Show that the electric field term dominates over the diffusion term in (5.8.10) in a typical situation. Compute D using ¯v given by the root-mean-squared speed of electrons in a Maxwell–Boltzmann distribution at room temperature and a constant scattering time of τ = 10⁻¹¹s, and assume the carrier density drops by a factor of two over a distance of 100 μm. Over the same distance there is a voltage drop of 1 V. Compare the diffusion velocity and the drift velocity terms in (5.8.10) under these circumstances.

v=-D Vn - n +-F. m (5.8.10)