Sergey L. Rumyantsev

Institute of High Pressure Physics PAS Warsaw Poland

We show that terahertz plasmons in AlGaN/GaN grating-gate structures efficiently modulate the reflection of room temperature thermal radiation, leading to spectra that are in agreement with the measurements of plasmon absorption using high-power external sources. For typical samples of a few square millimeters in size, the reflected radiation inten...

We investigated the noise and photoresponse characteristics of various optical transparencies of nanotube networks to identify an optimal randomly oriented network of carbon nanotube (CNT)-based devices for UV-assisted gas sensing applications. Our investigation reveals that all of the studied devices demonstrate negative photoconductivity upon exp...

The effect of ultraviolet (UV) or blue irradiation on graphene/n-doped silicon Schottky junctions toward gas sensing was investigated. Schottky diodes were subjected to oxidizing nitrogen dioxide (NO2, 1–3 ppm) and reducing tetrahydrofuran (THF, 50–200 ppm), showing significantly different responses observed on the current-voltage (I-V) characteris...

We investigated the temperature dependence of the conductance fluctuations in thin films of the quasi-two-dimensional 1T-TaS2 van der Waals material. The conductance fluctuations, determined from the derivative current-voltage characteristics of two-terminal 1T-TaS2 devices, appear prominently at the electric fields that correspond to the transitio...

We report on the low-frequency electronic noise in β-(AlxGa1−x)2O3 Schottky barrier diodes. The noise spectral density reveals 1/f dependence, characteristic of the flicker noise, with superimposed Lorentzian bulges at the intermediate current levels (f is the frequency). The normalized noise spectral density in such diodes was determined to be on...

We report results of the current–voltage characteristics and low-frequency noise in Au nanoparticle (AuNP)-decorated graphene–Si Schottky barrier diodes. Measurements were conducted in ambient air with addition of either of two organic vapors, tetrahydrofuran [(CH2)4O; THF] and chloroform (CHCl3), as also during yellow light illumination (592 nm),...

We report on the low-frequency electronic noise in (Al$_x$Ga$_{1-x}$)$_2$O$_3$ Schottky barrier diodes. The noise spectral density reveals 1/f dependence, characteristic of the flicker noise, with superimposed Lorentzian bulges at the intermediate current levels (f is the frequency). The normalized noise spectral density in such diodes was determin...

This work demonstrates a graphene/AlGaN/GaN sensing device with two-dimensional electron gas (2DEG) toward nitrogen dioxide (NO2), tetrahydrofuran, and acetone detection under UV light irradiation. We propose combining measurements of the DC characteristics with a fluctuation-enhanced sensing method to provide insight into the gas detection mechani...

Extending knowledge of the properties of low-dimensional van der Waals materials, including their reactivity to the ambiance, is important for developing innovative electronic and optoelectronic devices. Transition metal trichalcogenides with tunable optical band gaps and anisotropic conductivity are an emerging class among low- dimensional structu...

The effect of ultraviolet (UV) or blue irradiation on graphene/n-doped silicon Schottky junctions toward gas sensing was investigated. Schottky diodes were subjected to oxidizing nitrogen dioxide (NO2, 1–3 ppm) and reducing tetrahydrofuran (THF, 50–200 ppm), showing significantly different responses observed on the current-voltage (I-V) characteris...

The current response to sub-terahertz radiation was studied experimentally over a wide range of temperatures for AlGaN/GaN and graphene transistors. It was found that the responsivity is enhanced at low temperatures by about an order of magnitude for AlGaN/GaN and more than two orders of magnitude for graphene transistors. However, the responsivity...

One of the challenges of using carbon nanotubes electronics is achieving precise control of the conductivity type. It is particularly difficult to obtain the n-type conductive nanotubes. One of the most common methods of CNTs modification allowing to change their conductivity type is chemical functionalization. This paper describes the results of s...

Low‐frequency current fluctuations, i.e., electronic noise, in quasi‐1D (TaSe4)2I Weyl semimetal nanoribbons are discussed. It is found that the noise spectral density is of the 1/f type and scales with the square of the current, SI ~ I2 (f is the frequency). The noise spectral density increases by almost an order of magnitude and develops Lorentzi...

