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 are nearly 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° rotated around the [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 microtwin lamellas lying in {111} planes 70.5° inclined to the wafer surface. The different in-plane orientation of the 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 oxide layer buried under a 100-nm 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) planes are tilted in a characteristic pattern relative to the Si substrate.

Efficient algorithms for the simulation of strained heteroepitaxial growth with intermixing in 2+1 dimensions are presented. The first of these algorithms is an extension of the energy localization method [T. P. Schulze and P. Smereka, An energy localization principle and its application to fast kinetic Monte Carlo simulation of heteroepitaxial growth, J. Mech. Phys. Sol., 3 (2009), 521-538] from 1+1 to 2+1 dimensions. Two approximations of this basic algorithm are then introduced, one of which treats adatoms in a more efficient manner, while the other makes use of an approximation of the change in elastic energy in terms of local elastic energy density. In both cases, it is demonstrated that a reasonable level of fidelity is achieved. Results are presented showing how the film morphology is affected by misfit and deposition rate. In addition, simulations of stacked quantum dots are also presented.

Heteroepitaxy of hexagonal symmetry materials is more complicated than in the more usual case of cubic systems. In the growth of layers on the (0001) surfaces, the misfit dislocations always exhibit a screw component that leads to rotation of the epilayer in a 3 dimensional growth mode. The size of the islands will depend on many factors among which the substrate surface treatment, prior to growth, may be a predominant one. In this work, a comparative study is carried out for samples grown on plasma treated samples, with and without additional substrate annealing prior to epitaxy. It is found that the defect density can be brought below 109 cm−2, which is better than one order of magnitude in comparison to the layers grown on sapphire substrates. On top of the annealed substrates, the island growth is not obvious. Whereas, misorientations as large as a few degrees can be measured inside the layers on top of non annealed substrates, justifying the occurrence of high densities of threading dislocations.

The (1 0 0) face of γ-LiAlO2 has attracted attention as a possible substrate for GaN epitaxial growth. This is partly because this face has an excellent lattice and structural match to (1 0 0) GaN. This orientation would have a misfit of only −1.4% along the c-direction and −0.1% along the b-direction of LiAlO2. We find that in practice this orientation relationship does not occur; instead, (0 0 0 1) oriented GaN grows with a small tilt (0.6° towards the c-direction) between the film and substrate. Although the misfit along the substrate b direction is large (−6.3%) for this orientation, the tilt perfectly accommodates the −1.4% misfit in the c direction. We present characterization of these films by RHEED, X-ray diffraction, and TEM. We propose that the tilt is driven by a reduction of interface energy which occurs in polar, incoherent interfaces.