Imaging charge and spin diffusion of minority carriers in GaAs

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Room temperature electronic diffusion is studied in 3 mum thick epitaxial p+ GaAs lift-off films using a novel circularly polarized photoluminescence microscope. The method is equivalent to using a standard optical microscope and provides a contactless means to measure charge (L) and spin (Lₛ) diffusion lengths. The measured values of L and Lₛ are in excellent agreement with the spatially averaged polarization and a sharp reduction in these two quantities (L from 21.3 mum to 1.2 mum and Lₛ from 1.3 mum to 0.8 mum) is measured with increasing surface recombination. Outwards diffusion results in a factor of 10 increase in the polarization at the excitation spot.