Origin of dislocation-related photoluminescence bands in very thin silicon-germanium layers grown on silicon substrates

We measured the photoluminescence spectra of very thin and partially strained Si1-xGex (0.2 less than or equal to x less than or equal to 0.5) layers grown on silicon substrates with varying degrees of strain relaxation. We observed photoluminescence lines, so-called D lines, which arise from dislocations in the Si1-xGex/Si alloys. Surprisingly, we observed no D lines originating from the Si1-xGex layers. We identify the origin of the D lines as the penetrated dislocations in the Si substrates extending from the SiGe/Si interface with the assistance of transmission electron microscopy. We discuss possible mechanisms of the dominance of luminescence from the dislocations in the Si substrates over those in the SiGe layers. (C) 1997 American Institute of Physics. [S0003-6951(97)00552-4].