Arsenide Heterostructures Research Articles

Design and fabrication of S-band power amplifier for wireless sensor networks

This paper discusses the process of designing and manufacturing a wideband power amplifier operating in the S-band. To amplify a low power and broadband radio frequency signals from 2.1 GHz to 2.5 GHz, the proposed power amplifier uses a diagram of a two-stages amplification with peak offset amplification frequency 2.3 GHz. The power amplifier is designed with a center frequency difference of 2.2 GHz and 2.4 GHz respectively to achieve a bandwidth of 400 MHz. The proposed power amplifier (PA) uses RF transistor SHF-0589 using gallium arsenide heterostructure field-effect transistor (GaAs HFET) technology for high gain and low power consumption. The complete amplifier achieves power gain 21.1 dB inband 2.1-2.5 GHz and achieve maximum power gain of 22.5 dB at the frequency of 2.4 GHz; the output power rise up to 33 dBm; input reflection coefficient (S11) reaches -19.2 dB and output reflection coefficient reaches -17.2 dB. The designed amplifier circuit can be used for wireless sensor networks operating at S-band.

Insight into graphene/boron arsenide heterostructure used for high-performance lithium-ion battery anode materials: The first principles study

Two-dimensional (2D) van der Waals (vdW) heterostructures demonstrate potential applications in Lithium-ion batteries (LIBs) characterized by their elevated energy storage capacity and extended operational longevity as anode materials. The structures and electronic properties of graphene/boron arsenide (Gr/BAs) heterostructures, along with the adsorption and migration of lithium (Li) atoms within the structures, are methodically analyzed through first-principles studies underpinned by density functional theory. Our calculations indicate the metallic Gr/BAs heterostructures have the structural stability, where their mechanical strength is confirmed from the elastic constant. Its diffusion barrier of Li atoms (0.25 eV) is superior among similar anode materials. The Li atoms' diffusion coefficient within the Gr/BAs heterostructure at 300 K (1.27 × 10−10 m2/s) exceeds that observed in Gr (2.0×10−11 m2/s). Besides, the presence of Gr assists in maintaining the open-circuit voltage (OCV) of Gr/BAs heterostructures in the range of 0-1 V. The theoretical specific capacity of proposed heterostructure reaches 920 mAh/g. The present calculations suggest that the Gr/BAs heterostructure could serve effectively as an anode in LIBs due to its excellent electrical conductivity, small diffusion barriers and appropriate open-circuit voltage.

Giant electron-mediated phononic nonlinearity in semiconductor-piezoelectric heterostructures.

Efficient and deterministic nonlinear phononic interactions could revolutionize classical and quantum information processing at radio frequencies in much the same way that nonlinear photonic interactions have at optical frequencies. Here we show that in the important class of phononic materials that are piezoelectric, deterministic nonlinear phononic interactions can be enhanced by orders of magnitude via the heterogeneous integration of high-mobility semiconductor materials. To this end, a lithium niobate and indium gallium arsenide heterostructure is utilized to produce the most efficient three- and four-wave phononic mixing to date, to the best of our knowledge. We then show that the conversion efficiency can be further enhanced by applying semiconductor bias fields that amplify the phonons. We present a theoretical model that accurately predicts the three-wave mixing efficiencies in this work and extrapolate that these nonlinearities can be enhanced far beyond what is demonstrated here by confining phonons to smaller dimensions in waveguides and optimizing the semiconductor material properties.

Self-consistent Analysis for Optimization of AlGaAs/GaAs Based Heterostructure

The heterostructures are suitable for developing high-performance electronic and optoelectronic devices. In this work, a significant interest in the design and analysis of compound semiconductor Aluminium Gallium Arsenide (AlGaAs) and Gallium Arsenide (GaAs) heterostructures has been realized. These structures are fabricated with alternating layers of GaAs (a direct bandgap material) and AlGaAs (an indirect bandgap material) and have been used to design a range of high-performance devices, including lasers, solar cells, and field-effect transistors. A 30 nm AlGaAs consisting of a middle layer between two GaAs layers with a GaAs substrate has been reported. This work has been carried out at 300 K utilizing a quantum transport and self-consistent method for the proposed AlGaAs/GaAs one-dimensional heterostructure with a gate length of 2 nm and a voltage varying from 0 to 0.1 V. The measured values of doping density (nd) and electron density (ne) of AlGaAs/GaAs one-dimensional heterostructure are 8.96 × 1011 cm−3 and 2 × 1026 cm−3, respectively. The system response to geometric changes in several parameters has been realized. Hence, confined restricted states were computed using wave functions and energies. The GaAs layer on top of quantum well heterostructure interfaces has been used to modulate the wave functions (eigenstates) resulting in pseudo-one dimensional or small-dimension eigenstates. In this work, a comprehensive analysis of 1D AlGaAs/GaAs heterostructure through benchmarking with several homo-structures (various thicknesses) has been performed.

