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  1. 6 Grzegory I.

  2. 5 Bugajski M.

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1
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Role of the Thermal Stress on the Magnetophonon Peak Structure in the Parallel Transport of the GaAs/AlGaAs Multiple Quantum Wells

100%
Tomaka G., Cebulski J., Sheregii E., Ściuk W., Strupiński W., Dobrzański L.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
597-602
EN
The magnetophonon resonance in parallel transport of two types multiple quantum wells was studied. The transverse magnetoresistance was measured in pulsed magnetic fields up to 30 T (within temperature region from 77 to 340 K). A fine structure of magnetophonon resonance peaks which depends on temperature and does not depend on the type of multiple quantum wells, was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses.
2
Content available remote

Growth of GaN Metalorganic Chemical Vapour Deposition Layers on GaN Single Crystals

100%
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.
3
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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
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1997
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vol. 92
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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.
4
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Effect of Epitaxial Layer Thickness on Built-in Electric Field in Region of AlGaAs/SI-GaAs Interface: A Photoreflectance Study

100%
Ochalski T., Żuk J., Vlasukova L.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
935-939
EN
We present a study of detailed line shapes of photoreflectance spectra for Al_{0.3}Ga_{0.7} As/SI-GaAs epitaxial layers grown by MBE. All measurements were performed at 80 K under UHV conditions with a special care for the samples surface quality. A set of the photoreflectance spectra was collected for photon energies close to the GaAs and Al_{0.3}Ga_{0.7}As band gaps (E_{0}). The photoreflectance spectra originated in the vicinity of the Al_{0.3}Ga_{0.7}As/SI-GaAs interface were analyzed using the complex Airy function model of Franz-Keldysh oscillations. To examine the effect of the epitaxial layer thickness on parameters characterizing the interface, a step-by-step chemical etching was applied for stripping the top layers. The built-in electric field intensity, field inhomogeneity and phenomenological broadening parameter for interface regions were determined as a function of the epilayer thickness.
5
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Photoluminescence in Tilted Magnetic Field of Triply Negatively Charged Excitons Hybridized with a Continuum

100%
Van Hattem B., Corfdir P., Brereton P., Pearce P., Graham A., Stanley M., Hugues M., Hopkinson M., Phillips R.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
798-800
EN
We analyse the magneto-photoluminescence of triply negatively charged excitons coupled to a continuum of states. The excitonic complex is confined to a Stranski-Krastanow InAs/GaAs quantum dot embedded in a Schottky diode. Different orientations of the magnetic field have been investigated. A modelling of the Coulomb blockade together with the calculation of the electron Fock-Darwin spectrum has allowed us to predict the magnetic fields of anticrossing between the quantum dot energy states and the wetting layer Landau levels. Good agreement between the theoretical model and the experimental results has been obtained.
6
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Fine Structure of the Localized Emission from GaInNAs Layers Studied by Micro-Photoluminescence

100%
Kudrawiec R., Latkowska M., Sęk G., Misiewicz J., Ibáñez J., Henini M., Hopkinson M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
930-932
EN
GaInNAs bulk-like layers ( ≈ 20% In and ≈ 3% N) grown on GaAs substrate with various crystallographic orientations have been studied by micro-photoluminescence at low temperatures for a broad range of excitation conditions. In addition to photoluminescence peaks, which are associated with heavy- and light-hole free exciton recombination, a band of sharp lines was observed below the fundamental free exciton transition at low excitation. It shows that the localized emission which is typical of this alloy at low temperatures is composed of individual narrow photoluminescence lines which are associated with the recombination of single excitons. They can be localized on various local potential minima including those originating from the alloy content fluctuations and/or deep acceptor(donor)-like complexes.
7
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Photoreflectance Studies of InGaAs/GaAs/AlGaAs Single Quantum Well Laser Structures

100%
Ochalski T., Żuk J., Regiński K., Bugajski M.
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EN
We report on photoreflectance investigations of strained-layer In_{0.2}Ga_{0.8}As/GaAs/Al_{0.3}Ga_{0.7}As single quantum well laser structures grown by molecular beam epitaxy. All the observed photoreflectance spectral features were assigned to the e-hh transitions with Δn=0. The transition energies were determined and compared to their values calculated within the envelope function approximation. Assuming that one third of the total strain in the central In_{0.2}Ga_{0.8}As layer is relaxed by biaxial deformation of surrounding thin GaAs layers, it is possible to explain reasonably the results of our photoreflectance experiment.
8
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New Method for Studying Biaxial Deformation Effects on Optical Spectra of Quantum Wells

