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  1. 17 Acta Physica Polonica A

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  1. 17 Knap W.

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1
Content available remote

Universal Behaviour of Magnetoconductance due to Weak Localization in Two-Dimensional Systems - Example of GaInAs Quantum Wells

100%
Zduniak A., Dyakonov M. I., Litwin-Staszewska E., Knap W.
Acta Physica Polonica A
|
1995
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vol. 88
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issue 5
1053-1057
EN
Weak localization corrections to conductivity of a two-dimensional electron gas are studied by measurements of the magnetic field dependence of the conductivity in GalnAs quantum wells. We observe that, when presented as a function of the normalized magnetic field (x = B/B_{tr}, where B is the magnetic field, B_{tr} = ħ/4eτD, D is the diffusion constant and τ is momentum relaxation time), different samples show very similar high field behaviour. A theoretical description is developed that allows one to describe in a consistent way high and low field behaviour. The theory predicts universal (B^{-1/2}) behaviour of the conductivity correction for all 2D systems in the high field limit (r > 1). Low field behaviour depends strongly on spin and phase relaxation mechanisms. Comparison of the theory with experiment confirms the universal behaviour in the high field limit and allows one to estimate the spin and phase relaxation times for different GaInAs quantum wells.
2
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Far-Infrared Narrow-Band Photodetector Based on Magnetically Tunable Cyclotron Resonance-Assisted Transitions in Pure n-Type InSb

100%
Dmowski L. H., Cheremisin M., Skierbiszewski C., Knap W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
733-736
EN
We present the possibility of using magnetic field to enhance responsivity and to tune spectral range of far-infrared InSb detector (based on photoconductivity effect) beyond its standard range limited to about 30 cm^{-1}. We show that due to cyclotron resonance assisted transitions we can use it as a tunable detector working up to energies about 180 cm^{-1} (22 meV). We have used such a detector as a spectrometer for measurements of the Landau emission from GaAs emitter.
3
Publication available in full text mode
Content available

Terahertz Generation and Detection by Plasma Waves in Nanometer Gate High Electron Mobility Transistors

88%
Knap W., Łusakowski J., Teppe F., Dyakonova N., Meziani Y.
Acta Physica Polonica A
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2005
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vol. 107
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issue 1
82-91
EN
The high electron mobility transistors can act as a resonator cavity for the plasma waves that can reach THz frequencies for a nanometer size devices. As was predicted by Dyakonov and Shur in 1993, the steady state of the current flow in a gated 2D electron gas can become unstable leading to the emission of an electromagnetic radiation at the plasma wave frequencies. The theory predicted also that the plasma waves can be used for resonant detection of THz electromagnetic radiation. In the present paper we review our recent experiments on THz emission and detection performed on high electron mobility transistors based on different semiconductor structures: InGaAs/GaAlAs, GaAs/GaAlAs, and Si.
4
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Magnetoconductivity of GaAs Transistors as Detectors of THz Radiation

88%
Łusakowski J., Knap W., Kamińska E., Piotrowska A., Gavrilenko V.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
545-551
EN
Magnetotransport characterisation of field effect transistors processed on GaAs/GaAlAs heterostructure was done at 4.2 K for magnetic fields (B) up to 7 T. Three field effect transistors were processed on a single dice and differed by the length (L) of the gate. Electron mobility (μ) in field effect transistors was estimated from dependence of transistor's conductivity vs. B. The results show a decrease inμ with decreasing L that suggests that scattering by edges of the gated part of a transistor limits the electron mobility. Quality factor (Q) of transistors as resonant detectors of THz radiation was calculated. A high value of Q shows that such field effect transistors with sub-micron L are promising devices that can operate at THz frequencies.
5
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Mechanism of Radiation Coupling to Plasma Wave Field Effect Transistor Sub-THz Detectors

76%
Sakowicz M., Łusakowski J., Karpierz K., Grynberg M., Gwarek W., Knap W., Boubanga S.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1337-1342
EN
Detection of 100 GHz and 285 GHz electromagnetic radiation by GaAs/AlGaAs field effect transistors with the gate length of 150 nm was investigated at 300 K as a function of the angleαbetween the direction of linear polarization of the radiation and the symmetry axis of the field effect transistors. The angular dependence of the detected signal was found to be Acos²(α-α₀)+C. A response of the transistor chip (including bonding wires and the substrate) to the radiation was numerically simulated. Calculations confirmed experimentally observed dependences and allowed to investigate the role of bonding wires and contact pads in coupling of the radiation to the transistor channel.
6
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Terahertz Resonant Detection by Plasma Waves in Nanometric Transistors