We report on the electrical gating of the charge-density-wave phases and current in h-BN-capped three-terminal 1T-TaS2 heterostructure devices. It is demonstrated that the application of a gate bias can shift the source-drain current-voltage hysteresis associated with the transition between the nearly commensurate and incommensurate charge-density-...

We studied temperature-dependent photo response in the sub-THz regime (0.14 THz) of graphene and AlGaN/GaN-based field-effect transistors (FETs). Instead of measuring the voltage response using a lock-in amplifier, the current induced by the incoming sub-THz radiations was measured directly using the semiconductor parameters analyzer (SPA). Such an...

In this work, we studied the gate voltage dependence of THz transmission spectra of AlGaN/GaN grating-gate structures consisting of two-dimensional electron gas (2DEG) covered by high active area (2x2 mm 2) metal surface grating. Resonance absorption minima revealed in the measured THz spectra were related to 2D plasma resonances existing in the gr...

Temperature-dependences of RI and NEP in the sub-THz regime of graphene devices were measured and compared with GaN-based devices.

This work demonstrates a graphene/AlGaN/GaN sensing device with two-dimensional electron gas (2DEG) toward nitrogen dioxide (NO2), tetrahydrofuran, and acetone detection under UV light irradiation. We propose combining measurements of the DC characteristics with a fluctuation-enhanced sensing method to provide insight into the gas detection mechani...

We present investigations of the fin-shaped GaN/AlGaN field effect transistors with two lateral Schottky barrier gates exactly placed on the edges of the fin-shaped transistor channel. We call this kind of FinFET modification the EdgeFET. It allowed us to efficiently control the current flow in two-dimensional electron gas conduction channel. We pr...

The gas sensing properties of graphene back-gated field-effect transistor (GFET) sensors toward acetonitrile, tetrahydrofuran, and chloroform vapors were investigated with the focus on unfolding possible gas detection mechanisms. The FET configuration of the sensor device enabled gate voltage tuning for enhanced measurements of changes in DC electr...

This paper presents three types of single-pole single-throw RF switches utilizing AlGaN/GaN Schottky junction as distributed switching elements integrated in a coplanar waveguide structure. The switches are designed in shunt topology, which allows to achieve good high frequency performance. First type of switch is driven through RF port, while the...

We report on low-frequency current fluctuations, i.e. electronic noise, in quasi-one-dimensional (TaSe$_4$)$_2$I Weyl semimetal nanoribbons. It was found that the noise spectral density is of the 1/f type and scales with the square of the current, S~I^2 (f is the frequency). The noise spectral density increases by almost an order of magnitude and d...

We report on electrical gating of the charge-density-wave phases and current in h-BN capped three-terminal 1T-TaS$_2$ heterostructure devices. It is demonstrated that the application of a gate bias can shift the source-drain current-voltage hysteresis associated with the transition between the nearly commensurate and incommensurate charge-density w...

The nature of the low-frequency 1/f noise in electronic materials and devices is one of the oldest unsolved physical problems (f is the frequency). The fundamental question of the noise source-fluctuations in the mobility vs. number of charge carriers-is still debated. While there are several pieces of evidence to prove that the 1/f noise in semico...

We report the results of an investigation of low-frequency excess noise in high-current diamond diodes. It was found that the electronic excess noise of the diamond diodes is dominated by the 1/f and generation-recombination noise, which reveals itself as Lorentzian spectral features (f is the frequency). The generation-recombination bulges are cha...

The interaction of terahertz electromagnetic radiation with dilute graphene-epoxy composites was studied experimentally at frequencies from 0.25 to 4 THz. Composites with low graphene loading (≤1.2 wt. %) below the electrical percolation threshold revealed the total shielding effectiveness above ∼70 dB (1 mm thickness) at 1.6 THz frequency. The une...

We report results of an investigation of low-frequency excess noise in high-current diamond diodes. It was found that the electronic excess noise of the diamond diodes is dominated by generation - recombination noise, which reveals itself either as Lorentzian spectral features or as a 1/f noise spectrum (f is the frequency). The generation - recomb...

We report low-frequency noise characteristics of vertical GaN PIN diodes, focusing on the effects of the diode design, current, and temperature. The as-grown and regrown diodes, with and without surface treatment, have been studied. The noise in most of the GaN devices had a characteristic 1/f spectrum at high and moderate currents, while some devi...

