Posted by Steve Simon on February 24, 2014, 10:14 am, in reply to "Re: Holes"
Ah right. If n >> p, then to a good approximation the number of charge carriers is just n and you can say that the charge carrier is the electron. (The p's don't do much). Similarly, if p >> n, then to a good approximation, the number of charge carriers is p, and the charge carrier is the hole.
If you are so unlucky as to have n and p about the same size, then you really have to say that you have both electrons and holes carrying charge. I think if I had to define a number of charge carriers it would be n+p, but this number by itself maybe isn't so useful. For example, the conductivity in zero B field would be
sigma = n e^2 tau_e / m_e + p e^2 tau_h / m_h
the sum of the contribution from electrons and holes. But the pieces are weighted with the effective masses and scattering times, so just knowing (n+p) isn't enough.
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