Vadym Vyacheslavovych Korotyeyev

National Academy of Sciences of Ukraine | ISP · Department of Theoretical Physics

This study reviews recent advances in the modern field of terahertz plasmonics concerning the control of resonant properties of grating-gate plasmonic crystal structures. Particularly, we conducted both experimental and theoretical investigations of AlGaN/GaN grating-gate structures with a focus on investigations of the resonant structure of transm...

We present an extensive study of resonant two-dimensional (2D) plasmon excitations in grating-gated quantum well heterostructures, which enable an electrical control of periodic charge carrier density profile. Our study combines theoretical and experimental investigations of nanometer-scale AlGaN=GaN grating-gate structures and reveals that all ter...

We present a comprehensive study of the diverse phases of terahertz (THz) plasmonic crystals. Our research focuses on the electrically controlled modulation of plasmonic crystal phases by manipulating the charge carrier density profile through gate voltage application to gated cavities. Through a combination of experimental and theoretical investig...

We present a comprehensive study of resonant 2D plasmon excitations in the grating-gate plasmonic crystals based on AlGaN/GaN heterostructures. We show that plasmonic crystals are formed and their different phases are electrically controlled by tuning the charge carrier density profile. We conducted both experimental and theoretical investigations...

We present an extensive study of resonant two-dimensional (2D) plasmon excitations in grating-gated quantum well heterostructures, which enable an electrical control of periodic charge carrier density profile. Our study combines theoretical and experimental investigations of AlGaN/GaN grating-gate structures and reveals that all terahertz (THz) pla...

Terahertz time domain spectroscopy (TDS) of the two-dimensional (2-D) electrons in various commercial AlGaN/GaN heterostructures was performed in the frequency range of 0.1–2.0 THz at selected temperatures of 80 and 300 K. Experimental transmission spectra were analyzed using analytical model derived for the thin conductive layer on dielectric subs...

We have reviewed main peculiarities of amplitude and phase transmission/reflection spectra of different model semiconductor structures, including bare dielectric substrate, thin conductive layer placed between two dielectric media, thin conductive layer on dielectric substrate and hybrid plasmonic structures with thin conductive layer under metalli...

We present calculations of frequency and wavevector dispersion of conductivity of two-dimensional electrons confined in AlGaN/GaN heterostructures at the arbitrary level of the degeneracy and the presence of strongly inelastic scattering mechanism by the optical phonons. We found that the high-frequency conductivity deviates from that of the standa...

The modified rigorous coupled-wave analysis technique is developed to describe the optical characteristics of the plasmonic structures with the grating-gated delta-thin conductive channel in the far- and near-field zones of electromagnetic waves. The technique was applied for analysis of the resonant properties of AlGaN/GaN heterostructures combine...

The modified rigorous coupled-wave analysis technique is developed to describe the optical characteristics of the plasmonic structures with the grating-gated delta-thin conductive channel in the far- and near-field zones of electromagnetic waves. The technique was applied for analysis of the resonant properties of AlGaN/GaN heterostructures combine...

Temperature-dependent effective mass in AlGaN/GaN heterostructures was experimentally observed via THz time domain spectroscopy of 2D plasmons in the range of 80–300 K. Grating couplers with different periods and filling factors were developed in order to monitor the behavior of plasma resonances in transmission spectra in the frequency range of 0....

Two-dimensional plasmons were investigated by terahertz time domain spectroscopy observing experimentally the distinctive minima and inflection points in the transmission power amplitude and phase spectra, respectively. Gratings of different periods (600, 800, and 1000 nm) and filling factors (50 and 80%) were provided to the two-dimensional electr...

We have developed a theory of collective electron oscillations in two-dimensional semiconductor heterostructures subjected to a high electric field. The effect of the stationary electric field has been taken into account on both steady-state and high-frequency electron transport. The analysis has been conducted by solving Boltzmann-Vlasov equations...

We reported here the results of the calculations of wavevector dispersion of oscillations frequencies, $\omega'(k)$, and damping $\omega''(k)$ of the surface plasmon phonon polaritons (\mbox{SPPhP}) for the heavy-doped GaN sample. We showed that $\omega'(k)$- dependence consists of the three branches with the specific anticrossing behavior due to t...

