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1
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Terahertz Emission from Narrow Gap Semiconductors Photoexcited by Femtosecond Laser Pulses

100%
Adomavičius R., Urbanowicz A., Molis G., Krotkus A.
Acta Physica Polonica A
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2005
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vol. 107
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issue 1
132-136
EN
Large increase in the emitted terahertz power was observed for p-InAs samples with the p-doping levels of approximately 10^{16}-10^{17} cm^{-3}. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in the layer. Terahertz fields radiated by the samples of all three investigated Cd_xHg_{1-x}Te layers was of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification. Azimuthal angle and magnetic fields emission witness that it is caused by linear photo-Dember type processes.
2
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Optical Nonlinearities in PbSe Nanocrystals

100%
Aleksejenko G., Pačebutas V., Krotkus A.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
294-297
EN
The linear and nonlinear optical response of colloidal PbSe nanocrystals was investigated. Optical nonlinearity and its recovery dynamics in this system was measured and compared with other available experimental data. The saturation irradiance value for the bleaching effect and absorption cross-section were determined.
3
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Terahertz Emission from the Surfaces of InAs and Other Narrow-Gap Semiconductors

88%
Adomavičius R., Krotkus A., Molis G., Urbanowicz A., Malevich V.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
859-862
EN
THz pulses were used to investigate carrier dynamics in narrow-gap semiconductors. The measurement of the optically induced THz pulse absorption transients provided important insights into electron energy relaxation in the conduction band. In the second set of experiments, THz generation from the surfaces of various semiconductors was studied and compared. It was found that the most efficient THz emitters are semiconductors with a narrow band gap, large intervalley separation in the conduction band, and low nonparabolicity of the main valley.
4
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Optical Pump - Terahertz Probe Measurement of the Electron Dynamics in Ga_{1-x}Mn_xAs

88%
Šustavičiūtė R., Balakauskas S., Adomavičius R., Krotkus A., Sadowski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
311-314
EN
An optical pump - terahertz probe technique was used for measuring electron lifetime in various Ga_{1-x}Mn_xAs epitaxial layers with the subpicosecond temporal resolution. The measurements were performed on the samples with x up to 2%, which had large resistivities and were transparent in a THz frequency range. It has been found that an induced THz absorption relaxation is the fastest and electron lifetimes are the shortest for the samples with the smallest Mn content. For the samples with x=0.3% and x=2% this relaxation becomes much slower; its rate is comparable to the carrier recombination rate in Ga_{1-x}Mn_xAs substrate.
5
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Low-Temperature MBE Grown GaAs for Pulsed THz Radiation Applications

76%
Adomavičius R., Balakauskas S., Bertulis K., Geižutis A., Molis G., Krotkus A.
Acta Physica Polonica A
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2005
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vol. 107
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issue 1
128-131
EN
Attempts to optimize recombination characteristics of low-temperature MBE grown GaAs layers for their use in terahertz radiation devices are described and the characteristics of this material are compared with its alternative - As-ion implanted GaAs crystals.
6
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Transient Photoconductivity and Photoluminescence in InP:Cu

76%
Stalnionis A., Adomavic̆ius R., Krotkus A., Marcinkevic̆ius S., Leon R., Jagadish C.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
931-934
EN
Nonequilibrium photoexcited carrier dynamics in InP:Cu was investigated by two experimental techniques: the time-resolved photoluminescence up-conversion and the transient photoconductivity measurement. Both measurements show that doping with copper significantly modifies the photoexcited carrier relaxation in indium phosphide. There are several strong indications that this effect originates from the carrier trapping at metallic precipitates.
7
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Ultrafast Carrier Trapping and High Resistivity of MeV Energy Ion Implanted GaAs

64%
Korona K., Jasiński J., Kurpiewski A., Kamińska M., Jagadish C., Tan H., Krotkus A., Marcinkevicius S.
Acta Physica Polonica A
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1996
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vol. 90
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issue 4
851-854
EN
Semi-insulating GaAs wafers were implanted with MeV As, Ga, O or Si ions at doses ranging from 1×10^{14} to 5×10^{16} cm^{-2}. Their structural properties were studied by electron microscopy and the Rutherford backscattering-channeling. Time resolved photoluminescence, electrical conductivity and the Hall effect were used to determine carrier lifetime and electrical properties of the material. Annealing of the samples at 600°C led to the recovery of transport in conduction band. The As, Ga and O implanted samples became semi-insulating, while the Si implanted samples were n-type. Carrier trapping times were short, shorter than 1 ps for the highest dose used. Models explaining the fast photocarrier decay are discussed.
8
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Role of Arsenic Antisite Defect in Nonstoichiometric Gallium Arsenide

64%
Jasiński J., Kurpiewski A., Korοna K., Kamińska M., Ρalczewska M., Krotkus A., Marcinkievicius S., Liliental-Weber Z., Tan H. H., Jagadish C.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
747-750
EN
Over the last few years there have been many studies of GaAs layers grown at low temperatures (180-300°C), so called LT GaAs. The interest in LT GaAs was motivated by the potential application of 600oC annealed LT GaAs in microwave and fast optoelectronic devices because of its short photocarrier lifetime, reasonable mobility and high resistivity. These proper­ties are associated with the nonstoichiometry of LT GaAs. Recently, studies of comparable material, nonstoichiometric GaAs produced by arsenic ion implantation have been initiated. There is still a strong controversy as to whether the arsenic antisite (As_{Ga}) or arsenic precipitates are responsible for unique electrical properties of both materials. This paper presents the results of structural and electrical studies of high energy As implanted GaAs and comments on relationships between the structure and the resulting electrical properties.
9
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THz Time Domain Spectroscopy of Thin Gold Layers on GaAs

64%
Szczytko J., Adomavicius R., Papis E., Barańska A., Wawro A., Krotkus A., Piętka B., Łusakowski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1118-1120
EN
Thin layers of Au with the thickness of several nanometers were prepared on a semi-insulating GaAs substrate. The layers' thickness was determined by ellipsometry. THz time-domain spectroscopy was applied to determine a complex index of refraction of thin Au layers. The obtained results allow for a more precise modeling of the performance of semiconductor devices at THz frequencies.
10
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Terahertz Spectroscopy of Ordered PbSc_{1/2}Nb_{1/2}O_3 Ceramics

64%
Macutkevič J., Adomavičius R., Krotkus A., Valušis G., Grigalaitis R., Banys J., Bormanis K., Sternberg A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
883-886
EN
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.
11
Content available remote

Study of Terahertz Emission from Surfaces of Cu(InGa)Se_2 Layers

64%
Koroliov A., Arlauskas A., Balakauskas S., Šoliūnas M., Maneikis A., Krotkus A., Šetkus A., Tamošiūnas V.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
846-848
EN
In this contribution, we report on investigations of THz emission from Cu(In,Ga)Se_2 layers, deposited from a single copper-deficient sputtering target. Emission from Cu(In,Ga)Se_2 layer surface and from multilayer structure with transparent ZnO layers were studied. It was determined that additional undoped ZnO layer reduces the amplitude of THz emission, while additional n-type ZnO layers increase the emission amplitude again. This effect can be attributed to stronger electric field in the heterostructure between p-type Cu(In,Ga)Se_2 and n-type ZnO layers.
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