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1
Content available remote

Electronic States in Type-II Superlattices

100%
Machowska-Podsiadlo E., Bugajski M.
Acta Physica Polonica A
|
2009
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vol. 116
|
issue S
S-65-S-68
EN
In this paper the electronic states in type-II superlattices are demonstrated. Band dispersions of InAs/GaSb periodic structure were calculated with the respect of the light and the heavy holes states mixing at InAs/GaSb interfaces. The effect of narrow energy band gap of InAs was taken into account and the wavelengths corresponding to optical transitions in the superlattice were presented.
2
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Theoretical Analysis of Optical Gain in Quantum Well Lasers Including Valence-Band Mixing Effect

100%
Łepkowski S. P., Bugajski M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
903-907
EN
The linear optical gain in the AlGaAs/GaAs quantum well lasers is studied theoretically, taking into account the valence-band mixing effect. Our approach is based on the multiband effective-mass theory (k p method) and the density-matrix formalism. In order to obtain the valence bands' structure we employ the 4×4 Luttinger-Kohn Hamiltonian, neglecting the coupling to the split-off band. The spectral dependence of the linear optical gain is calculated using the density-matrix method with interband relaxation. Finally, we analyse the spatial distribution of the optical gain in the quantum well region for the photon energy corresponding to the peak value of the linear gain.
3
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Angular and Temperature Tuning of Emission from Vertical-External-Cavity Surface-Emitting Lasers (VECSELs)

81%
Wójcik-Jedlińska A., Muszalski J., Bugajski M., Łukowski M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1437-1443
EN
In this paper we demonstrate how the tuning of the VECSEL heterostructure can be precisely determined. Since the VECSEL active region is embodied in a microcavity, the photoluminescence signal collected from the chip surface is modified by the resonance of this cavity. The angle resolved photoluminescence measurements combined with the temperature tuning of the structure allowed us to precisely determine VECSEL emission features. The investigated structure consists of GaAs cavity with six InGaAs quantum wells and is designed for lasing at 980 nm.
4
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Photoreflectance Studies of InGaAs/GaAs/AlGaAs Single Quantum Well Laser Structures

81%
Ochalski T., Żuk J., Regiński K., Bugajski M.
Acta Physica Polonica A
|
1998
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vol. 94
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issue 3
463-467
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.
5
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High Resistivity AlGaAs Grown by Low Temperature MBE

81%
Radomska D., Ratajczak J., Regiński K., Bugajski M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
492-496
EN
Al_{0.3}Ga_{0.7}As layers were grown by molecular beam epitaxy using substrate temperature 200-300°C, tetrameric As and two values of As/Ga+Al flux ratio i.e. 3 or 8. The post-growth annealing was performed in situ at 600°C for 20 min under As-overpressure. The samples were characterised by reflection high-energy electron diffraction, transmission electron microscope and room-temperature I-V measurements of n^{+}/LT grown layer /n^{+} resistors. The resistivity and trap-filled limited voltage have been determined. The best layers exhibited ρ of the order of 10^{9} Ω cm, were monocrystalline, uniformly precipitated and without dislocations.
6
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Monte Carlo Studies of Quantum Cascade Lasers

81%
Borowik P., Thobel J., Bugajski M., Adamowicz L.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue S
S-49-S-51
EN
Results of multi particle Monte Carlo studies of a mid-infrared QCL structure, for the first time fabricated by Page et al., are presented. It has been demonstrated that for the considered structure design at least 9 electron energy levels per laser segment should be used to correctly describe the electric current properties. Mechanisms responsible for electron population on higher laser level are discussed.
7
Publication available in full text mode
Content available

3D self-consistent solution of Poisson and Schrödinger equations for electrostatically formed quantum dot

81%
Machowska-Podsiadło E., Mączka M., Bugajski M.
Bulletin of the Polish Academy of Sciences: Technical Sciences
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2007
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vol. 55
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issue 2
8
Publication available in full text mode
Content available

Resonant Cavity Enhanced Photonic Devices

71%
Bugajski M., Muszalski J., Ochalski T., Kątcki J., Mroziewicz B.
Acta Physica Polonica A
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2002
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vol. 101
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issue 1
105-118
EN
In the present paper we review our recent works on technology, basic physics, and applications of one-dimensional photonic structures. We demonstrate spontaneous emission control in In_xGa_{1-x}As/GaAs planar microcavities with distributed Bragg reflectors. In general, observed trends are in agreement with theoretical predictions. We also demonstrate the operation of resonant-cavity light emitting diodes and optically pumped vertical cavity light emitting diodes developed recently at the Department of Physics and Technology of Low-Dimensional Structures of the Institute of Electron Technology.
9
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Time-Resolved Microwave Spectroscopy of High Electron Mobility GaAs/AlGaAs Structures

