first calibrating the experimentally fabricated junctionless transistor. The study of the proposed gallium oxide gated junctionless phototransistor shows that the gallium oxide thickness of 30 nm is the best-optimized thickness with a maximum responsivity of 4.38 × 104 A/W and detectivity of 1.1 × 1012 Jones achieved at a very less required V gs = −0.03 V. The spectral response has been performed and it has been calculated that the proposed architecture is best sensitive for 210 nm wavelength and sensitivity reduces significantly outside the deep UV solar spectrum. The time response analysis has also been presented, and it is concluded that the junctionless phototransistor has the advantage of less gate voltage requirements than other gallium oxide-based phototransistors with quite high responsivity in the deep UV solar spectrum. [ABSTRACT FROM AUTHOR]

This paper presents a TCAD based investigation of virtually fabricated Π-shaped Gate p-GaN HEMT for reliable enhancement mode operation. A detailed comparison with the Conventional T-Gate counterpart, with a focus towards the trap related dispersive effect reveals the superiority of Π-shaped Gates P-GaN HEMT for suppressing both the vertical substrate and gate leakage currents, thereby enhancing the breakdown characteristics of the device. A modification of the electric fields, into a stepped profile, demonstrates effective suppression of the leakage through the surface defects, and spillover into GaN buffer, thereby mitigating the trap related dispersive effects. Dispersive effect of the two devices has also been compared using current Slump Ratio (SR) which is lower for Π-shaped Gate P-GaN HEMT. Further analysis into laterally scaled drain-access regions, demonstrates superiority of Π-shaped Gates in achieving a reliable thermal operation, and applicability of Π-shaped Gate P-GaN HEMT for future RF and High Power applications. • Π – Shaped Gate results in an improvement of reverse breakdown and thermal profile ensuring reliability for p - GaN devices. • A parallel arrangement of MS Schottky diodes improves the current handling capacity of the p – GaN layer with a Π – Gate. • Π – Gate limits the leakage of electrons through the surface defects and suppresses the trap related gate – lag phenomenon. • Pulsed IV of Π - Gate reveals significantly suppressed trap – related dispersive effects for laterally scaled devices. • Field modification due to Π – Gate limits hole deficiency in p - GaN layer and improves the threshold voltage instability. [ABSTRACT FROM AUTHOR]

Dopingless tunnel field effect transistor (DL-TFET) exhibits a great potential for lowering the sub-threshold current and hence increases the ION/IOFF ratio because of its electrostatically doped source and drain. An analytical model for double gate dopingless tunnel field transistor (DG-DL TFET) is developed, for the first time, by calculating the source and drain work-function-induced doping and using it for solving the 2D Poisson's equation in various regions. Electric potentials, energy band diagrams, electric field, corresponding drain current characteristics, and trans-conductance are obtained through the developed model and are validated by performing extensive device simulation for different gate and drain bias voltages. An excellent match between modeled and simulated results proves the efficacy of the developed model. The ION current obtained in Si-based dopingless TFET is 0.16 µA/µm, IOFF has reduced to 0.296 fA/µm and ION/IOFF obtained from the proposed device structure is 5.4 × 108, and the sub-threshold swing is 50.77 mV/decade. The DG-DL TFET is analyzed for resistive load inverter characteristics and has been further investigated for realizing digital logic functions by controlling the gates of the device independently. The realization of NAND gate requires one "p-type DG-DL TFET", whereas OR gate requires one "n-type DG-DL TFET". The implementations of single bias-controlled logics are useful as they render energy-efficient operations and simultaneously increase the packaging density. [ABSTRACT FROM AUTHOR]

In this paper we propose and investigate the application of Electromagnetic Band Gap (EBG) substrate for improving the performance of Hemispherical Dielectric Resonator Antenna (HDRA). Our designed EBG shows a band gap in the frequency range of 1.75–2.25 GHz and the HDRA is resonant at 2 GHz which falls within the bandgap of the EBG. When combined with the EBG substrate the −10 dB bandwidth shows an improvement from 11.25% to 30%. On engineering the height of the HDRA on EBG substrate the gain is improved from 6.13 dBi to 9 dBi. To validate the results, simulations are carried out on CST Microwave Studio and HFSS. [ABSTRACT FROM AUTHOR]

