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1
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The Symmetry of the EL2 Defect in the Metastable State

100%
Trautman P., Baranowski J.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 4
609-612
EN
We measured recovery of the optical absorption of EL2 under [100] and [111] uniaxial stress during heating of the crystal. The recovery step, occurring at about 45 K in n-type GaAs, splits into two components under [111] stress, and no splitting is observed under [100] stress. The same behavior under uniaxial stress shows the recovery occurring at 125 K in semi-insulating GaAs. A fraction of centers recovering at lower temperature can be altered by excitation of metastability with polarized light or by excitation under stress. These results indicate that EL2 in the metastable state is trigonally distorted from the tetrahedral symmetry of the ground state.
2
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Light Induced Ordering of the EL2 Defects in the Metastable State

100%
Trautman P., Baranowski J.
Acta Physica Polonica A
|
1993
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vol. 84
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issue 4
677-680
EN
We tried to detect a strain in the crystal induced by the ordering of the EL2 defects in the metastable state by measuring linear dichroism and birefringence. We found that this strain is below the detection limit of our experiments and lower than that induced by 1 MPa of external stress. The observed dependence of orientation of the EL2 defects in the metastable state on the polarization of light used to transform EL2 to the metastable state is consistent with the attribution of the metastability of EL2 to the transformation of the isolated As_{Ga} to the V_{Ga}A_{Si} defect and is in conflict with the As_{Ga}-A_{Si} defect pair model of EL2.
3
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Hydrogen in InP-Bonding and Passivation

100%
Baranowski J., Tatarkiewicz J.
Acta Physica Polonica A
|
1991
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vol. 79
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issue 2-3
263-265
EN
A tight-binding total energy calculation shows that the possible hydrogen-indium bond in InP is long and weak whereas hydrogen-phosphorus bond is short and strong. The model explains the known experimental data, especially the lack of local vibrational modes of InH in InP implanted with protons and hydrogen passivation of acceptors but not donors in InP.
4
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Photoreflectance Measurements of InGaAs/GaAs Quantum Wells

81%
Tomaszewicz T., Korona K., Bożek R., Baranowski J.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 5
965-968
EN
Samples with InGaAs/GaAs quantum wells were grown by metallo-organic chemical vapour deposition in order to detect and analyze GaSb islands deposited on the surface. Results of photoreflectance measurements of quantum wells are reported. The correspondence between broadening of quantum well transition lines and GaSb structures has been observed.
5
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Deep Level Transient Spectroscopic Studies of MOCVD GaN Layers Grown on Sapphire

81%
Śliwiński A., Korona K., Pakuła K., Baranowski J.
Acta Physica Polonica A
|
1996
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vol. 90
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issue 5
955-958
EN
The deep level transient spectroscopy of GaN heteroepitaxial layers grown on sapphire was studied. The samples were Mg doped during the growth. The as-grown material is n-type. It becomes p-type after annealing. The samples were measured in the temperature range from 77 K to 420 K. In n-type GaN, one peak (EG1) with activation energy 0.75 eV was detected. In p-type, at least three peaks were observed: AS1 at temperature about 300 K and AS2, AS3 at about 400 K. The dominating one is AS3. It has an activation energy about 1.1 eV.
6
Content available remote

Model of Hopping between Deep Centers in Low Temperature GaAs

81%
Korona K., Kamińska M., Baranowski J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
337-340
EN
A model explaining hopping conductivity via EL2 deep centers in low temperature GaAs is presented. It is proposed that the wave function of the EL2 center consists of a localized part and of an external one. The model can describe such features as large wave function radius of hopping centers, changes of the conductivity during transition of EL2 to the metastable state and a high potential fluctuation amplitude.
7
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Exciton in 2D Cubic Inclusion in Hexagonal GaN

