Main scientific achievements
(after 1997)
- X-ray diffuse scattering (XDS) in semiconductor single crystals was studied using high
resolution diffractometry, both experimentally and theoretically. Correspondence between
technological processes (annealing) as well as the concentration of free electron carriers
and the characteristic images of XDS scattering was established. Using simulation method
defects with orthorhombic symmetry have been identified in GaAs crystals heavily doped
with tellurium. XDS was also used to study defects in multilayer structures: InAs,
InSb, GaSb on GaAs substrate.
- Magnetic ordering in EuTe/PbTe superlattices was studied using diffraction of thermal
neutrons. Both components are semiconductors and in helium temperatures they
practically become insulators. EuTe is antiferromagnetic with the Néel temperature TN
about 9.6 K. Stresses caused by misfit of the lattice constants and finite widths of the
layers (several to several tens of monolayers) lead to a substantial change in TN relative to
bulk EuTe. Neutron diffraction spectra show correlations between the ordering of
magnetic moments in subsequent EuTe layers, or the existence of magnetic interactions
between the layers.
- Antiferromagnetic coupling between ferromagnetic layers has been observed for the first
time in an all-semiconductor superlattice structure EuS/PbS by neutron scattering and
reflectivity measurements.
- In another ferromagnetic semiconductor system, GaMnAs/GaAs, neutron reflectivity
experiments revealed a long range ferromagnetic order despite the fact that Mn moments
are diluted and located randomly. A ferromagnetic interlayer exchange coupling in
GaMnAs/GaAs superlattices has been found by means of polarized neutron reflectivity
measurements.
- New structural model of the metastability of the EL2 center in GaAs has been proposed.
Results are based on reciprocal space mapping of diffuse X-ray scattering using
synchrotron radiation.
- High resolution x-ray diffraction and computer simulations have been applied to study of
anisotropy of strain relaxation in thin InxGa1-xN epilayers deposited on GaN sublayer
grown on sapphire. The biaxial (in-plane and out-of-plane) strain components and the
hydrostatic strain component in thick undoped and Si doped GaN layers have been
extracted.
- A parabolic curvature of the crystallization front of Si:Ge single crystals has been revealed
and studied by x-ray section topography with synchrotron-radiation.
- Dislocations in GdCa4O(BO3)3 single crystals grown by Czochralski method have been
revealed by x-ray diffraction topography.
- The microstructure of AlGaN MOCVD layers grown at low pressure has been studied by
high-resolution x-ray diffractometry.
- The weak (pseudo-forbidden) reflections have been used to study Be impurities in GaAs
layers and a theoretical model of Be atom locations in the crystal lattice has been
proposed.
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