DETERMINATION OF DIFFUSION-COEFFICIENTS IN DEGENERATE ELECTRON-GAS USING MONTE-CARLO SIMULATION

We propose a method for determining diffusion coefficients in degenera te semiconductors from an ensemble Monte Carlo simulation. The basic i dea is that what is relevant for this problem is not the whole electro n distribution function, but its perturbation in response to an additi on of ''excess carriers.'' Starting from the Boltzmann transport equat ion, we derive the equation of evolution for this ''excess electron di stribution function.'' Pie propose an interpretation in terms of scatt ering events suffered by particles, allowing one to solve the problem by Monte Carlo simulation. We simulate two sets of carriers, coupled b y an ''exchange scattering'' mechanism which is properly defined. The first set represents the uniform background density in the semiconduct or, whereas the second one represents the excess carriers. Only the la tter is used for calculating diffusion coefficients. This method is ap plied to a highly degenerate two-dimensional electron gas in a doped G aAs quantum well. The diffusivity-field characteristics are calculated and discussed. (C) 1997 American Institute of Physics.