STRAIN RELAXATION OF GE1-XSIX BUFFER SYSTEMS GROWN ON GE(001)

We have investigated the strain relaxation behavior of biaxial tensile strained Ge1-xSix buffer systems grown on Ge (001) by a high-resoluti on x-ray reciprocal space mapping technique. The molecular beam epitax y grown structures contain a linearly graded buffer, followed by a uni form buffer and a modulation-doped heterostructure with a high mobilit y two-dimensional hole gas in a Ge channel. Our quantitative measureme nts of the in-plane strain show that the lower part of the graded buff er is completely strain relaxed, while the top part of this region and the uniform alloy buffer are partly strain relaxed showing a linear i ncrease of strain towards to surface. (C) 1995 American Institute of P hysics.