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Wyświetlanie 1-14 z 14
Tytuł:
Field Dependence of Spin Lifetimes in Wurtzite Materials
Autorzy:
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2044501.pdf
Data publikacji:
2005-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.20.Nr
71.70.Ej
71.70.Fk
Opis:
We present first-principles calculations of the zero field spin splitting of energy bands in wurtzite materials. Our calculations reveal that the huge electric fields originating from strong piezo- and pyroelecric character of nitrides do not increase the spin splitting of bands in nitride heterostructures. This implicates long spin lifetimes in quantum structures based on these materials and weak possibility of tuning with external electric field.
Źródło:
Acta Physica Polonica A; 2005, 108, 5; 777-780
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Spin Splitting in III-V Semiconductors
Autorzy:
Skierkowski, A.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2044536.pdf
Data publikacji:
2005-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.Ar
71.70.Ej
71.20.-b
71.20.Nr
Opis:
We present first-principles studies of the zero field spin splitting of energy bands in typical III-V semiconductors. Our calculations reveal that the strain induces linear-k spin splitting of the conduction band in theΓ point, which is linear in strain, and determine the magnitude of the so-called acoustic phonon constant that characterizes the magnitude of the spin splitting. In addition, we show that optical phonons lead to spin-flip processes and we present quantitative results for the spin-phonon deformation potentials in GaAs. Most importantly, the calculations show that the linear-k spin splitting can be resonantly enhanced when bands cross in a particular point of the Brillouin zone. This resonant enhancement of the bulk inversion asymmetry coupling constant by more than one order of magnitude was observed in both valence and conduction bands and can be steered by the application of the external stress. This allows tailoring of the spin relaxation and spin precession of conduction electrons in nanostructures to a much larger extent than was hitherto assumed.
Źródło:
Acta Physica Polonica A; 2005, 108, 5; 867-872
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Density Functional Studies of Nonlinear Elastic Properties for Zinc-Blende Nitrides
Autorzy:
Łopuszyński, M.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047721.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
43.25.+y
62.50.+p
Opis:
In this paper we present a method of calculating third-order elastic constants C$\text{}_{ijk}$ and its application to zinc-blende nitrides AlN, GaN, and InN. Our approach is based on accurate ab initio calculations of both energy and stress as a function of applied strain. Ab initio computations are performed within density functional theory framework. To assess the reliability of the presented method, we compare our theoretical findings for GaAs with experimental results for C$\text{}_{ijk}$ available for this material.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 443-447
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of Spin Lifetimes in [110] Strained GaAs
Autorzy:
Skierkowski, A.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047003.pdf
Data publikacji:
2006-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Eq
71.70.Fk
71.70.Ej
72.25.Rb
Opis:
We present first-principles studies of the zero field spin splitting of conduction band in [110] strained GaAs that determine spin lifetimes in semiconductors. Our calculations reveal strong anisotropy of the linear-k spin splitting in the (110) plane of the Brillouin zone and very minor in the (001) plane. This provides a qualitative understanding of the difference in the spin lifetimes in the GaAs/AlAs heterostructures grown along [100] and [110] crystallographic directions.
