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1
Content available remote

Magnetoresistance of n-CdTe in the "Persistent" State

100%
Kossacki P., Karpierz K.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
737-740
EN
In this paper we present results of measurements done on photoexcited carriers in high purity n-CdTe at liquid helium temperature. The photocurrent under near band gap illumination was measured, as well as the long term (≈ 15 hours) photoconductive decay after switching off the light. The transverse magnetoresistance was measured in high magnetic fields in two cases: 1) under external illumination, 2) in the "persistent" state after ≈ 15 h of photocurrent decay. It was shown that in high magnetic fields this magnetoresistance exhibits a quadratic dependence on magnetic field (Δρ/ρ ≈ B^{2}) in both cases.
2
Content available remote

Intra-Shallow-Donor Photoconductivity in Semi-Insulating GaAs

100%
Karpierz K., Sadowski M.
Acta Physica Polonica A
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1991
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vol. 79
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issue 1
121-124
EN
The far-infrared photoconductivity of a semi-insulating GaAs sample was measured at 4.2 K as a function of magnetic field up to 7 T. Apart from a peak corresponding to the 1s - 2p_{+1} transition of the hydrogen-like shallow donor, a well-pronounced structure was observed which does not appear in n-type GaAs.
3
Content available remote

Studies of Magnetoresistance in GaAs:Te Crystals with Structural Disorder at Doping Limit

81%
Tarkowski T., Słupiński T., Karpierz K.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
726-728
EN
Transverse magnetoresistance was studied in monocrystalline GaAs:Te doped above the equilibrium doping limit and annealed to partially deactivate donor impurities. It is shown that in a sample with partial deactivation of Te impurities, which exhibits structural fluctuations in microscale, both strong positive and some negative magnetoresistances arise, which are difficult to understand within the relaxation time approximation in degenerated homogeneous semiconductor. It is discussed that a consideration of the role of spatial fluctuations (in carrier concentration, conductivity, etc.), e.g. as proposed by Herring, allows for an understanding of positive component of magnetoresistance observed in the sample with a distinct microscopic structural disorder. With the aim to better understand the transport in GaAs:Te, a model material doped above the doping limit, we discuss both positive and negative components of measured magnetoresistance.
4
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Magnetotransmission Measurements of Intra-Shallow-Donor Transitions in Semi-Insulating GaAs

81%
Karpierz K., Kożuchowski K., Grynberg M.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
617-619
EN
In this paper we present the results of an investigation of the 1s-2p_{+} intra-shallow-donor transition by means of an extremely difficult magnetotransmission experiment performed on semi-insulating GaAs. We report the temperature dependence of the transition intensity. We noticed the absence in the absorbance spectra of a well-pronounced structure which is observed at low magnetic fields in photoconductivity measurements. The results are discussed in terms of a fluctuating potential from ionized centres in semi-insulating GaAs.
5
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Response of Indium Antimonide at Sub-Terahertz and Terahertz Frequencies

81%
Yavorskiy D., Karpierz K., Grynberg M., Łusakowski J.
Acta Physica Polonica A
|
2017
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vol. 132
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issue 2
338-339
EN
Responsivity of a bulk InSb detector at liquid helium temperature was studied in the frequency range 0.1 THz
6
Content available remote

Nonstandard Absorption on Donors in Uniformly Doped II-VI 0D Structures

81%
Karpierz K., Szot M., Grynberg M.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
237-241
EN
The new approach to the understanding of intrashallow donor transition in the reduced dimensionality systems is presented. The magnetospectroscopy experiments done on the CdTe/CdMgTe quantum well based samples, uniformly n-doped, show indications that the surprising lack of spectral sensitivity on applied photon energy can be understood as a result of sample response coming from its different regions. This "non spectroscopic" behaviour (in a sense of the Zeeman splitting) is a consequence of the properties of systems with reduced dimensionality where variety of centre locations in the structure results in continuous density of states available for absorption.
7
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Magnetophotoconductivity Due to Intra-Shallow-Donor Transitions in Semi-Insulating GaAs

81%
Karpierz K., Sadowski M., Grynberg M.
Acta Physica Polonica A
|
1991
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vol. 80
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issue 2
291-294
EN
The paper concerns investigations of shallow centres in semi-insulating (SI) GaAs samples. A very sensitive measuring method - magnetophotoconductivity due to intra-shallow-donor transitions - was used. We report the behaviour of intra-impurity transitions as well as an additional structure in low magnetic fields for different far-infrared wavelengths (70.6 μm, 96.5 μm, 118.8 μm, 163 µm). The results are discussed in terms of a fluctuating potential from ionized centres in SI GaAs. The physical mechanism responsible for the low magnetic field structure is proposed.
8
Content available remote

Local Electric In-Plane Potential Fluctuations in the CdTe/CdMgTe Based Multiple Quantum Wells

