Semiconductor Physics and Devices, Neamen, 6.28

6.28
Plot excess carrier distribution versus x and t when Eo = 0 and when Eo != 0.



Figure 1: Excess Carrier Distribution in Intrinsic Gaas, Eo = 0 V/cm, Infinite carrier lifetime.
The amplitude of carrier distribution in Figure 2 is different from Figure 1 because GaAs and Si different diffusision coefficients.
Figure 2: Excess Carrier Distribution in Intrinsic Si, Eo = 0 V/cm, Infinite carrier lifetime.

Figure 3: Excess Carrier Distribution in Intrinsic Gaas, Eo = 10 V/cm, Infinite carrier lifetime.

Figure 4: Excess Carrier Distribution in Intrinsic Si, Eo = 10 V/cm, Infinite carrier lifetime.
Is is rotated differently from the rest of the plots because the other view looked too similar to Eo = 0, because of the lower mobility of Si.

Reviewing Laplace Transforms, Cauchy-Reimann conditions

Ok, I saw this discussed in both Truxal and in Ogata, so it must be worth working to understand it. Be aware that much of this article will contain language very close to that used by Truxal and by Ogata. So, don't quote me.

In order for functions in the complex plane to be useful to us engineers, the function must be"analytic." This means that the derivative of the function must be unique.

Points at which complex functions are not analytic are called "singular." These include zeroes and poles. Think about a zero on a surface in the s-plane.
Delta s can approach the zero from any direction. The derivative could parallel to the real axis, by letting omega be constant and letting delta sigma approach zero, or parallel to the imaginary axis by letting sigma be constant and letting delta omega approach zero.

Semiconductor Physics and Devices, Neamen 6.26

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.

First Post

When I sit down to study, I find that I have a hard time concentrating. I get distracted and end up surfing the internet. If I sit at the dining table, away from the computer, then I get sleepy. If I try to sit in the TV room, the distraction is even worse.

So, I figure, that if I use the computer to record my approaches to my studies, then maybe I'll be able to focus better while sitting at my desk. This way, I'll be using my computer for studying instead of leaving my mind to wander.

If there are many subsequent posts, then I guess it worked. If not, then probably I got distracted again and reverted to old habits.