E. Dastjerdy

Shiraz University, Chimaz, Fārs, Iran

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Publications (3)4.62 Total impact

  • E. Dastjerdy, R. Ghayour, H. Sarvari
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    ABSTRACT: In this work we used a three-dimensional quantum mechanical simulation approach to simulate a silicon nanowire MOSFET with square cross section. Different gate structures such as double-gate and gate-all-around with a square gate around the wire (square gate-all-around) and with an octagonal gate around the wire (octagonal gate-all-around) are investigated. The Poisson and the Schrödinger equations are solved self-consistently in this analysis. For solving the Poisson equation the Newton-Raphson method and for solving the Schrödinger equation the non-equilibrium Green's function approach are used. By this simulator the drain current and the electron density and their variations versus the gate voltage are obtained. The transconductance (gm), the gate capacitance (CG) and then the cut-off frequency (fT) are calculated. The short channel effects (i.e. the subthreshold slope and the drain off-current) versus variation of the silicon thickness are obtained. We compared gm, CG and fT for different structures of silicon nanowire MOSFET, i.e. the double-gate, the square gate-all-around and the octagonal gate-all-around due to variation of the gate voltage, the oxide thickness and the silicon thickness. Some advantages for the proposed gate-all-around structure over the other structures are observed.
    Physica E Low-dimensional Systems and Nanostructures 08/2012; · 1.86 Impact Factor
  • Esmaeil Dastjerdy, Rahim Ghayour, Hojjat Sarvari
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    ABSTRACT: In order to investigate the specifications of nanoscale transistors, we have used a three dimensional (3D) quantum mechanical approach to simulate square cross section silicon nanowire (SNW) MOSFETs. A three dimensional simulation of silicon nanowire MOSFET based on self consistent solution of Poisson-Schrödinger equations is implemented. The quantum mechanical transport model of this work uses the non-equilibrium Green’s function (NEGF) formalism. First, we simulate a double-gate (DG) silicon nanowire MOSFET and compare the results with those obtained from nanoMOS simulation. We understand that when the transverse dimension of a DG nanowire is reduced to a few nanometers, quantum confinement in that direction becomes important and 3D Schrödinger equation must be solved. Second, we simulate gate-all-around (GAA) silicon nanowire MOSFETs with different shapes of gate. We have investigated GAA-SNW-MOSFET with an octagonal gate around the wire and found out it is more suitable than a conventional GAA MOSFET for its more I on /I off , less Drain-Induced-Barrier-Lowering (DIBL) and less subthreshold slope. KeywordsNEGF–silicon nanowire–DG-MOSFET–GAA MOSFET–quantum transport
    Central European Journal of Physics 01/2011; 9(2):472-481. · 0.91 Impact Factor
  • H. Sarvari, R. Ghayour, E. Dastjerdy
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    ABSTRACT: In this paper, based on the simple Pz orbital model for the Hamiltonian of graphene nanoribbon, we have analyzed the Graphene Nanoribbon Field Effect Transistors (GNRFET). The Non-Equilibrium Green's Function (NEGF) is used to solve the Schrödinger equation self-consistently with two-dimensional (2D) Poisson equation. The Poisson equation is solved in 2D coordinates using the Finite Difference Method (FDM). In fact, we have assumed that the potential in the width of channel is invariant and the 2D Poisson equation is sufficient to be solved. The “edge effect” that is due to uncompleted bonding of atoms on the edge of the ribbon affects the GNR behavior significantly. In order to calculate the current–voltage characteristic of GNRFET, the Landauer formula is used. We have analyzed the double gate GNRFET with 10nm channel length and source/drain doped reservoirs in the mode space for both cases, with and without the edge effect. We have computed the gate capacitance and transconductance of the device in order to calculate the intrinsic cut-off frequency and switching delay. We have also investigated the Ion/Ioff ratio versus oxide thickness for switching applications of GNRFET. The results show that the edge effect changes the device specifications considerably.
    Physica E Low-dimensional Systems and Nanostructures 01/2011; 43(8):1509-1513. · 1.86 Impact Factor