71%
Nogajewski K., Karpierz K., Łusakowski J., Grynberg M., Kossut J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1259-1265
EN
Unusual features in the magnetophotoconductivity spectra registered under far infrared illumination of the CdTe/CdMgTe based multiple quantum wells, uniformly n-doped are presented. It is shown that each spectrum exhibits one or two peaks of non-symmetrical shape, with position of their maxima dependent on the voltage applied to the sample. The peaks, observed in the configuration of the crossed electric and magnetic fields, are strongly shifted by a relatively weak in-plane electric field - of the order of 10-50 V/cm. Two different approaches to explain the observed influence are presented. Both are based on a two-step process leading to the photoconductivity signal. The first approach assumes that only the process of photon absorption is influenced by the external fields, the second one assumes that only the process of phonon assisted electron transfer from the excited donor state into the conduction band is influenced by the external fields.
9
Content available remote

Sub-Terahertz Emission from Field-Effect Transistors

71%
Yavorskiy D., Karpierz K., Kopyt P., Grynberg M., Łusakowski J.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 2
335-337
EN
Several commercially available field-effect GaInAs-based transistors were studied as emitters of electromagnetic radiation. The emitters were tested either at room or at liquid helium temperature. To spectrally analyse emitted radiation, we applied three different experimental techniques: a spectrum analyser with antennas and mixers, a Michelson interferometer and a magnetic-field-tunable InSb detector. We show that the emission consists of a fundamental frequency of 11.5 GHz and its multiple harmonics spanning the emission band up to about 400 GHz. Analysis of the results allows us to suggest that the emission is caused by a Gunn effect and a high harmonics content is related to a pulse-like time dependence of the current.
10
Content available remote

FIR Magnetooptical Measurements on MOCVD Grown InAs

71%
Andrearczyk T., Karpierz K., Bożek R., Stępniewski R., Grynberg M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
699-703
EN
In this paper we report results of magnetooptical measurements done on standard InAs MOCVD layers grown on GaAs. Extremely narrow lines (half-widths of the order of 20 mT) - narrower than found by other authors in high quality MBE InAs epilayers on GaAs - as well as the lines of typical half-widths have been found both in the photoconductivity spectra and in the transmission spectra. A detailed comparison with the theoretical dependence of shallow donor and Landau level energies on magnetic field leads to the conclusion that they originate from cyclotron resonance and impurity-shifted cyclotron resonance transitions in that material.
11
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Content available

The Nature of Potential Fluctuations in the MBE CdTe/CdMgTe Quantum Well in a Magnetic Field: Experiment and Theory

62%
Szot M., Karpierz K., Avetisyan A., Djotyan A., Kossut J., Grynberg M.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
379-387
EN
Far infrared photoconductivity spectra of CdTe/Cd_{0.8}Mg_{0.2}Te quantum well uniformly n-type doped with iodine in barriers and in the well were investigated as a function of the magnetic field. The spectra were recorded for several fixed far infrared photon energies and peaks corresponding to intra donor transitions were observed. The magnetic field at which the peaks were observed was the same for all far infrared photon energies used. This is interpreted as an evidence of the presence of fluctuations of the electrostatic potential - quantum dots which reduce the dimensionality of the potential in which a shallow donor is placed. A characteristic size of the fluctuations was found to be of 23-25 nm and 30-40 nm. Theoretical calculations show a nonmonotonic dependence of the electron binding energy on the donor centre in such quantum dot, as a function of magnetic field. This explains why the position of experimentally observed peak is insensitive to far infrared photon energy used. Temperature evolution of spectra and the theoretical model proposed, indicate similarities between fluctuations in the two-dimensional structure investigated and fluctuations in bulk systems.
12
Content available remote

Influence of Interface-Induced Disorder on Classical and Quantum Conductivity of CdTe:IN Epitaxial Layers

62%
Łusakowski J., Karpierz K., Grynberg M., Karczewski G., Wojtowicz T., Contreras S., Callen O.
Acta Physica Polonica A
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1997
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vol. 92
|
issue 5
911-914
EN
An influence of disorder originated from the substratelayer interface on electrical properties of CdTe:In layers was investigated by means of the Hall effect and magnetoresistance measurements at low temperatures. An estimation of a scattering rate due to interface-induced disorder is given. Characteristic features of a magnetic field dependence of magnetoresistance are explained by an influence of quantum interference of scattered electron waves both in the hopping and the free electron conductivity regimes.
13
Content available remote

Mechanism of Radiation Coupling to Plasma Wave Field Effect Transistor Sub-THz Detectors

62%
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
|
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.
14
Content available remote

High Magnetic Field Effects on Plasma Wave THz Detection in Field-Effect Transistors

52%
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.
15
Content available remote

Magnetoplasmons in a High Electron Mobility GaAs/AlGaAs Heterostructure

52%
Białek M., Karpierz K., Piętka B., Grynberg M., Łusakowski J., Czapkiewicz M., Fronc K., Wróbel J., Umansky V.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1096-1098
EN
We have observed a multimode spectrum of magnetoplasmons in the Hall bars processed on a high electron mobility GaAs/AlGaAs heterostructure. We have found that the dispersion relation of these excitation follows square root dependence. Calculated wavelength of the fundamental magnetoplasmon mode fits to the width of sample.
16
Content available remote

Terahertz Detection by the Entire Channel of High Electron Mobility Transistors

42%
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
|
2008
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vol. 114
|
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.
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