Źródło:
Acta Physica Polonica A; 2006, 110, 3; 353-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strain Induced k-Linear Spin Splitting in III-V Semiconductors
Autorzy:
Skierkowski, A.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047724.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Fk
71.15.Rf
71.70.Ej
71.55.Eq
Opis:
We present theoretical studies of the linear-k strain induced spin splitting of the conduction band in the zinc-blende semiconductors. The studies are based on ab initio calculations performed within the density functional theory with non-scalar relativistic effects fully taken into account. This permits one to construct effective Hamiltonian for the strain induced linear-k spin splitting of the zinc-blende semiconductors. This Hamiltonian reproduces fully the structure of the strain induced linear-k spin splitting and generalizes previously introduced and commonly used effective Hamiltonian.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 455-460
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure Dependence of Elastic Constants in Zinc-Blende III-N and Their Influence on the Light Emission in Nitride Heterostructures
Autorzy:
Łepkowski, S. P.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2038098.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.50.+p
Opis:
We studied the nonlinear elasticity effects for the case of III-N compounds. Particularly, we determined the pressure dependences of elastic constants, in zinc-blende InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We found significant and almost linear increase in C$\text{}_{11}$, C$\text{}_{12}$ with pressure for considered nitrides compounds. Much weaker dependence on pressure was observed for C$\text{}_{44}$. We also discussed pressure dependences of two-dimensional Poisson's ratio and elastic anisotropy coefficient. Finally, we showed that the pressure dependence of elastic constants results in significant reduction of the pressure coefficient of the energy emission in cubic InGaN/GaN quantum wells and essentially improves the agreement between experimental and theoretical values.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 559-566
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Nonlinear Elasticity and Electromechanical Coupling on Optical Properties of InGaN/GaN and AlGaN/AlN Quantum Wells
Autorzy:
Łepkowski, S. P.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2046928.pdf
Data publikacji:
2006-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.De
62.20.Dc
77.65.-j
Opis:
We present theoretical studies of effects of the nonlinear elasticity and the electromechanical coupling on the optical properties of InGaN/GaN and AlGaN/AlN quantum wells. In these structures, due to the lattice misfit between constituents, the quantum wells are compressively strained and the intrinsic hydrostatic pressure is present. Therefore, the nonlinear elasticity is investigated by taking into account the pressure dependence of elastic stiffness tensor for the strained quantum wells. We show that this effect leads to (i) decrease in the volumetric strain and (ii) increase in the polarization-induced built-in electric field in the quantum wells. Consequently, the interband transition energies in the quantum wells decrease when the nonlinear elasticity of nitrides is considered. On the other hand, we show that the effect of electromechanical coupling, i.e., co-existence of ordinary and converse piezoelectric effects results in increase in the interband transition energies in the considered quantum wells. It turns out that the influence of the nonlinear elasticity on the optical properties is stronger than the influence of electromechanical coupling for InGaN/GaN quantum wells, while for AlGaN/GaN the opposite situation is observed.
Źródło:
Acta Physica Polonica A; 2006, 110, 2; 237-242
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferromagnetism in Cr-Based Diluted Magnetic Semiconductors
Autorzy:
Blinowski, J.
Kacman, P.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/1933725.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Gm
75.50.Pp
75.50.Dd
Opis:
It has been recently established that in zinc chalcogenides with Cr$\text{}^{2+}$ paramagnetic ions the p-d interactions are ferromagnetic. We clarify the origins of this property and make predictions concerning other Cr-based diluted magnetic semiconductors. The observation of the ferromagnetic p-d interaction resuscitated hopes for ferromagnetic d-d exchange interactions in diluted magnetic semiconductors. We have calculated the nearest-neighbor superexchange integrals in Cr-based diluted magnetic semiconductors. No simple correlation between the signs of p-d and d-d interactions has been found. Still, there are extended energy regions where the calculated superexchange is ferromagnetic and the act ual parameters of DMS with Cr$\text{}^{2+}$ seem to match these regions.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 683-686
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stability and Band Offsets of Heterovalent SiC/GaN Interfaces
Autorzy:
Städele, M.
Majewski, J. A.
Vogl, P.
Powiązania:
https://bibliotekanauki.pl/articles/1934004.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.Fx
73.20.Dx
Opis:
We present first-principles calculations of structural and electronic properties of heterovalent SiC/GaN [001] interfaces. We have investigated interfaces consisting of one and two mixed layers with lateral c(2 × 2), 2 × 1, 1 × 2, 2 × 2 arrangements. Abrupt polar [001] interfaces are energetically unstable with respect to reconstruction. The preferred bonding configurations are found to be Si-N and Ga-C, which correspond to cation-anion bonding. The valence band offsets of the energetically most favorable structures are 1.39 eV for the interface with a mixed Ga/Si layer and 0.45 eV with a mixed C/N layer, with the top of the valence band lying higher in SiC.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 917-920
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bands, Bonds, and Polarizations in Nitrides - from Electronic Orbitals to Electronic Devices
Autorzy:
Majewski, J. A.
Zandler, G.
Vogl, P.
Powiązania:
https://bibliotekanauki.pl/articles/2027476.pdf
Data publikacji:
2001-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Kp
77.65.Ly
Opis:
A key property of the nitrides is the fact that they possess large spontaneous and piezoelectric polarization fields that allow a significant tailoring of the carrier dynamics and optical properties of nitride devices. In this paper, based on first-principles calculations of structural and electronic properties of bulk nitrides and their heterostructure, we investigate the potential of this novel material class for modern device applications by performing self-consistent Monte Carlo simulations. Our studies reveal that the nitride based electronic devices have characteristics that predispose them for high power and high frequency applications. We demonstrate also that transistor characteristics are favorably influenced by the internal polarization induced electric fields.