76%
Teppe F., El Fatimy A., Boubanga S., Knap W., Seliuta D., Valusis G., Chenaud B.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
815-820
EN
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.
7
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Electron-Electron Interaction Effects in Quantum Hall Regime of GaN/AlGaN Heterostructures

76%
Siekacz M., Dybko K., Maude D., Potemski M., Knap W., Skierbiszewski C.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
269-273
EN
We measured the activation of resistivity at quantum Hall minima in high mobility two-dimensional electron gas confined at AlGaN/GaN interface. The effective g-factor and effective mass was deduced. The electron-electron interactions modify both quantities compared to their bare band values. It is found that the influence of interactions is much more pronounced onto g-factor than effective mass. The relative spin susceptibility was also calculated and compared with available theories. The best agreement was found with the ideal two-dimensional gas model in random phase approximation.
8
Content available remote

Terahertz Photovoltaic Response of Si-MOSFETs: Spin Related Effect

64%
Videlier H., Dyakonova N., Teppe F., Consejo C., Chenaud B., Knap W., Lusakowski J., Tomaszewski D., Marczewski J., Grabiec P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
927-929
EN
We report on investigations of photovoltaic response of Si-MOSFETs subjected to terahertz radiation in high magnetic fields. Then a DC drain-to-source voltage is developed that shows singularities in magnetic fields corresponding to paramagnetic resonance conditions. These singularities are investigated as a function of incident frequency, temperature and two-dimensional carrier density. We tentatively attribute these resonances to spin transitions of the electrons bound to Si dopants and discuss the possible physical mechanism of the photovoltaic signal generation.
9
Content available remote

Weak Antilocalization in Quantum Wells

64%
Knap W., Skierbiszewski C., Litwin-Staszewska E., Kobbi F., Zduniak A., Robert J., Pikus G., Iordanskii S., Mosser V., Zekentes K.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
427-432
EN
Spin relaxation in degenerated two-dimensional (2D) electron gas is studied by measurements of the magnetic field dependence of the weak an­tilocalization corrections to the conductivity in GaInAs quantum wells. Con­sistent quantitative (up to order of magnitude) description of weak antilocal­ization data on GaAs like heterojunctions and quantum wells was obtained. Our results show that spin precession around the effective magnetic field direction as described by the Dyakonov-Perel model is the main spin relax­ation mechanism in degenerated 2D electron gas in semiconductors with no inversion symmetry.
10
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High Magnetic Field Effects on Plasma Wave THz Detection in Field-Effect Transistors

64%
Boubanga-Tombet S., Nogajewski K., Teppe F., Knap W., Karpierz K., Łusakowski J., Grynberg M., Dyakonov M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
939-940
EN
Experiments on terahertz radiation detection with InGaAs/InAlAs field-effect transistor in quantizing magnetic field are reported. We observed oscillations of the photovoltaic signal analogous to the Shubnikov-de Haas oscillations, as well as their strong enhancement at the cyclotron resonance conditions. The results are described quantitatively within the frame of a theory which takes into account a new source of nonlinearity related to the Landau quantization of the conduction band.
11
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THz Double-Grating Gate Transistor Detectors in High Magnetic Fields

64%
But D., Dyakonova N., Coquillat D., Teppe F., Knap W., Watanabe T., Tanimoto Y., Boubanga Tombet S., Otsuji T.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1080-1082
EN
Double-grating-gate field-effect transistors have a great potential as terahertz detectors. This is because the double grating gate serves not only for carrier density tuning but also as an efficient THz radiation coupler. In this paper, we present characterization of these transistors using high magnetic fields. Low and high magnetic field data are used to determine the electron mobility and electron concentration, respectively, in different parts of the transistor channel.
12
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Terahertz Detection by the Entire Channel of High Electron Mobility Transistors

52%
Sakowicz M., Łusakowski J., Karpierz K., Knap W., Grynberg M., Köhler K., Valusis G., Gołaszewska K., Kamińska E., Piotrowska A., Caban P., Strupiński W.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1343-1348
EN
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.
13
Publication available in full text mode
Content available

