Circularly polarized luminescence microscopy for the imaging of charge and spin diffusion in semiconductors

Room temperature electronic diffusion is studied in 3 μm 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 both the charge (L) and spin (L _s) diffusion lengths simultaneously. The measured values of L and L_s are in excellent agreement with the spatially averaged polarization and a sharp reduction in these two quantities (L from 21.3 to 1.2 μm and L_s from 1.3 to 0.8 μm) is found with increasing surface recombination velocity. Outward diffusion results in a factor of 10 increase in the polarization at the excitation spot. The range of materials to which the technique can be applied, as well as a comparison with other existing methods for the measurement of spin diffusion, is discussed.