We report low-frequency noise characteristics of vertical GaN PIN diodes, focusing on the effects of the diode design, current and temperature. The as-grown and regrown diodes, with and without surface treatment have been studied. The noise in most of the GaN devices had a characteristic 1/f spectrum at high and moderate currents, while some device...

We report on the effect of forward current stress on the low frequency noise in the 4H-SiC rectifier p +-n diodes rated at 20 and 10 kV. The 4H-SiC diodes with 20 kV blocking voltage were the most sensitive to the forward current stress. Even the stress by the current density j =13 A/ cm 2 for 30 min led to a noticeable increase in the forward volt...

The nature of the low-frequency current fluctuations, i.e. carrier number vs. mobility, defines the strategies for noise reduction in electronic devices. While the 1/f noise in metals has been attributed to the electron mobility fluctuations, the direct evidence is lacking (f is the frequency). Here we measured noise in h-BN encapsulated graphene t...

The exceptionally large active surface-to-volume ratio of carbon nanotubes makes it an appealing candidate for gas sensing applications. Here, we studied the DC and low-frequency noise characteristics of a randomly oriented network of carbon nanotubes under NO2 gas atmosphere at two different wavelengths of the UV light-emitting diodes. The UV irra...

RF switches, which use a combination of graphene and two-dimensional high-density electron gas (2DEG) in the AlGaN/GaN system, were proposed and studied in the frequency band from 10 MHz to 114.5 GHz. The switches were integrated into the coplanar waveguide, which allows them to be used in any system without the use of, e.g., bonding, flip-chip and...

A graphene-based gas sensor fabricated in a FET (GFET) configuration and its sensitivity towards ethanol and methane is reported. Detection of ethanol at the level of 100 ppm was observed under pulsed UV irradiation and after cleaning by UV light in the N2 ambient. Reduction of the frequency of UV irradiation pulses resulted in increased changes in...

Low‐frequency current fluctuations, i.e., noise, in the quasi‐2D van der Waals antiferromagnetic semiconductor FePS3 with the electronic bandgap of 1.5 eV is investigated. The electrical and noise characteristics of the p‐type, highly resistive, thin films of FePS3 are measured at different temperatures. The noise spectral density is of the 1/f‐typ...

We demonstrate that polymer composites with a low loading of graphene, below 1.2 wt. %, are efficient as electromagnetic absorbers in the THz frequency range. The epoxy-based graphene composites were tested at frequencies from 0.25 THz to 4 THz, revealing total shielding effectiveness of 85 dB (1 mm thickness) with graphene loading of 1.2 wt. % at...

Terahertz plasmon resonances were studied at 4.2K and 300K in GaN-based grating gate structures using two THz spectroscopy techniques: Fourier-Transform Infrared Spectroscopy and Time Domain Spectroscopy. Gratings of different periods were coupled to the two-dimensional electron gas in AlGaN/GaN in order to investigate the dispersion law of 2D-plas...

Study aged and as-fabricated nanotube transistors, and examine the noise spectra under laboratory air and dry air environment. Noise study as function of device length in order to understand the relative contribution of contact noise to total device noise.

We report on the study of the magnetic ratchet effect in AlGaN/GaN heterostructures superimposed with a lateral superlattice formed by a dual-grating gate structure. We demonstrate that irradiation of the superlattice with a terahertz beam results in the direct ratchet current, which shows giant magneto-oscillations in the regime of Shubnikov–de Ha...

AlGaN/GaN fin-shaped and large-area grating gate transistors with two layers of two-dimensional electron gas and a back gate were fabricated and studied experimentally. The back gate allowed reducing the subthreshold leakage current, improving the subthreshold slope and adjusting the threshold voltage. At a certain back gate voltage, transistors op...

We investigated low-frequency current fluctuations, i.e. noise, in the quasi-two-dimensional (2D) van der Waals antiferromagnetic semiconductor FePS3 with the electronic bandgap of 1.5 eV. The electrical and noise characteristics of the p-type, highly resistive, thin films of FePS3 were measured at different temperatures. The noise spectral density...

Noise spectroscopy can be employed to explore the hidden characteristics of material for its potential application in various aspects of technology. For instance, vapors of different chemicals induced Lorentzian components in noise spectra of graphene with distinctive features. Later, this kind of study was further extended to other materials. It c...

