Kaushal Nigam

Bio: Kaushal Nigam is an academic researcher from Jaypee Institute of Information Technology. The author has contributed to research in topics: Tunnel field-effect transistor & Gate dielectric. The author has an hindex of 17, co-authored 55 publications receiving 812 citations. Previous affiliations of Kaushal Nigam include Indian Institute of Information Technology, Design and Manufacturing, Jabalpur & Indian Institutes of Information Technology.

A Charge-Plasma-Based Dielectric-Modulated Junctionless TFET for Biosensor Label-Free Detection

Abstract: To reduce the fabrication complexity and cost of the nanoscale devices, a charge-plasma concept is introduced for the first time to implement a dielectric-modulated junctionless tunnel field-effect transistor (DM-JLTFET) for biosensor label-free detection. The formation of p+ source and n+ drain regions in DM-JLTFET is done by the deposition of platinum (work function = 5.93 eV) and hafnium (work function = 3.9 eV) materials, respectively, over the silicon body. Furthermore, a nanogap cavity embedded within the gate dielectric is created by etching the portion of gate oxide layer toward the source end for sensing biomolecules. For this, the sensing capability of DM-JLTFET has been investigated in terms of variation in dielectric constant, charge density, length, and thickness of the cavity at different bias conditions. Finally, a comparative study between DM-JLTFET and MOSFET biosensor is investigated. The implementation of proposed device and all the simulations have been performed by using ATLAS device simulator.

Drain Work Function Engineered Doping-Less Charge Plasma TFET for Ambipolar Suppression and RF Performance Improvement: A Proposal, Design, and Investigation

Abstract: A novel device configuration is presented for doping-less charge plasma tunnel FET (TFET) for suppression of ambipolar nature with improved high-frequency figures of merit. For this, the drain electrode, which is used to induce n+ drain region, is separated into two sections of high and low work functions. The work function of the drain electrode section near to channel is considered relatively higher than other part for restricting the tunneling of holes at drain/channel interface for negative gate bias. This concept creates asymmetrical charge carrier concentration in the drain region, which increases the tunneling width at the drain/channel interface. Therefore, the proposed device offers better performance in terms of ambipolar current, parasitic capacitance, and RF parameters. In this regard, a comparative study of the proposed device is performed with conventional and dual-metal gate doping-less TFETs. Furthermore, the optimization of the length and higher work function of the drain electrode near to channel is discussed in detail for the proposed device. Apart from above-mentioned advantages, the doping-less nature of the proposed device provides fabrication simplicity and immunity against random dopant fluctuations in comparison with the physically doped TFET.

Design and Analysis of Polarity Controlled Electrically Doped Tunnel FET With Bandgap Engineering for Analog/RF Applications

Abstract: In this paper, we investigate a polarity controlled electrically doped tunnel FET (ED-TFET) based on the bandgap engineering for analog/RF applications. The proposed device exhibits a heavily doped n-type Si-channel with two distinctive gate: 1) control gate (CG) and 2) polarity gate (PG). First, the work function of 4.72 eV is considered for CG and PG to convert the layer beneath CG and PG of intrinsic type. Further, a bias of −1.2 V is applied at PG terminal to induce a p+ region, so that, it follows the similar trend as like a n+-i-p+ gated structure of conventional TFET. To improve the ON-state current of the proposed device, we investigate an interfacing of III–V with IV group material for heterojunction. It shows higher ON-state current in the order of $10^{-4}$ A/ $\mu \text{m}$ , ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio (in the order of $10^{12}$ ) at ${V}_{\sf DS} = 0.7$ V. Further, its higher transconductance ${g} _{m}\approx 1.02$ mS and different RF performance parameters in the range of terahertz, enables its potential for analog/RF applications. However, linearity parameters are analyzed to give the assurance of the device for high-frequency applications. Moreover, a nonquasi-static RF model is adopted to analyze the behavior of the proposed ED-TFET in high frequency region. Based on this, the small-signal parameters were extracted and verified upto 500 GHz. The modeled result shows excellentmatching with the Y-parameters upto 500 GHz.

Dielectric and work function engineered TFET for ambipolar suppression and RF performance enhancement

Abstract: A novel approach to suppress the ambipolar behaviour and enhance RF parameters is proposed for the first time. For this, the dielectric and gate material work function engineering is used to suppress the ambipolar behaviour individually. Further, the combination of gate dielectric and gate material work function engineering is used to suppress the ambipolar conduction in huge amount and to eliminate the hot carriers effects. Apart from these, the proposed work improves the ON-state current and RF figures of merit for symmetric devices.

