HIGH RESOLUTION TEM-CL FROM THE CROSS-SECTIONAL SPECIMENS OF GaAs/AlGaAs QWs

Abstract
One of the advantages of the scanning transmission electron microscope cathodoluminescence (STEM-CL) technique is its higher spatial resolution in comparison with CL performed in a scanning electron microscope (SEM-CL). Our studies of cross-sectional specimens of a GaAs/AlGaAs quantum well structure have clearly demonstrated this. We believe that it is the first time that STEM-CL has been applied successfully to an electron transparent cross-sectional specimen. The aim of this study was to investigate the effect of different growth sequences on QW luminescence and to compare the quality of the successive QW sets. CL spectra were obtained from the cross-sectional samples by directing the electron beam onto each of QWs in turn. We observed marked differences in these spectra. Monochromatic CL images were also generated and they revealed clearly resolved emission from each of the separate sets of QWs in the structure. A spatial resolution of about 50nm was achieved transverse to the QWs in the monochromatic images of this particular structure.