In this paper Gate Material Engineered (GME) Gate-Stack (GS) silicon nanowire Schottky-Barrier (SB) Gate All Around (GAA) MOSFET and Single Material Gate Stack Schottky-Barrier Source/Drain Gate All Around (SM-GS-SB-S/D GAA) structures are proposed for low- power wireless applications. The Analog/RF performance for wireless applications of these devices are demonstrated. The effect of Schottky-Barrier (Metal) S/D is studied for Single Metal (SM)–SB-GAA, (Dual Metal) DM-SB-GAA, SM-GS-SB-GAA and GME-GS-SB-GAA MOSFETs, and it is found that GME-GS-SB-GAA MOSFET with metal drain source shows much improved performance in terms of transconductance ( g m ), output conductance ( g d ), Early Voltage ( V EA ), Maximum Transducer Power Gain, cut-off frequency ( f T ), and I on / I off ratio. Further, harmonic distortion for wireless applications is also studied using ATLAS-3D device simulator. Due to low parasitic S/D resistance the metal Source/Drain DM-GS-SB-S/D-GAA MOSFET demonstrates remarkable I on of~31.8 μA/μm and saturation transconductance g m of~68.2 μS with improved third order derivative of transconductance g m3 . [ABSTRACT FROM AUTHOR]

In an optical fiber based SPR sensor, a segment of metal clad silica fiber is used as the sensing element and resonant coupling occurs to the surface plasmon mode excited at the interface of the metal and ambient which surrounds the sensing element. When polychromatic light is transmitted through the sensing element, the spectrum of light detected at the other end shows minima at a resonance wavelength. In wavelength interrogation, the shift in the resonance wavelength is a measure of change in the refractive index of the ambient. Alternatively, intensity interrogation can be used in which the change in transmitted power at a given wavelength is a measure of change in refractive index of the ambient. The sensitivity and detection accuracy of the sensor depend on the numerical aperture (NA) of the multimode optical fiber used to fabricate the sensor. In the present work, we have carried out a study of the dependence of the sensitivity and detection accuracy on numerical aperture to obtain the optimal value for a multimode optical fiber which is used to fabricate the sensing element under both wavelength and intensity interrogation. For a gold clad sensing element with l/a = 33.33 for the refractive index of the ambient in the range 1.33 to 1.38, the optimized numerical aperture is obtained as NA = 0.2 for spectral interrogation mode. At this optimal value, the sensitivity is estimated to be 4040 nm/RIU and detection accuracy lies between 20 and 48 μm−1. In single wavelength intensity interrogation, at the He–Ne laser wavelength (633 nm), the optimized numerical aperture is obtained as NA = 0.42. Experimental results on a sensing element fabricated with gold coating on the core of a plastic clad silica fiber are also reported. [ABSTRACT FROM AUTHOR]

This work presents a systematic study to achieve the best result of having high breakdown voltage with high-frequency operation for a 150 nm GaN HEMT device (fabricated) using different field plate engineering techniques. The device breakdown voltage, cut-off frequency and maximum frequency should be high for high power and high frequency applications. The conventional device has a lower breakdown voltage but good cut-off and maximum frequency ranges. Field plate engineering has been done for breakdown improvement. However, the device's frequency operation is hampered by the typical source and gate field plate. As a result, an Air bridge source connected field plate and floating gate field plate architectures are explored and investigated. The best outcome is obtained with air bridge source connected field plate with V BOff = 100 V maintaining the cut-off frequency and maximum frequency at 29.8 GHz and 50.3 GHz respectively which is suitable for high power and high frequency applications. • Systematic study to achieve high V BOff with high-frequency operation for a 150nm GaN HEMT device using field plate engineering techniques. • The conventional device has a lower breakdown voltage but good cut-off and maximum frequency ranges. • Field plate engineering has been done for breakdown improvement. • However, the device's frequency operation is hampered by the typical source and gate field plate. • An Air bridge source connected field plate and floating gate field plate architectures are explored. • The best outcome is obtained with air bridge source connected field plate. • It has V BOff =100 V maintaining the cut-off frequency and maximum frequency at 29.8 GHz and 50.3 GHz respectively. • It is suitable for high power and high frequency applications. [ABSTRACT FROM AUTHOR]

Abstract: In this work an extensive study on the linearity distortion behaviour of AlGaN/GaN MISHFET is performed and compared with those of conventional HFET structures. The contribution of higher order terms in a Taylor series expansion of small signal drain current is considered by evaluating higher order transconductance coefficients. Linearity figures of merit such as input intercept power, intermodulation distortion and other higher order harmonics have been investigated for both the structures. The impact of gate biasing on the linearity is also examined. The influence of critical technology parameters such as gate length, doping density, dopant layer thickness and gate insulator thickness is investigated to optimize the MISHFET structure for better linearity characteristics. Improved linearity performance has been observed for insulated gate structure proving its superiority over conventional HFETs for RF wireless and low noise applications. The results obtained reveal that by careful optimization of technology parameters, a suitably designed MISHFET architecture is more linear than its conventional counterparts. [Copyright &y& Elsevier]