We report on the investigations of the fin-shaped GaN/AlGaN field effect transistors with two lateral Schottky barrier gates exactly placed on the edges of the fin-shaped transistor channel. This kind FinFET modification (EdgeFET) allowed us to efficiently control the current flow in two-dimensional electron gas conduction channel. We present exper...

Polymer composite films containing fillers comprising quasi-1D van der Waals materials, specifically transition metal trichalcogenides with 1D structural motifs that enable their exfoliation into bundles of atomic threads, are reported. These nanostructures are characterized by extremely large aspect ratios of up to ≈106 . The polymer composites wi...

Noise defines the minimum level of the operational signal and is an important figure of merit for various devices. Here, we studied the low-frequency (1/f) noise characteristics of randomly oriented networks of carbon nanotubes and examined the effect of ultraviolet (UV) light on it. The amplitude of 1/f noise in our devices was strongly affected b...

We report polymer composite films containing fillers comprised of quasi-one-dimensional (1D) van der Waals materials, specifically transition metal trichalcogenides containing 1D structural motifs that enable their exfoliation into bundles of atomic threads. These nanostructures are characterized by extremely large aspect ratios of up to 10^6. The...

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects. Fabricated Schottky barrier diodes (SBDs) de...

We report anomalous behavior of the response in GaN/AlGaN fin-shaped field effect transistors at sub-THz frequency range. For transistors with the gate length much bigger than the width of the channel an unusual growth of the absolute value of the response signal was observed with applying positive gate voltage.

Electrical and noise properties of graphene contacts to AlGaN/GaN heterostructures were studied experimentally. It was found that graphene on AlGaN forms a high-quality Schottky barrier with the barrier height dependent on the bias. The apparent barrier heights for this kind of Schottky diode were found to be relatively high, varying within the ran...

We report on the synthesis of the epoxy-based composites with graphene fillers and testing their electromagnetic shielding efficiency by the quasi-optic free-space method in the extremely high frequency (EHF) band (220 – 325 GHz). The curing adhesive composites were produced by a scalable technique with a mixture of single-layer and few-layer graph...

We report on the current oscillations in quasi-2D 1T-TaS2 charge-density-wave two-dimensional devices. The MHz-frequency range of the oscillations and the linear dependence of the frequency of the oscillations on the current closely resemble the narrow band noise, which was often observed in the classical bulk quasi-1D trichalcogenide charge-densit...

We report on the synthesis of the epoxy-based composites with graphene fillers and testing their electromagnetic shielding efficiency by the quasi-optic free-space method in the extremely high frequency (EHF) band (220 - 325 GHz). The curing adhesive composites were produced by a scalable technique with a mixture of single-layer and few-layer graph...

We report on the investigations of the fin-shaped GaN/AlGaN field effect transistors (FinFETs) with two lateral Schottky barrier gates exactly placed at the edges of the fin-shaped transistor channel. This kind of FinFET modification (called EdgeFET) allowed us to efficiently control the current flow in two-dimensional electron gas conduction chann...

We report on current oscillations in quasi two-dimensional (2D) 1T-TaS2 charge-density-wave devices. The MHz-frequency range of the oscillations and the linear dependence of the frequency of the oscillations on the current resemble closely the "narrow band noise," which was often observed in the classical bulk quasi-one-dimensional (1D) trichalcoge...

GaN/AlGaN lateral Schottky diodes, FinFETs and EdgeFETs were fabricated and studied. All these devices have fin-shaped active area, characterized by small input capacitance and are promising for high frequency applications.

We report measurements of low-frequency electronic noise in ordered superlattice, weakly-ordered and random-packed thin films of 6.5 nm PbSe quantum dots prepared using several different ligand chemistries. For all samples, the normalized noise spectral density of the dark current revealed a Lorentzian component, reminiscent of the generation-recom...

The low-frequency amplitude and phase noise spectra of magnetization waves, i.e. magnons, was measured in the yttrium iron garnet (YIG) waveguides. This type of noise, which originates from the fluctuations of the physical properties of the YIG crystals, has to be taken into account in the design of YIG-based RF generators and magnonic devices for...

