A near-field scanning optical microscopy study of the uniformity of GaAs surface passivation

We have achieved spatially resolved photoluminescence (PL) from metalorganic vapor phase epitaxy (MOVPE) grown GaAs surfaces by near-field scanning optical microscopy (NSOM). We have performed the topography, reflection, and PL measurements by NSOM combined with the topography measurements by atomic force microscopy (AFM) on the as-grown and (NH4)(2)S-passivated GaAs samples. The uniformity of GaAs with a thin Al0.65Ga0.35As cap layer has also been studied and compared with the (NH4)(2)PS treated samples. We found the submicron scale variations in PL intensity which were not correlated to the topographic features. The PL intensity variation was related to the changes in the surface state density. Semiquantitative analyses of the resolution limits of NSOM-based PL measurements and surface state variations are presented. (C) 1996 American Institute of Physics.