Abstract: In Single Gate HEMT (SGHEMT) shortening of gate length below 100 nm leads to reduction in Transconductance , which reduces the unloaded voltage gain of the device, thereby reducing the maximum frequency of oscillation . The main reason for this reduction in with in the Single Gate HEMT (SGHEMT) is its inability to maintain the desired channel aspect ratio (). At such a miniaturization level, not only depends on the channel depth but also on the channel thickness of the device . Moreover, the variation of may switch the device characteristics from quantum regime to classical regime . The Double Gate HEMT (DGHEMT)  has emerged as a solution for further reduction in and provides enhancements over SGHEMT by virtue of its double gate and also for same due to double heterojunctions, which virtually increases the value of . In the present work, extensive simulation work has been carried out using ATLAS device simulator  in order to study the effect of and on DGHEMT and SGHEMT. An analytical model has also been proposed for SGHEMT and DGHEMT to incorporate the effect of variation of and . [Copyright &y& Elsevier]

Abstract: This paper presents an approximate solution of a 2-D Poisson’s equation in the channel region, based on physical correspondence between MOSFET and HEMT, with the approximation that the vertical channel potential distribution is a cubic function of position to study not only tied gate but separate gate bias conditions as well. An analytical expression for both front and back heterointerface potential is derived and threshold voltage is obtained iteratively from the proposed potential model. The threshold voltage behavior for tied and separated double-gate HEMT is investigated for various device dimensions. The back gate effect of the separated double gate HEMT is investigated for the depleted back channel only. The results obtained are verified by comparing them with simulated and experimental results. [Copyright &y& Elsevier]

An investigation of temperature model for an AlGaN/GaN MISHFET is presented and a relative comparison is done with conventional HFET structures. The proposed analytical model demonstrates its inherent ability to operate at higher temperature. The contributions from various temperature dependent material parameters are taken into account alongwith the effect of temperature on the sheet carrier concentration and threshold voltage of the device. The model is further extended to predict the temperature dependence of transconductance, cut off frequency and pinch-off characteristics. The investigated temperature range is from 25°C–300°C. Non linear Fermi potential (Ef) variation with the sheet carrier concentration (ns), and the highly dominant effects of spontaneous and piezoelectric polarization at the AlGaN/GaN heterointerface are also considered. AlGaN/GaN MISHFETs demonstrate larger drain currents, cut-off frequency and better pinch-off characteristics at high temperatures. The model is based on closed form expression and does not involve elaborate computation. The analytical results on the transport characteristics of both the devices are compared with available experimental data and are in good agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1942–1949, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24461 [ABSTRACT FROM AUTHOR]

Abstract: Double gate MOSFET has been regarded as the most promising candidate for future CMOS devices, for excellent short channel effects (SCEs) immunity and high current drivability due to double gate coupling. The alignment between the top and bottom gates should be concern to fully realize the benefits of the double-gate configuration, as gate misalignment causes degradation in the device performance. Use of graded channel architectures somehow reduces the effect of gate misalignment. We scrutinize that how the misalignment affects the small signal behavior and device characteristics like conductances, capacitances and cut-off frequency, for uniformly doped and graded channel double gate architectures. Considering the fact that gate misalignment can occur on any side of the gate, extensive simulations have been carried out using high–low (H–L), low–high (L–H) and low–high–low (L–H–L) doping profiles for both source (DGS) and drain side (DGD) gate misalignment. [Copyright &y& Elsevier]

The dual-material double-gate (DMDG) silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) is the leading contender for sub-100-nm devices because it utilizes the benefits of both double-gate and dual-material-gate structures. One major issue of concern in the DMDG-MOSFET is the alignment between the top and the bottom gate that critically influences the device performance. In this paper, we have investigated the effects of gate misalignment in the DMDG SOI n-MOSFET. In this regard, analytical modeling and extensive simulations have been carried out to analyze the gate misalignment effects on device performance like surface potential, electric field, threshold voltage, subthreshold slope, drain-induced barrier lowering, drain current, and transconductance. Considering the fact that gate misalignment can occur on any side of the gate, both source- and drain-side misalignments have been discussed. Analytical and simulated results are found to be in good agreement, which authenticate our proposed model for the DMDG structure. [ABSTRACT FROM AUTHOR]

Abstract: In this paper analytical modeling for a novel three region gate dielectric engineered AlGaN/GaN Metal Insulator Semiconductor heterostructure field effect transistor (MISHFET) device architecture is presented which shows high transconductance and enhanced cut-off frequency at quarter micron gate lengths. Using a three region analysis along the horizontal direction in the gate dielectric region the expressions for transconductance and cut-off frequency of the device are obtained. It has been observed that using these gate dielectric schemes, improvements on device performance are observed over conventional MISHFET structures. Relative comparison of T and Γ-gate shaped structures is done with uniform gate dielectric profile and enhancement in microwave performance is observed. The proposed model is capable of modeling electrical characteristics like drain current, output conductance and threshold voltage of various other existent structures like uniform gate dielectric MISHFETs, HFETs and T-gate HFETs. The present model is based on closed form expression and does not involve any fitting parameter. The results obtained are compared with experimental data and show excellent agreement, thereby proving the validity of the model. [Copyright &y& Elsevier]

