Effects of Space Charge on Mobility, Diffusion, and Recombination of Minority Carriers

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Abstract
A computer has been used to solve the coupled nonlinear equations, including space charge, that govern the motion of pulses of minority carriers in semiconductors. The advantages of using the computer are that one does not have to assume space‐charge neutrality, and one can treat drift, diffusion, and recombination simultaneously. The use of a mass action recombination law enabled the calculation of the decrease of life‐time with increase in pulse size. The electric field due to a pulse of uncompensated minority carriers was found to decay initially with the dielectric relaxation time, but a small field distortion was found to persist. This space charge influenced the mobility and diffusion of minority carriers. It was found that the decrease in mobility with large pulse size was less severe than predicted by the conventional theory based on charge neutrality. There were indications that diffusion, in the presence of space charge, was also less than that predicted by conventional theory.