there is such an equation pn = ni^2 exp(Va/Vt) in junction given in textbook. I am wondering how true it is against other equations. suppose Va is zero,
pn = ni^2 exp(Va/Vt) => pn = ni^2
at same time p is p(0)= Ni^2/Nd, and n(0) = Ni^2/Na,
so p(0) x n(0) = Ni^4/NaNd, and is supposed to equal ni^2, that would lead
Ni^4/NaNd = Ni^2 => NaNd = Ni^2.
But this Na and Nd, they are the dopant of p and n junction, their product doesn't equal to Ni^2.
First, let me warn you that I'm not an engineer nor a student -- all I've got is this library book called "Microelectronic Devices and Circuits" by Clifton G. Fonstad, so I could be very very wrong, but are you sure about this line:
For a p-n junction wouldn't there be two different expressions for n_0 and p_0, one for each side of the junction? In other words, if you had a p-n junction (fixed-width font like Courier required):
Then I think if you multiply them together you get ni^2 in both cases.
But I dunno... I'm just trying to learn this stuff myself, and a lot of it is barely making sense. Maybe somebody who actually knows what he's talking about can give you a better (correct) answer.
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