T. Wojtowicz

• Institute of Physics of the Polish Academy of Sciences

In this work, we used 20 nm thick CdTe/SnTe/CdTe [001] quantum wells to make 6- and 8-terminal nano-structures with the etched cross-junctions of sub-micron width with walls directed along the [10], [01], and [11] surface crystallographic directions. We studied the low-temperature quantum magneto-transport to investigate the impact of lateral confi...

Hg1−xCdxTe is a unique material with its bandgap being tunable by temperature, pressure, and cadmium content over a wide range, from 1.6 eV to an inverted bandgap of −0.3 eV. This makes Hg1−xCdxTe one of the key materials for infrared and terahertz detectors, whose characteristics largely depend on the material's noise properties. In this work, we...

Despite several theoretical predictions regarding the physics and application of quantum wells (QWs) of topological crystalline insulators (TCI), no quantized charge transport via helical or chiral edge states has been experimentally demonstrated for such a class of systems. In this study, we report here on a successful growth by molecular beam epi...

Self-assembled, highly anisotropic nanostructures are spontaneously formed in the molecular beam epitaxy of antimony triselenide on GaAs substrates. These one dimensional (1D) nanostripes have all the orientation parallel to the...

SnTe-based narrow-gap semiconductors are scientifically promising materials, known, among others, from their topological and thermoelectric properties [1-3]. Structural investigations performed recently by us also gave interesting results, suggesting a possibility of obtaining in MBE-grown layers of topological crystalline insulator SnTe(001) a def...

SnTe-related alloys, compounds and nanostructures are promising and currently investigated candidate materials for topological crystalline insulators or semimetals, as well as thermoelectrics or superconductors [1-5]. Some of their crucial properties are protected by crystal symmetry thus it is important to study their crystallographic quality, ext...

Spectroscopy of shallow donors is a tool to test theoretical models and to reveal properties of semiconductors. In this work we consider intra-shallow impurity transitions by studying a CdTe/(Cd, Mg)Te structure grown by a molecular beam epitaxy in which both a CdTe quantum well and (Cd, Mg)Te barries are uniformly doped with iodine donors. Measure...

The nanohardness and Young’s modulus of Pb1–xCdxTe single crystals prepared by the self-selecting vapor growth (SSVG) method and thick, MBE-grown layers with a total Cd content of up to 7% metal atoms were studied using the nanoindentation technique; the nanohardness and Young’s modulus were calculated by the Oliver and Pharr method. Significant ha...

Modulation-doped CdTe quantum wells (QWs) with Cd0.7Mg0.3Te barriers were studied by photoluminescence (PL) and far-infrared Fourier spectroscopy under a magnetic field at 4.2 K and by Raman spectroscopy at room temperature. Two samples were tested: a sample which contained ten QWs (MQW) and a sample with one QW (SQW). The width of each QW was equa...

\alpha$-Sn is an elemental topological material, whose topological phases can be tuned by strain and magnetic field. Such tunability offers a substantial potential for topological electronics. However, InSb substrates, commonly used to stabilize $\alpha$-Sn allotrope, suffer from parallel conduction, restricting transport investigations and potenti...

Pb1 xSnxTe and SnTe are intensively studied narrow-gap semiconductors, potentially useful, among others, as topological, photosensitive, thermoelectric or superconducting materials [1 6]. For our research we selected heterostructures composed of Pb1 xSnxTe or SnTe rock salt layers and CdTe(001) buffer grown on commercially available substrate, 2° o...

Quantum dots consisting of an axial Zn0.97Mg0.03Te insertion inside a large-bandgap Zn0.9Mg0.1Te nanowire core are fabricated in a molecular-beam epitaxy system by employing the vapor-liquid-solid growth mechanism. In addition, this structure is coated with a thin ZnSe radial shell that forms a type-II interface with the dot semiconductor. The resu...

The helical spin texture on the surface of topological crystalline insulators (TCI) makes these materials attractive for application in spintronics. In this work, spin-polarization and electronic structure of surface states of (111)-oriented Pb$_{1-x}$Sn$_x$Se TCI epitaxial films are examined by angle -- as well as spin-resolved photoemission spect...

The helical spin texture on the surface of topological crystalline insulators (TCI) makes these materials attractive for application in spintronics. In this work, spin-polarization and electronic structure of surface states of (111)-oriented Pb1−xSnxSe TCI epitaxial films are examined by angle- as well as spin-resolved photoemission spectroscopy (S...

