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1
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Dielectric Function Theory Calculations of Polaritons in GaN

100%
Korona K. P., Stępniewski R., Baranowski J. M.
Acta Physica Polonica A
|
1997
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vol. 92
|
issue 5
867-869
EN
Properties of polaritons (free excitons coupled with photons of similar energy) in gallium nitride are investigated by performing calculations based on dielectric function theory including all three excitons A, B and C (characteristic for the wurtzite structure). Moreover the excited states of excitons have been taken into account by adding Elliott's components to dielectric function. Energies, polarizabilities and damping constants of excitons are determined. It is shown that due to inter-exciton interactions the B and C excitons are strongly damped. It is estimated that the characteristic time of B to A relaxation is t_{BA}=1 ps. The exciton C lifetime is estimated τ_{C}=0.2 ps.
2
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Origin of Centres Involved in Blue and Orange Luminescence of 6H-SiC

100%
Wysmołek A., Baranowski J. M., Kamińska M.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
957-960
EN
We present new results of luminescence of n-type 6H-SiC crystals. We have found two shallow donors with ionization energies at 60 meV and 140 meV. We have shown that the blue luminescence is not affected by the ionization of the shallower donor and is related to deeper donor which we attribute to N at C-site. We propose that the origin of the more shallower donor at 60 meV is related to carbon vacancy. We have found that the intensity of the orange luminescence increases under infrared illumination. This result confirms that the orange luminescence is due to conduction band-deep centre transitions. We believe that deep centre responsible for the orange luminescence is the silicon vacancy.
3
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Crystallographic Properties of Bulk GaN Crystals Grown at High Pressure

76%
Leszczyński M., Grzegory I., Bockowski M., Jun J., Porowski S., Jasiński J., Baranowski J. M.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 4
799-802
EN
Gallium nitride bulk crystals grown at about 15 kbar and 1500 K have been examined by using the high resolution X-ray diffractometry. An anal­ysis of a set of the rocking curves of various Bragg reflections enabled us to estimate a dislocation density. For the crystals of dimensions lower than about 1 mm it is lower than 10^{-5} cm^{-2}. For bigger samples the crystallo­graphic quality worsens. With an application of the reciprocal lattice map­ping we could distinguish between internal strains and mosaicity which are both present in these crystals The results for the bulk crystals are compared with those for epitaxial layers.
4
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Some Optical and Epr Properties of Strain-Free GaN Crystals Obtained by Ammono Method

76%
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 Properties of High Temperature Annealed Heteroepitaxial GaN:Mg Layers

76%
Wojdak M., Baranowski J. M., Suchanek B., Pakuła K., Jun J., Suski T.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1059-1062
EN
In this paper we present for the first time luminescence and electrical measurements of GaN:Mg heteroepitaxial layers annealed at very high temperatures up to 1500°C and at high pressures of nitrogen up to 16 kbar. The presence of high nitrogen pressure prevents GaN from thermal decomposition. It was found that annealing in the presence of additional Mg atmosphere leads to a high quality p-type epitaxial layer of the hole concentration equal to 2×10^{17} cm^{-3} and mobility 16 cm^{2}/(V s). However, annealing at high temperatures without additional magnesium causes conversion to n-type. It is also shown that in the high temperature annealed GaN:Mg epilayers the donor-acceptor luminescence is the dominant recombination channel.
6
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Growth of GaN Metalorganic Chemical Vapour Deposition Layers on GaN Single Crystals

64%
Pakula K., Baranowski J. M., Stępniewski R., Wysmołek A., Grzegory I., Jun J., Porowski S., Sawicki M., Starowieyski K.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
861-864
EN
The homoepitaxial growth of GaN layers has been achieved for the first time. Bulk GaN single crystals which have been used as a substrate have been grown from diluted solution of atomic nitrogen in the liquid gallium at 1600°C and at nitrogen pressure of about 15-20 kbar. It is shown that a terrace growth of GaN epitaxial layer has been realized. The high quality of the GaN film has been confirmed by luminescence measurements. The analysis of donor-acceptor and exciton luminescence is presented.
7
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GaSb Dots Grown on GaAs Surface by Metalorganic Chemical Vapour Deposition

64%
Bożek R., Babiński A., Baranowski J. M., Stępniewski R., Klusek Z., Olejniczak W., Starowieyski K., Wróbel J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
974-976
EN
We report metaloorganic chemical vapour deposition growth of an anisotropic GaSb islands on GaAs (001) surface with a typical dimensions around 200 nm. Results of investigations employing scanning electron microscope, scanning tunnelling microscope and ph9tocapacitance are presented.
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