Źródło:
Acta Physica Polonica A; 2001, 100, 2; 249-260
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Calculations of Cohesive and Electronic Properties of Quaternary AlGaInN Alloys
Autorzy:
Łopuszyński, M.
Bartoszek, J.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047722.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Dk
61.66.-f
62.20.Dc
64.30.+t
Opis:
We present theoretical studies of the AlGaInN nitride quaternary alloys. The studies are based on ab initio calculations performed within the density functional theory and virtual crystal approximation. The equilibrium lattice constants, bulk moduli, and elastic constants were calculated for the whole possible range of concentrations of the alloy constituents. The theoretical values were then fitted with second- and third-order polynomials. For all properties studied, the considerable bowing was observed.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 449-454
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Elasticity in Wurtzite GaN/AlN Planar Superlattices and Quantum Dots
Autorzy:
Łepkowski, S. P.
Majewski, J. A.
Jurczak, G.
Powiązania:
https://bibliotekanauki.pl/articles/2044495.pdf
Data publikacji:
2005-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.-n
62.20.Dc
62.50.+p
Opis:
The elastic stiffness tensors for wurtzite GaN and AlN show a significant hydrostatic pressure dependence, which is the evidence of nonlinear elasticity of these compounds. We have examined how pressure dependence of elastic constants for wurtzite nitrides influences elastic and piezoelectric properties of GaN/AlN planar superlattices and quantum dots. Particularly, we show that built-in hydrostatic pressure, present in both quantum wells of the GaN/AlN superlattices and GaN/AlN quantum dots, increases significantly by 0.3-0.7 GPa when nonlinear elasticity is used. Consequently, the compressive volumetric strain in quantum wells and quantum dots decreases in comparison to the case of the linear elastic theory. However, the z-component of the built-in electric field in the quantum wells and quantum dots increases considerably when nonlinear elasticity is taken into account. Both effects, i.e., a decrease in the compressive volumetric strain as well as an increase in the built-in electric field, decrease the band-to-band transition energies in the quantum wells and quantum dots.
Źródło:
Acta Physica Polonica A; 2005, 108, 5; 749-754
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure and Temperature Dependence of Threshold Current in Semiconductor Lasers Based on InGaAs/GaAs Quantum-Well Systems
Autorzy:
Maziarz, M.
Piechal, B.
Bercha, A.
Bohdan, R.
Trzeciakowski, W.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2047719.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Px
85.60.Jb
Opis:
In the present paper we demonstrate that wide-range wavelength tuning of semiconductor lasers can be achieved by applying high pressure and low temperature. We report the experimentally measured dependence of the threshold current and emission energy on pressure and temperature in InGaAs/GaAs quantum-well lasers and provide the simple theoretical explanation of the physics behind the experimental findings.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 437-442
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of Semiconductor Nanostructures with nextnano$\text{}^{3}$
Autorzy:
Birner, S.
Hackenbuchner, S.
Sabathil, M.
Zandler, G.
Majewski, J. A.
Andlauer, T.
Zibold, T.
Morschl, R.
Trellakis, A.
Vogl, P.
Powiązania:
https://bibliotekanauki.pl/articles/2046896.pdf
Data publikacji:
2006-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.43.Cd
73.21.Fg
73.61.Ey
77.65.Ly
85.30.Tv
73.40.Mr
Opis:
nextnano$\text{}^{3}$ is a simulation tool that aims at providing global insight into the basic physical properties of realistic three-dimensional mesoscopic semiconductor structures. It focuses on quantum mechanical properties such as the global electronic structure, optical properties, and the effects of electric and magnetic fields for virtually any geometry and combination of semiconducting materials. For the calculation of the carrier dynamics a drift-diffusion model based on a quantum-mechanically calculated density is employed. In this paper we present an overview of the capabilities of nextnano$\text{}^{3}$ and discuss some of the main equations that are implemented into the code. As examples, we first discuss the strain tensor components and the piezoelectric effect associated with a compressively strained InAs layer for different growth directions, secondly, we calculate self-consistently the quantum mechanical electron density of a Double Gate MOSFET, then we compare the intersubband transitions in a multi-quantum well structure that have been obtained with a single-band effective mass approach and with an 8-band k·p model, and finally, we calculate the energy spectrum of a structure in a uniform magnetic field.
Źródło:
Acta Physica Polonica A; 2006, 110, 2; 111-124
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-14 z 14

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