The Research for Approaches to Increase Power of the Compact THz Emitters Based on Low-Temperature Gallium Arsenide Heterostructures

The design and technological conditions for the manufacture of photoconductive antennas based on low-temperature gallium arsenide (LT-GaAs) have been developed. The optimized photoconductive THz antenna is made based on LT-GaAs with the flag geometry of the contacts and with the interdigitated structure including metal closing through the dielectric of each second period. LT-GaAs samples were obtained by molecular beam epitaxy at temperatures of 210 °C, 230 °C, 240 °C on GaAs substrates (100). Dark and photocurrent were measured depending on the bias voltage of the LT-GaAs heterostructure at the EP6 probe station. Full wave finite element method solver has been used to investigate the proposed plasmon PCA electrical and optical behavior by combining the Maxwell's wave equation with the drift-diffusion/Poisson equations.

Boron arsenide heterostructures: lattice-matched heterointerfaces and strain effects on band alignments and mobility

BAs is a III–V semiconductor with ultra-high thermal conductivity, but many of its electronic properties are unknown. This work applies predictive atomistic calculations to investigate the properties of BAs heterostructures, such as strain effects on band alignments and carrier mobility, considering BAs as both a thin film and a substrate for lattice-matched materials. The results show that isotropic biaxial in-plane strain decreases the band gap independent of sign or direction. In addition, 1% biaxial tensile strain increases the in-plane electron and hole mobilities at 300 K by >60% compared to the unstrained values due to a reduction of the electron effective mass and of hole interband scattering. Moreover, BAs is shown to be nearly lattice-matched with InGaN and ZnSnN2, two important optoelectronic semiconductors with tunable band gaps by alloying and cation disorder, respectively. The results predict type-II band alignments and determine the absolute band offsets of these two materials with BAs. The combination of the ultra-high thermal conductivity and intrinsic p-type character of BAs, with its high electron and hole mobilities that can be further increased by tensile strain, as well as the lattice-match and the type-II band alignment with intrinsically n-type InGaN and ZnSnN2 demonstrate the potential of BAs heterostructures for electronic and optoelectronic devices.

Рассеяние электронов и дырок глубокими примесями в полупроводниковых гетероструктурах с квантовыми ямами

Electron and hole scattering by deep impurities in gallium arsenide heterostructures with two quantum wells under arbitrary doping profile was considered within the strongly localized potential approximation. The de-pendence of scattering rate on the carrier energy was shown to reproduce the step-like form of the density of states for size quantization subbands of the heterostructure accounting for the contribution of the overlap integral of the carrier wave functions. For hole subbands of negative effective mass the scattering rates at the subband edges have singularities common for one-dimensional systems.

Transport properties of near surface InAs two-dimensional heterostructures

Two-dimensional electron systems confined to the surface of narrowband semiconductors have attracted great interest since they can easily integrate with superconductivity (or ferromagnetism) enabling new possibilities in hybrid device architectures and study of exotic states in proximity to superconductors. In this work, we study indium arsenide heterostructures where a combination of a clean interface with superconductivity, high mobility, and spin-orbit coupling can be achieved. The weak antilocalization measurements indicate the presence of strong spin-orbit coupling at high densities. We study the magnetotransport as a function of top barrier and density and report a clear observation of integer quantum Hall states. We report improved electron mobility reaching up to 44 000 cm2/Vs in undoped heterostructures and well developed integer quantum Hall states starting as low as 2.5 T.

N-GaAs diode with photoresponsivity based on 3-aminorhodanine thin films.

In this paper, the electrical characteristics of a 3-aminorhodanine (aRh)/n-gallium arsenide (n-GaAs) heterostructure were investigated in dark and under various illumination conditions. Although the structure shows a low rectifying rate, the photocurrent in both the forward and reverse biasing increases with increasing illumination intensity. The photodiode exhibits a large detectivity (the capability of detecting visible light), approaching 3.9×1011 Jones at room temperature. On illumination with light (100 mW/cm2), the current value in the aRh/n-GaAs heterostructure is 2.8×105 times, when compared to its dark value at zero applied voltage. The obtained responsivity value at the bias of 2V and under the illumination intensity of 100 mW/cm2 is 0.16A/W, which is high for any organic-inorganic hybrid photodiode. The photocurrent-to-dark-current ratio is 6.5×104. Results show that an aRh/n-GaAs self-powered photodiode introduces new opportunities for dynamic systems needing partially low or zero external energy inputs.

