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‎doc/bjtexample.tex‎

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\documentclass[11pt]{article}
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\newcommand{\devsim}{\mbox{DEVSIM}}
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\newcommand{\devsimllc}{\mbox{DEVSIM LLC}}
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\newcommand{\gmsh}{\mbox{Gmsh}}
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\newcommand{\matplotlib}{\mbox{matplotlib}}
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\newcommand{\numpy}{\mbox{NumPy}}
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\newcommand{\python}{\mbox{Python}}
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\newcommand{\visit}{\mbox{VisIt}}
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\usepackage{indentfirst}
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\usepackage{fullpage}
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\usepackage{helvet}
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\renewcommand{\familydefault}{\sfdefault}
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\usepackage{mathptmx}
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%\usepackage[dvips,colorlinks,breaklinks,pagebackref,citecolor=blue,urlcolor=blue,bookmarks,bookmarksnumbered,linkcolor=blue]{hyperref}
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\usepackage[colorlinks,breaklinks,pagebackref,citecolor=blue,urlcolor=blue,bookmarks,bookmarksnumbered,linkcolor=blue]{hyperref}
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\title{\devsim\ BJT Example}
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\author{Juan E. Sanchez\\ juan.sanchez@devsim.com}
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\setcounter{secnumdepth}{2}
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\begin{document}
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\maketitle
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\thispagestyle{empty}
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\section{Introduction}
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This package includes the examples for the article ``Semiconductor Device Simulation Using \devsim''. In this example, the meshing, modeling, simulation, and visualization for a bipolar junction transistor~(BJT) is developed.
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%\section{Installation}
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%\subsection{\devsim}
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\devsim\ is an open source simulation software for technology computer-aided design~(TCAD) and is developed by \devsimllc. It uses a generalized partial-differential equation~(PDE) approach to perform semiconductor device simulation on a mesh. The software and documentation is available from \url{http://www.devsim.org}.
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In addition to \devsim, the following software packages are used to perform meshing, analysis, and visualization of results.
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~\\~\\
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\noindent
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\begin{tabular}{p{1.5cm}p{5cm}p{5cm}p{2cm}}
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\hline\noalign{\smallskip}
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Name & Description & Website & License$^a$ \\
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\gmsh & Mesh Generator & \url{http://geuz.org/gmsh} & GPL\\
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\matplotlib & Python 2D Plotting Library & \url{http://matplotlib.org} & \matplotlib \\
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\numpy & Python Scientific Computing & \url{http://numpy.org} & BSD\\
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\python & Scripting Language & \url{http://python.org} & PSF\\
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\visit & Visualization Tool & \url{http://visit.llnl.gov} & BSD\\
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\noalign{\smallskip}\hline\noalign{\smallskip}
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\end{tabular}
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\section{Running the Examples}
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\begin{minipage}{\textwidth}
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Here are some of the files in the package used for simulation.
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\begin{tabular}{ll}
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\texttt{bjt.geo} & Mesh description for \gmsh\\
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\texttt{bjt.msh} & Resulting gmsh mesh\\
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\texttt{initial\_guess.py} & Creates initial guess from Potential only simulation\\
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\texttt{refinement.py} & Sets up E-field based refinements for creating background mesh\\
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\texttt{netdoping.py} & Specifies analytical doping profile\\
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\texttt{bjt\_refine.py} & Runs \devsim\ to create a background mesh\\
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\texttt{bjt\_bgmesh.pos} & Background mesh generated by \devsim\ for refinement using \gmsh\\
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\texttt{physics/} & subdirectory containing physics files used in simulation.
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\end{tabular}
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\end{minipage}
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\subsection{Meshing and Refinement}
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The file \texttt{bjt.geo} contains the initial mesh specification for the bjt structure. This file is run through \gmsh\ in order to create a triangular mesh for use in \devsim. The resulting mesh file is called \texttt{bjt.msh}. In order to create a mesh suitable for devsim, the \texttt{bjt\_refine.py} script is run to create a background mesh with element sizes appropriate for simulation. The background mesh is then used with the original mesh specification to create a refined mesh. This procedure is repeated until the mesh is sufficiently refined for use in \devsim.
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\begin{minipage}{\textwidth}
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The steps are:
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\begin{verbatim}
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gmsh -2 bjt.geo
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devsim bjt_refine.py
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gmsh -2 bjt.geo -bgm ./bjt_bgmesh.pos
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devsim bjt_refine.py
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gmsh -2 bjt.geo -bgm ./bjt_bgmesh.pos
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devsim bjt_refine.py
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gmsh -2 bjt.geo -bgm ./bjt_bgmesh.pos
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devsim bjt_refine.py
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gmsh -2 bjt.geo -bgm ./bjt_bgmesh.pos
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devsim bjt_refine.py
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\end{verbatim}
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\end{minipage}
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\\~\\
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The resulting mesh from each \devsim\ run can be visualized by running Visit.
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\begin{verbatim}
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visit bjt_refine.tec
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\end{verbatim}
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\subsection{Simulation}
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The dc and ac sweeps used in the publication are listed in \texttt{simsbatch.txt}. These simulations can be run in sequence or in parallel.
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\subsubsection{$V_c$ sweep}
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For a given value of $V_b$, sweep $V_c$ from $0$ to $1.5$~V.
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\begin{verbatim}
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bjt_circuit2.py 0.1 &> data/vb2_0.1.out
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\end{verbatim}
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\subsubsection{$V_b$ sweep}
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For a given value of $V_c$, sweep $V_b$ from $0$ to $1.0$~V.
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\begin{verbatim}
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devsim bjt_circuit3.py 0.0 &> data/vc_0.0.out
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\end{verbatim}
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\subsubsection{$V_e$ sweep}
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For a given value of $V_c$, sweep $V_e$ from $0$ to $-1.0$~V.
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\begin{verbatim}
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devsim bjt_circuit4.py 0.0 &> data/ve_0.0.out
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\end{verbatim}
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\subsubsection{Small-signal ac sweep}
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For a given value of $V_c$, sweep $V_e$ from $0$ to $-1.0$~V. Do a small signal frequency sweep from fmin to fmax with given points per decade.
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\begin{verbatim}
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devsim bjt_circuit5.py 0.0 1e3 1e11 3 &> data/ssac_0.0.out
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\end{verbatim}
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\subsection{Visualization}
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The \texttt{data/} directory contains scripts used to generate the plots used for publication. A script was written to collect the data from the simulations to create plots using \texttt{matplotlib}. This script is in the \texttt{data/} directory and is called \texttt{prep.sh}.
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\begin{tabular}{ll}
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\texttt{ft.py} & Small-signal ft simulation\\
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\texttt{gummel.py} & Ic, Ib versus Vbe.\\
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\texttt{ic\_vec.py} & Ic versus Vce.\\
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\end{tabular}
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\end{document}
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