We study experimentally and theoretically the temperature dependence of transverse magnetic routing of light emission from hybrid plasmonic-semiconductor quantum well structures where the exciton emission from the quantum well is routed into surface plasmon polaritons propagating along a nearby semiconductor-metal interface. In II-VI and III-V dire...

Challenges and opportunities arising upon molecular-beam-epitaxial growth of topological crystalline insulator heterostructures composed of a rock-salt SnTe(001) layer of varying thickness (from 80 to 1000 nm) and a zinc-blende 4-μm-thick...

Results of comparative structural characterization of bare and Zn-covered ZnTe nanowires (NWs) before and after thermal oxidation at 300 °C are presented. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and Raman scattering not only unambiguously confirm the conversion of the out...

ZnTe/CdSe/(Zn,Mg)Te core/double-shell nanowires are grown by molecular beam epitaxy by employing the vapor-liquid-solid growth mechanism assisted with gold catalysts. A photoluminescence study of these structures reveals the presence of an optical emission in the near infrared. We assign this emission to the spatially indirect exciton recombination...

Many conductors, including recently studied Dirac materials, show saturation of coherence length on decreasing temperature. This surprising phenomenon is assigned to external noise, residual magnetic impurities, or two-level systems specific to noncrystalline solids. Here, by considering the SnTe-class of compounds as an example, we show theoretica...

In a Fe/(Cd,Mg)Te/CdTe quantum well hybrid structure, short-range and long-range ferromagnetic proximity effects are found to coexist. The former is observed for conduction band electrons, while the latter is observed for holes bound to shallow acceptors in the CdTe quantum well. These effects arise from the interaction of charge carriers confined...

Self-assembled Cd(Se,Te) quantum dots with various Se compositions embedded in the ZnTe matrix are grown by molecular beam epitaxy. A huge redshift of the near band edge emission, from 2.1 eV to 1.5 eV, with an increasing Se content in the dots is observed. It is accompanied by an increase in the excitonic lifetime by the factor of 10. We associate...

The cyclotron and magnetoplasmon resonances were studied at 2 K in grating metamaterials fabricated on wafers with one or two modulation doped CdTe/CdMgTe quantum wells. The gratings (with the period varied between 2 μm and 8 μm) were prepared with an electron beam lithography either by etching or by evaporation of Au. The gratings were studied wit...

Grating metamaterials were fabricated with electron beam lithography on CdTe/CdMgTe modulation doped structures with two non-interacting quantum wells. Two types of samples were studied: with etched gratings and with gratings formed by deposition of Au stripes. The polarization properties at THz frequencies of the gratings were determined at room t...

We study the quantum beats in the polarization of the two-pulse photon echo from donor-bound exciton ensembles in semiconductor quantum wells. To induce these quantum beats, a sequence composed of a circularly polarized and a linearly polarized picosecond laser pulse in combination with an external transverse magnetic field is used. This results in...

Spin-dependent photon echoes in combination with pump-probe Kerr rotation are used to study the micro- scopic electron spin transport in a CdTe/(Cd,Mg)Te quantum well in the hopping regime. We demonstrate that, independent of the particular spin relaxation mechanism, the hopping of resident electrons leads to a shortening of the photon echo decay t...

In this paper we show that the spatial degeneracy of chiral edge channels, expected for the quantum Hall ferromagnet state, is spontaneously lifted in agreement with theoretical studies performed within the Hartree- Fock approximation. We indicate also that separated edge currents which flow in parallel, may nevertheless cross at certain points, gi...

We report the observation of tens of minor lines of the combinational spin-flip Raman scattering in a CdTe:Mn quantum well by means of the high-resolution optical spectroscopy. Classification of this manifold leads to four characteristic values of energy, that correspond to four different types of pair clusters of Mn ions: the nearest, second, thir...

Magneto-optical spectroscopy based on the transverse magneto-optical Kerr effect (TMOKE) is a sensitive method for investigating magnetically-ordered media. Previous studies were limited to the weak coupling regime where the spectral width of optical transitions considerably exceeded the Zeeman splitting in magnetic field. Here, we investigate expe...

Magneto-optical phenomena such as the Faraday and Kerr effects play a decisive role for establishing control over polarization and intensity of optical fields propagating through a medium. Intensity effects where the direction of light emission depends on the orientation of the external magnetic field are of particular interest as they can be used...