Towards modular binary to gray converter design using LTEx module of quantum-dot cellular automata

A modular approach to realize the ultra-fast quantum-dot cellular automata (QCA) generic binary to gray converter is presented in this paper. The novel designs here validated fully exploit the intrinsic repetitive capabilities of the Layered T Exclusive OR (LTEx) module in the QCA domain. An efficient logic formulation of QCA design metrics like O-Cost and delay is proposed for the n-bit QCA binary to gray converter designs. The QCA implementation of n-bit LTEx binary to gray converter is compared with the conventional converters. An attempt has been made to enhance the speed of modular binary to gray converter designs. The proposed 4, 8, 16, 32, 64-bit binary to gray converters need 4.35, 15.88, 15.96, 15.7, 16.68% less O-cost and 11.57, 2.61, 9.32, 12.64, 29.25% less effective area, respectively. Thus the proposed layouts offer the smaller feature size, reduced circuit complexity exploiting the modular based design approach. The simulation results have been carried out in the renowned computer aided design tool, namely QCADesigner 2.0.3 with gallium arsenide heterostructure based parameter environment.

Неразрушающие методы контроля арсенидных и нитридных гетероструктур с квантовой ямой

Неразрушающие методы контроля арсенидных и нитридных гетероструктур с квантовой ямой

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures.

Search for Majorana fermions renewed interest in semiconductor–superconductor interfaces, while a quest for higher-order non-Abelian excitations demands formation of superconducting contacts to materials with fractionalized excitations, such as a two-dimensional electron gas in a fractional quantum Hall regime. Here we report induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures and development of highly transparent semiconductor–superconductor ohmic contacts. Supercurrent with characteristic temperature dependence of a ballistic junction has been observed across 0.6 μm, a regime previously achieved only in point contacts but essential to the formation of well separated non-Abelian states. High critical fields (>16 T) in NbN contacts enables investigation of an interplay between superconductivity and strongly correlated states in a two-dimensional electron gas at high magnetic fields.

Even denominators in odd places

Odd-denominator fractional quantum Hall states are routinely observed in high-mobility gallium arsenide heterostructures. Now, a 5/2 state has been observed in an oxide heterostructure — an unexpected state in an unexpected material.

Residual strain in cadmium telluride/gallium arsenide (001) heterostructures as a function of temperature

Optical studies of residual strain in cadmium telluride (CdTe) films grown using molecular beam epitaxy on gallium arsenide (GaAs) substrate have been performed using photoreflectance techniques. Measurements have been conducted to determine the fundamental transition energy, heavy-hole and light-hole transition energy critical-point parameters in a range of temperatures between 12 and 300K. There are problems inherent in the fabrication of optoelectronic devices using high-quality CdTe films, due to strain effects resulting from both the lattice mismatch (CdTe: 14.6%) and the thermal expansion coefficient difference. The CdTe film exhibits compressive stress causing valence-band splitting for light and heavy holes. We have used different models to fit the obtained experimental data and, although the critical thickness for the CdTe has been surpassed, the strain due to the lattice mismatch is still significant. However, the strain due to the thermal expansion is dominant. We have found that the fundamental transition energy, E0, is affected by the compressive strain and the characteristic values are smaller than those reported. In addition, the total strain is compressive for the full measured range, since the strain due to the lattice mismatch is one order of magnitude higher than that calculated from the thermal expansion.

Tunneling current in Si-doped n type-GaAs heterostructures infrared emitter

In the present work, we measured the forward bias current-voltage (I–V) characteristics of Si-doped n type gallium arsenide (GaAs) heterostructures infrared emitter over a wide temperature range from 350 to 77 K. Results showed that the slopes of the exponential curve changed slowly with temperature. The analysis of the various tunneling mechanisms indicated that the tunneling current varied approximately as a function of ∼ exp(− αE g + βeV) where the parameters α and β varied indistinctively with temperature and voltage. The dependence of forward tunneling current on the temperature and bias can be explained by thermally induced band gap shrinkage and bias induced route change respectively. These results will be helpful for application of the optoelectronics device in both high and low temperature ambiences.

