In situ relaxed Si1−xGex epitaxial layers with low threading dislocation densities grown on compliant Si-on-insulator substrates

High quality relaxed ${\mathrm{Si}}_{\mathrm{0.6}}{\mathrm{Ge}}_{\mathrm{0.4}}$ films as thick as 1.0 μm have been achieved as grown on silicon-on-insulator (SOI) substrates with 200 Å Si(100)-oriented compliant substrates. This represents the thickest relaxed layers grown by this technique. A greater than five order of magnitude reduction in threading dislocation density was achieved by compliant growth compared to growth on unmodified Si(100) substrates. Additionally, for the first time (to the best of our knowledge) we show that it is not necessary to separate the growth and relaxation processes, and relaxation during growth is governed by the nature of the compliant substrate structure that causes dislocations to terminate at the unique crystalline-amorphous ${\mathrm{SiO}}_{\mathrm{2}}$ interface. Results indicate that utilizing SOI as a compliant substrate which is effective in producing high quality ${\mathrm{Si}}_{\text{1−x}}{\mathrm{Ge}}_x$ films can be extended to other films, where film relaxation (via dislocation nucleation and growth) cannot be conveniently separated from the synthesis method (e.g., SiC).