81%
Suffczyński M., Stępniewski R., Baranowski J.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
993-996
EN
An inclusion of cubic GaN in an otherwise hexagonal matrix is considered to be equivalent to an effective quantum well. The exciton binding energy in a quantum well of a finite potential barrier height in the conduction and valence bands is calculated in the effective mass approximation with a variational envelope function type of Bastard and Takagahara. The exciton binding energy and the energy of exciton recombination line are computed, as a function of the well width, for realistic potential barrier heights and band-offset ratios.
8
Publication available in full text mode
Content available

Multiband GaN/AlGaN UV Photodetector

81%
Korona K., Drabińska A., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2006
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vol. 110
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issue 2
211-217
EN
We present optical and electrical measurements made on GaN/AlGaN photodetector structure capable to detect three UV ranges, tuned by external voltage. The highest band at energy of about 3.85 eV is nearly independent of bias applied to the Schottky contact. Photosensitivity of the second band at about 3.65 eV changes strongly with the bias. Signal in this range increases about 20 times when the bias changes from 0 V to -4 V. Photosensitivity of the third band (3.4 eV) appears for strong reverse bias (-3 V). Characteristics of the detector are in qualitative agreement with numerical model, however deep centers present in the AlGaN layers cause quantitative discrepancies. The concentration of defects of the order of 10^{16} cm^{-3} was estimated from current transients.
9
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An Estimate of the Energy Gap of InN from Measurements of the Fundamental Absorption Edge

81%
Trautman P., Pakuła K., Witowski A., Baranowski J.
Acta Physica Polonica A
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2005
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vol. 108
|
issue 5
903-908
EN
Optical absorption between 0.4 and 4.5 eV of an InN layer grown by metalorganic vapour phase epitaxy on sapphire was measured at 296 and 12 K. The layer was also characterized by measurements of the Hall effect and of infrared reflectivity in the region of the plasma edge, which determined the concentration, mobility, and effective mass of electrons in the conduction band. The energy gap of InN was estimated to be equal to 0.9±0.2 eV. It was obtained from the spectral position of the fundamental absorption edge. Corrections to the energy gap resulting from the broadening of the fundamental absorption edge, from the Burstein-Moss shift, and from a band-gap shrinkage due to the impurity potential were included.
10
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Mechanism of Thermal Interaction of In with GaAs

81%
Barcz A., Adamczewska J., Baranowski J., Kwiatkowski S.
Acta Physica Polonica A
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1993
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vol. 84
|
issue 4
801-803
EN
General behavior of In/GaAs couple heat-treated at 570°C for 2 hours was studied with secondary-ion-mass spectrometry, scanning electron microscopy, Rutherford backscattering spectroscopy and Nomarski microscopy. It is shown that, besides the well-known InGaAs crystallites which epitaxially grow upon dissolution of the substrate, In interacts with the substrate dislocations to form In(Ga)As dendrites. The driving force for this process is presumably excess arsenic reported to be present in the vicinity of the individual dislocations.
11
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Transmission Electron Microscopy and Luminescence Studies of Quantum Well Structures Resulting from Stacking Fault Formation in 4H-SiC Layers

71%
Borysiuk J., Wysmołek A., Bożek R., Strupiński W., Baranowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1067-1072
EN
Transmission electron microscopy and photoluminescence studies of quantum well structures related to stacking faults formation in 4H-SiC homoepitaxial layers are reported. The investigated 4H-SiC layers were deposited on 8° misoriented Si-terminated (0001) surface of high quality 4H-SiC substrate. It is found that the planar defects created by direct continuation from the SiC substrates are cubic 3C-SiC stacking faults. These defects are optically active, giving rise to characteristic luminescence band in the spectral range around 2.9 eV, which consist of several emission lines. The observed energy and intensity pattern of this emission is discussed of in terms of single, double and multiple quantum wells formed from neighboring 3C-SiC SF layers embedded in 4H-SiC material.
12
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Electrical and ESR Studies of GaN Layers Grown by Metal Organic Chemical Vapour Deposition

