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Wyświetlanie 1-15 z 16
Tytuł:
Photoreflectance of Epitaxial InGaAs Quantum Rods
Autorzy:
Nedzinskas, R.
Karpus, V.
Čechavičius, B.
Kavaliauskas, J.
Valušis, G.
Li, L.
Khanna, S.
Linfield, E.
Powiązania:
https://bibliotekanauki.pl/articles/1505523.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Cr
81.05.Ea
Opis:
Photoreflectance spectroscopy and photoluminescence have been used to study the optical properties and electronic structure of InGaAs quantum rods grown by molecular beam epitaxy. Spectral features associated with interband optical transitions localized in the quantum rod and the surrounding quantum well regions are examined. Experimental results are compared with calculations performed within the envelope function approximation. A red shift of the quantum rod- and a blue shift of the quantum well-related optical transitions, along with a significant increase in PL intensity have been observed if an $As_4$ source is used instead of an $As_2$ source during the molecular beam epitaxial growth.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 164-166
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strong Electric Field Driven Carrier Transport Non-Linearities in n-Type GaAs/AlGaAs Superlattices
Autorzy:
Subačius, L.
Venckevičius, R.
Kašalynas, I.
Seliuta, D.
Valušis, G.
Schmidt, J.
Lisauskas, A.
Roskos, H.
Alekseev, K.
Köhler, K.
Powiązania:
https://bibliotekanauki.pl/articles/1505524.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.65.Cd
06.60.Jn
73.90.+f
Opis:
Nanosecond pulsed technique was used to study and discriminate strong electric field induced effects in carrier transport in silicon doped GaAs/$Al_{0.3}Ga_{0.7}As$ superlattices at room temperature. The experiment shows that the superlattice can serve as gain media to employ parametric phenomena for microwave amplification.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 167-169
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge Carrier Transport Properties in Single-Walled Carbon Nanotube Fibers
Autorzy:
Ksenevich, V.
Seliuta, D.
Martūnas, Z.
Kašalynas, I.
Valušis, G.
Galibert, J.
Kozlov, M.
Samuilov, V.
Powiązania:
https://bibliotekanauki.pl/articles/1813401.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.63.Fg
Opis:
Transport properties via temperature dependences of sample resistance R(T) and influence of microwave field of 10 GHz on the conductivity of the single-walled carbon nanotubes fibers are investigated. The R(T) dependences studied within 4.2-300 K can be well approximated by the Mott law for 3D variable range hopping below T=80 K and by typical law for fluctuation-induced tunnelling model within the temperature range 80-300 K. We associate the observed increase in the conductivity with microwave power by increase in hopping probability of the charge carriers between single-walled carbon nanotubes.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 1039-1042
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy Spectrum of InAs Quantum Dots in GaAs/AlAs Superlattices
Autorzy:
Nedzinskas, R.
Čechavičius, B.
Kavaliauskas, J.
Karpus, V.
Krivaitė, G.
Tamošiūnas, V.
Valušis, G.
Schrey, F.
Unterrainer, K.
Strasser, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813385.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
Opis:
Photo- and contactless electroreflectance spectroscopies were applied to study optical properties and electronic structure of GaAs/AlAs superlattice systems with embedded InAs quantum dots. The observed interband transitions related to the quantum dot ground and excited states, as well as optical transitions in the combined system formed by the InAs wetting layer and GaAs/AlAs superlattice are discussed.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 975-978
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Quantum Effects in Carbonaceous Materials Near the Metal-Insulator Transition by Means of THz Photoconductivity
Autorzy:
Dorosinets, V.
Ksenevich, V.
Seliuta, D.
Martūnas, Z.
Valušis, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813203.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.Rn
Opis:
A series of carbonaceous fibers with conductivity tuned to the metal-insulator transition were prepared by heat treatment of chemically modified polymer precursors. Peculiar behaviour of the resistivity versus temperature dependence R(T) at low temperatures suggests quantum corrections to the Drude conductivity due to weak localization and electron-electron interaction dominating in the conductivity. The THz conductivity method is employed to study the modification of the density of states and provides evidence for a strong change in density of states at the Fermi level caused by the quantum effects.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 875-878
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radiative Recombination Spectra of Heavily p-Type δ-Doped GaAs/AlAs MQWs
Autorzy:
Kundrotas, J.
Čerškus, A.
Valušis, G.
Lachab, M.
Khanna, S.
Harrison, P.
