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1
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Crystal Orientation Dependence of the Fundamental Optical Transition in type-II W-Design Quantum Well Structures

100%
Ryczko K.
Acta Physica Polonica A
|
2014
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vol. 126
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issue 5
1149-1153
EN
Using a multiband k·p theory the band structure properties of type-II W-design AlSb/InAs/GaInSb/InAs/AlSb quantum wells on GaSb substrates of various crystallographic orientations have been investigated. Such structures are predicted for the emission in a broad range of mid infrared from below 3 μm to beyond 10 μm. The energy of the fundamental optical transition and the corresponding oscillator strength have been determined in function of the layer structure details and versus the substrate orientation. In addition, the resulting optical anisotropy in such type-II quantum wells has been derived.
2
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Lateral Coupling within the Ensemble of InAs/InGaAlAs/InP Quantum Dashes

51%
Ryczko K., Sęk G., Misiewicz J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
805-808
EN
In this work we investigate the electronic structure of coupled quantum dashes. The respective confined state energy levels are calculated for various cross-sectional shapes and sizes of the dashes and in function of the lateral distance between them. The results are confronted with the existing experimental data on the optical transitions in such structures. It has been concluded that for realistic system parameters (geometry and spatial in-plane separation) the obtained direct coupling is weak and in most of the applications the dashes can be considered individually, as long as the ensemble is strongly inhomegeneous.
3
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Landauer Conductance of Generalized Fibonacci-Type Semiconductor Superlattices

45%
Salejda W., Kubisa M., Misiewicz J., Ryczko K., Tyc M.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
514-518
EN
The quantum model of quasi-one-dimensional generalized Fibonacci semiconductor superlattice with the mass of charge carriers depending on the position in superlattice is formulated. The Landauer electrical conductance σ_{L} of generalized Fibonacci semiconductor superlattice is studied analytically and numerically. The dynamical maps allowing us to calculate σ_{L} of the studied systems are presented. It is shown that σ_{L} as a function of incident energy E of charge carriers oscillates strongly and exhibits the resonant character. We have verified numerically that σ_{L}(E) reaches its local maximum for energies E corresponding to energy eigenvalues of charges in superlattice.
4
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Optical Transitions between Confined and Unconfined States in p-Type Asymmetric GaAs/InGaAs/AlGaAs QW Structures

45%
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.
5
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Content available

Skyrmions in a Hole Gas with Large Spin Gap and Strong Disorder

45%
Bryja L., Ryczko K., Wójs A., Misiewicz J., Potemski M.
Acta Physica Polonica A
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2006
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vol. 110
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issue 2
163-168
EN
In the photoluminescence excitation spectra of two-dimensional valence holes with large spin gap and strong disorder we find evidence for quantum Hall ferromagnetism and small skyrmions around the Landau level filling factorν=1. This interpretation is supported by numerical calculations.
6
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Influence of Built-in Electric Field on Forbidden Transitions in In_xGa_{1-x}As/GaAs Double Quantum Well by Three-Beam Photoreflectance

39%
Sęk G., Ryczko K., Misiewicz J., Bayer M., Wang T., Forchel A.
Acta Physica Polonica A
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2001
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vol. 100
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issue 3
417-424
EN
Photoreflectance spectroscopy has been used to study optical transitions in In_{0.045}Ga_{0.955}As/GaAs double quantum well at 80 K. The derivative nature of this contactless electromodulation technique allows for the observation of excited state transitions in the low-dimensional structure including the symmetry-forbidden ones. Excitonic symmetry-forbidden transitions can be observed due to the effect of mixing of heavy and light hole excitons and/or due to some asymmetry in the structure. We have shown that the built-in electric field in the region of double quantum well is weak enough (less than 0.5 kV/cm) not to cause any significant energetic shift of features due to quantum confined Stark effect, on one hand. On the other hand, it is sufficient to change strongly the oscillator strength of forbidden transitions. To change the internal electric field, we have used photoreflectance in the three-beam mode with a third beam continuously illuminating the sample and causing changes of the built-in electric fields due to the photovoltage effect. This method works as a contactless forward bias and allows for a change of the field down to the flat band conditions. We have shown that changes of built-in electric field by amount of a few tenths of kV/cm can modify the intensity of forbidden transitions significantly. We show that, although the mixing of excitons is still important, a very weak built-in electric field can be dominant in the observation of forbidden excitonic transitions in double quantum well.
7
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New Numerical Matrix Methods of Solving the Quasi-One-Dimensional Effective-Mass Equation

39%
Salejda W., Tyc M., Andrzejewski J., Kubisa M., Misiewicz J., Just M., Ryczko K.
Acta Physica Polonica A
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1999
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vol. 95
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issue 6
881-896
EN
New efficient numerical methods of computing eigenvalues and eigenvectors of quasi-one-dimensional effective-mass Hamiltonian with arbitrary coordinate dependence of charge carrier mass are presented. Within the proposed approach the effective-mass equation is replaced by a nonsymmetric or symmetric matrix eigenproblem which can be analysed numerically with the help of existing computer routines. The presented methods are verified in special semiconductor heterostructure cases that are solvable within other approaches. A generalization of the presented methods for nonparabolic materials is also discussed.
8
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Nonlinear Zeeman Splitting of Holes in Doped GaAs Heterostructures

