G. Tomaka - Academia.edu (original) (raw)

Papers by G. Tomaka

Experimental results of the magnetotransport measurements (longitudinal magnetoresistance R xx an... more Experimental results of the magnetotransport measurements (longitudinal magnetoresistance R xx and the Hall resistance R xy) are presented over a wide interval of temperatures for several samples of Hg 1−x Cd x Te (x ≈ 0.13–0.15) grown by MBE—thin layers (thickness about 100 nm) strained and not strained and thick ones with thickness about 1 μm. An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behavior of the Hall resistance is registered in the same temperature interval. These peculiarities of the R xx and R xy for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS) [C. Brüne et al., Phys. Rev. Lett. 106, 126803 (2011)]. In the case of not strained layers it is assumed that the QHC on the TPSS (or on the resonant interface states) contributes also to the conductance of the bulk samples.

Opto-Electronics Review, 2017

Abstract The review of peculiarity of growth and experimental results of the magneto-transport me... more Abstract The review of peculiarity of growth and experimental results of the magneto-transport measurements (longitudinal magneto-resistance R xx and the Hall resistance R xy ) over a wide interval of temperatures for several samples of Hg 1− x Cd x Te ( x ≈ 0.13–0.15) grown by MBE is presented in this paper. An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behaviour of the Hall resistance was shown in the same temperature interval. These peculiarities of the R xx and R xy for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS). In the case of not strained layers it is assumed that the QHC on the TPSS contributes also to the conductance of the bulk samples. The experimental results on magneto-transport (QHC and SdH) obtained for the strained 100 nm thickness Hg 1− x Cd x Te layer are interpreted on the basis of the 8 × 8 kp model and an advantage of the Hg 1− x Cd x Te as topological insulators is shown. This article is an expanded version of the scientific reports presented at the International Conference on Semiconductor Nanostructures for Optoelectronics and Biosensors 2016 ICSeNOB2016, May 22–25, 2016, Rzeszow, Poland.

Solid State Communications, 2017

SPIE Proceedings, 2001

Magnetophonon Resonance in parallel transport of three types of Multiple Quantum Wells was studie... more Magnetophonon Resonance in parallel transport of three types of Multiple Quantum Wells was studied. They consisted of ten QW of GaAs and ten AlGaAs barriers, and were obtained by the Metal Organic Vapor Deposition an semi-insulating GaAs. The MPR research were performed in pulsed magnetic fields up to 30 T. The transverse magneto resistance was measured between 77K and 340K and the MPR oscillations extracted by subtracting a voltage linear in magnetic field. The oscillating part of magneto resistance (Delta) (rho) xx was recorded. A fine structure of MPR peaks was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses.

Materials Science and Engineering: A, 2000

... Rev. B, 43 (1991), p. 9649. [7] TP Sosin and W Trzeciakowski. Acta Phys. Polon. A, 87 (1995),... more ... Rev. B, 43 (1991), p. 9649. [7] TP Sosin and W Trzeciakowski. Acta Phys. Polon. A, 87 (1995), p. 151. [8] P. Wickboldt, E. Anastassakis and R. Sauer et al.. Phys. Rev. B, 35 (1987), p. 1362. [9] PP Lottici, G. Attolini and E. Chimenti et al.. Solid State Comm., 99 (1996), p. 537. ...

physica status solidi (c), 2009

ABSTRACT The experimental results for the magneto-transport in the InGaAs/InAlAs double quantum w... more ABSTRACT The experimental results for the magneto-transport in the InGaAs/InAlAs double quantum wells (DQW) structures of two different shapes of wells and different value of the electron density obtained in pulse magnetic fields are reported. The Magnetophonon Resonance (MPR) was observed for both types of the structures at 77-125 K temperatures. Four kinds of LO-phonons are taken into account to interpret the MPR oscillations in DQW and a method of the Landau Level calculation in DQW is elaborated for this aim. The particularity of MPR in DQW is the great number of Landau levels caused by SAS-splitting of electron states and great number of the phonon assistance electron transitions between Landau levels. The significant role of carriers statistics is shown too. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Physical Review B, 2016

Spin Orbitronics and Topological Properties of Nanostructures

Opto-electronics Review, 2000

The structure of magnetoresistance curves as a function of magnetic field from 0 to 14 T at tempe... more The structure of magnetoresistance curves as a function of magnetic field from 0 to 14 T at temperatures from 0.4 to 6.0 K for macroscopic samples of the quasi-free-standing (QFS) graphene monolayer on SiC substrate, are observed and analyzed, and also the spatial and depth frequency distribution of phonons have been measured using the micro-Raman spectroscopy (MRS). That one enables us to interpret the obtained resonance magnetoresistance curves based on the electron-phonon (e-p) interaction taking into account the actually observed phonon spectrum in researched samples: in the case of a linear e-p interaction the observation of the corresponding peaks on the Rxx(B){R}_{xx}(B)Rxx(B) curves is difficult because an uninterrupted background is created. While nonlinear MPR with simultaneous G-phonon emission and D-phonon absorption occur in magnetic fields below 5 T against the background of MPR due to linear e-p interaction as well as Shubnikov--de Haas oscillations.

Acta Physica Polonica A

The magnetophonon resonance in parallel transport of two types multiple quantum wells was studied... more The magnetophonon resonance in parallel transport of two types multiple quantum wells was studied. The transverse magnetoresistance was measured in pulsed magnetic fields up to 30 T (within temperature region from 77 to 340 K). A fine structure of magnetophonon resonance peaks which depends on temperature and does not depend on the type of multiple quantum wells, was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses.

