We explore theoretically the possibility of obtaining efficient light emiss
ion from Si-Ge semiconductor nano-onions. Our motivation stems from the str
ong luminescence recently observed from II-VI nano-onions, combined with th
e technological significance of the Si-Ge system. We calculate the electron
ic properties of a range of hypothetical Si-Ge nano-onions using the tight-
binding method and determine the combination of. size,; strain, and materia
ls which optimizes the production of visible luminescence. We predict that
small (less than around 30 Angstrom diameter) Si-covered Ge nano-onions wil
l be visible light emitters.