71%
Suchanek B., Palczewska M., Pakuła K., Baranowski J., Kamińska M.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
1001-1004
EN
Electrical transport and ESR studies were performed on the state-of-theart GaN layers grown on sapphire substrate using metal organic chemical vapour deposition technique. For undoped samples electron concentration below 2×10^{17} cm^{-1} and mobility up to 500 cm^{2}/(V s) were achieved whereas hole concentration up to 7×10^{17} cm^{-3} and mobility about 16 cm^{2}/(V s) were obtained for intentionally Mg doped samples and subsequently annealed. Temperature dependence of mobility was discussed. ESR revealed the presence of two resonance absorption lines. One of them with g_{⊥}=1.9487 and g_{∥}=1.9515, commonly observed in n-type GaN was due to shallow donor. The second ESR line was an isotropic one of g=2.0032 and it is discussed.
13
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Content available

Magneto-Luminescence Study of Silicon-Vacancy in 6H­Si

62%
Wysmołek A., Wardak K., Stępniewski R., Baranowski J., Potemski M., Tymicki E., Grasza K.
Acta Physica Polonica A
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2006
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vol. 110
|
issue 3
437-442
EN
The magneto-spectroscopy studies of luminescence related to silicon-vacancy, in high quality 6H-SiC crystals grown by the seeded physical vapor transport method, are presented. The superior optical quality of these crystals allowed us to resolve a doublet structure of the 1.398 eV emission line (V_2 line), commonly assigned to the transitions involving two singlet states of the silicon-vacancy. Experiments performed in magnetic fields up to 20 T showed that each doublet constituent of the V_2 line splits into four components for the magnetic field parallel to the c-axis of the 6H-SiC crystals. This result could be hardly explained in terms of a singlet to singlet transition. The analysis of the angle-resolved luminescence experiments in high magnetic fields serves us to discuss the symmetry of the defect states responsible for the V_2-line in silicon carbide.
14
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Tuning of Spectral Sensitivity of AlGaN/GaN UV Detector

62%
Korona K., Drabińska A., Trajnerowicz A., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
|
2003
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vol. 103
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issue 6
675-681
EN
GaN/AlGaN photodetector that exhibits new interesting property is presented. Its spectral sensitivity depends upon bias voltage. Under positive or low negative bias the detector is sensitive mainly to the ultrafiolet radiation absorbed by AlGaN layer 3.7-3.8 eV. Under negative bias U_B below -4 V, the detector is sensitive mainly to the radiation absorbed by GaN (3.4-3.6 eV). The effect can be explained based on numerical calculations of the electric field and potential profiles of this structure. The damping of GaN signal is attributed to activity of 2D electron gas formed on the GaN/AlGaN interface by spontaneous polarization. The reappearing of the signal is attributed to tunneling of holes through AlGaN, stimulated by a high electric field.
15
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Optical and Electrical Measurements of Low-Temperature InAlAs

62%
Korona K., Wysmołek A., Bożek R., Kamińska M., Baranowski J., Weber E.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
825-828
EN
Photoluminescence, photocurrent, thermally stimulated current and photoinduced current transient spectroscopy measurements done on molecular beam epitaxy In_{0.52}Al_{0.48}As layer, lattice matched to InP are reported. The investigated layers were grown on semi-insulating InP wafers, at temperature range from 215 to 450°C. It was found that the Fermi level was pinned to a dominant midgap center (most likely similar to EL2 center). Moreover, there were at least 7 other defects but with much smaller concentrations. Their activation energies were equal to 0.076, 0.11, 0.185, 0.295, 0.32 and 0.40 eV. The layers exhibited a very low luminescence and a small photocurrent.
16
Publication available in full text mode
Content available

