Structural characterisation and stability of Si1-xGex/Si(100) heterostructures grown by molecular beam epitaxy

In the last few years the research efforts have been addressed to relaxed S i1-xGex buffer layers on Si substrate reported to as 'virtual substrates'. This paper focuses on the relaxation mechanism of Si1-xGex/Si(1 0 0) hetero structures grown by solid source molecular beam epitaxy. On this purpose. w e have grown samples with different Ge concentrations (0.035 <x <0.34) and thicknesses (32-475 nm). By comparing unrelaxed samples grown at 350 degree sC, 450 degreesC and 550 degreesC and processed with isochronal post-growth thermal annealing, we found a subsequent higher dislocation density in the low growth temperature samples, caused by the thermal treatment. We attrib ute this peculiar behaviour to the interaction between point defects and di slocations which promotes the climb mechanism of dislocation dynamics and w hich reduces the activation energy for the relaxation. (C) 2001 Elsevier Sc ience B.V. All rights reserved.