71%
Khachepuridze A., Ivanov V., Godlewski M., Regiński K., Bugajski M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
387-391
EN
Mechanism of the optical detection of cyclotron resonance via emission from 2D electron gas in modulation doped quantum wells and in high electron mobility structures of GaAs/AlGaAs is discussed based on the results of time-resolved optical detection of cyclotron resonance. An important role of impact ionization processes is demonstrated. We also show that microwave radiation destroys emission enhancement at the Fermi level and the relevant mechanism is proposed.
10
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The Study of Thermal Properties of GaAs/AlGaAs Quantum Cascade Lasers

71%
Pruszyńska-Karbownik E., Karbownik P., Szerling A., Kosiel K., Bugajski M.
Acta Physica Polonica A
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2009
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vol. 116
|
issue S
S-60-S-61
EN
Temperature change in quantum cascade laser can be estimated by studying the device resistance change. Using this method we compared quantum cascade laser structure mounted on diamond heat spreader and without heat spreader. We have shown that the use of heat spreader reduces temperature increase even by 40%.
11
Content available remote

Visible Light Emission from Porous Silicon

71%
Bugajski M., Wesołowski M., Lewandowski W., Ornoch J., Kątcki J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
914-918
EN
The aim of this paper is the study of porous Si prepared by preferential anodic dissolution in concentrated HF acid solutions. Porous silicon layers exhibited extremely efficient luminescence in the 700-900 nm range at room temperature. Basic characteristics of this luminescence strongly suggest the intrinsic origin of the process, directly related to quantum confinement. The additional transmission-electron-microscopy and electron-diffraction studies - were performed to support hypothesis that luminescence originates from silicon nanostructures.
12
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Fermi-Edge Singularity in Excitonic Spectra of Modulation Doped AlGaAs/GaAs Quantum Wells

62%
Bugajski M., Regiński K., Godlewski M., Wesołowski M., Holtz P., Buyanov A., Monemar B.
Acta Physica Polonica A
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1996
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vol. 90
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issue 4
751-754
EN
The dynamic response of an electron Fermi sea to the presence of optically generated holes gives rise to an enhanced interaction of correlated electron-hole pairs near the Fermi level, resulting in an enhanced oscillator strength for optical transitions, referred to as the Fermi-edge singularity. We studied this effect in modulation-doped quantum wells which provide confined dense Fermi sea, spatially separated from dopant atoms, easily accessible for investigations under low excitation conditions. The Fermi-edge singularity was observed in both photoluminescence and photoluminescence excitation experiments, although in the case of photoluminescence the samples had to be either co-doped with acceptors in the wells to provide necessary localization of holes or designed to allow for nearly resonant scattering between the electronic states near the Fermi energy and the next unoccupied subband of the 2D electron gas.
13
Content available remote

Molecular Beam Epitaxy Growth for Quantum Cascade Lasers

62%
Kosiel K., Szerling A., Kubacka-Traczyk J., Karbownik P., Pruszyńska-Karbownik E., Bugajski M.
Acta Physica Polonica A
|
2009
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vol. 116
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issue 5
806-813
EN
The fabrication of quantum cascade lasers emitting at 9 μm is reported. The devices operated in pulsed mode at up to 260 K. The peak powers recorded at 77 K were over 1 W and the slope efficiency η ≈ 0.5-0.6 W/A per uncoated facet. This has been achieved by the use of GaAs/Al_{0.45}Ga_{0.55}As heterostructure, with the "anticrossed-diagonal" design. Double plasmon planar confinement with Al-free waveguide has been used to minimize absorption losses. The double trench lasers were fabricated using standard processing technology, i.e., wet etching and Si_{3}N_{4} for electrical insulation. The quantum cascade laser structures have been grown by molecular beam epitaxy, with Riber Compact 21 T reactor. The stringent requirements - placed particularly on the epitaxial technology - and the influence of technological conditions on the device structure properties were presented and discussed in depth.
14
Content available remote

Fermi-Edge Singularity in Luminescence Spectra of P-Type Modulation Doped AlGaAs/GaAs Quantum Wells