Linfield, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813382.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.67.De
71.30.+h
Opis:
We present a study of the photoluminescence properties of heavily Be δ-doped GaAs/AlAs multiple quantum wells measured at room and liquid nitrogen temperatures. Possible mechanisms for photocarriers recombination are discussed, with a particular focus on the peculiarities of the excitonic and free carriers-acceptors photoluminescence emissions occurring below and above the Mott metal-insulator transition. Moreover, based on a simple theoretical model, it is found that the critical impurities concentration to observe the Mott transition in the multiple quantum wells samples exhibiting 15 nm wells width and 5 nm thick barrier layers is ≈3×$10^{12} cm^{-2}$.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 963-966
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Detection by the Entire Channel of High Electron Mobility Transistors
Autorzy:
Sakowicz, M.
Łusakowski, J.
Karpierz, K.
Knap, W.
Grynberg, M.
Köhler, K.
Valusis, G.
Gołaszewska, K.
Kamińska, E.
Piotrowska, A.
Caban, P.
Strupiński, W.
Powiązania:
https://bibliotekanauki.pl/articles/1811985.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.75.+a
78.20.Ls
85.30.Tv
07.57.Kp
Opis:
GaAs/AlGaAs and GaN/AlGaN high electron mobility transistors were used as detectors of THz electromagnetic radiation at liquid helium temperatures. Application of high magnetic fields led to the Shubnikov-de Haas oscillations of the detection signal. Measurements carried out with a simultaneous modulation of the intensity of the incident THz beam and the transistor gate voltage showed that the detection signal is determined by the electron plasma both in the gated and ungated parts of the transistor channel. This result is of importance for understanding the physical mechanism of the detection in high electron mobility transistors and for development of a proper theoretical description of this process.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1343-1348
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Detection with δ-Doped GaAs/AlAs Multiple Quantum Wells
Autorzy:
Seliuta, D.
Čechavičius, B.
Kavaliauskas, J.
Krivaitė, G.
Grigelionis, I.
Balakauskas, S.
Valušis, G.
Sherliker, B.
Halsall, M.
Lachab, M.
Khanna, S.
Harrison, P.
Linfield, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813214.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.-w
85.30.De
Opis:
The authors demonstrate selective detection of terahertz radiation employing berylliumδ-doped GaAs/AlAs multiple quantum wells. The sensitivity up to 1 V/W within 4.2-7.3 THz range at liquid helium temperatures is reached. The Franz-Keldysh oscillations observed in photo- and electroreflectance spectra allowed one to estimate built-in electric fields in the structures studied. It was found that the electric field strength in the cap layer region could vary from 10 kV/cm up to 26 kV/cm, depending on the structure design and temperature.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 909-912
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Resonant Detection by Plasma Waves in Nanometric Transistors
Autorzy:
Teppe, F.
El Fatimy, A.
Boubanga, S.
Knap, W.
Seliuta, D.
Valusis, G.
Chenaud, B.
Powiązania:
https://bibliotekanauki.pl/articles/1813191.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Nr
71.45.Lr
72.30.+q
Opis:
The plasma waves in gated two-dimensional electron gas have a linear dispersion law, similar to the sound waves. The transistor channel is acting as a resonator cavity for the plasma waves, which can reach frequencies in the THz range for a sufficiently short gate length field effect transistors. A variety of possible applications of field effect transistor operating as a THz device were suggested. In particular, it was shown that the nonlinear properties of plasma oscillations can be utilized for THz tunable detectors. During the last few years THz detection related to plasma wave instabilities in nanometer size field effect transistors was demonstrated experimentally. In this work we review our recent experimental results on the resonant plasma wave detection at cryogenic and room temperatures.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 815-820
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Spectroscopy of Ordered $PbSc_{1//2}Nb_{1//2}O_3$ Ceramics
Autorzy:
Macutkevič, J.
Adomavičius, R.
Krotkus, A.
Valušis, G.
Grigalaitis, R.
Banys, J.
Bormanis, K.
Sternberg, A.
Powiązania:
https://bibliotekanauki.pl/articles/1813210.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Gm
77.80.-e
77.80.Bh
Opis:
The ordered $PbSc_{1//2}Nb_{1//2}O_3$ ceramics were studied by THz transmission spectroscopy in the temperature range of 80-300 K. Below ferroelectric phase transition temperature the strength of central mode gradually decreases and gives evidence for a mixed displacive and order-disorder character of the transitions. Ferroelectric phase transition is connected with an abrupt freezing and rise of polar nanoregions into ferroelectric domains.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 883-886
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes
Autorzy:
Valušis, G.
Seliuta, D.
Tamošiūnas, V.
Širmulis, E.
