Laboratory-based Characterization of Heteroepitaxial Structures: Advanced Experiments Not Needing Synchrotron Radiation

It is demonstrated that a complex X-ray characterization of semiconductor films epitaxially grown on metal oxide buffer layers and Si(111) substrates is possible using laboratory-based equipment. This is demonstrated with epi-Germanium on Pr2O3 as buffer material. Pole figure measurements prove that epi-Ge layers grow nearly completely single crystalline with exactly the same in-plane orientation (type A) as the Si(111) substrate, while the lattice of the oxide layer is 180 [111] surface normal (type B). Only a small fraction (less than 0.6 vol. %) of the epi-Ge exhibits type B rotation twins. The main structural defects are micro twin lamellas lying in {111} planes 70.5 inclined to the wafer surface. The different in-plane orientation of Si substrate and epi-Ge on one side and the Pr2O3 buffer layer on the other side allows a very sensitive analysis of strain and defects even for a 10 nm thick oxide layer buried under some hundred nm of Ge. The epi-Ge layers are nearly fully relaxed and the Pr2O3 buffer layer is compressively strained. Due to the existing defects the Ge (111) netplanes are tilted in a characteristic pattern relative to the Si substrate.