DIRECT MEASUREMENT OF PHOTOLUMINESCENCE SPATIAL-DISTRIBUTION NEAR THEGAAS ALGAAS QUANTUM-WELL EDGE USING A SCANNING NEAR-FIELD OPTICAL MICROSCOPE/

Spatial distribution of photoluminescence (PL) from quantum well semic onductor structures was studied. The structures containing active laye r of GaAs (10 nm) surrounded with 25 nm Al0.42Ga0.58As barrier layers were grown by MBE on GaAs substrate. The wet etching process was used to prepare wire structures of the active layer with different wire wid th. The scanning near-field optical microscope (SNOM) with shear-force feedback was used to scan the surface topography with simultaneous sp ectra storage for each surface Feint. The tapered optical fiber with A l-coated tip (aperture size less than 0.3-0.4 mu m) was used. The tip was used both for the sample illumination and PL light collection. A l iquid-nitrogen-cooled CCD-camera was used to detect the spectra. PL sp ectrum evolution across the wires direction was stored. The 1hh-le ban d peak in PL spectrum can be clearly seen with maximal intensity in th e middle of the wire. The carrier diffusion model with the same model parameters for all structure sizes can quantitatively describe the obt ained distribution of PL signal. We have assumed in the model that the re is a dead region at the sidewalls. The diffusion length remains the only fitting parameter of the model, and the best fit values were fou nd. (C) 1998 Published by Elsevier Science B.V. All rights reserved.