62%
Bugajski M., Godlewski M., Regiński K., Holtz P., Bergman J., Monemar B.
Acta Physica Polonica A
|
1998
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vol. 94
|
issue 2
265-270
EN
We have studied an enhancement of the oscillator strength for optical transitions near the Fermi energy in p-type modulation-doped quantum wells, which, so far, deserved much less attention than analogous n-type systems, because of the complicated valence band structure involved. The relatively wide (L=150 Å) quantum wells and high doping levels were used, containing more than one occupied subband. The enhancement in the photoluminescence intensity at the Fermi energy resulted from the strong correlation and multiple scattering of holes near the Fermi edge by the localized electrons.
15
Content available remote

Mid-Infrared GaAs/AlGaAs Quantum Cascade Lasers Technology

62%
Szerling A., Karbownik P., Kosiel K., Kubacka-Traczyk J., Pruszyńska-Karbownik E., Płuska M., Bugajski M.
Acta Physica Polonica A
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2009
|
vol. 116
|
issue S
S-45-S-47
EN
The fabrication technology of AlGaAs/GaAs based quantum cascade lasers is reported. The devices operated in pulsed mode at up to 260 K. The peak powers recorded at 77 K were over 1 W for the GaAs/Al_{0.45}Ga_{0.55}As laser without anti-reflection/high-reflection coatings.
16
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Inter-Island Energy Transfer in AlGaAs/GaAs Quantum Wells Grown by Molecular Beam Epitaxy

62%
Godlewski M., Holz P., Bergman J., Monemar B., Regiński K., Bugajski M.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 5
1007-1011
EN
The results of photoluminescence, time-resolved photoluminescence, photoluminescence excitation and photoluminescence kinetics studies are presented for a Al_{0.3}Ga_{0.7}As/GaAs quantum well system grown without growth interruptions at the interfaces. The time-resolved photoluminescence measurements show drift of excitons towards lower energy states induced in a quantum well by potential fluctuations. We present also a first direct evidence for migration of free excitons from the 24 to 25 ML regions of the quantum well and interpret these results within a linear rate model, deriving the transition rate of 290 ps^{-1}. Such inter-island migration processes have been observed till now only in growth interrupted structures.
17
Content available remote

Influence of Growth Conditions on Exciton Properties in Thin Quantum Wells of GaAs/AlGaAs

62%
Godlewski M., Bergman J. P., Holtz P. O., Monemar B., Bugajski M., Regiński K., Kaniewska M.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
719-722
EN
Exciton properties in growth interrupted quantum wells of GaAs/AlGaAs are compared with those observed for structures grown with­out growth interruption during the molecular beam epitaxy process. We report observation of quasi-localized excitons in quantum well structures grown without growth interruptions. Quasi-localized excitons drift towards the states of a lower potential energy in the quantum well. For growth in­terrupted MBE structures islands with a constant quantum well thickness become large compared to the exciton radius. Free or lightly localized exci­tons are observed in that case.
18
Publication available in full text mode
Content available

GaAs/AlGaAs (~9.4 μm) quantum cascade lasers operating at 260 K

52%
Kosiel K., Bugajski M., Szerling A., Kubacka-Traczyk J., Sankowska I., Karbownik P., Trajnerowicz A., Karbownik E., Pierściński K., Pierścińska D.
Bulletin of the Polish Academy of Sciences: Technical Sciences
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2010
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issue 4
19
Content available remote

Low Threshold Room Temperature AlGaAs/GaAs GRIN SCH SQW Lasers Grown by MBE

52%
Kaniewska M., Regiński K., Muszalski J., Kryńska D., Litkowiec A., Kaniewski J., Wesołowski M., Bugajski M.
Acta Physica Polonica A
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1996
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vol. 90
|
issue 4
847-850
EN
Low threshold room temperature AlGaAs/GaAs graded-index separate-confinement heterostructure single quantum well (GRIN SCH SQW) lasers were prepared by MBE. The influence of the growth temperature on the laser parameters was studied. Due to the high temperature MBE growth and the use of p-contact layer in the form of thin quasi-metallic beryllium layer significant reduction of the threshold current was achieved.
20
Content available remote

Identification of Residual Impurities in Si-Doped MBE Grown GaAs

52%
Kaniewska M., Regiński K., Kaniewski J., Muszalski J., Ornoch L., Adamczewska J., Marczewski J., Bugajski M., Mizera E.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 4
775-778
EN
The changes of dopant vaporization enthalpy in GaAs:Si grown by mole­cular beam epitaxy revealed the presence of residual donors related to group VI elements. This has been confirmed by deep level transient spectroscopy studies of AlGaAs:Si layers grown in the same MBE system. It is argued that a commonly observed deep trap labelled E2 is probably related to Te, Se or S. The measurements have been performed on near-ideal Al Schottky barriers grown in situ by MBE.
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