100%
Sosin T., Trzeciakowski W.
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EN
The effects of large deformation were studied by preparing thin (20-30 μm) membranes with quantum-well layers on top. A small gas pressure of a few bar deforms the membrane substantially and changes the optical spectra of the quantum wells. We present the results of the photolumines­cence and absorption from GaAs/AlGaAs and from InGaAs/GaAs quantum wells subjected to tensile and to compressive biaxial strain. The light-hole lines shift more than two times faster than the heavy-hole lines so that they cross under tensile strain.
9
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Optical Properties of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} Epitaxial Layers

100%
Świątek K., Piskorski M., Piotrowski T.
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EN
Photoluminescence spectra of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} layers (x = 0.2-0.5, y = 0.02-0.03) grown by liquid-phase epitaxy on GaSb substrates were studied in a wide temperature range (14-295 K). The temperature changes of energy and intensity of the layer and substrate emission were measured. Linear part of the temperature-induced energy shift of the Al_{0.20}Ga_{0.80}As_{0.02}Sb_{0.98} band-to-band emission exhibits a slope of -0.3 meV/K and -0.45 meV/K at temperatures 150 K and 295 K, respectively.
10
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On Second-Harmonic Generation in Nonparabolic Quantum Wells

100%
Załużny M.
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EN
The second-harmonic generation due to the intersubband transitions in nonparabolic two-level quantum well systems is discussed theoretically taking into account the depolarization effect.
11
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Reflectivity Studies of Lattice Vibrations and Free Electrons in MBE Grown GaN Epitaxial Layers

100%
Iller A., Jantsch W., Marks J., Pastuszka B., Diduszko R.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
336-340
EN
We have observed a sharp structure with a peak at the frequency of the E_{1}-TO phonon in the reflectivity of GaN epitaxial layers grown by molecular beam epitaxy on Si substrates. The simulations of the reflection performed show that the observed shape can be explained by assuming both collective lattice vibrations and free carriers contributions to the dielectric function. We assumed the Lorentz oscillator to describe the contribution of the collective lattice vibrations and the Drude-Lorentz model for that of free carriers. Fitting the calculated reflectivity to the spectrum obtained experimentally allowed us to evaluate lattice and free carrier parameters.
12
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Two-Electron Transition in Homoepitaxial GaN Layers

100%
Fiorek A., Baranowski J., Wysmołek A., Pakuła K., Wojdak M., Grzegory I., Porowski S.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
742-744
EN
It is shown that the luminescence mapping is a powerful method to help identify optical transitions. Two-electron transition was identified in the homoepitaxial GaN layer by this technique. It was found that the donor and acceptor bound exciton emissions are spatially displaced and show intensity maxima at different places of the epitaxial layer. It was also found that the 3.45 eV line, suspected as "two-electron transition", follows exactly the donor bound exciton spatial distribution. Donor bound exciton recombines leaving the neutral donor in the excited 2s state. Thus, 1s-2s excitation being equal to 22 meV corresponds to 29 meV hydrogenic donor binding energy. This is the first identification of the two-electron transition in GaN.
13
Content available remote

Photoreflectance Measurements of InGaAs/GaAs Quantum Wells

80%
Tomaszewicz T., Korona K., Bożek R., Baranowski J.
Acta Physica Polonica A
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1996
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vol. 90
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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.
14
Content available remote

Investigation of Localized Electric Field in the Type-II InAs/GaAsSb/GaAs Structure

80%
Lee S., Kim J., Yoon S., Kim Y., Lee S., Honsberg C.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1213-1216
EN
The effect of localized electric field (F) was investigated in the type-II InAs/GaAsSb/GaAs structures. To compare type-I to type-II, two types of samples with different Sb contents was grown by molecular beam epitaxy, whose Sb contents are 3% (type-I) and 16% (type-II), respectively. In the both samples, we performed excitation power dependent-photoreflectance at 10 K and the result showed that the period of the Franz-Keldysh oscillation, revealed above the band gap (E_{g}) of GaAs, was broadened in the only type-II system, which means that F was also increased because it is proportional to the period of the Franz-Keldysh oscillation while the period of the Franz-Keldysh oscillations stayed unchanged in type-I system. This phenomenon is explained by that the F was affected by the band bending effect caused by the spatially separated photo-excited carriers in the interface between GaAsSb and GaAs. The F changed linearly as a function of square root of excitation power as expected for the F. Moreover, F was calculated using fast Fourier transform method for a qualitative analysis, which is in a good agreement with the theory of triangular well approximation.
15
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Exciton Absorption in GaN

