The relaxation of mobile space charge in solids

Abstract

AbstractThe system of differential equations governing the relaxation of free space charge in semiconductors and in insulators with trapped space charge is discussed neglecting diffusion. In both cases general solutions can be given if symmetrical initial distributions are considered. They are of the form magnified image respectively, where δp is the free space charge, ξ the space coordinate, t the time, t the dielectric relaxation time, t the relaxation time of electrons in p‐type semiconductors under complete hole extraction. In the case of small disturbance δp≪p0 at any place an exponential decay with t occurs (dielectric relaxation). In the case of large disturbance δp≫p0 within t the space charge is steeply reduced tot he regime of small disturbance, decaying further exponentially with t. The propagation velocity of steep space charge gradients is initially proportional to the central charge concentration and decays (dielectric relaxation) or grows exponentially with the constant t or t.