Terahertz radiation emission from an electrically excited AlGaN/GaN heterostructure with a surface metal grating was studied under conditions of two-dimensional (2D) electron heating by the lateral electric field. Intensive peaks related to nonequilibrium 2D plasmons were revealed in the terahertz emission spectra with up to 4 times selective ampli...

We investigate ultra-high frequency electrical properties of nanoscale $n^+$-$i$-$n^+$ diodes made of polar semiconductors. The calculations show that the coupling between optical vibrations of the lattice and the ballistic electrons strongly modifies and enhances the time-of-flight effects giving rise to narrow resonances of the diode impedance in...

We investigate ultrahigh frequency electrical properties of nanoscale n+−i−n+ diodes made of polar semiconductors. The calculations show that the coupling between optical vibrations of the lattice and the ballistic electrons strongly modifies and enhances the time-of-flight effects giving rise to narrow resonances of the diode impedance in the rest...

We have presented the results of terahertz time-domain spectroscopy measurements and a rigorous electrodynamic modeling of the optical characteristics of grating-based AlGaN/GaN plasmonic structures with low-doped two-dimensional electron gas in the frequency range of 0.1...1.5 THz. Two samples with grating aspect ratios (strip width/period) of 2.4...

We report the results of Monte Carlo simulation of electron dynamics in stationary and space- and time-dependent electric fields in compensated GaN samples. We have determined the frequency and wavevector dependencies of the dynamic conductivity, $\sigma_{\omega,q}$. We have found that the spatially dependent dynamic conductivity of the drifting el...

We report the studies on optical properties of a GaN/AlGaN heterostructure with a surface metal grating. The fabricated structures were optimized for the observation of 2D plasmon resonances in the spectral range of 2–5 THz. The spectra of the equilibrium optical transmission were experimentally investigated and the 2D plasmon resonance was found....

Transport theory for modeling the electric characteristics of high-quality p-n diodes has been developed. This theory takes into account a non-uniform profile of p- doping, finite thickness of the quasi-neutral regions and possible non-uniformity of the bulk recombination coefficient. The theory is based on related solutions of the Poisson equation...

We present the analysis of high-frequency (dynamic) conductivity with the spatial dispersion, σ(ω, q), of two-dimensional electron gas (2DEG) subjected to a high electric field. We found that at finite wavevector, q, and at high fields, the high-frequency conductivity shows following peculiarities: strong non-reciprocal dispersion, oscillatory beha...

The theory of non-linear interaction of electromagnetic radiation with hybrid plasmonic structure, which consists of the two-dimensional quantum heterostructure integrated with a plasmonic element in the form of a metal grating, is developed. In particular, the non-linear effect of a detection of high-frequency radiation by a drifting two-dimension...

The paper is focused on the investigation of magneto-transport phenomena in the compensated bulk-like GaN sample. Particularly, we studied the diffusion coefficient of the electrons in parallel and crossed configurations of moderate electric (E=1...10 kV/cm) and magnetic (H=1...4 T) fields. We found that E-field dependencies of the transverse-to-cu...

We report on the studies of the surface plasmon polaritons in n-GaN epitaxial layers. The grating etched on the surface of the epitaxial layer is used to excite surface plasmon polaritons by means of terahertz photons. The experimental reflectivity spectrum for p-polarized radiation demonstrates a set of resonances associated with excitation of dif...

We studied space charge distribution phenomena in planar GaN nanowires and nanoribbons (NRs). The results obtained at low voltages demonstrate that the electron concentration changes not only at the edges of the nanoribbon, but also in the middle part of the nanoribbon. The effect is stronger with decreasing nanoribbon width. Moreover, the spatial...

We studied electric current and noise in planar GaN nanowires (NWs). The results obtained at low voltages provide us with estimates of the depletion effects in the NWs. For larger voltages, we observed the space-charge limited current (SCLC) effect. The onset of the effect clearly correlates with the NW width. For narrow NWs the mature SCLC regime...

