In x-ray topographs of Si/Ge_xSi_1−x/Si(001) heterosystems, the intensity variations, which are associated with inhomogeneous GeSi thickness, are observed. The layers of GeSi and Si were grown by molecular beam epitaxy. The growth conditions preserving the pseudomorphic state of the intermediate SiGe layer from misfit dislocation appearance were kept. The topographs were recorded using a spherically bent monochromator as well as a flat one. The observed contrast peculiarities are established to be Moiré (translation fault) fringes. The displacement of interference fringes due to the crystal angular position variation is observed. For Pendellösung maxima, the dependence of their angular positions on nondiffracted layer thickness is established. The image simulated in the framework of semikinematical approach demonstrates the main contrast peculiarities observed in the topograph.

We present self-assembly of InAs/InAlAs quantum dots by the droplet epitaxy technique on vicinal GaAs(111)A substrates. The small miscut angle, while maintaining the symmetries imposed on the quantum dot from the surface, allows a fast growth rate thanks to the presence of preferential nucleation sites at the step edges. A 100 nm InAlAs metamorphic layer with In content $\ge$ 50% directly deposited on the GaAs substrate is already almost fully relaxed with a very flat surface. The quantum dots emit at the 1.3 μm telecom O-band with fine structure splitting as low as 16 μeV, thus making them suitable as photon sources in quantum communication networks using entangled photons.

We demonstrate the feasibility of growing GaAs nanomembranes on a plastically-relaxed Ge layer deposited on Si (111) by exploiting selective area epitaxy in MBE. Our results are compared to the case of the GaAs homoepitaxy to highlight the criticalities arising by switching to heteroepitaxy. We found that the nanomembranes evolution strongly depends on the chosen growth parameters as well as mask pattern. The selectivity of III-V material with respect to the SiO₂ mask can be obtained when the lifetime of Ga adatoms on SiO₂ is reduced, so that the diffusion length of adsorbed Ga is high enough to drive the Ga adatoms towards the etched slits. The best condition for a heteroepitaxial selective area epitaxy is obtained using a growth rate equal to 0.3 ML/s of GaAs, with a As BEP pressure of about 2.5 × 10⁻⁶ torr and a temperature of 600 °C.

This study provides new insight into the mechanisms governing solid state dewetting (SSD) in SiGe alloys and underscores the potential of this bottom-up technique for fabricating self-organized defect-free nanostructures for CMOS-compatible photonic and nanoimprint applications. In particular, we investigate the SSD of Si_1−xGe_x thin films grown by molecular beam epitaxy on silicon-on-insulator (SOI) substrates, focusing on and clarifying the interplay of dewetting dynamics, strain elastic relaxation, and SiGe/SOI interdiffusion. Samples were annealed at 820 °C, and their morphological and compositional evolution was tracked using atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy, considering different annealing time steps. A sequential process typical of the SiGe alloy has been identified, involving void nucleation, short finger formation, and ruptures of the fingers to form nanoislands. XRD and Raman data reveal strain relaxation and significant Si-Ge interdiffusion over time, with the Ge content decreasing from 29% to 20% due to mixing with the underlying SOI layer. EDX mapping confirms a Ge concentration gradient within the islands, with higher Ge content near the top.

We investigated a molecular beam epitaxy growth of GaAs nanocrystals on 4H-SiC(0001) substrates covered by ultra-thin oxide layer. Two growth approaches were explored: direct heteroepitaxy and droplet epitaxy. Under the standard GaAs homoepitaxy conditions, direct heteroepitaxy on SiC resulted in low-density, poorly oriented GaAs nanocrystals, likely due to limited interaction between the GaAs and the underlying crystalline SiC surface. In contrast, droplet epitaxy enabled better control over the nanocrystal density and their vertical alignment. By optimizing the arsenization conditions and the oxide layer thickness, self-catalyzed GaAs nanocrystals oriented along the [111] direction were achieved. These results highlight the potential of droplet epitaxy for the integration of vertically aligned III-V nanocrystals on SiC substrates, paving the way for future nanoscale photonic applications.