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1
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Nature of Donors in SiC

100%
Suchanek B., Dwiliński R., Kamińska M., Palczewska M., Vlaskina S.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
321-324
EN
6H-SiC samples were examined by ESR technique in temperature range from 5 K up to 300 K. Two kinds of ESR lines were observed: a single line at g = 2.0054 ± 0.0007, called X-line, and a triplet corresponding to isolated nitrogen defect. Ionization energy of X defect was determined as about 60 meV and the ionization energy of isolated nitrogen was determined as about 200 meV below SiC conduction band.
2
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Competition of Radiation Processes in 6H-SiC Observed by Luminescence

100%
Wysmołek A., Mroziński P., Dwiliński R., Vlaskina S., Kamińska M.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
437-440
EN
We report on the results of photoluminescence and thermoluminescence measurements of various 6H-SiC crystals. At low temperature in all n-type samples two bands with maxima at 2.7 eV (blue) and 1.8 eV (orange) were detected. In the p-type material only blue band was observed. The mea­surements performed at a broad range of temperatures showed totally dif­ferent behaviour of photoluminescence intensity of both bands. The pre­sented results could be explained in the model assuming well established donor-acceptor pair recombination for the blue band emission and the con­duction band - deep defect transition for the orange band. The proposed model was confirmed by thermoluminescence measurements of the orange band which showed peaks at 30 K, 80 K, 100 K, 150 K attributed to ioniza­tion of subsequent shallow donor levels.
3
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On GaN Crystallization by Ammonothermal Method

86%
Dwiliński R., Baranowski J., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L.
Acta Physica Polonica A
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1996
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vol. 90
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issue 4
763-766
EN
GaN crystals are grown using ammonothermal method at pressures below 5 kbar and temperatures below 550°C. In this method, GaN is synthesised from high purity metallic gallium. The main role in the low temperature GaN crystallization is played by the chemically active and dense ammonia and dissolved mineralizer. Morphology of the obtained crystals as well as solubility experiments prove that gallium nitride is dissolved and crystallised from solution. Physical properties of GaN crystals obtained using ammonothermal method depend on the growth conditions and the type of mineralizer. All GaN samples reveal very intensive photoluminescence, also at room temperature. The spectra of crystals grown with lithium compound mineralizer are shifted towards higher energies in comparison to crystals grown with potassium based mineralizer. At helium temperatures, phosphorescence is also observed.
4
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Some Optical and Epr Properties of Strain-Free GaN Crystals Obtained by Ammono Method

86%
Dwiliński R., Baranowski J. M., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L., Palczewska M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
737-741
EN
AMMONO GaN is grown spontaneously from ammonia solution in form of regular, well shaped, few micrometer crystals. Photoluminescence spectra of these crystals are characterized by fixed positions of very narrow exciton lines (FWHM down to 1 meV), where free excitons A, B, C, resolved two donor bound excitons and acceptor bound exciton are visible. Fixed position of exciton lines is in contrast to small changes of line energies which have been always observed for epitaxial GaN layers because of strain present in them. Free electron concentration of AMMONO GaN is less than few times 10^{15} cm^{-3}, as estimated from EPR signal of shallow donor. The above-mentioned facts qualified these crystals as state of the art strain-free, model material for basic parameter measurements of GaN. In this work, results of PL and EPR measurements performed on AMMONO GaN crystals are presented and discussed.
5
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Optical and Electrical Studies of FR1 and FR2 Defects in GaAs

86%
Dwiliński R., Palczewska M., Kaczor P., Korona K., Wysmołek A., Bożek R., Kamińska M.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
613-616
EN
The systematic EPR, optical absorption, photoluminescence and thermally stimulated current studies of acceptor defects in bulk GaAs were performed. For the first time, parallel EPR and optical absorption experiments allowed to find the absorption spectrum due to the photoionization of FR1 defect with the threshold at 0.19 eV. Photoluminescence studies showed two families of bands in the energy range of about 1.25 to 1.35 eV. We tentatively ascribed them to FR1 and FR2 complexes with shallow donors. Thermally stimulated current measurements showed two peaks at 90 K and 110 K assigned to FR1 and FR2 respectively.
6
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GaN Layers Grown by Reactive Ion Plating

73%
Żubka A., Dwiliński R., Suchanek B., Janik W., Wysmołek A., Kwiatkowski S., Kamińska M., Shaginyan L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
1058-1062
EN
GaN layers grown on ceramics, sapphire or SiC substrates using reactive ion plating method are presented. In reactive ion plating method gallium from a hot source reacts on a heated substrate with nitrogen partially ionized. Rutherford backscattering technique was applied to check the composition of the samples and gallium to nitrogen ratio was found to be close to one. However, Rutherford backscattering studies showed also a remarkable amount of unintentional impurities present in the layers. The structure of GaN was determined using reflection high-energy electron diffraction. It appeared that polycrystal and monocrystal can be grown, depending on growth conditions. Absorption spectra taken on the layers grown on sapphire showed a tail of band to band absorption starting at about 370 nm. Carrier concentration was of the order of 1019-1020 cm^{-3} at room temperature and did not change much with temperature decrease. No luminescence from the layers was detected, most probably due to high concentration of impurities.
7
Content available remote

GaN Synthesis by Ammonothermal Method

73%
Dwiliński R., Wysmołek A., Baranowski J., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L., Jacobs H.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
833-836
EN
It is shown that ammonothermal method can be successfully used to synthesize GaN powder of good crystallographic quality from ammonia solution at high pressure and a moderate temperature. The size of obtained GaN powder grains was of a few micrometers. The improvement of the powder crystalline quality (examined by X-ray rocking curve, scanning electron microscopy and luminescence measurements) with increasing molar proportion of mineralizer was observed. It was therefore possible to conclude that high molar proportion of mineralizer in ammonia solution plays a crucial role in the polycrystal growth process. Visible luminescence of high efficiency from the GaN powder was found.
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