Manoj Kumar

Bio: Manoj Kumar is an academic researcher from University of Delhi. The author has contributed to research in topics: MOSFET & Subthreshold conduction. The author has an hindex of 8, co-authored 21 publications receiving 148 citations. Previous affiliations of Manoj Kumar include Maharaja Agrasen Institute of Technology & Indian Institute of Technology Delhi.

Analytical modeling of gate-all-around junctionless transistor based biosensors for detection of neutral biomolecule species

Abstract: In recent times, FET-based sensors have been widely used in industrial and domestic applications due to their low cost and high sensitivity. In this paper, a nanogap-embedded gate-all-around junctionless transistor (GAA JLT) is proposed for label-free electrochemical detection of neutral biomolecule species such as Uricase, Protein, ChOx, APTES and Streptavidin. Shifts in subthreshold current, threshold voltage and capacitance are used to predict the response of the sensor. Impact of cavity width, cavity length, and gate length on the sensitivity of a junctionless transistor has also been investigated in detail. An analytical model has been developed for a GAA JLT-based biosensor. The results are compared with an inversion mode transistor-based biosensor using TCAD numerical simulation. The GAA JLT shows very high sensitivity due to the gate all around structure and bulk conduction mechanism.

Analytical modeling of Junctionless Accumulation Mode Cylindrical Surrounding Gate MOSFET JAM-CSG

Abstract: This paper presents physics based analytical model for center potential, electric field and subthreshold drain current of Junctionless Accumulation Mode Cylindrical Surrounding Gate MOSFET JAM-CSG. The expressions are derived from Poisson's equation in cylindrical co-ordinate system based on parabolic potential approximation PPA. The influence of technology parameter variations such as gate length, silicon pillar diameter and oxide thickness on electrical characteristics is studied in detail. Developed analytical model results are validated through the good agreement with simulated data obtained from ATLAS 3D simulator. Copyright © 2016 John Wiley & Sons, Ltd.

Charge plasma technique based dopingless accumulation mode junctionless cylindrical surrounding gate MOSFET: analog performance improvement

Abstract: A charge plasma technique based dopingless (DL) accumulation mode (AM) junctionless (JL) cylindrical surrounding gate (CSG) MOSFET has been proposed and extensively investigated. Proposed device has no physical junction at source to channel and channel to drain interface. The complete silicon pillar has been considered as undoped. The high free electron density or induced N+ region is designed by keeping the work function of source/drain metal contacts lower than the work function of undoped silicon. Thus, its fabrication complexity is drastically reduced by curbing the requirement of high temperature doping techniques. The electrical/analog characteristics for the proposed device has been extensively investigated using the numerical simulation and are compared with conventional junctionless cylindrical surrounding gate (JL-CSG) MOSFET with identical dimensions. For the numerical simulation purpose ATLAS-3D device simulator is used. The results show that the proposed device is more short channel immune to conventional JL-CSG MOSFET and suitable for faster switching applications due to higher I ON/I OFF ratio.

A new T-Shaped Source/Drain Extension (T-SSDE) Gate Underlap GAA MOSFET with enhanced subthreshold analog/RF performance for low power applications

Abstract: In the proposed work, a novel T-Shaped Source/Drain Extension (T-SSDE) Gate Underlap Gate All Around (GAA) MOSFET is presented and its performance is compared with that of corresponding Conventional Gate Underlap GAA MOSFET using ATLAS-3D device simulator. A quantitative study of main figure of merits (FOMs) for T-SSDE Underlap GAA has been carried out at different Gate Underlap lengths. It is shown that in T-SSDE, short channel effects (SCEs) are suppressed due to enhanced carrier transport efficiency. The results show an improvement in drain current, I on / I off ratio, transconductance, high unity-gain frequency f T and superior analog/RF performance as compared to conventional Gate Underlap GAA MOSFET, thus, making it a better substitute of conventional Underlap Gate GAA devices for faster switching and low power applications.

Comparative Analyses of Circular Gate TFET and Heterojunction TFET for Dielectric-Modulated Label-Free Biosensing

Abstract: This paper compares circular gate (CG) tunnel field effect transistor (TFET) and uniform gate Heterojunction (HJ) TFET as label-free biosensors based on dielectric modulation. Neutral and charged biomolecules with different values of dielectric constant are considered. Sensitivities of partially filled nanogaps arising out of steric hindrance in both the biosensors for concave, convex, increasing and decreasing step profiles of biomolecules are compared. The effect of probe position on sensitivities of the two biosensors is reported for various cases. A status map is presented, plotting the sensitivities of some of the most significant works in applications of FET as label-free biosensors along with sensitivities of the proposed devices. CG TFET exhibits higher sensitivity than HJ TFET due to its non-uniform gate architecture. The sensitivities of the TFETs are highly dependent on the position of biomolecules (steric hindrance and probe position) with respect to the tunnel junction. A maximum sensitivity of $1.31\times 10^{8}$ ( $3.382\times 10^{6}$ ) is achieved for fully filled nanogap in CG TFET (HJ TFET) for dielectric constant 12.

