electron mobility

Assume that the mobility of electronics in silicon at T=300K is MUn=1300cm^2/V-s. Also assume that the mobility is limited by latice scattering and varies as T^-(3/2). Determine electron mobility at (a) T=200K and (b) T=400K. (There are numerous graphs in the book and no formulas that I could find to help solve this problem. I tried extrapolating the information from one of the graphs but I couldn't get anywhere. How do I solve this problem?)

Quasi Fermi Level

I'm having trouble getting the answer the back of the book does after trying to calculate the quasi fermi level. The book gets Efn-Efi=.3498eV; Efi-Efp=.2877eV Q. An n-type silicon sample with Nd=10^16cm-3 is steadily illuminated such that g'=10^21cm-s^-1. If tn0=tp0=10^-6s, calculate the position of the quasi-Fermi levels for electrons and holes with respect to the intrinsic level (assume that ni=1.5x10^10cm^-3) I am trying to use Efn-Efi=kt*ln((no+deltan)/ni) ... however, the problem I'm having is with no + delta n over ni. Is no=nd=10^16? If so, then what is the excess delta n? I thought tn0*g' would give me delta n, but this does not reflect the correct answer in the b... click for more

Excess carrier concentrations and diffusion current density

Consider a bar of p-Si that is homogeneously doped to a value of 3x10^15 at T=300K. The applied electric field is zero. A light source is incident on the end of the semiconductor. The excess-carrier concentration generated at x=0 is deltap(0)=deltan(0)=10^13/cm^3. Neglect surface effects. Mun=1200/cm^2/Vs. Mup=400/cm^2/Vs. Taun=5*10^-7s. Taup=10^-7s. (a) Calculate the steady state excess electron and hole concentrations as a function of distance into the semiconductor. (b) Calculate the diffusion current density as a function of x. What are the solutions, and how did you get them? Thanks

mobility and transit time

Consider the 2.0micrometer long GaAs device where the E-field is 5kV/cm and Mn*=.067M0. (a) Calculate the transit time of an electron through the device if the mobility is 8000 cm^2V-s. (b) The mean free path of an electron (average velocity x scattering time) is the average distance an electron travels between two consecutive scattering events. Calculate the mean free path of a GaAs electron at room temperature. (c) How does the mobility of a semiconductor depend on T? and why? How did you do it, and what are the answers? Thank you.

Angles of twist

Two thin-walled circular tubes, one having a seamless section, the other a split section(see attachment), are subjected to the action of identical twisting moments. Both tubes have equal outer diameter "Do", inner diameter "Di", and thickness "t". Determine the ration of their angles of twist.