Molecular Beam Epitaxy of Ultra-High-Quality AlGaAs/GaAs Heterostructures: Enabling Physics in Low-Dimensional Electronic Systems

Among very-low-disorder systems of condensed matter, the high-mobility two-dimensional electron gas (2DEG) confined in aluminum gallium arsenide (AlGaAs)–gallium arsenide (GaAs) heterostructures holds a privileged position as a platform for the discovery of new electronic states driven by strong Coulomb interactions. Molecular beam epitaxy (MBE), an ultra-high vacuum (UHV), thin-film deposition technique, produces the highest quality 2DEGs and has played a central role in a number of discoveries that have at their root the interplay of reduced dimensionality, strong electron-electron interactions, and disorder. This review attempts to describe the latest developments in heterostructure design, MBE technology, and the evolution of our understanding of disorder that result in improved material quality and facilitate discovery of new phenomena at ever finer energy scales.

Ultrafast decay of non‐equilibrium (hot) phonons in GaN‐based 2DEG channels

AbstractFast and ultrafast decay of non‐equilibrium longitudinal optical phonons (hot phonons) is discussed on examples of two‐dimensional electron gas (2DEG) channels confined in nominally‐undoped nitride and selectivelydoped arsenide heterostructures subjected to pulsed dc electric power. At a low–moderate power, a nonmonotonous dependence of the hot‐phonon lifetime on the 2DEG density is found. The fastest decay takes place at ∼2.5 × 1012 cm–2 in GaInAs 2DEG channel and at ∼7 × 1012 cm–2 in GaN 2DEG channel. The result is discussed in terms of plasmon–LO‐phonon resonance. The hot‐phonon lifetime decreases when the supplied power is increased if the 2DEG density exceeds the resonance density. The shortest hot‐phonon lifetime of 60 fs is obtained at/above 50 nW/electron for the lattice‐matched AlInN/AlN/GaN 2DEG channel (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fast pulsed gallium arsenide heterostructure diodes

Switching of properties of gallium arsenide heterostructure diodes has been studied. It is shown that use of a graded-gap base region or a wide-gap “wall” (abrupt heterojunction) enables control over the distribution of injected carriers and their accumulation near the p-n junction, which leads to a faster reverse-voltage recovery (60–70 ps). Structures are considered in which an impurity gradient is used, together with the gradient of the energy gap, in order to make the working voltage higher.

Y-coupled quantum cascade lasers

Spectroscopy at midand far-infrared wavelengths is important for environmental sensing (trace analysis, pollutants), medical diagnostics (blood analysis, breath control), and is a promising candidate for future high-security applications (airport security, identification of hazardous chemicals).1 Sensing chemical components in gases and liquids requires powerful coherent light sources with narrow spectral bandwidth and small divergence.2, 3 In the past decade, this demand has promoted quantum cascade lasers (QCLs), which enhance the performance and shrink down the dimensions of today’s midand farinfrared sensor systems.4 In contrast to conventional semiconductor lasers, QCLs can be designed to hit the target wavelength of a spectroscopic application. The coupling of semiconductor lasers results in an increased output power,5 stable single-mode operation, and wavelength tunability.6, 7 When integrated in a spectroscopic measurement system, monolithic coupling schemes can maximize the sensitivity, selectivity, and applicability of the sensor. However, a homogeneous laser beam is essential to avoid complicated optics and high losses of light. Therefore, the light inside the laser cavity has to be understood and controlled. Figure 1 shows a sketch of a Y-coupled QCL with corresponding dimensions. Two laser waveguides (branches) spaced by 60μm merge into a single trunk towards a single facet. The Yshaped QCLs have a waveguide width of 10μm and imply a bending radius of 8.3mm. The lasers were fabricated from a gallium arsenide/aluminum gallium arsenide heterostructure by lithography, etching, sputtering, and evaporation techniques.8 The devices were operated with 100ns current pulses at 78K. Their emission wavelength peaks at 10.5μm. To analyze the output beams on both sides of the laser, both the single and double facets were imaged with a midinfrared micro-bolometer camera. The image of the single facet Figure 1. Sketch of the Y-shaped quantum cascade laser (QCL) with corresponding dimensions. Near-field images illustrate the intensity distributions emitted from (left) the single facet and (right) the double facet.

Surface-gated quantum Hall effect in an InAs heterostructure

We demonstrate low leakage surface gating of an indium arsenide heterostructure with the two-dimensional electron gas close to the surface. Gating is made possible by growing an aluminum oxide layer on top of the device. We find that the depletion point can be changed by applying a positive gate voltage and we see hysteresis when the voltage is swept below depletion.