Gate-All-Around Charge Plasma-Based Dual Material Gate-Stack Nanowire FET for Enhanced Analog Performance

Abstract: In this paper, a gate-all-around (GAA) charge plasma-based dopingless dual material gate nanowire FET is proposed (CP-DM). This structure is further explored by adding gate-stack (high-k + SiO2) feature (CP-GS-DM). In these dopingless structures, source/drain is induced using a charge plasma concept by an appropriate selection of work functions for source/drain electrodes. The dopingless devices offer low thermal budget with easier fabrication steps and reduced random dopant fluctuations effect. Both the dopingless structures are investigated for analog performance, and results are compared with those obtained from the GAA junctionless dual material (JL-DM) gate and the JL gate-stacked DM gate (JL-GS-DM), respectively. The charge plasma-based dopingless devices when compared with their JL counterpart show improvement in drive current ( ${I}_{\text {D}}$ ), transconductance ( ${g}_{m}$ ), transconductance gain factor ( ${g}_{m}/{I}_{D}$ ), output conductance ( ${g}_{\text {ds}}$ ), early voltage ( ${V}_{\text {AE}}$ ), intrinsic gain ( $A_{\text {v}}$ ), drain-induced barrier lowering, and subthreshold slope. Thus, dopingless structures show enhanced analog performance with reduced short channel effects. The charge plasma based dopingless gate stacked dual material gate (CP-GS-DM) shows the best performance of all the structures. The analysis is further carried out for investigating the device design parameters effect on performance, namely, total gate length, ${L}_{G}$ , and ratio of control gate length to total gate length, $L_{\text {M1}}/{L}_{G}$ . This way dopingless charge plasma-based devices incorporate DM and GS features that make these devices interesting and reliable candidates for analog application with cost-effective fabrication.

Modeling and Simulation of AlGaN/GaN MOS-HEMT for Biosensor Applications

Abstract: HEMT technology is being used for development of biosensors. Many floating gate HEMT-based biosensors have been experimentally developed but little work has been reported on modeling of MOSHEMT-based biosensors. Therefore in this paper an analytical model of AlGaN/GaN MOSHEMT-based biosensor has been developed for the first time to detect the biomolecule species, such as protein, streptavidin, ChOx, and uricase by using a dielectric modulation approach. In this paper, the cavity length and the dielectric constant of the MOSHEMT device are optimized to improve the sensitivity of the device. The proposed structure of the MOSHEMT has been simulated on an ATLAS TCAD device simulator and the simulated results show a significant change in drain current, shift in threshold voltage, change in channel potential below the cavity region, and the capacitance on introducing biomolecules in the nanogap cavity. The results of analytical model have been verified and they show good agreement with simulated results. The sensitivity of the device can be enhanced by optimizing the device parameters, such as nanogap cavity length and width, and also by varying the gate length of the device.

N+ Pocket-Doped Vertical TFET for Enhanced Sensitivity in Biosensing Applications: Modeling and Simulation

Abstract: This article examines the performance of N+ pocket-doped vertical tunnel field-effect transistor (VTFET)-based label-free biosensors with the help of an analytical model developed for electrostatic potential, electric field, and drain current along with an extensive verification of the simulated device data. The model incorporates the effects of dielectric constant as well as charge and renders a generalized solution applicable for both neutral and charged biomolecules. Besides, the sensitivity has been analyzed by measuring the shift in drain current due to a change in the dielectric constant. It has been observed that the proposed sensor shows a large deviation in drain current, and hence, ${I}_{ \mathrm{\scriptscriptstyle ON}}$ can be used as an appropriate sensing parameter. The variations in the drain current and threshold voltage ( ${V}_{th}$ ) due to the impact of positive/negative charged biomolecules have also been studied. Extensive TCAD simulations have been performed to investigate the device performance when the nanogaps are fully filled, three-quarterly filled, half-filled, quarterly filled, and unequally filled. Furthermore, a comparison has been made with MOSFET-based biosensors.