Low-temperature high-field electron transport is studied for compensated bulk GaN subjected to crossed electric and magnetic fields. The electron kinetics, distribution function, and field dependencies of the magneto transport characteristics are analyzed by using the Monte-Carlo method. At zero magnetic field, for an ionized impurity concentration...

We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaNepitaxial layers. Reflection and emission of radiation in the frequency range of 2–20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with...

High-field electron transport studied in crossed electric and magnetic fields in bulk GaN with doping of 1016 cm-3, compensation around 90% at the low lattice temperature (30 K). It was found the range of the magnetic and electric fields where the non-equilibrium electron distribution function has a complicated topological structure in the momentum...

The results of experimental and theoretical researches of steady-state and high-frequency electric characteristics of planar AlGaN/GaN heterostructure nanowires are presented. A strong depletion effect associated with electron trapping on the edge states is observed for narrow nanowires with widths ∼ 200 — 400 nm. The spatial distributions of the e...

We present an analytical model based on hydrodynamic equations and a pseudo-two-dimensional Poisson equation to study the response of a nanometric field-effect transistor channel in the THz domain. This model allows to study different kinds of external excitations of plasma modes and different geometries. We calculate the two first-order responses...

Steady-state electric characteristics of quantum heterostructures Al x Ga 1–x As/GaAs/Al x Ga 1–x As with -doped barriers have been analyzed in this work. It has been shown that at high doping the additional low-conductive channels are formed in the barrier layers. Current-voltage characteristics of the structure were obtained in the wide interval...

The peculiarities of space-charge limited electronic transport in semiconductor AlGaN/GaN nanowire heterostructures under the effect of external UV excitation are studied experimentally and theoretically with particular emphasis of biophotonic and bioelectronic applications.

We report on the transmission of a terahertz (THz) radiation through prototype structures based on a p-type silicon substrate. In particular, the bare substrate and progressively more complicated multilayer structures were investigated, allowing to address the effect on the transmission of different factors, such as the orientation of interdigitate...

We derive at first-order the carrier and velocity conservation equations and a pseudo-2D (P2D) Poisson equation in order to obtain an analytical model suitable for the study of the optical and electrical excitations of the plasma modes in a gated semiconductor channel of arbitrary thickness. We calculate the dispersion relation of the plasma waves...

The theory of interaction between electromagnetic waves and a plasmonic structure consisting of the subwavelength metal grating locating over the layer of a two-dimensional (2D) electron gas has been developed. The frequency dependences of the transmission, reflection, and loss coefficients are shown to have a resonant behavior relating to the exci...

We have studied the high-frequency response of drifting electron gas on time- and spatial-dependent harmonic perturbation in frame of the exact solution of Boltzmann transport equation using Monte-Carlo method. It was demonstrated that results obtained by Monte-Carlo for the case of low-density electron gas differ from ones that are given by conven...

Theory of the plasmonic structure “grating - 2DEG” that consists of subwavelength metallic grating and a layer of the 2D-electron gas under the grating is presented. It is shown that frequency dependencies of the transmission, reflection and losses coefficients in THz frequency range have resonance behavior which relates to the 2D-plasmon excitatio...

The theory of THz radiation transmission through the film of compensated GaN of cubic modification under action of electric and magnetic fields has been developed. In the THz frequency range, spectra of the dynamic mobility tensor have been obtained for applied steady-state electric fields of several kV/cm and magnetic fields of several T. The spec...

Conditions required for the streaming effect and the optical-phonon transit-time resonance to take place in a compensated bulk GaN are analyzed in detail. Monte Carlo calculations of the high-frequency differential electron mobility are carried out. It is shown that the negative dynamic differential mobility can be realized in the terahertz frequen...

We have studied the high-frequency properties of the non-equilibrium electron gas in GaN samples subjected to electric and magnetic fields. Spectra of the complex tensor of the dynamical mobility have been calculated for THz frequency range. For the compensated GaN and low temperatures, in the intervals of electric fields of the few $kV/cm$ and mag...