The emergence of graphene and two-dimensional van der Walls materials renewed interest to investigation of the low-frequency noise in the low-dimensional systems. The layered van der Waals materials offers unique opportunities for studying the low-frequency noise owing to the properties controlled by the thickness of these materials, and tunable ca...

We report measurements of low-frequency electronic noise in ordered superlattice, weakly-ordered and random-packed thin films of 6.5 nm PbSe quantum dots prepared using several different ligand chemistries. For all samples, the normalized noise spectral density of the dark current revealed a Lorentzian component, reminiscent of the generation-recom...

Micron-scale single-crystal nanowires of metallic TaSe3, a material that forms -Ta-Se3-Ta-Se3- stacks separated from one another by a tubular van der Waals (vdW) gap, have been synthesized using chemical vapor deposition (CVD) on a SiO2/Si substrate, in a process compatible with semiconductor industry requirements. Their electrical resistivity was...

We report on switching among three charge-density-wave phases - commensurate, nearly commensurate, incommensurate - and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced by application of an in-plane bias voltage. The switching among all phases has been achieved over a wide temperature range, from 77 K to 400 K. The lo...

We demonstrate that the charge-density-wave devices with quasi-two-dimensional 1T-TaS2 channels show remarkable immunity to bombardment with 1.8 MeV protons to a fluence of at least 1014 H⁺cm⁻². The current-voltage characteristics of these devices do not change as a result of proton irradiation, in striking contrast to most conventional semiconduct...

We report on switching among three charge-density-wave phases - commensurate, nearly commensurate, incommensurate - and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced by application of an in-plane electric field. The electric switching among all phases has been achieved over a wide temperature range, from 77 K to 40...

Micron-scale single-crystal nanowires of metallic TaSe3, a material that forms -Ta-Se3-Ta-Se3- stacks separated from one another by a tubular van der Waals (vdW) gap, have been synthesized using chemical vapor deposition (CVD) on a SiO2/Si substrate, in a process compatible with semiconductor industry requirements. Their electrical resistivity was...

We report experimental results, which show that the low-frequency noise of magnonic devices is dominated by the random telegraph signal noise rather than 1/f noise- A striking contrast to many electronic devices (f is a frequency). It was also found that the noise level of surface magnons depends strongly on the power level, increasing sharply at t...

We report results regarding the electron transport in vertical quasi-two-dimensional (2D) layered 1T-TaS 2 charge-density-wave (CDW) devices. The low-frequency noise spectroscopy was used as a tool to study changes in the cross-plane electrical characteristics of the quasi-2D material below room temperature. The noise spectral density revealed stro...

We report results regarding the electron transport in vertical quasi-2D layered 1T-TaS2 charge-density-wave devices. The low-frequency noise spectroscopy was used as a tool to study changes in the cross-plane electrical characteristics of the quasi-2D material below room temperature. The noise spectral density revealed strong peaks - changing by mo...

Proton radiation damage is an important failure mechanism for electronic devices in near-Earth orbits, deep space and high energy physics facilities. Protons can cause ionizing damage and atomic displacements, resulting in device degradation and malfunction. Shielding of electronics increases the weight and cost of the systems but does not eliminat...

We report on the investigations of AlGaN/GaN field effect transistors with two lateral Schottky barrier gates on the sides of two dimensional electron gas. This kind of "EdgeFETs" allowed us to efficiently control the current flow in the 2DEG conduction channel and due to depletion regions at a certain range of reverse biasing form a nanowire which...

We report on comparison studies between a novel transistor like device and two dimensional Fin Field-Effect transistor towards their applications in a terahertz resonant detector. Both device structures have been fabricated on the same wafer of GaN/AIGaN epistructure during one processing run. The proposed here the transistor-like structure has two...

We describe the low-frequency current fluctuations, i.e. electronic noise, in quasi-one-dimensional ZrTe3 van der Waals nanoribbons, which have recently attracted attention owing to their extraordinary high current carrying capacity. Whereas the low-frequency noise spectral density, SI/I², reveals 1/f behavior near room temperature, it is dominated...

Magnonics is a rapidly developing subfield of spintronics, which deals with devices and circuits that utilize spin currents carried by magnons - quanta of spin waves. Magnon current, i.e. spin waves, can be used for information processing, sensing, and other applications. A possibility of using the amplitude and phase of magnons for