Thin epitaxial Pb1−xCdxSe films with cadmium content x ≤ 0.36 have been grown by molecular beam epitaxy (MBE) on highly resistive, lattice matched (0 0 1) ZnTe/GaAs hybrid substrates. The High Resolution X-ray Diffraction (HRXRD) indicates that the films crystallize in the rock salt structure. Up to x = 0.12 the Pb1−xCdxSe films are (0 0 1) oriente...

Two classes of topological superconductors and Majorana modes in condensed matter systems are known to date: one in which disorder induced by impurities strongly suppresses topological superconducting gap and is detrimental to Majorana modes, and another where Majorana fermions are protected by a disorder-robust topological superconductor gap. Obse...

We study optical pumping of resident electron spins under resonant excitation of trions in n-type CdTe/(Cd,Mg)Te quantum wells subject to a transverse magnetic field. In contrast to the comprehensively used time-resolved pump-probe techniques with polarimetric detection, we exploit here a single beam configuration in which the time-integrated inten...

The exchange interaction between magnetic ions and charge carriers in semiconductors is considered to be a prime tool for spin control. Here, we solve a long-standing problem by uniquely determining the magnitude of the long-range p−d exchange interaction in a ferromagnet-semiconductor (FM-SC) hybrid structure where a 10-nm-thick CdTe quantum well...

We report on the observation and systematic study of polarization sensitive magnetic quantum ratchet effects induced by alternating electric fields in the terahertz frequency range. The effects are detected in (Cd,Mn)Te-based quantum well (QW) structures with inter-digitated dual-grating-gate (DGG) lateral superlattices. A dc electric current excit...

We study Rabi oscillations detected in the coherent optical response from various exciton complexes in a 20-nm-thick CdTe/(Cd,Mg)Te quantum well using time-resolved photon echoes. In order to evaluate the role of exciton localization and inhomogeneous broadening we use selective excitation with spectrally narrow ps pulses. We demonstrate that the t...

The exchange interaction between magnetic ions and charge carriers in semiconductors is considered as prime tool for spin control. Here, we solve a long-standing problem by uniquely determining the magnitude of the long-range $p-d$ exchange interaction in a ferromagnet-semiconductor (FM-SC) hybrid structure where a 10~nm thick CdTe quantum well is...

In this work, heterojunctions of p-ZnTe:N/CdTe:Mg/n-CdTe:I/GaAs for photovoltaic and photodiode application were grown epitaxially by using molecular beam system. Current-voltage profile of the heterojunction device was studied in dark and under various illumination intensities. The obtained photocurrent is found to depend on the light intensity. T...

Magnetophotoluminescence measurements at liquid helium temperatures were carried out on asymmetric double quantum wells based on CdTe/CdMgTe heterostructures. Due to doping with shallow iodine donors, a two-dimensional electron gas was present in the quantum wells. The samples studied differed with the quantum well widths and doping level. We show...

h i g h l i g h t s A heterostructure (HS)"p-ZnTe:N/CdTe:Mg/n-CdTe:I/GaAs" was prepared through MBE. Influence of applied voltage and frequency on its electrical nature was studied.-Ve capacitance was explained in the light of some literature based on facts. The Barrier height, carrier concentration and cut off voltage were also estimated. Results...

Two classes of topological superconductors and Majorana modes in condensed matter systems are known to date: one, in which disorder induced by impurities strongly suppresses topological superconducting gap and is detrimental to Majorana modes, and the other, where Majorana fermions are protected by disorder-robust topological superconductor gap. In...

We study Rabi oscillations detected in the coherent optical response from various exciton complexes in a 20 nm-thick CdTe/(Cd,Mg)Te quantum well using time-resolved photon echoes. In order to evaluate the role of exciton localization and inhomogeneous broadening we use selective excitation with spectrally narrow ps-pulses. We demonstrate that the t...

Previous research on asymmetric double quantum wells (ADQW) based on CdTe concerned only samples with the barrier or one of the wells formed by a diluted magnetic semiconductor, mainly CdMnTe. This type of material allows to manipulate the shape of the barrier and observe magnetically tuned interwell coupling [1] or exciton transfer [2]. In the pre...

In this work we report on fabrication of quantum wires and quantum point contacts from the modulation doped CdMgTe/Cd(Mn)Te structures, with the application of a high-resolution electron-beam lithography. We emphasize on methods which were not yet utilized for these substrate materials. In particular, we describe the so-called shallow-etching appro...

We report on the fabrication and characterization of a new type of mid-infrared photodetector. The infrared sensitive element of the detector is a PbSe single quantum well(SQW) embedded in an intrinsic region of a CdTe p-i-n diode. Electron-beam-induced current (EBIC) measurements confirm the location of the PbSeSQW near the middle of the intrinsic...

