Strain in buried self-assembled SiGe wires studied by grazing-incidence x-ray diffraction

Abstract

For the calculation of strain fields of buried self-assembled SiGe wires in a SiGe/Si multilayer, an analytical model has been developed. It is applied for a simulation of the diffraction pattern from buried wires, which were investigated by grazing-incidence x-ray diffraction. The simulations are based on the distorted-wave Born approximation, and using the analytical approach for calculating the inhomogeneous elastic strain fields within the wires and in the surrounding Si matrix, computation times can be considerably decreased. In the measured reciprocal space maps, satellite intensity maxima indicate a good lateral and vertical correlation of the wire positions. Both from the grazing-incidence diffraction and from photoluminescence, an average Ge content in the wires of 20% is found, considerably lower than the deposited value of 45%. The resulting lateral maximum elastic relaxation of the wire lattice is about 85% on the top ridge.