Localization Effects in GaN/AlGaN Quantum Well - Photoluminescence Studies

52%
Chwalisz B., Wysmołek A., Bożek R., Korona K., Stępniewski R., Knap W., Pakuła K., Baranowski J., Grandjean N., Massies J., Prystawko P., Grzegory I.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
573-578
EN
Exciton localization in GaN/AlGaN quantum well structures is studied by photoluminescence. An anomalous temperature behavior of the photoluminescence from the quantum well is observed. With increasing temperature the energy position of the excitonic emission line first decreases up to 20 K, then increases, reaching a maximum around 90 K, and then decreases again in the higher temperature range. The observed behavior is discussed in terms of localization at the interface potential fluctuations. It is argued that the temperature activated migration and subsequent release of the excitons from traps that occurs between 20 K and 90 K are responsible for the observed S-like shape of the energy dependence. The obtained results allow a direct characterization of the energy fluctuations present in GaN/AlGaN quantum wells grown by different techniques.
14
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Polarity Related Problems in Growth of GaN Homoepitaxial Layers

52%
Leszczyński M., Prystawko P., Śliwinski A., Suski T., Litwin-Staszewska E., Porowski S., Paszkiewicz R., Tłaczała M., Beaumont B., Gibart P., Barski A., Langer R., Knap W., Frayssinet E.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
427-430
EN
Homoepitaxial layers of GaN were grown by metalorganic chemical vapour deposition on single crystals obtained by high-pressure, high-temperature technology. For each metalorganic chemical vapour deposition run, four samples were placed, (00.1) and (00.1̲) faces of the Mg-doped insulating and undoped highly-conductive substrates. The layers were examined using X-ray diffraction, photoluminescence and far-infrared reflectivity. It was found that the (00.1̲) easier incorporates donors resulting in higher free-electron concentrations in the layers grown on these sides of the crystals, both, undoped and Mg-doped.
15
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THz Emission Related to Hot Plasmons and Plasma Wave Instability in Field Effect Transistors

52%
Dyakonova N., El Fatimy A., Meziani Y., Coquillat D., Knap W., Teppe F., Buzatu P., Diforte-Poisson M., Dua C., Piotrowicz S., Morvan E., Delage S.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
924-926
EN
The current flowing in two-dimensional channel of field effect transistors can generate different types of charge density perturbations. They can have a form of uncorrelated hot plasmons or plasma waves. The mechanism of plasma wave generation depends on the parameter ωt and on boundary conditions of the channel. At ωt ≪ 1 only hot plasmons can be generated. The THz emission due to radiative decay of hot plasmons has a broad spectrum and can be only poorly controlled by the transistor gate. The tunability of THz emission can be obtained in the case of the Dyakonov-Shur plasma wave instability. In this work we present experimental studies of THz emission in InGaP/InGaAs/GaAs and GaN/AlGaN based field effect transistors. We report on two types of emission onset: (i) a smooth one typical for hot plasmons generation and (ii) threshold-like one characteristic for plasma waves instabilities. The tunability and spectra of emission change depending on the transistor configuration. We discuss the results suggesting several possible mechanisms of plasma wave excitation.
16
Content available remote

Terahertz Detection of Quantum Cascade Laser Emission by Plasma Waves in Field Effect Transistors

52%
Teppe F., Consejo C., Torres J., Chenaud B., Solignac P., Fathololoumi S., Wasilewski Z., Zholudev M., Dyakonova N., Coquillat D., El Fatimy A., Buzatu P., Chaubet C., Knap W.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 5
930-932
EN
We report on the resonant detection of a 3.1 THz radiation produced by a quantum cascade laser using a 250 nm gate length GaAs/AlGaAs field effect transistor at liquid nitrogen temperature. We show that the physical mechanism of the detection is related to the plasma waves excited in the transistor channel. The detection is enhanced by increasing the drain current and driving the transistor into saturation regime. These results clearly show that plasma wave nanometer-size transistors can be used as detectors in all-solid-state terahertz systems where quantum cascade lasers act as sources.
17
Content available remote

Terahertz Response of a Point Contact Based on CdTe/CdMgTe Quantum Well in Magnetic Field

52%
Grigelionis I., Białek M., Grynberg M., Czapkiewicz M., Kolkovskiy V., Wiater M., Wojciechowski T., Wróbel J., Wojtowicz T., But D., Knap W., Łusakowski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1069-1072
EN
A photoresponse at THz frequencies of a quantum point contact fabricated on a CdTe/CdMgTe quantum well was studied at low temperatures as a function of magnetic field. The spectra show a structure which was interpreted as resulting from the cyclotron resonance and magnetoplasmon excitations. The wavelength of the fundamental magnetoplasmon mode was found to be about 2 μm which coincides with one of dimensions of the point contact. We also discuss the possibility of coupling of magnetoplasmon modes to shallow impurity transitions in the quantum well.
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