Heterostructures of Si1-xGex/Si with Ge content x from 14 to 67%, grown on
Si by atmospheric pressure chemical vapor deposition (APCVD) at 650 or 700
degrees C, have been studied by photoluminescence (PL) spectroscopy, Normar
ski microscopy after Schimmel etching, atomic force microscopy (AFM) and se
condary ion mass spectroscopy (SIMS). For SiGe grown by APCVD with a low Ge
content (<40%), strain relaxation is achieved by misfit dislocation format
ion. For high Ge content (>40%), the relaxation mode is influenced by the d
eposition temperature, where the energetically most favorable mechanism wil
l dominate. Al 700 degrees C, the SiGe is relaxed by 3D island formation an
d the PL alloy band can be correlated to island structuring of the surface.
At 650 degrees C, the SiGe is relaxed by misfit dislocations due to the in
creased density of born-in point defects at low temperatures. (C) 2000 Else
vier Science S.A. All rights reserved.