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The simulation of a double-tunnel junction with the SENS simulator gives access to the frequency-dependent and static behavior of shot noise. The concept of basic paths in a multi-state process provides a clear interpretation of the noise regimes, and allows locating cut-offs in autocorrelation functions and spectral densities.
We have developed a code for the simulation of graphene-based devices consisting of cascaded armchair sections with width discontinuities, in the presence of a generic potential landscape. This is based on a scattering-matrix approach and on the solution of the Dirac equation in the reciprocal space. The presence of width discontinuities requires a particular treatment of the continuity equation for...
We present a numerical method which allows an approximate but fast computation of the potential profile in a graphene sample subject to the electrostatic action of biased gates, including the effect of different contributions, such as those from doping or from charged impurities. The procedure is applied to the evaluation of the effect of a biased probe, coupled to the graphene flake through a space-dependent...
Herein, we consider examine the possibility of photodetectors with reduced signal-to-noise based on a three quantum well structure with one single well and one double well. This structure facilitates photon detection through the following sequence of events: photon absorption, phonon emission, and then photon absorb of a photon having the same wavelength as the first one. Even though this design two...
In order to investigate the distributed semiconductor device high frequency operation, we are developing a 2D/3D time-domain electromagnetic physical simulator. It is based on a self-consistent solution of both the Maxwell equations and the free carrier macroscopic conservation equation sets issued from the Boltzmann general transport equation. Its large potential application field presently concerns...
We use a hydrodynamic model self-consistently coupled to a 1D Poisson solver to simulate the excitation by optical beating as well as by electrical perturbation of plasma waves in n+nn+ InGaAs diodes at room temperature. We calculate the electric field response and the velocity response of the carriers in the middle of the diode regions. Our results show clearly the presence of three-dimensional plasma...
By means of a numerical hydrodynamic (HD) model coupled with Poisson pseudo-2D equation, we simulate the drain current response of a high electron mobility transistor (HEMT) to a THz signal applied to its gate and/or to its drain contacts in order to obtain the optimal configuration in terms of detection.
This paper presents a two dimensional numerical simulation on the program and retention operation of charge trapping memory. The developed simulator self-consistently solves two-dimensional Poisson equation, carrier continuity equation and trapped charge conservation equation. Driftdiffusion transport scheme is used for modeling the charge transport in the trapping layer. Major physical models, such...
In this paper we present a hydrodynamical model for the charge and the heat transport in graphene. The macroscopic variables are moments of the electron, hole and phonon distribution functions, and their evolution equations are derived from the Boltzmann equations by integration. The system of equations is closed by means of the maximum entropy principle and all the main scattering mechanisms are...
In modern FET/HEMT structures the Gunn-effect is not usually considered as one of the mechanisms able to realize high-frequency (near terahertz (THz)) oscillations of the current. Physically, the effect is caused by the suppression effect of the remote Coulomb interaction which takes place in the gated region of the conducting channel. In the present work we propose a way to overcome this limitation...
In this paper we perform, by means of Discontinuous Galerkin (DG) Finite Element Method (FEM) based numerical solvers for Boltzmann-Poisson (BP) semiclassical models of hot electronic transport in semiconductors, a numerical study of reflective boundary conditions in the BP system, such as specular reflection, diffusive reflection, and a mixed convex combination of these reflections, and their effect...
We derive a local equation of motion for the electronic single-particle density matrix in the presence of one- as well as two-body scattering processes. This is done by applying the mean-field approximation to the many-electron dynamics obtained via a recently proposed Markov limit, able to furnish many-body Lindblad-type scattering superoperators. The resulting time evolution at finite/high carrier...
A novel algorithm for a reduction of the computational burden associated to the time-dependent simulation of quantum transport with pure states is presented. The algorithm is based on using the superposition principle and the analytical knowledge of the free timeevolution of an initial state outside of the active region, together with absorbing layers. It is specially suited to study (many-particle...
The so-called Numerov process provides a three-point interpolation with an ∼η5 accuracy in grid's size η, much better than the standard finite-difference scheme that keeps the ∼η2 terms. Such a substantial improvement is achieved with a negligible increase in computational cost. As the method is applicable to second-order differential equations in one dimension, it is an ideal tool for solving, e...
The solution of the two-dimensional (2D) Wigner equation has become numerically feasible in recent times, using the Monte Carlo method [1] fortified with the notion of signed particles [2]. The calculation of the Wigner potential (WP) in these 2D simulations consumes a considerable part of the computation time. A reduction of the latter is therefore very desirable, in particular, if self-consistent...
In this work we present a multiscale simulation of a solid state dye sensitized solar cell including the real morphology of the active layer. In order to include the real morphology the device domain is split into two different regions: one treated using an effective material approximation and another one using the real structure of the blend. The real morphology has been measured using electron tomography...
A 3D Finite Element Monte Carlo simulation with 2D Schro¨dinger based quantum correction are employed to forecast the performance of SOI Si FinFET devices scaled to gate length of 10.7 nm. The performance of these devices are greatly affected by the exact device geometry and thus the accurate description of cross-sections is essential. We chose three cross-sections: rectangular (REC), wide- (WTRI)...
We will discuss recent development in the simulation of Boltzmann-Poisson systems and Wigner transport by deterministic numerical solvers. We have proposed to solve linear transport problems using a Discontinuous Galerkin (DG) Finite Element Method (FEM) approach that allows adaptivity and accuracy by a flexible choice of basis functions, as well as numerical efficiency by parallelization and scalability...
Magnetic Tunnel Junctions (MTJs) — the basic structures of the Spin-Transfer Torque Magnetic RAMs (STT-MRAM) currently reaching the market — present a complex and probabilistic switching behavior. Although some analytical models describing this behavior exist, they can not describe all the switching regimes of the MTJs. They can model low (“subcritical”) and high (“supercritical”) currents, but not...
Covalent functionalization of carbon nanotubes (CNTs) might be an option to optimize the behavior of CNT field effect transistors (FETs) [1] (despite all related technological problems). In principle, the atoms or molecules used for functionalizing are placed randomly along the CNT or they are high-ordered in decoration patterns. Here, only high-ordered functionalization patterns are studied (i) to...
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