Temporal Evolution of Multi-Carrier Complexes in Single GaN/AlGaN Quantum Dots

62%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 5
879-884
EN
Microphotoluminescence of low-density GaN/Al_xGa_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The narrow lines in the microphotoluminescence spectra due to the single quantum dots are observed. Both energy and intensity of these lines show temporal fluctuations. Statistical analysis based on the correlation matrix allowed us to identify objects, which are affected by photo-induced electric field fluctuations. Relations between emission lines participating in the spectrum are discussed.
17
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Single GaN/AlGaN Quantum Dot Spectroscopy

62%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
233-236
EN
Microphotoluminescence of low-density GaN/Al_{x}Ga_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The detailed analysis of the emission from these structures enables the observation of pairs of lines separated by the energy up to 3 meV. They behave in a different way under different excitation power that suggests that this doublet structure can be associated with the exciton and trion (or biexciton recombination). It is observed that for different quantum dots the energy of the charged exciton complex emission could be higher or lower than the neutral exciton one. It is discussed in terms of a competition between attractive e-h and repulsive e-e (h-h) Coulomb interaction that occurs because of the existence of the built-in electric field that separates electrons and holes in the dot.
18
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Raman Piezospectroscopy of Phonons in Bulk 6H-SiC

62%
Grodecki K., Wysmołek A., Stępniewski R., Baranowski J., Hofman W., Tymicki E., Grasza K.
Acta Physica Polonica A
|
2009
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vol. 116
|
issue 5
947-949
EN
Raman piezospectroscopy of high quality 6H-SiC crystals is presented. The crystals used in experiments were grown by the seeded physical vapor transport method. Uniaxial stress up to 0.9 MPa, obtained using a spring apparatus, was applied along [11-20] and [10-10] directions. It was found that the application of uniaxial stress led to different energy shifts of the observed phonon excitations in the investigated 6H-SiC crystals. The obtained pressure coefficients vary in the range 0.98-5.5 cm^{-1} GPa^{-1} for different transverse optical phonon modes. For longitudinal optic phonon modes pressure coefficients in the range 1.6-3.6 cm^{-1} GPa^{-1} were found. The data obtained could be useful in evaluation of local strain fields in SiC based structures and devices including epitaxial graphene.
19
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Luminescence Dynamics of Exciton Replicas in Homoepitaxial GaN Layers

62%
Korona K., Baranowski J., Pakuła K., Monemar B., Bergman J., Grzegory I., Porowski S.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 4
841-844
EN
Photoluminescence of excitons and their phonon replicas in homoepitaxial MOCVD-grown gallium nitride (GaN) layers have been studied by picosecond (ps) time-resolved photoluminescence spectroscopy. The time-resolved photoluminescence spectroscopy has shown that the free excitons and their replicas have the fastest dynamics (decay time of about 100 ps). Then, the excitons-bound-to-donors emission rises (with the rise time similar to the free excitons decay time) and decays with t=300 ps. The excitons-bound-to-acceptors has the slowest decay (about 500 ps). It has been found that the ratio of excitons-bound-to-acceptors and excitons-bound-to-donors amplitudes and their decay times are different for 1-LO replicas and then for zero-phonon lines, whereas the ratio of amplitudes and the decay time of the 2-LO replicas are similar to the ones of the zero-phonon lines.
20
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Raman Studies of Defects in Graphene Grown on SiC

62%
Grodecki K., Bożek R., Borysiuk J., Strupinski W., Wysmolek A., Stępniewski R., Baranowski J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
595-596
EN
The Raman scattering studies of multi-layer graphene obtained by high temperature annealing of carbon terminated face of 4H-SiC(000-1) substrates are presented. Intensity ratio of the D and G bands was used to estimate the average size of the graphene flakes constituting carbon structures. The obtained estimates were compared with flake sizes from atomic force microscopy data. We found that even the smallest structures observed by atomic force microscopy images are much bigger than the estimates obtained from the Raman scattering data. The obtained results are discussed in terms of different average flake sizes inside and on the surface of the multi-layer graphene structure, as well as different type of defects which would be present in the investigated structures apart from edge defects.
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