Strain relaxation and surface morphology of compositionally graded Si/Si_1-xGe_x buffers

Systematic studies of strain relaxation were performed in a series of compositionally graded SiGe buffer layers grown without and with a subsequent constant composition SiGe layer by x-ray reciprocal space mapping techniques. The analysis of these experiments yields depth dependent strain values as well as misfit dislocation densities. The higher the grading rate (%Ge/μm) the higher the residual in-plane strain at the epitaxial surface. Atomic force microscopy studies show that the rms surface roughness increases systematically with increasing final Ge content of the graded layers and rises with increasing grading rate.© 1998 American Vacuum Society.