An optical technique was used to measure local variations in minority carrier diffusion length associated with dislocation networks in ordered GaInP. Two-dimensional images of the luminescence resulting from carrier generation along a line source were obtained using an optical microscope coupled to a scanning electron microscope. Minority carrier diffusion lengths were determined from the spatial distribution of the recombination luminescence. The use of double heterostructures of AlGaInP/GaInP/AlGaInP restricts diffusion to the plane of the epilayer. Because the technique offers high spatial resolution, it was possible to measure variations in carrier transport associated with the dislocation bands produced due to lattice mismatch with the substrate. Minority carrier diffusion lengths were correlated to the intensity fluctuations commonly observed in cathodoluminescence across several light and dark bands. In multiple regions of the sample, increased cathodoluminescence intensity occurred in areas of decreased diffusion length. Modelling showed that increased luminescence intensity could correspond to regions of decreased effective minority carrier lifetime, due to the combined effect of variations in non-radiative and radiative recombination rates.

Imaging Charge Transport and Dislocation Networks in Ordered GaInP. N.M.Haegel, S.E.Williams, C.Frenzen, C.Scandrett: Physica B, 2009, 404[23-24], 4963-6