Synchrotron x-ray characterization of structural defects in epi-Ge/Pr2O3/Si(1 1 1) layer stacks

Epi-Ge/Pr2O3/Si(1 1 1) layer structures were studied by synchrotron grazing incidence diffraction to analyse the structural perfection of the top epi-Ge and the oxide buffer layer independently. The dominating features for the epi-Ge layer are pronounced streaks of diffuse scattering in the (1 1 1) directions that are caused by microtwins and stacking faults lying in the {1 1 1} glide planes 70.50 tilted to the wafer surface. It is confirmed that grains of type B orientation in the epi-Ge layer are located near the oxide-Ge interface only. The few nanometres thick Pr2O3 buffer layer shows similar streaks of diffuse scattering indicating a high concentration of structural defects in the tilted {1 1 1} planes. The relatively poor crystallographic quality of the oxide layer with an in-plane domain size of about 35 nm, a mosaicity of 0.70 and a strain variation of 0.8% is discussed as a possible reason for structural imperfections in the upper epi-Ge layer. Measurements on samples with different epi-Ge thicknesses show that the epi-Ge layer has no influence on the strain state of the Pr2O3 buffer layer.