Using the excitation-dependent radiative efficiency to assess asymmetry in the defect-related density of states

Measurements of steady-state radiative efficiency versus photoexcitation rate probe the carrier-density-dependent competition between nonradiative and radiative mechanisms in semiconductors. Nonradiative recombination through defect levels is proportional to the product of defect level occupation and carrier density in the opposing band. Band-to-band radiative recombination scales with the product of band densities. The excitation rate required for defect level saturation establishes the effective density of participating defects. More subtle features in the changeover from defect-related to radiative-dominated recombination, and its temperature dependence, provide additional insight into the distribution of defect levels. In this letter, the authors consider the effect of asymmetry about the midgap. © 2007 American Institute of Physics. DOI: 10.1063/1.2709986