39%
Kubisa M., Ryczko K., Jadczak J., Bryja L., Misiewicz J., Potemski M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
609-611
EN
Polarization-resolved photoluminescence from two-dimensional GaAs/GaAlAs heterostructures doped with acceptors was studied in high magnetic fields. Measurements were carried out in low temperatures up to 2 K and magnetic field up to 21 T. Experiments performed in the Faraday configuration enabled to resolve hole states with different spin orientation. We observed a nonlinear behavior of valence-band g factor in strong magnetic fields. To explain obtained results, a detailed theoretical calculation was carried out based on the Luttinger model for valence-band states. We examined the spin splitting of hole levels under the influence of both external magnetic field and built-in electric field existing in doped heterostructures. Changes of hole g factor with the width of the structure and the density of two-dimensional carriers are discussed.
9
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GaAs-Based Quantum Well Exciton-Polaritons beyond 1 μm

33%
Pieczarka M., Podemski P., Musiał A., Ryczko K., Sęk G., Misiewicz J., Langer F., Höfling S., Kamp M., Forchel A.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
817-820
EN
Realization of the Bose-Einstein condensate can provide a way for creation of an inversion-free coherent light emitter with ultra-low threshold power. The currently considered solutions provide polaritonic emitters in a spectral range far below 1 μm limiting their application potential. Hereby, we present optical studies of InGaAs/GaAs based quantum well in a cavity structure exhibiting polaritonic eigenmodes from 5 to 160 K at a record wavelength exceeding 1 μm. The obtained Rabi splitting of 7 meV was almost constant with temperature, and the resulting coupling constant is close to the calculated QW exciton binding energy. This indicates the very strong coupling conditions explaining the observation of polaritons at temperatures where the exciton dissociation is already expected, and allows predicting that room temperature polaritons could still be formed in this kind of a system.
10
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Room Temperature Carrier Kinetics in the W-type GaInAsSb/InAs/AlSb Quantum Well Structure Emitting in Mid-Infrared Spectral Range

33%
Syperek M., Ryczko K., Dallner M., Dyksik M., Motyka M., Kamp M., Höfling S., Misiewicz J., Sęk G.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1224-1228
EN
Room temperature carrier kinetics has been investigated in the type-II W-design AlSb/InAs/Ga_{0.80}In_{0.20}As_{0.15}Sb_{0.85}/InAs/AlSb quantum well emitting in the mid-infrared spectral range (at 2.54 μ m). A time-resolved reflectance technique, employing the non-degenerated pump-probe scheme, has been used as a main experimental tool. Based on that, a primary carrier relaxation time of 2.3±0.2 ps has been found, and attributed to the initial carrier cooling process within the quantum well states, while going towards the ground state via the carrier-optical phonon scattering mechanism. The decay of a quasi-equilibrium carrier population at the quantum well ground states is primarily governed by two relaxation channels: (i) radiative recombination within distribution of spatially separated electrons and holes that occurs in the nanosecond time scale, and (ii) the hole tunnelling out of its confining potential, characterized by a 240±10 ps time constant.
11
Content available remote

Optimizing the InGaAs/GaAs Quantum Dots for 1.3 μm Emission

27%
Maryński A., Mrowiński P., Ryczko K., Podemski P., Gawarecki K., Musiał A., Misiewicz J., Quandt D., Strittmatter A., Rodt S., Reitzenstein S., Sęk G.
|
EN
Hereby we present comprehensive experimental and theoretical study on fundamental optical properties and electronic structure of GaAs-based quantum dots grown using metalorganic chemical vapor deposition technique. The substantial redshift of emission, to the second telecommunication window of 1.3 μm, in comparison to standard InGaAs/GaAs quantum dots is obtained via strain engineering utilizing additional capping layer of In_{0.2}Ga_{0.8}As in this context referred to as strain reducing layer. It ensures lowering of the energy of the ground state transition to more application relevant spectral range. Optical properties of the quantum dot structure has been experimentally characterized by means of photoreflectance spectroscopy and power-dependent photoluminescence revealing 3 transitions originating from hybrid states confined in an asymmetric double quantum well formed of the wetting layer and strain reducing layer, as well as higher states of the quantum dots themselves with the first excited state transition separated by 67 meV from the ground state transition. Origin of the observed transitions was confirmed in theoretical modelling using 1-band single-particle approach for the quantum well part, and excitonic quantum dot spectrum obtained within 8 band k·p formalism followed by configuration interaction calculations, respectively. Additionally, photoluminescence excitation spectroscopy measurements allowed to identify a spectral range for efficient quasi-resonant excitation of the investigated quantum dots into the 2D density of states to be in the range of 835-905 nm.
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