Abstract
SiGe quantum wire (QWR) structures grown by gas source molecular beam epitaxy have been characterized by cathodoluminescence (CL) imaging and spectroscopy. At T≊5 K, the CL spectra obtained with a focused beam contain SiGe luminescence features associated with electron-hole plasma recombination. When the electron beam is defocused three separate SiGe no-phonon luminescence features and their transverse optic phonon replicas are observed. These features are related to recombination in the SiGe (100) quantum wells (QWs), SiGe (111) QWs, and the SiGe QWRs. The high generation rates associated with the focused electron beam quenches the luminescence and results in electron-hole plasma recombination in the adjacent SiGe (100) QWs, and saturation of the radiative processes. Defocusing the electron beam reduces the injection level and nonradiative processes, enabling the SiGe bound exciton features to be observed. Monochromatic CL imaging of the SiGe (100) QWs show that at low temperatures the CL image is broadened by exciton diffusion and becomes sharper at higher temperatures (T=50–70 K) reflecting nonexcitonic recombination.
Published Version
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