We have analyzed low-temperature behavior of two-dimensional electron gas in polar heterostructures subjected to a high electric field. When the optical phonon emission is the fastest relaxation process, we have found existence of collective wave-like excitations of the electrons. These wave-like excitations are periodic in time oscillations of the...

We have developed theory for the interaction of THz radiation with a sub-wavelength metallic grating. The structure of electric fields of the electromagnetic wave under the metallic grating has been studied in the near-field zone. Spatial distributions of the electric field components and the electric energy density have been obtained for the trans...

We report on measurements of radiation transmission in the 0.220-0.325 THz and 0.75-1.1 THz frequency ranges through GaN quantum wells grown on sapphire substrates at nitrogen and room temperatures. Significant enhancement of the transmitted beam intensity with applied voltage is found at nitrogen temperature. This effect is explained by changes in...

We have investigated nonlinear electron transport in GaN induced by high-electric field transients by analyzing the temporal dependence of the electron drift velocity and temperature. For picosecond transients, our calculations have established that the electron dynamics retain almost all the features of the steady-state velocity-field characterist...

We report on measurements of radiation transmission in the 0.220-0.325 THz frequency range through GaN quantum wells grown on sapphire substrates at nitrogen and room temperatures. Significant enhancement of the transmitted beam intensity with applied voltage is found at nitrogen temperature. This effect is explained by changes in the mobility of t...

We present a self-consistent theory of ballistic electron transport in n(+) - i - n(+) diodes for steady-state and high-frequency regimes. The theory takes into account real injection/exclusion processes at the n(+) - i interfaces, space-charge effects in the base region and diffusive electron transport in contacts. Numerical results are obtained f...

We analyzed the steady-state electron transport for bulk GaN in frame of two opposite approaches: the electron temperature approach that assumes a high-density electron gas and numerical single-particle Monte-Carlo method that assumes a low-density electron gas and does not take into account electron-electron (e-e) scattering. We have also presente...

We investigated ultra-high frequency electrical properties of nanoscale n+-i-n+ diodes made of polar semiconductors. We found the optical vibrations instability and the large effect of the negative dynamic resistance. These effects indicate that the nanoscale diodes are capable of generating electromagnetic radiation in the 10 THz range.

We investigated the current-voltage characteristics and impedance of the ballistic n+-i-n+ diode made by InAs in THz frequency range. We found the optimal diode parameters and the electrical conditions to amplify and generate THz radiation.

The electron distribution function and transport characteristics of hot electrons in GaN semiconductor are calculated by the Monte Carlo method. We studied the electron transport at temperatures of 10, 77, and 300 K under low and moderate electric fields. We found that, at low temperatures and low electric fields (a few hundreds of V/cm), the secon...

We present a theoretical study of two-terminal nitride-based oscillators utilizing two different hot-electron transport regimes determined by the interaction of the electrons with polar optical phonons, which are capable to generate current/voltage oscillations in the THz-frequency range. The first is the limited space-charge accumulation (LSA) reg...

We discuss the basic properties of the transient hot-electron transport and dynamic mobility in group-III nitrides under dominant electron–polar-optical-phonon scattering determining their capability for applications in THz frequency range. For bulk samples with high electron concentration, we provide the phase-plane analysis of the time-dependent...

We investigated the terahertz (THz)-frequency resonances of two-dimensional electron conductivity under the streaming transport in a GaN quantum well at the nitrogen temperature. The calculation results found that the negative microwave mobility can occur in the narrow windows near the optical-phonon transit-time resonance frequencies, which can be...

We studied anisotropic electron distributions in group-III-nitride quantum wells and analyzed formation of the streaming regime under moderate electric fields. We found that the streaming effect can occur in high-mobility heterostructures (μ≥30 000  cm ²/ V s ) with low electron concentrations (n≤10¹²  cm ^-2) at tem...

In this report, we discuss the basic properties of transient hot-electron transport and high-frequency conductivity in group-III nitrides that determine their capability for applications in THz frequency range. Bulk samples, ultra-short diodes as well as quantum heterostructures are considered.