The Design of CMOS Radio-Frequency Integrated Circuits: RF CIRCUITS THROUGH THE AGES

Abstract: This expanded and thoroughly revised edition of Thomas H. Lee's acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems. The chapters on low-noise amplifiers, oscillators and phase noise have been significantly expanded as well. The chapter on architectures now contains several examples of complete chip designs that bring together all the various theoretical and practical elements involved in producing a prototype chip. First Edition Hb (1998): 0-521-63061-4 First Edition Pb (1998); 0-521-63922-0

Performance Assessment of A Novel Vertical Dielectrically Modulated TFET-Based Biosensor

Abstract: A vertical dielectrically modulated tunnel field-effect transistor (V-DMTFET) as a label-free biosensor has been investigated in this paper for the first time and compared with lateral DMTFET (L-DMTFET) using underlap concept and gate work function engineering. To improve the performance of lateral biosensor (LB), a heavily doped front gate ${n}^{+}$ -pocket and gate-to-source overlap is introduced in the vertical biosensor (VB). The integrated effect of lateral tunneling as well as vertical tunneling in VB leads to enhanced ON-state current and decrease the subthreshold swing. To evaluate sensing ability of these devices, charged and charged neutral biomolecules are immobilized in nanogap cavity independently. A deep analysis has been performed to show the effect of variation in dielectric constant ( $k$ ), charge density ( $\rho $ ), ${x}$ -composition of Ge, % volume filling of ${t}_{\textsf {cavity}}$ , length and thickness of a ${n}^{+}$ -pocket and sensitivity of electrical parameters is also incorporated. Dual-pocket (front and back gate pocket) VB is studied and compared with the LB and VB in the tabular form. Noise characteristic of dielectrically modulated field-effect transistor, L-DMTFET, and V-DMTFET is also evaluated.

A New Design Approach of Dopingless Tunnel FET for Enhancement of Device Characteristics

Abstract: Formation of abrupt tunneling junction for the sub-nanometer tunnel FET (TFET) is crucial for achieving better electrical behavior. This task is more challenging in the case of dopingless TFETs (DL TFETs). In this concern, we propose a novel design of DL TFET, wherein a metallic layer has been placed in the oxide region at the space present between gate and source electrode (used for inducing p+ region) of conventional dopingless n-TFET to overcome the issue of low on-state current ( $\text{I}_{\mathrm{on}}$ ) due to presence of tunneling barrier. Proposed modification is helpful for achieving steeper tunneling junction at the source/channel interface, which enables higher tunneling generation rate of charge carriers at this interface. The optimization for work function of the metal layer (ML) has been performed for improving $\text {I}_{\mathrm{on}}$ , point subthreshold swing and threshold voltage ( $\text {V}_{\text {th}}$ ). Finally, the impact of the ML misalignment from the gate/source terminal and optimization of its length is also presented.

A Novel PNPN-Like Z-Shaped Tunnel Field- Effect Transistor With Improved Ambipolar Behavior and RF Performance

Abstract: To suppress the ambipolar behavior and improve RF performance in tunnel field-effect transistors (TFETs), a Z-shaped (ZS)-TFET is proposed. The proposed ZS-TFET is more scalable than other vertical band-to-band-based TFETs and provides higher ON-state current ( ${I} _{ {\mathrm{\scriptscriptstyle ON}}}$ ), larger ON/OFF current ratio ( ${I} _{ {\mathrm{\scriptscriptstyle ON}}}/{I} _{ {\mathrm{\scriptscriptstyle OFF}}}$ ) and lower subthreshold swing compared to conventional TFETs. These advantages stem from the tunneling junction in the ZS-TFET being perpendicular to the channel direction, which facilitates the formation of a relatively large tunneling junction area. The ZS body makes use of both vertical and horizontal fields while suppressing the lateral parasitic tunneling current. In addition, by using a ZS gate in the proposed device, the energy band diagram near the source is modulated to create an N+ source pocket which creates a downward band bending of the potential, similar to PNPN-like structures. Finally, the proposed structure significantly improves the analog/RF figure-of-merit.

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.