Development of a two-dimensional systems with reconfigurable one-dimensional topological superconductor channels became primary direction in experimental branch of Majorana physics. Such system would allow to probe non-Abelian properties of Majorana quasiparticles and realize the ultimate goal of Majorana research - topological qubit for topologica...

In this work we use electrostatic control of quantum Hall ferromagnetic transitions in CdMnTe quantum wells to study electron transport through individual domain walls (DWs) induced at a specific location. These DWs are formed due to hybridization of two counter-propagating edge states with opposite spin polarization. Conduction through DWs is foun...

We report on the observation of magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with an asymmetric lateral dual grating gate superlattice subjected to an external magnetic field applied normal to the quantum well plane. A dc electric current excited by cw terahertz laser radiation shows 1/B-oscillations with an...

Catalyst-free growth of ZnO nanowires using reactive magnetron sputtering at room temperature is reported. We discuss the growth of the nanowires using reactive magnetron sputtering as a function of argon and oxygen flow values changing at a set ratio of 10:2. A transition from nanostructured Zn to nanowire ZnO growth is observed at 20 sccm Ar and...

Multidimensional coherent optical spectroscopy is currently one of the most powerful tools for investigating complex quantum mechanical systems. While it was conceived decades ago in magnetic resonance spectroscopy using micro- and radio-waves it has recently been extended into the visible and UV spectral range. However, resolving MHz energy splitt...

CdTe nanowires with the average diameter of only 40 nm coated with (Cd,Mg)Te shells are grown using Au-catalyzed vapor–liquid–solid growth mechanism in a system for molecular beam epitaxy. High optical quality of individual nanowires is revealed by means of low temperature cathodoluminescence and micro-luminescence. It is found that, the optical em...

Larmor's theorem holds for magnetic systems that are invariant under spin rotation. In the presence of spin-orbit coupling this invariance is lost and Larmor's theorem is broken: for systems of interacting electrons, this gives rise to a subtle interplay between the spin-orbit coupling acting on individual single-particle states and Coulomb many-bo...

Larmor's theorem holds for magnetic systems that are invariant under spin rotation. In the presence of spin-orbit coupling this invariance is lost and Larmor's theorem is broken: for systems of interacting electrons, this gives rise to a subtle interplay between the spin-orbit coupling acting on individual single-particle states and Coulomb many-bo...

We use spontaneous (two-pulse) and stimulated (three-pulse) photon echoes for studying the coherent evolution of optically excited ensemble of trions which are localized in semiconductor CdTe/CdMgTe quantum well. Application of transverse magnetic field leads to the Larmor precession of the resident electron spins, which shuffles optically induced...

We present a theoretical and experimental study of the interplay between spin-orbit coupling (SOC), Coulomb interaction, and motion of conduction electrons in a magnetized two-dimensional electron gas. Via a transformation of the many-body Hamiltonian we introduce the concept of spin-orbit twisted spin waves, whose energy dispersions and damping ra...

The optically induced spin polarization in (Cd,Mn)Te/(Cd,Mn,Mg)Te diluted-magnetic-semiconductor quantum wells is investigated by means of picosecond pump-probe Kerr rotation. At 1.8 K temperature, additionally to the oscillatory signals from photoexcited electrons and Manganese spins precessing about an external magnetic field, a surprisingly long...

Ferromagnetic transitions between quantum Hall states with different polarization at a fixed filling factor can be studied by varying the ratio of cyclotron and Zeeman energies in tilted magnetic field experiments. However, an ability to locally control such transitions at a fixed magnetic field would open a range of attractive applications, e.g. f...

Ferromagnetic transitions between quantum Hall states with different polarization at a fixed filling factor can be studied by varying the ratio of cyclotron and Zeeman energies in tilted magnetic field experiments. However, an ability to locally control such transitions at a fixed magnetic field would open a range of attractive applications, e.g. f...

We employ time-resolved photoluminescence combined with scanning electron microscopy and modeling to evaluate the lifetimes of excitons and free carriers in core-shell ZnTe-Zn1-xMgxTe nanowires. We find that electron tunneling through the shell to the surface controls the decay dynamics. The photoluminescence of single nanowires reveals contributio...

