Substrate engineering by hydrogen or helium implantation for epitaxial growth of lattice mismatched Si/sub 1-x/Ge/sub x/ films on silicon

Abstract

Strain relaxed Si/sub 1-x/Ge/sub x/ layers on Si[100] are used as virtual substrates for the growth of, for example, Si/Si/sub 1-x/Ge/sub x/ quantum well structures. We investigated the effects of He/sup +/ ion implantation and subsequent annealing on pseudomorphic Si/sub 1-x/Ge/sub x//Si[100] heterostructures grown by molecular beam epitaxy (MBE). A narrow defect band was generated by ion implantation slightly underneath the interface inducing the formation of strain relieving misfit dislocations during subsequent thermal annealing. Nearly complete strain relaxation of Si/sub 1-x/Ge/sub x/ layers with Ge fractions up to 30 at.% was obtained at temperatures as low as 850/spl deg/C and the samples appeared free of threading dislocations within the SiGe layer to the limit of transmission cross-sectional electron microscopy. We thus have developed a method for producing high-quality, thin, relaxed Si/sub 1-x/Ge/sub x/ films on Si[100] with threading dislocation densities below 10/sup 7/ cm/sup -2/ by standard techniques as molecular beam epitaxy and ion implantation. The heterostructures were analyzed using X-ray diffraction, Rutherford backscattering/channeling spectrometry and transmission electron microscopy.