Journal of Crystal Growth

Opto-Electronics Review

In Ge - Si heterostructure system, strain and compositional changes can be used to change the fun... more In Ge - Si heterostructure system, strain and compositional changes can be used to change the fundamental indirect absorption edge. It is well known that increase in Ge content in the GexSi1-x shifts fundamental band edge to the longer wavelengths and causes strong increase in absorption coefficient. Theoretical description of increase in efficiency of solar cells based on this system in comparison with the silicon solar cells is given. A construction of photodiodes using heterostructure Ge 0.2 Si 0.8 / Si is proposed.

The complexinvestigationofthemagneto-transport effects in structures containing multiple quantum ... more The complexinvestigationofthemagneto-transport effects in structures containing multiple quantum well (MQWs)basedontheGaAs/AlGaAs-heterostructures has been performed.TheMQWsinvestigated have different electron densities in QWs.The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH)observed at low temperatures (0.6–2K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D.P"och etal.,Phys.Rev.B79(2009)195434)including the screening of this interaction.

International Journal of Modern Physics B, 2007

ABSTRACT We have studied the parallel magneto-transport in DQW-structures of two different potent... more ABSTRACT We have studied the parallel magneto-transport in DQW-structures of two different potential shapes: quasi-rectangular and quasi-triangular. The quantum beats effect was observed in Shubnikov-de Haas (SdH) oscillations for both types of the DQW structures in perpendicular magnetic filed arrangement. We developed a special scheme for the Landau levels energies calculation by means of which we carried out the necessary simulations of beating effect. In order to obtain the agreement between our experimental data and the results of simulations, we introduced two different quasi-Fermi levels which characterize symmetric and anti-symmetric states in DQWs. The existence of two different quasi Fermi-Levels simply means, that one can treat two sub-systems (charge carriers characterized by symmetric and anti-symmetric wave functions) as weakly interacting and having their own rate of establishing the equilibrium state.

International Conference on Solid State Crystals 2000: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, 2001

ABSTRACT Magnetophonon Resonance in parallel transport of three types of Multiple Quantum Wells w... more ABSTRACT Magnetophonon Resonance in parallel transport of three types of Multiple Quantum Wells was studied. They consisted of ten QW of GaAs and ten AlGaAs barriers, and were obtained by the Metal Organic Vapor Deposition an semi-insulating GaAs. The MPR research were performed in pulsed magnetic fields up to 30 T. The transverse magneto resistance was measured between 77K and 340K and the MPR oscillations extracted by subtracting a voltage linear in magnetic field. The oscillating part of magneto resistance (Delta) (rho) xx was recorded. A fine structure of MPR peaks was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses.

Photovoltaic and Photoactive Materials — Properties, Technology and Applications, 2002

ABSTRACT In the search for higher photovoltaic (PV) conversion efficiencies, multiple band gap co... more ABSTRACT In the search for higher photovoltaic (PV) conversion efficiencies, multiple band gap concepts have received increased theoretical attention in the last few years. Many dual band gap systems are based on the semiconductor couple GexSi1-x/Si. However, this is not the optimum theoretical pairing for maximum system efficiency, because of both economic and technological criteria. The Si cell may work at a moderate concentration of infrared light which would be unconverted by GaAs (energy lower than about 1.5 eV). However, by changing the basic solar cell material from Si to a GexSi1-x alloy, with the least possible modification, solar technology can fully profit from present knowledge and future improvements [1–4].

Physica E-Low-Dimensional Systems & Nanostructures, 2008

The experimental results obtained for magnetotransport in the InGaAs/InAlAs double quantum well (... more The experimental results obtained for magnetotransport in the InGaAs/InAlAs double quantum well (DQW) structures of two different shapes of wells are reported. A beating effect occurring in the Shubnikov-de Haas (SdH) oscillations was observed for both types of structures at low temperatures in the parallel transport when the magnetic field was perpendicular to the layers. An approach for the calculation of the Landau level energies for DQW structures was developed and then applied to the analysis and interpretation of the experimental data related to the beating effect. We also argue that in order to account for the observed magnetotransport phenomena (SdH and integer quantum Hall effect), one should introduce two different quasi-Fermi levels characterizing two electron subsystems regarding the symmetry properties of their states, symmetric and anti-symmetric ones, which are not mixed by electron-electron interaction. r

Physical Review B, 2009

The experimental results obtained for the magnetotransport in pulsed magnetic fields in the InGaA... more The experimental results obtained for the magnetotransport in pulsed magnetic fields in the InGaAs/InAlAs double quantum well (DQW) structures of two different shapes of wells and different values of the electron density are reported. The magnetophonon resonance (MPR) was observed for both types of structures within the temperature range 77-125 K. Four kinds of LO phonons are taken into account to interpret the MPR oscillations in the DQW and a method of the Landau level calculation in the DQW is elaborated for this aim. The peculiarity of the MPR in the DQW is the large number of the Landau levels caused by SAS splitting of the electron states (splitting on the symmetric and anti-symmetric states) and the large number of the phonon assistance electron transitions between Landau levels. The significant role of the carrier statistics is shown too. The behavior of the electron states in the DQWs at comparably high temperatures has been studied using the MPR. It is shown that the Huang and Manasreh [Manasreh [Phys. Rev. B 54, 2044 (1996)] model involving screening of exchange interaction is confirmed.