An extended defect as a sensor for free carrier diffusion in a semiconductor

We use confocal photoluminescence microscopy to study carrier diffusion near an isolated extended defect (ED) in GaAs. We observe that the carrier diffusion length varies non-monotonically with carrier density, which we attribute to competition between point defects and the extended defect. High density laser illumination induces a permanent change in the structure of the extended defect, more significantly an apparent change in the effective polarity of the defect, and thus a drastic change in its range of influence. The inferred switch of principal diffusing species leads to a potential design consideration for high injection optoelectronic devices.