Running a Simulation

Running

Press Run Simulation, and then two or three windows appear. What matters afterwards is knowing where the solver tells you whether to believe the result.

01Before it solves

Run Simulation first reads the table and the settings panels. Anything it cannot make sense of stops the run with a message naming the row and the field — a thickness that is not a number, a substrate row carrying both dopings, a rear contact voltage given in two places at once. Nothing is solved until the structure is complete, so an error here costs you no time.

02What opens

A normal solve opens two windows:

• Band Diagram — the bands and carrier profiles, with the individual traces switchable. Carrier densities start on a linear scale; Log scale: carriers switches them. See The Plot Window.
• Model Results — the numbers, in four tabs: Electrostatics, Boundary Conditions, Layer Transport and Derived. See The Results Window.

If Find Quantised States is ticked, the bound-state results follow in a window of their own. All of these are separate from the main window and stay open while you edit, but a fresh solve redraws them in place rather than opening new ones alongside.

03Did it converge?

This is the one thing to check every time, and it is the third row of the Electrostatics tab:

Solution converged           Yes
Iterations (used / limit)   10 / 1000

A converged solution is one where the electrostatics settled. Most do so in ten or twenty iterations out of the thousand allowed, so a healthy run leaves the count nowhere near the limit — which makes a failure unmistakable. If it did not settle, the row reads No — reached iteration limit with the count sitting at 1000.

Treat everything else in both windows as unreliable at that point. The plot is still drawn, and it still looks like a band diagram.

04If it says no

Check the structure before the settings. The solver already retries on its own — when a direct attempt fails it starts from flat bands and walks to the target in steps, without telling you — so a failure has usually survived more than one strategy.

By far the most common cause is asking for something outside a zero-current model rather than anything numerical: a junction biased into forward conduction, or two contacts of the same type with a voltage between them. Both are real currents, and this solver holds current at zero by construction. If a warning appeared when you pressed the button, read it — it is usually describing exactly this.

05C–V takes a different route

With CV calculation ticked, the run button does something else. You are asked for the sweep range first, then a progress bar works through the bias points — it has a Stop button, and a long sweep is the one place in EpiSolve where you may want it.

What follows is the capacitance plot and its own results window. The ordinary plot, results and bound-state windows do not appear — a C–V run gives you C–V outputs and nothing else. See Capacitance–Voltage.

Because of that, it is worth running the structure once with CV calculation unticked before you sweep it. That gives you the equilibrium band diagram and the convergence check described above, on the same structure, in a couple of seconds — and a structure that will not solve at equilibrium is not going to give you a meaningful capacitance curve either.