Challenges of high Ge content silicon germanium structures

High germanium content silicon germanium (SiGe) structures are of special importance for future silicon based microelectronics. The lattice mismatch of more than 1% causes large elastic strain, the energy of which increases with the square of the strain. This high strain energy does not allow a straight continuation of the growth and science of pseudomorphic SiGe as in the existing very successful heterobipolar transistor technology. This paper overviews three different strategies to overcome the barrier connected with lattice mismatched hard, covalent bound material couples. These strategies utilize at least one of the ingredients: metastable growth, strain adjustment and corrugated surface morphology. Impact on resonance phase operation of transistors, on the high performance symmetrical CMOS and on self-aligned quantum dot formation is shown. # 2003 Elsevier B.V. All rights reserved