CORRELATION BETWEEN OXYGEN DISTRIBUTION AND LUMINESCENCE EFFICIENCY IN SIGE SI LAYER STRUCTURES MEASURED BY CATHODOLUMINESCENCE IMAGING ANDSPECTROSCOPY/

SiGe layers and quantum wells grown on Si by low-pressure chemical vap our deposition (LPCVD) have been investigated by cathodoluminescence ( CL) imaging and spectroscopy. Monochromatic imaging of the shallow bou nd exciton luminescence from the SiGe layers showed that in some cases it was not uniform. Dark regions were observed with dimensions mainly in the range 100-200 mu m. As the density and size of these regions i ncreased, the overall luminescence efficiency decreased. In this paper we report an investigation of the possibility that oxygen incorporati on in the SiGe layer structures is responsible for the decrease in lum inescence efficiency. Luminescence systems created in Si by radiation damage, known to be associated with carbon-oxygen and carbon-carbon co mplexes, were used to investigate the depth and spatial distribution o f oxygen. A SiGe sample which contained a high density of dark regions was shown to have a high oxygen concentration close to the interface, either in the Si buffer layer or the substrate. Monochromatic CL imag es showed that the oxygen distribution was non-uniform, and that the a reas where the oxygen concentration increased could be correlated with the regions where the shallow bound exciton luminescence efficiency d ecreased. This implies that oxygen incorporation in the SiGe layers du ring growth creates the non-radiative regions.