ABSTRACT
Fully relaxed, linearly graded Si1-x,Gex, virtual substrates (VS) have been grown by low-energy plasma-enhanced chemical vapour deposition (LEPECVD) in the concentration range between x=0.4 and x=l. High resolution transmission electron microscopy inspection of the dislocation structure in LEPECVD-grown VSs has been carried out in order to obtain additional information on optimising growth parameters and post-growth annealing. It has also been shown that island growth is not self-limiting and that islands continue to grow larger with increasing layer thickness or annealing above 750°C. A significant lowering of the threading dislocation (TD) density has resulted from the concept of graded buffer layer growth, first demonstrated by molecular beam epitaxy. This concept has been applied to the method of LEPECVD. Plastic relaxation by the nucleation of misfit dislocation is generally characterised by the presence of TDs, one of which is attached to opposite sides of each misfit segment.
