Publications on the project |
045 X-ray diffraction analysis and scanning micro-Raman spectroscopy of structural irregularities and strains deep inside the multilayered InGaN/GaN heterostructure |
Authors: | V.V. Strelchuk, V.P. Kladko, E.A. Avramenko, O.F. Kolomys, N.V. Safryuk, R.V. Konakova, B.S. Yavich, M.Ya. Valakh, V.F. Machulin and A.E. Belyaev | |
Summary: | High resolution Xray diffraction analysis and scanning confocal Raman spectroscopy are used
to study the spatial distribution of strains in the InxGa1 – xN/GaN layers and structural quality of these layers
in a multilayered lightemitting diode structure produced by metal–organic chemical vapor deposition onto
(0001)oriented sapphire substrates. It is shown that elastic strains almost completely relax at the heteroint
erface between the thick GaN buffer layer and InxGa1 – xN/GaN buffer superlattice. It is established that the
GaN layers in the superlattice are in a stretched state, whereas the alloy layers are in a compressed state. In
magnitude, the stretching strains in the GaN layers are lower than the compressive strains in the InGaN lay
ers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a smaller number
of dislocations and the distribution of dislocations is more randomly disordered. In microRaman studies on
scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric
gradient distributions of strains and crystal imperfections of the epitaxial nitride layers along the direction of
growth. It is shown that the emission intensity of the InxGa1 – xN quantum well is considerably (more than
30 times) higher than the emission intensity of the GaN barrier layers, suggesting the high efficiency of trap
ping of charge carriers by the quantum well.
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Keywords: | Semiconductors, III nitrides, high resolution X-ray diffractometry | |
Edition: | Semiconductors | | | 2010,
1199-1210,English |
045 X-ray diffraction study of deformation state in InGaN/GaN multilayered structures |
Authors: | Kladko V.P., Kuchuk A.V., Safryuk N.V., Machulin V.F., Belyaev A.E., Konakova R.V., Yavich B.S. | |
Summary: | High resolution Xray diffraction analysis and scanning confocal Raman spectroscopy are used
to study the spatial distribution of strains in the InxGa1 – xN/GaN layers and structural quality of these layers
in a multilayered lightemitting diode structure produced by metal–organic chemical vapor deposition onto
(0001)oriented sapphire substrates. It is shown that elastic strains almost completely relax at the heteroint
erface between the thick GaN buffer layer and InxGa1 – xN/GaN buffer superlattice. It is established that the
GaN layers in the superlattice are in a stretched state, whereas the alloy layers are in a compressed state. In
magnitude, the stretching strains in the GaN layers are lower than the compressive strains in the InGaN lay
ers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a smaller number
of dislocations and the distribution of dislocations is more randomly disordered. In mic | |
Keywords: | Multilayered structure, strain relaxation, misfit dislocation | |
Edition: | Semiconductor Physics, Quantum Electronics, Optoelectronics | | | 2010,
1-7,English |
045 Influence of template type and buffer strain on structural properties of GaN multilayer quantum wells grown by PAMBE. X-Ray study |
Authors: | V.P. Kladko, A.V. Kuchuk, N.V. Safryuk, V.F. Machulin, P.M. Lytvyn, V.G. Raicheva, A.E. Belyaev, Yu.I. Mazur, E.A. DeCuir Jr, M.E. Ware, and G.J. Salamo | |
Summary: | The influence of template type and residual strain of the buffer layer on the structural properties
of GaN/AlN superlattices (SLs) was studied using high resolution x-ray diffraction. Using
sapphire substrates, an effective thinning of the GaN quantum wells and the corresponding
thickening of the AlN barriers were observed in SL structures grown on thin, strained AlN
templates as compared with SL structures grown on thick, relaxed GaN templates. Moreover, a
bimodal strain relaxation of SL structures in dependence of template type was observed. The
SLs grown on AlN templates relax predominantly by the formation of misfit dislocations, while
the SLs grown on GaN templates relax predominantly by cracking of the layers. We explain
these effects by the influence of residual strain in the buffer/template systems used for the
growth processes of SL layers. A correlation is made between the strain state of the system and
the cracking processes, the dislocation density, the radius of curvature and the layer thickness. | |
Keywords: | Quantum wells, residual strain, high resolution x-ray diffraction | |
Edition: | | | | 2011,
025403(8),English |
045 Substrate effects on the strain relaxation in GaN/AlN short-period superlattices |
Authors: | V.P. Kladko, A.V. Kuchuk, P.M. Lytvyn, O.M. Yefanov, N.V. Safriuk, A.E. Belyaev, Yu.I. Mazur, E.A. DeCuir Jr, M.E. Ware, and G.J. Salamo | |
Summary: | We present a comparative study of the strain relaxation of GaN/AlN short-period superlattices (SLs) grown on two
different III-nitride substrates introducing different amounts of compensating strain into the films. We grow by
plasma-assisted molecular beam epitaxy (0001)-oriented SLs on a GaN buffer deposited on GaN(thick)-on-sapphire
template and on AlN(thin)-on-sapphire template. The ex-situ analysis of strain, crack formation, dislocation density,
and microstructure of the SL layers has established that the mechanism of strain relaxation in these structures
depends on the residual strain in substrate and is determined mainly by the lattice mismatch between layers. For
growth on the AlN film, the compensating strain introduced by this film on the layer prevented cracking; however,
the densities of surface pits and dislocations were increased as compared with growth on the GaN template.
Three-dimensional growth of the GaN cap layer in samples with pseudomorphly grown SLs on the AlN template is
observed. At the same time, two-dimensional step-flow growth of the cap layer was observed for structures with
non-pseudomorphly grown SLs on the GaN template with a significant density of large cracks appearing on the
surface. The growth mode of the GaN cap layer is predefined by relaxation degree of top SL layers. | |
Keywords: | Short-period superlattices, threading dislocations, AFM topography | |
Edition: | Nanoscale Research Letters | | | 2012,
289 (1-9),English |
045 Modelling of X-Ray diffraction curves for GaN nanowires on Si(1 1 1) |
Authors: | V.P. Kladko, А.V. Kuchuk, H.V. Stanchu, N.V. Safriuk, A.E. Belyaev, A. Wierzbicka, M. Sobanska, K. Klosek, Z.R. Zytkiewicz | |
Summary: | X-ray diffraction curves and reciprocal space maps from self induced GaN nanowires on Si(1 1 1) substrates
were examined theoretically and experimentally. Numerical simulation shows how distribution of such
NWs parameters as diameter, length, strain and orientation influence broadening of X-ray diffraction peak
profiles. Calculated shape of symmetric 0002 GaN reciprocal space map well correlates with experimental
result, which indicates the validity of selected theoretical model | |
Keywords: | Nanowires, reciprocal space maps, mosaicity
parameters | |
Edition: | Journal of Crystal Growth | | | 2014,
348-350,English |
The events in the framework of the project |
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045 Kladko Vasyl P.Doctor of sciences (physics & mathematics) Head of Department +380445255758
045 3. Diagnostics of nanostructures Purpose: Expected results:Issue of new types of products: methods, theories Stage 1: Stage 2: Stage 3: Stage 4: Stage 5:
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