Influence of radiative recombination on the minority-carrier transport in direct band-gap semiconductors

Abstract

When radiative (band to band) lifetimes and nonradiative (multiphonon via flaws) lifetimes become comparable, as is the case for GaAs, the customary diffusion equation for minority carriers under low level injection conditions must be augmented by terms originating from photon transport. Using the generalized van Roosbroeck–Shockley relation between absorption and emission as well as radiative transfer theory, the relevant equations for free carrier transport are derived. Subsequently, it is shown that the influence of the reabsorbed recombination radiation on carrier transport while unimportant at low doping levels becomes important for n-type GaAs at high doping levels. We also determine the external luminescence flux taking due account of multiple emission and absorption events inside the sample.