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Wyszukujesz frazę "Köhler, K." wg kryterium: Autor


Wyświetlanie 1-6 z 6
Tytuł:
Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs
Autorzy:
Binder, J.
Korona, K.
Borysiuk, J.
Wysmołek, A.
Baeumler, M.
Köhler, K.
Kirste, L.
Powiązania:
https://bibliotekanauki.pl/articles/1492933.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
72.40.+w
73.61.Ey
Opis:
In this work we present measurements of GaInN/GaN light emitting diodes (LEDs) with an active layer consisting of three quantum wells made of $Ga_{0.9}In_{0.10}N$ that have different widths (1.8 nm, 2.7 nm, 3.7 nm). A comparison of emission and absorption (photocurrent) on the same sample revealed a shift in energy, with the emission energy being significantly lower. The shifts are about 0.02 eV, 0.03 eV, and 0.04 eV for the quantum wells having the widths of 1.8 nm, 2.7 nm, and 3.7 nm, respectively. This can be explained by a shift of the ground state energy caused by the quantum confined Stark effect. Calculations show that due to the spontaneous polarization and the piezoelectric effect a strong electric field of the order of 1 MV/cm was present in the GaInN quantum wells. Simulations of ground-state energies in the model of an infinite square well under the influence of an electric field with a matched effective well width were performed and used to interpret the experimental results.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 918-920
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:
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:
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:
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:
Fluorescence Properties of An Electron Acceptor Substituted Bis-Pyrazolo-Pyridine Derivative: NO$\text{}_{2}$-DMPP
Autorzy:
Rechthaler, K.
Schamschule, R.
Parusel, A. B. J.
Rotkiewicz, K.
Piorun, D.
Köhler, G.
Powiązania:
https://bibliotekanauki.pl/articles/1995490.pdf
Data publikacji:
1999-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.50.Dq
34.70.+e
Opis:
The fluorescence properties of 3,5-dimethyl-1,7-diphenyl-4 -(4'-nitro-phenyl)-bis-pyrazolo-[3,4-b;4',3'-e]-pyridine (NO$\text{}_{2}$-DMPP) and its parent compound 3,5-dimethyl-1,7-diphenyl-bis-pyrazolo-[3,4-b;4',3'-e]-pyridine (BPP, without the nitrophenyl substituent) were investigated. BPP is a highly fluorescent blue emitter and the fluorescence properties, the emission wavelength, and the fluorescence quantum yield, depend only slightly on solvent. On the contrary, acceptor substituted NO$\text{}_{2}$-DMPP shows dual fluorescence: A long-wavelength component experiences a red-shift with increasing solvent polarity but is efficiently quenched when the polarity exceeds that of solvents like 1,2-dichloroethane or 1-bromopropane. A weak short-wavelength component changes only slightly its position and intensity upon variation of the solvent but its yield increases strongly at low temperatures. The experimental results are discussed in the context of the results of semiempirical calculations which show that fluorescence originates from two closely lying fluorescent states which change their sequence and properties when the polarity of the solvent is varied. A twisted intramolecular charge transfer (TICT) state does most likely not contribute to the emission properties, because of its high energy.
Źródło:
Acta Physica Polonica A; 1999, 95, 3; 321-334
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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