Diffusion-driven and excitation-dependent recombination rate in blue InGaN/GaN quantum well structures

We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above similar to 5 x 10(18) cm(-3), a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses. (C) 2014 AIP Publishing LLC.