Nanoscopic measurements of surface recombination velocity and diffusion length in a semiconductor quantum well

We use a near-field microscopic technique to probe photoluminescence from the edge area of a quantum well. Near the edge, surface recombination gives rise to a gradual variation of the photoluminescence signal on a micrometer length scale. The overall shape in this transition region depends strongly on the excitation intensity. From solving two dimensional diffusion equations, we deduce the surface recombination velocity and the diffusion length. It is shown that the surface recombination velocity decreases with increasing intensity due to the saturation of nonradiative defect states.