MSE 460: Electronic Materials and Processing I mselogo.gif

Problem set #7; assigned March 9
  1. For the two-level system described in section 4.3.2, make a plot of the chemical potential Dm as a function of f, the quasi-equilibrium occupation function for photons. Use E=1 eV and kBT=0.026 eV.
  2. Eq. 4.44 describes the absorption coefficient of a semiconductor with a direct band-gap. Use the data in Fig. 4.6 to estimate appropriate values of Eg and a0 to describe the absorption coefficient of GaAs. Then use these parameter to calculate the coefficient Brad for GaAs using Eq. 4.58. This "semiconductor archive" is a convenient place to find parameters for semiconductors. You can do the integral numerically if you prefer. Use the room temperature value for kBT.
  3. Consider what happens when intrinsic Si is photoexcited so that the photoexcited carrier density is large compared to the intrinsic carrier density. Assume that Auger recombination dominates and that the generation rate of carriers is uniform. Derive an equation that relates the steady-state carrier concentration to the generation rate. Your answer will be in terms of the coefficients An and Ap given in section 4.5.4.
  4. If the product of the cross-section and areal density of traps is equal to 1, what do you expect for the surface recombination velocity of p-type Si?


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On 09 Mar 2009, 09:28.