# 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.

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