Photoluminescence from very thin and partially-strained Si1-xGex layers grown on Si substrates was measured, where x ranged from 0.2 to 0.5. Various degrees of strain relaxation were present. Photoluminescence lines (D lines) were observed which arose from dislocations in the SiGe/Si system. No D lines were found to originate from the SiGe layers. By means of transmission electron microscopy, the origin of the D lines was identified as being threading dislocations, in the Si substrates, which extended from the SiGe/Si interface. Luminescence from dislocations in the Si substrates thus predominated over that from those in the SiGe layers.

H.Lee, S.H.Choi, T.Y.Seong: Applied Physics Letters, 1997, 71[26], 3823-5