Balakauskas, S.
Gradauskas, J.
Sužiedėlis, A.
Ašmontas, S.
Anbinderis, T.
Narkūnas, A.
Papsujeva, I.
Lisauskas, A.
Roskos, H. G.
Köhler, K.
Powiązania:
https://bibliotekanauki.pl/articles/2041684.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.50.-h
85.30.De
72.30.+q
Opis:
We suggest a novel approach to detect broad band, 0.078-2.52 THz, electromagnetic radiation at room temperature using an asymmetrically-shaped bow-tie diode based on a modulation-doped GaAs/AlGaAs structure. We show that the voltage sensitivity in the range from 0.078 THz up to 0.8 THz has a plateau and its value is within 0.3-0.5 V/W. We consider the bow-tie diode design to increase the sensitivity of the device.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 184-187
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamics of the Electric Field in a GaAs/AlGaAs Superlattice after Femtosecond Optical Excitation: Application of Time-Resolved Spectroscopic Techniques
Autorzy:
Lisauskas, A.
Blöser, C.
Sachs, R.
Roskos, H.
Juozapavičius, A.
Valušis, G.
Köhler, K.
Powiązania:
https://bibliotekanauki.pl/articles/1178281.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.65.Sq
78.47.+p
Opis:
We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/AlGaAs superlattice after pulsed optical excitation at low temperature. The electric field dynamics is investigated by tracing the spectral position of the Wannier-Stark transitions as a function of delay time. We determine the electron sweep-out time, extract detailed information about the picosecond-time-scale drift of the charge carriers by comparing the measured data with the results of semi-classical self-consistent model calculations, and evaluate the two experimental techniques with respect to their ability to provide information about the carrier and field dynamics.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 250-255
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Study of Optical Transitions in Be-Doped GaAs/AlAs Multiple Quantum Wells
Autorzy:
Kundrotas, J.
Čerškus, A.
Ašmontas, S.
Valušis, G.
Sherliker, B.
Halsall, M.
Harrison, P.
Steer, M.
Powiązania:
https://bibliotekanauki.pl/articles/1178273.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.-y
78.55.-m
Opis:
We present a photoluminescence study of optical transitions in Be acceptor-doped GaAs/AlAs multiple quantum wells at room and liquid nitrogen temperatures. We investigate excitonic spectra and reveal acceptor-impurity induced effects in multiple quantum wells having different width.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 245-249
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Finite-Difference Time-Domain Simulation of Mid- and Far-Infrared Quantum Cascade Lasers
Autorzy:
Tamošiūnas, V.
Kancleris, Ž.
Dagys, M.
Simniškis, R.
Tamošsiūnienė, M.
Valušis, G.
Strasser, G.
Unterrainer, K.
Powiązania:
https://bibliotekanauki.pl/articles/2041682.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.30.+q
78.66.-w
85.30.De
Opis:
We present simulations of mid- and far-infrared quantum cascade lasers operating with/without external magnetic field. Maxwell-Bloch solver based on the finite-difference time-domain method was used in our investigation. Reduction of the far-infrared quantum cascade laser emission intensity is associated with increased optical losses in highly doped layers when magnetic field is changed from 4.2 T to 6.2 T. A simulated emission spectrum of mid-infrared disc-shaped quantum cascade laser with 60μm radius is consistent with the experimentally observed irregular spacing between quantum cascade laser emission lines.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 179-183
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical and Terahertz Characterization of Be-Doped GaAs/AlAs Multiple Quantum Wells
Autorzy:
Čechavičius, B.
Kavaliauskas, J.
Krivaitė, G.
Seliuta, D.
Širmulis, E.
Devenson, J.
Valušis, G.
Sherliker, B.
Halsall, M.
Steer, M.
Harrison, P.
Powiązania:
https://bibliotekanauki.pl/articles/2041764.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.-w
85.30.De
Opis:
We report on optical, photoreflectance and surface photovoltage, as well as terahertz photocurrent investigation of Be-doped GaAs/AlAs multiple quantum wells at room and liquid helium temperatures, respectively. From the Franz-Keldysh oscillations observed in photoreflectance spectra we determine built-in electric fields within the structure. Interband transition energies calculated by the transfer matrix method are in qualitative agreement with experimentally determined values for the samples having various, from 2×10$\text{}^{10}$ up to 2.5×10$\text{}^{12}$ cm$\text{}^{-2}$, Be doping densities. The photocurrent observed in the range of 5.4-7.3 THz we associate with photoionization of Be-acceptor states.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 328-332
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 16

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