Highly nonlinear defect-induced carrier recombination rates in semiconductors

Defects in semiconductors can induce recombination of carriers and thus can strongly influence the efficiency and performance of solid-state devices. In the analysis of device performance, defect-induced recombination is often assumed to depend linearly on the carrier concentration or to be given by a sum of Shockley-Read-Hall expressions taken independently for each known defect level. Under these assumptions, defect-induced recombination increases with carrier concentration more slowly than both band-to-band radiative recombination and Auger recombination and becomes relatively less important at higher carrier concentrations. However, we show that defects with multiple defect levels can induce recombination with a highly nonlinear dependence on carrier concentration. For such defects, the usual assumptions about the relative importance of different recombination mechanisms at different carrier concentrations may fail. In order to demonstrate the potential impact of this phenomenon on realistic devices, we incorporate the defect-induced recombination rates obtained from our analysis into a microscopic InGaN/GaN light-emitting diode (LED) model. Our results indicate that a particular class of defects with plausible properties can induce a loss of optical efficiency at carrier concentrations relevant for high-power LED operation. © 2013 AIP Publishing LLC.