Modeling of threshold voltage and subthreshold slope of nanoscale DG MOSFETs

Abstract

analytical models for the threshold voltage and subthreshold slope of fully depleted symmetric double gate (DG) n-MOSFETs have been presented in this paper. 2D Poisson's equation has been solved with suitable boundary conditions to obtain the surface potential at the Si/SiO 2 interface. The minimum surface potential has been employed to derive analytical expressions for the threshold voltage and subthreshold slope. Also, these expressions have been modified taking into account the effect of bandgap narrowing due to heavy channel doping and quantum-mechanical effects. In addition, the 2D numerical simulation results obtained using the device simulator ATLAS for the surface potential, the threshold voltage and subthreshold slope have been presented. Further our analytical data have been compared with numerical simulation results for various DG MOSFETs, and our analytical simulation results have also been compared with reported experimental data in the literature. A good agreement is observed among the three, ensuring the validity of our present model. The proposed model is simple and makes it easy to understand the influence of physical phenomena such as quantum-mechanical effects on the electrical parameters, such as the threshold voltage, compared to other models published elsewhere.

Analytical model for threshold voltage of double gate bilayer graphene field effect transistors

“…According to the definition, threshold voltage is defined as the gate voltage at which the minimum surface potential is twice of the Fermi potential [26], i.e. U min ð0; yÞ ¼ 2/ f ð23Þ where / f = KT/qln(N D /n i ) is the Fermi potential.…”

A Subthreshold Swing Model for Symmetric Double-Gate (DG) MOSFETs with Vertical Gaussian Doping

“…Since scalability and on-off characteristics of DG-MOSFETs are defined by the subthreshold slope of the device, accurate modeling of DG MOSFETs are of great importance for the designing of switching circuits for VLSI and ULSI applications. A number of theoretical models for the subthreshold swing for DG MOSFETs have been proposed for the undoped [4][5][6] and uniformly doped [7][8][9][10][11] channels. Liang et al [4] proposed a subthreshold swing model for undoped DG MOSFETs where the effect of doping on the subthreshold characteristics was ignored.…”

“…Further, they had also emphasized that doped channels could provide better control of the threshold voltage (than the undoped devices) without changing the gate material leading to the multi-threshold processes which are of great interests for analog applications [12,15]. Based on the above assumptions, a number of subthreshold swing models [7][8][9][10][11] were also reported for DG MOSFETs with doped channels. Bhattacherjee et al [7] presented an analytical model to consider only the effect of channel length on the subthreshold swing parameter of DG-MOSFETs with a doped channel.…”

“…Based on the above assumptions, a number of subthreshold swing models [7][8][9][10][11] were also reported for DG MOSFETs with doped channels. Bhattacherjee et al [7] presented an analytical model to consider only the effect of channel length on the subthreshold swing parameter of DG-MOSFETs with a doped channel. Agrawal et al [8] reported a model based on the assumption that the effective subthreshold conduction path would be located at Si-SiO 2 interfaces under both the gates as was considered in [16].…”

Compact modeling and simulation of nanoscale fully depleted DG-SOI MOSFETS

“…Bhattacherjee et al [11] presented a threshold voltage model by considering the minimum channel potential equal to the twice of Fermi voltage. The short channel threshold voltage models of Double Gate MOSFETs [12] and the threshold voltage as a gate voltage at which the minimum carrier charge sheet density Q inv reaches a value Q TH adequate to achieve the device turn-on condition [13] was considered.…”