80%
Sobol M., Bardyszewski W.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
534-538
EN
The absorption coefficient of the wurtzite-type GaN is described in terms of three almost totally decoupled excitons A, B, C associated with split valence bands of Γ_{9}, Γ_{7} and Γ_{7} symmetries using a spherically symmetric approximation for the standard effective-mass Hamiltonian. The excitonic equations are solved within the subspace of optically active states of s-symmetry. The effects of crystal field and spin-orbit coupling are discussed. The results show that the spherical approximation is in perfect agreement with experimental findings.
16
Content available remote

Large Filling-Factor-Dependent Spin Splitting in Magnetooptic Kerr Effect in GaAs/AlGaAs Multiple Quantum Wells

80%
Dudziak E., Bozym J., Pruchnik D., Wasilewski Z.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
291-296
EN
Magnetooptic Kerr effect in GaAs/Al_{0.312}Ga_{0.688}As multiple quantum wells was investigated in the integer quantum Hall regime. The measurements have been performed in magnetic fields up to 14.5 T, at the temperature of 1.8 K. Experimental data indicate the discontinuous behavior of the magnetooptic Kerr effect spectrum as a function of the filling factor. For odd filling factor values ν=3 and 5 we observe the large spin splitting. The effects cannot be explained in the one-particle model.
17
Content available remote

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

80%
Teisseyre H., Szymański M., Khachapuridze A., Skierbiszewski C., Feduniewicz-Żmuda A., Siekacz M., Łucznik B., Kamler G., Kryśko M., Suski T., Perlin P., Grzegory I.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
467-472
EN
The intention of this work is to discuss and report on our research on nonpolar laser structures grown on bulk GaN crystal substrates along the (11¯20) nonpolar direction. The main advantages of such nonpolar structures are related to the elimination of the built-in electric fields present in commonly used systems grown along the polar (0001) axis of nitride crystals. We demonstrated the optically pumped laser action on separate confinement heterostructures. Laser action is clearly shown by spontaneous emission saturation, abrupt line narrowing, and strong transversal electric polarization of output light. The lasing threshold was reached at an excitation power density of 260 kW/cm^2 for a 700μm long cavity (at room temperature).
18
Content available remote

Dispersion of Bloch Modes in a Multilayer Structure with Alternating Left-Handed and Right-Handed Materials

80%
Vukovic S., Aleksic N., Timotijevic D.
Acta Physica Polonica A
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2007
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vol. 112
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issue 5
1061-1066
EN
We study all-evanescent eigenmodes of a one-dimensional infinite periodic structure with alternating left-handed and right-handed materials that propagate perpendicularly to the surface or guided eigenmodes. Investigation of dispersion properties of such Bloch modes is shown to be crucial for understanding of an efficient radiation energy transport across the periodic multilayer structure. Frequency pass bands and gaps are found as a function of the two orthogonal wave vectors: the Bloch wave vector k_B and the surface wave vector k_S. We demonstrate that pass bands of both TE- and TM-polarizations can exist and, under certain conditions, may overlap.
19
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Optical Transitions between Confined and Unconfined States in p-Type Asymmetric GaAs/InGaAs/AlGaAs QW Structures

80%
Sitarek P., Ryczko K., Misiewicz J., Reuter D., Wieck A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
849-851
EN
We present contactless surface photovoltage spectroscopy and photoreflectance studies of 10 nm wide, p-type doped asymmetric GaAs/InGaAs/AlGaAs quantum well structures. The MBE grown structures differ in spacer thickness between the quantum well and the reservoir of holes. The doping causes that quantum well is placed in electric field. The surface photovoltage spectroscopy measurements gave us detailed information about the optical transitions between confined states and between confined and unconfined states. The comparison of experimental and numerical analysis allows us to identify all features present in the surface photovoltage spectroscopy and photoreflectance spectra. It has been found that spacer layer thickness has significant influence on surface photovoltage spectroscopy spectra.
20
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Hopping Excitons in GaInNAs - Simulation οf Micro- and Macrophotoluminescence Spectra

80%
Baranowski M., Latkowska M., Kudrawiec R., Misiewicz J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
899-901
EN
Model of hopping excitons has been applied to explain the origin of sharp lines observed in microphotoluminescence spectra of GaInNAs layers. It has been shown that shape of the micro- and macrophotoluminescence spectra results from the exciton hopping between localizing centers and this phenomenon is responsible for the observation of sharp lines in microphotoluminescence experiment. In addition, the influence of different model parameters on photoluminescence spectra and their characteristic parameters such as the Stokes shift and full width at half maximum has been investigated.
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