fix convergence issue

update documentation

doc/bjtexample.tex

@@ -53,6 +53,7 @@ \section{Running the Examples}
 \texttt{initial\_guess.py}  & Creates initial guess from Potential only simulation\\
 \texttt{refinement.py}  & Sets up E-field based refinements for creating background mesh\\
 \texttt{netdoping.py}  & Specifies analytical doping profile\\
+\texttt{bjt\_dd.py} & Creates the zero bias drift diffusion solution for later sweeps\\
 \texttt{bjt\_refine.py} & Runs \devsim\ to create a background mesh\\
 \texttt{bjt\_bgmesh.pos} & Background mesh generated by \devsim\ for refinement using \gmsh\\
 \texttt{physics/} & subdirectory containing physics files used in simulation.
@@ -67,15 +68,15 @@ \subsection{Meshing and Refinement}
 The steps are:
 \begin{verbatim}
 gmsh -format msh2 -2 bjt.geo
-devsim bjt_refine.py
+python bjt_refine.py
 gmsh -format msh2 -2 bjt.geo -bgm ./bjt_bgmesh.pos
-devsim bjt_refine.py
+python bjt_refine.py
 gmsh -format msh2 -2 bjt.geo -bgm ./bjt_bgmesh.pos
-devsim bjt_refine.py
+python bjt_refine.py
 gmsh -format msh2 -2 bjt.geo -bgm ./bjt_bgmesh.pos
-devsim bjt_refine.py
+python bjt_refine.py
 gmsh -format msh2 -2 bjt.geo -bgm ./bjt_bgmesh.pos
-devsim bjt_refine.py
+python bjt_refine.py
 \end{verbatim}
 \end{minipage}
 \\~\\
@@ -84,31 +85,40 @@ \subsection{Meshing and Refinement}
 \begin{verbatim}
 visit bjt_refine.tec
 \end{verbatim}
+
+\subsection{Zero bias drift diffusion solution}
+When creating a new device, it is necessary to create initial zero bias solution for all the subsequent sweeps.
+\begin{verbatim}
+python bjt_dd.py
+\end{verbatim}
+This creates \texttt{bjt\_dd\_0.msh} file that is read in the next section.
+
 \subsection{Simulation}
 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.
 
+
 \subsubsection{$V_c$ sweep}
 For a given value of $V_b$, sweep $V_c$ from $0$ to $1.5$~V.
 \begin{verbatim}
-bjt_circuit2.py 0.1 &> data/vb2_0.1.out
+python bjt_circuit2.py 0.1 &> data/vb2_0.1.out
 \end{verbatim}
 
 \subsubsection{$V_b$ sweep}
 For a given value of $V_c$, sweep $V_b$ from $0$ to $1.0$~V.
 \begin{verbatim}
-devsim bjt_circuit3.py 0.0 &> data/vc_0.0.out
+python bjt_circuit3.py 0.0 &> data/vc_0.0.out
 \end{verbatim}
 
 \subsubsection{$V_e$ sweep}
 For a given value of $V_c$, sweep $V_e$ from $0$ to $-1.0$~V.
 \begin{verbatim}
-devsim bjt_circuit4.py 0.0 &> data/ve_0.0.out
+python bjt_circuit4.py 0.0 &> data/ve_0.0.out
 \end{verbatim}
 
 \subsubsection{Small-signal ac sweep}
 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.
 \begin{verbatim}
-devsim bjt_circuit5.py 0.0 1e3 1e11 3 &> data/ssac_0.0.out
+python bjt_circuit5.py 0.0 1e3 1e11 3 &> data/ssac_0.0.out
 \end{verbatim}
 
 \subsection{Visualization}

simdir/README.md

@@ -0,0 +1 @@
+See the ``doc/bjtexample.pdf`` for information about the simulation scripts in this directory.

simdir/physics/ramp2.py

@@ -94,7 +94,7 @@ def rampbias(device, contact, end_bias, step_size, min_step, max_iter, rel_error
         try:
             devsim.solve(type="dc", absolute_error=abs_error, relative_error=rel_error, maximum_iterations=max_iter)
         except devsim.error as msg:
-            if msg[0].find("Convergence failure") != 0:
+            if str(msg).find("Convergence failure") != 0:
                 raise
             devsim.set_parameter(device=device, name=GetContactBiasName(contact), value=last_bias)
             step_size *= 0.5

simdir/setup_dd.py

@@ -18,7 +18,6 @@
 def run(device, region):
 
     # this is our solution variable
-    CreateSolution(device, region, "Potential")
     CreateSolution(device, region, "Electrons")
     CreateSolution(device, region, "Holes")