6.26
Here, we consider n-type germanium which is to be used in a Haynes-Shockley experiment.
See figure 6.11 in the text.
Sample length == L = 1 cm, V1 = 2.5 V, Lab = .75 cm.
Carrier injection occurs at A and arrives at B 160 u sec later. Pulse width is 75.5 u sec.
Solve for hole mobility == Up, and the diffusion constant of holes == Dp.
Given the distance from A to B, the electric field strength in the germanium, and the time at which the peak of the carrier distribution reaches B, we can approximate the hole mobility according to equation 6.79. The values given in the problem yield a hole mobility of 1875 cm2/V-s.
I tried my best to puzzle out the equation 6.81 was assembled, but couldn't quite work it out. So on blind faith, I just applied it. According to this approximation, Dp = 48.9 cm2/s.
According to the Einstein relation, D/u = kT/q = 25.9 meV. It seems that the approximations do hold, because the ratio of Dp/Up = 26.0 meV.
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