Abdeljalil NACHAOUI and Nabil R. NASSIF
This paper is concerned with the analysis of global uniqueness of the solution to the drift—diffusion models, for stationary flow of charges carriers in semiconductor devices. Two…
Abstract
This paper is concerned with the analysis of global uniqueness of the solution to the drift—diffusion models, for stationary flow of charges carriers in semiconductor devices. Two uniqueness cases are found. Firstly, small applied voltages with a proof introducing new ‘quasi‐monotony condition’ verified for solutions in W and not necessarily in H. Secondly, large applied voltage to the semiconductor with small 2D domain, and not large doping functions. These uniqueness cases allow the construction of algorithms that yield converging sequences of solutions.
This paper analyses a method of local scaling analysis for the discrete continuity equations of a semiconductor. The basic purpose is to give an algorithm that eliminates all…
Abstract
This paper analyses a method of local scaling analysis for the discrete continuity equations of a semiconductor. The basic purpose is to give an algorithm that eliminates all occurrences of overflows and underflows by appropriately scaling each equation of the system obtained when we discretize the partial differential equations:
Nayla HAYECK, Abdeljalil NACHAOUI and Nabil R. NASSIF
Using the topological degree of Leray‐Shauder, and Grisvard's results for elliptic equations with mixed boundary conditions, we extend Mock's results for the steady‐state Van…
Abstract
Using the topological degree of Leray‐Shauder, and Grisvard's results for elliptic equations with mixed boundary conditions, we extend Mock's results for the steady‐state Van Roosbroeck system, with the change from Neuman to Dirichlet boundary conditions occuring at a flat angle. Similar results are obtained for continuity equations that include a general recombination rate.
François Lefèvre and Nabil Nassif
We introduce the drift‐diffusion model with appropriate jump conditions at the junction of the MODFET transistor (AlGaAs/GaAs). We propose a quasi‐variational inequality (QVI…
Abstract
We introduce the drift‐diffusion model with appropriate jump conditions at the junction of the MODFET transistor (AlGaAs/GaAs). We propose a quasi‐variational inequality (QVI) model for this device. We assume that the electron density is bounded and piecewise constant. These hypotheses imply that the Poisson’s equation becomes linear with respect to the electrostatic potential. The QVI model keeps a coupling with the continuity equation. Free boundaries arise in the medium AlGaAs near the Schottky‐gate contact and in the high mobility medium (GaAs) under the effect of the electron affinity discontinuity at the junction. Numerical results of the QVI model show their location versus the applied gate voltage V/up> and the molar fraction X of the AlXGa(1‐X)As medium. The inequality seems to be a reasonable simplification of the non‐linear Poisson’s equation.
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Nadia Lamari, Mohamed Mfitih and Nabil Nassif
In this paper, we present the results of submicron pseudomorphic AlGaAs/InGaAs/ GaAs HEMT simulations. Our main interest is the study of electronic temperature behavior in the…
Abstract
In this paper, we present the results of submicron pseudomorphic AlGaAs/InGaAs/ GaAs HEMT simulations. Our main interest is the study of electronic temperature behavior in the device and improvement of the current‐voltage characteristic curves. Three types of models are being used. The first is the well known drift‐diffusion model. The second is of the hydrodynamic type and the third is a combination of the two preceding models. The numerical treatment is based on the discretization by the Galerkin finite element method for both Poisson and continuity equations with the streamline‐diffusion method being used for the energy equation. A comparison of the different approaches have been realized and a synthesis on the validity of each of these models is being drawn.
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Stig Stenslie and Kjetil Selvik
The chapter compares the survival of old regime elites in Tunisia and Egypt after the 2011 uprisings and analyses its enabling factors. Although democracy progressed in Tunisia…
Abstract
The chapter compares the survival of old regime elites in Tunisia and Egypt after the 2011 uprisings and analyses its enabling factors. Although democracy progressed in Tunisia and collapsed in Egypt, the countries show similarities in the old elite’s ability to survive the Arab Spring. In both cases, the popular uprisings resulted in the type of elite circulation that John Higley and György Lengyel refer to as ‘quasi-replacement circulation’, which is sudden and coerced, but narrow and shallow. To account for this converging outcome, the chapter foregrounds the instability, economic decline and information uncertainty in the countries post-uprising and the navigating resources, which the old elites possessed. The roots of the quasi-replacement circulation are traced to the old elites’ privileged access to money, network, the media and, for Egypt, external support. Only parts of the structures of authority in a political regime are formal. The findings show the importance of evaluating regime change in a broader view than the formal institutional set-up. In Tunisia and Egypt, the informal structures of the anciens régimes survived – so did the old regime elites.