In this work, a physics based analytical model has been proposed for an open gate AlGaN/GaN HEMT for electrical detection of biomolecules-uricase, glucose, biotin and cytochrome -c. The proposed device is easy to fabricate and offers high sensitivity at low operating voltages as complete gate area has been used for immobilizing biomolecules. The analytical model has been developed for evaluating drain current sensitivity and threshold voltage sensitivity by considering that the gate electrode is immersed in solution of de-ionized (DI) water. Results obtained by analytical model are in good agreement with previously reported experimental data and have also been verified with simulation results. Detailed sensitivity analysis has been carried out by evaluating additional electrical parameters such as gate-source capacitance, channel potential, channel conductance and transconductance to detect the presence of biomolecules. Barrier thickness, channel width to length ratio (W/L sd) and Al composition in barrier layer have been optimized to obtain high sensitivity. The maximum drain current and threshold voltage sensitivity obtained for uricase is 3.95 × 108 and 820 mV respectively. • A physics based analytical model has been developed for detection of biomolecules using open gate AlGaN/GaN MOS-HEMT. • Due to the superior properties of AlGaN/GaN MOS-HEMT it shows high sensitivity for polar liquids. • The maximum drain current and threshold voltage sensitivity obtained for Uricase is 3.95×108 and 820mV respectively. • The proposed sensor uses open gate surface for biomolecule immobilization, therefore it is easy to fabricate. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a two-dimensional potential distribution formulation is presented for multi-material gate poly-crystalline silicon thin film transistors. The developed formulation incorporates the effects due to traps and grain-boundaries. In short-channel devices, short-channel effects and drain-induced barrier lowering (DIBL) effect exists, and are accounted for in the analysis. The work aims at the reduction of DIBL effect and grain-boundary effects i.e. to reduce the potential barriers generated in the channel by employing gate-engineered structures. A study of work-functions and electrode lengths of multi-material gate electrode is done to suppress the potential barriers, hot electron effect and to improve the carrier transport efficiency. Green''s function approach is adopted for the two-dimensional potential solution. The results obtained show a good agreement with simulated results, thus, demonstrating the validity of our model. [Copyright &y& Elsevier]

In this work, a comprehensive analytical model for AlGaN/GaN MISHFET has been presented to evaluate the drain current characteristics, transconductance, and cut-off frequency of the insulated device. The model takes into account polynomial dependence of sheet carrier density on position of quasi Fermi level to consider the quantum effects and to validate it from subthreshold to high conduction region. The effect of spontaneous and piezoelectric polarization at the AlGaN/GaN interface and parasitic source/drain resistances have also been incorporated in the analysis. Its advantages over conventional HFET structure are discussed in detail. For a MISHFET with quarter micron gate length, the cut-off frequency is reported to be 52 GHz. The MISHFET shows remarkable 36% increase in drain saturation current. The model has a broad utility as it is equally applicable to HFETs as well. The present model is based on closed form expression and does not involve any fitting parameter. The results obtained are compared with experimental data and show excellent agreement, thereby proving the validity of the model. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 331–338, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23073 [ABSTRACT FROM AUTHOR]

Part I of this paper dealt with the simulation study, using ATLAS 2D, of analog-circuit performance metrics for the dual-material-gate (DMG) silicon-on-nothing (SON) MOSFET. It was reported that, out of the several combinations in the DMG design studied, the DMG device with LM1 /L ratio as 1/2 amalga- mates the advantages of using a high metal work-function gate M1 and low metal work-function gate M2 in the most efficient manner. This paper focuses upon the effect of double-layer gate stack (DGS) (high.k/SiO2) on the single-material-gate (SMG) SON and the DMG SON MOSFETs. Improved Early voltage and reduced output conductance of the DMG SON MOSFETs are the driving forces behind the observed increase in intrinsic gain and fT-gain relationship for the DMG devices over SMG SON MOSFETs, with the DMG SON MOSFETs having LM1 /L ratio as 1/2, proving to be the best choice among various LM1/L ratios studied. A further improvement in intrinsic gain in DMG DGS SON MOSFETs comes about because of increased gate control on the channel, thus establishing design guidelines aiming at higher gain and better fT-gain relationship. [ABSTRACT FROM AUTHOR]