High quality n-(CdMgTe:I/n-CdTe:I)/(p-CdTe:N/p-ZnCdTe:N/p-ZnTe:N)/p-GaAs heterojunction diodes have been fabricated by molecular beam epitaxial growth. The illumination effect on the complex impedance and conductivity of heterostructure diode was investigated. The illumination intensities were taken up to the 200 mW/cm2 with frequency range of 42 H...

The excitation of coherent optical phonons in solids provides a pathway for ultrafast modulation of light on a sub-ps time scale. Here, we report on efficient 3.6 THz modulation of light reflected from hybrid metal/semiconductor plasmonic crystals caused by lattice vibrations in a few-nm-thick layer of elemental tellurium. We observe that surface p...

We report on the growth, cathodoluminescence and micro-photoluminescence investigation of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature,...

In a spin-polarized electron gas, Coulomb interaction couples the spin and motion degrees of freedom to build propagating spin waves. The spin wave stiffness Ssw quantifies the energy cost to trigger such excitation by perturbing the kinetic energy of the electron gas (i.e. putting it in motion). Here we introduce the concept of spin–orbit stiffnes...

Excitation of coherent optical phonons in solids provides a pathway for ultrafast modulation of light on a sub-ps timescale. Here, we report on efficient 3.6 THz modulation of light reflected from hybrid metal/semiconductor plasmonic crystals caused by lattice vibrations in a few nm thick layer of elemental tellurium. We observe that surface plasmo...

Photoluminescence spectra of a (001)-Cd0.99Mn0.01Te quantum well were taken with linear-polarization resolution and using an in-plane magnetic field. Because the quantum well contained a two-dimensional electron gas, the spectra consisted of several features. Since the quantum well layer was formed by a diluted magnetic semiconductor, the spectra s...

Photoinduced exciton spin states in diluted magnetic semiconductor CdTe=Cd0.88Mn0.12Te quantum wells (QWs) were investigated by the time-resolved Kerr rotation (TRKR) technique at various temperatures and applied magnetic fields. Two oscillation components were observed in the TRKR signals. One component is ascribed to the spin precession of a loca...

The spin-orbit field acting on the spin waves of a spin-polarized electron gas is studied by inelastic light scattering on a CdMnTe quantum well. Above-barrier illumination allows us to vary the electronic density and control the collective Rashba and Dresselhaus coupling constants. We demonstrate that the enhancement between the single-particle an...

At low temperature single CdTe quantum dot (QD) photoluminescence (PL) spectra contains four transitions resulting from the ground state, s-shell carriers recombination: the neutral exciton (X0), positively and negatively charged excitons (X+ and X-, respectively), and the biexciton (2X). With increasing temperature these PL peaks redshift, broaden...

n-CdTe/p-CdMnTe/p-GaAs diluted magnetic diode was grown by molecular beam epitaxy technology. The forward- and reverse-bias capacitance–voltage (C–V), conductance–voltage (G–V), series resistance–voltage (R s–V), impedance–voltage (Z–V), and phase–voltage (θ–V) characteristics of this diode have been analyzed in the frequency range of 5 kHz to 1 MH...

Magneto-transport measurements of Shubnikov-de Haas (SdH) oscillations have been performed on two-dimensional electron gases (2DEGs) confined in CdTe and CdMnTe quantum wells. The quantum oscillations in CdMnTe, where the 2DEG interacts with magnetic Mn ions, can be described by incorporating the electron-Mn exchange interaction into the traditiona...

Arrays of crystalline ZnTe nanowires grown by vapor�liquid�solid mechanism were covered with cobalt in a molecular beam epitaxy system. Magnetic and structural characterization of such core/shell nanowires was performed. Using scanning electron microscopy and transmission electron microscopy it was found that the mean shell thickness of cobalt was...

Hybrid structures synthesized from different materials have attracted considerable attention because they may allow not only combination of the functionalities of the individual constituents but also mutual control of their properties. To obtain such a control an interaction between the components needs to be established. For coupling the magnetic...

We study nanoscale morphology of PbTe/CdTe multilayer heterostuctures grown by molecular beam epitaxy on hybrid GaAs/CdTe (100) substrates. Nominally, the structures consist of 25 repetitions of subsequently deposited CdTe and PbTe layers with comparable thicknesses of 21 and 8 nm, respectively. However, the morphology of the resulting structures c...

We study the impact of the nanowire shape anisotropy on the spin splitting of excitonic photoluminescence. The experiments are performed on individual ZnMnTe/ZnMgTe core/shell nanowires as well as on ZnTe/ZnMgTe core/shell nanowires containing optically active magnetic CdMnTe insertions. When the magnetic field is oriented parallel to the nanowire...

