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Anonymous

Two functions in graphs?

So when I’m running the simulations, on all of my graphs, I’m getting two functions. A red one, and a blue one. Which of these two functions is the proper one to use? For instance, when looking at the Electric Field plot (at equilibrium), the tool displays both a red function and a blue function that are not the same. They have slightly different values. So if I am trying to use the data for calculations, which function should I use?

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    Michael McLennan

    If you mouse over the red curves, you’ll notice that they are labeled “DA” or “Depletion Approximation.” This is the solution that you would get with an analytical approximation of the device physics. If you read a textbook description of a PN junction, for example, they usually refer to the depletion approximation, which assumes that the depletion of carriers around the PN junction is constant and abruptly stops (square shape). You can see this, for example, in the very square shape of the red curve on the “Net Charge Density (at Equilibrium)” plot.

    The blue curve is the actual solution that you get from solving the equations with no such approximation. It is the more accurate of the two, so you should focus on that.

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