We report on the study of two-step grown crystalline II-VI semiconductor nanowires (NWs) covered with ferromagnetic metal. In the first step ZnTe nanowires were grown by a vapor-liquid-solid mechanism (VLS) on GaAs (111)B substrates covered with Au thin film. Solid source molecular beam epitaxy and Au-based nanocatalysts were used for these purpose...

We present photoluminescence studies of CdTe and CdMnTe quantum dots grown in two adjacent layers. We show that when the dots are 8 nm apart, their magnetooptical properties - Zeeman shifts and transition linewidths - are analogous to those of individual CdTe or CdMnTe dots. When the dots are grown closer, at a distance of 4 nm, it becomes possible...

We demonstrate an efficient method to engineer the quantum confinement in a system of two quantum dots grown in a vertical stack. We achieve this by using materials with a different lattice constant for the growth of the outer and inner barriers. We monitor the resulting dot morphology with transmission electron microscopy studies and correlate the...

Terahertz magnetospectroscopy experiments on high quality CdTe/CdMgTe quantum wells were carried out at low temperatures and high magnetic fields. Samples of two different geometries were considered: a large-area grid-gated sample and a split-gate quantum point contact (QPC). The spectra show features originating from a cyclotron resonance transiti...

The electric and thermoelectric properties of novel, CdTe/PbTe layered nanocomposite material are investigated. The molecular beam epitaxy (MBE) method was used for preparation of samples with well controlled distances (from 20 to 70 nm) between the layers of CdTe nanograins embedded in PbTe thermoelectric matrix as well as with number of these lay...

We report on reduction of optical losses in n-CdTe/p-ZnTe thin-film solar cells grown by molecular beam epitaxy. The investigated thin-film devices were grown from elemental sources on monocrystalline, semi-insulating, (100)-oriented GaAs substrates. The optical losses have been reduced by a texturing of the device surface and by depositing of a Zn...

We report the first results of electron beam lithography processes performed on polymethyl methacrylate (FNMA) and hydrogen silsesquioxane (HSQ) resists, which have been pre-backed in vacuum at T <= 90 degrees C. For such low temperature processing the lithographical resolution is reduced as compared to standard procedures, however, the exposure co...

Magnetic-field tunable semiconductor detectors are used in THz spectroscopy due to their sensitivity and possibility to respond to photons in a broad frequency range. We compare THz detectors processed on high electron mobility GaAs/GaAlAs and CdTe/CdMgTe quantum wells. Transmission, photocurrent and photovoltage measurements were carried out as a...

THz response of a number of samples based on CdTe/CdMgTe quantum wells grown by a molecular beam epitaxy was investigated at low temperatures and high magnetic fields. The experiments involved magnetotransport, photocurrent, and transmission measurements carried out with a monochromatic THz sources or a Fourier spectrometer. Samples of different ge...

Fabrication of compact detectors and emitters is essential for development of THz technology. Field-effect transistors (FETs) are promising current- and voltage-driven suitable for this purpose. We report on a THz detection with FETs fabricated on a CdMnTe/CdMgTe quantum well. Both resonant and non-resonant detection in magnetic fields and at low t...

GaAs nanowires were grown on (111)B GaAs substrates using the vapour-liquid-solid mechanism. The Au/Pt nanodots used to catalyse wire growth were defined lithographically and had varying diameter and separation. An in-depth statistical analysis of the resulting nanowires, which had a cone-like shape, was carried out. This revealed that there were t...

We report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd(1-x)Mn(x)Te. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experimen...

In this work we discuss experimental data which can explain reasons for the limited energy conversion efficiencies observed in monocrystalline, thin-film CdTe-based solar cells grown molecular beam epitaxy. Two kinds of samples has been investigated and discussed – p- and n-type doped CdTe layers with metallic Schottky barriers and p-i-n heterojunc...

In this work, our recent progress in the growth and optical studies of telluride nanowire heterostructures containing a small molar fraction of magnetic Mn-ions of only a few percent is overviewed. ZnMnTe/ZnMgTe core/shell nanowires (NWs) are grown by molecular beam epitaxy by employing the vapor-liquid-solid growth mechanism assisted with gold cat...

Raman scattering is well known as an efficient, nondestructive experimental method to study a variety of physical properties of semiconductors. The sensitivity of modern Raman spectroscopy is illustrated by several results obtained for semiconductor bulk crystals, thin layers, or low-dimensional structures, containing selected transition metals. Am...