Search Results (86)

A Q-enhanced notch filter for interference-rejection LNAs is proposed in this brief. The active capacitance is introduced into the notch filter to improve the quality factor by the negative resistance effect. The designed notch filter achieves excellent performance with a narrow attenuation bandwidth from 5.75 GHz to 5.95 GHz, which can be applied to suppress interference from the IEEE 802.11a. To validate the feasibility of the proposed trap filter in both GaAs process technology and principle, a 3–15 GHz ultra-wideband low-noise amplifier was designed and fabricated using a 0.15-micron gallium arsenide pseudomorphs field-effect transistor process. The frequency-dependent feedback loops are employed between gate and drain stages for wideband input matching and gain flatness. The notch filter is inserted between two stages of the LNA. The measurement results show that the interference-rejection LNA achieves a maximum gain of 24.5 dB and a minimum noise figure of 1.8 dB in the operating band. The notch filter has a maximum interference-rejection ratio of 35.2 dB at 5.8 GHz with almost no effect on the desired gain of the LNA. The LNA has a power consumption of 168 mW, including the notch filter with a size of 1.93 × 0.72 mm². Full article

Terahertz (THz) metamaterial absorbers have become a prominent research topic in recent years. In this paper, a hexa-band metamaterial absorber is designed for bio-medical sensing applications. The design can detect changes in the surrounding medium’s refractive index and operates in the refractive index range of 1.3–1.4, with six prominent absorption peaks. The proposed structure comprises a square ring resonator made up of gold with a boss-cross structure at the center, on top of a Gallium Arsenide (GaAs) substrate having a thickness of 8 μm. When the surrounding medium’s refractive index is 1.4, it offers six absorption peaks at 0.537 THz, 2.573 THz, 3.025 THz, 3.146 THz, 3.489 THz, 3.7348 THz, with corresponding peak absorption of 75%, 92.9%, 98.4%, 98.71%, 94.1%, and 99.34%, respectively. The structure has been designed at n = 1.4 instead of n = 1, as several biological specimens, such as blood, breast cells, etc., have refractive index in the range of 1.3–1.4, and it offers 6 bands for n = 1.4. This choice was made because many biomedical applications have a refractive index around 1.4. The design parameters were selected through a parametric analysis, so as to achieve maximum absorption peaks. The design has also been tested with different polarization angles, and it has been discovered that the absorber is polarization-insensitive. This design can inspire future research on the biomedical application of THz absorbers. Full article

Reliable power generation from solar cells is critical for spacecraft operation. High-energy laser irradiation poses a significant threat, as it can potentially cause irreversible damage to solar cells, which is difficult to detect remotely using conventional techniques such as radar or optical imaging. Spectral detection offers a potential approach through unique “spectral fingerprints,” but the spectral characteristics of laser-damaged solar cells remain insufficiently documented. This study investigates the scattering spectral characteristics of triple-junction GaAs (Gallium Arsenide) solar cells subjected to nanosecond pulsed laser irradiation to establish spectral signatures for damage assessment. GaAs solar cells were irradiated at varying energy densities. Bidirectional Reflectance Distribution Function (BRDF) spectra (400–1200 nm) were measured. A thin-film interference model was used to simulate damage effects by varying layer thicknesses, thereby interpreting experimental results. The results demonstrate that as the laser energy density increases from 0.12 to 2.96 J/cm², the number of absorption peaks in the visible range (400–750 nm) decreases from three to zero, and the oscillation in the near-infrared range vanishes completely, indicating progressive damage to the GaInP (Gallium Indium Phosphide) and GaAs layers. This study provides a spectral-based approach for remote assessment of laser-induced damage to solar cells, which is crucial for satellite health monitoring. Full article

Despite the remarkable developments in advanced materials, silicon and gallium arsenide remain among the leading semiconductors of our time. Nanomechanical studies of these semiconductor crystals, including nanoindentation-induced structural phase transformations and dislocation generation, remain important for science and technology. Of particular interest are studies on the onset of plasticity. What phenomenon initiates plastic deformation in Si and GaAs during nanoindentation? Through complex experiments and computer simulations, significant progress has been made in answering this question over the past twenty years. Indeed, equipping nanoindentation systems with the ability to record Raman spectra and exploring new interatomic interaction models for classical molecular dynamics have opened up new avenues for studying the non-trivial interplay between structural phase transformations and dislocation activity in semiconductor crystals. The diversity of high-pressure phases, especially silicon, and the largely unexplored sequences of transformations between them continue to inspire new scientific challenges. This article reviews selected works introducing the reader to the fascinating and still open topic of nanoindentation-induced incipient plasticity in silicon and gallium arsenide. Full article

In the last decades, small satellites such as CubeSats and PocketQubes have become popular platforms for scientific and applied missions in low Earth orbit (LEO). However, prolonged exposure to atomic oxygen, ultraviolet radiation, and thermal cycling in LEO leads to gradual degradation of onboard solar panels, reducing mission lifetime and performance. This study addresses the need to quantify and compare the degradation behavior of different solar cell technologies and protective coatings used in nanosatellites and pico-satellites. The aim is to evaluate the in-orbit performance of monocrystalline silicon (Si), gallium arsenide (GaAs), triple-junction (TJ) structures, and copper indium gallium selenide (CIGS) cells under varying orbital and satellite parameters. Telemetry data from recent small satellite missions launched after 2020, combined with numerical modeling in GNU Octave, were used to assess degradation trends. The models were validated using empirical mission data, and statistical goodness-of-fit metrics (RMSE, R²) were applied to evaluate linear and exponential degradation patterns. Results show that TJ cells exhibit the highest resistance to LEO-induced degradation, while Si-based panels experience more pronounced power loss, especially in orbits below 500 km. Furthermore, smaller satellites (<10 kg) display higher degradation rates due to lower thermal inertia and limited shielding. These findings provide practical guidance for the selection of solar cell technologies, anti-degradation coatings, and protective strategies for long-duration CubeSat missions in diverse LEO environments. Full article

Gallium Arsenide (GaAs) Schottky technology stands out for its superior performance in terms of conversion loss for terahertz mixers at room temperatures, which establishes it as a dominant solution in receivers for high-data-rate wireless communications. However, Indium Gallium Arsenide (InGaAs) Schottky mixers offer a notable advantage in terms of reduced power requirements due to their lower barrier height, enabling optical pumping with the incorporation of photodiodes acting as photonic local oscillators (LOs). In this study, we present the first comparative analysis of GaAs and InGaAs diode technologies under both electrical and optical pumping, which are also being compared for the first time, particularly in the context of a wireless communication system, transmitting up to 80 Gbps at 0.3 THz using 16-quadrature amplitude modulation (QAM). The terahertz transmitter and the optical receiver’s LO are based on modified uni-traveling-carrier photodiodes (MUTC-PDs) driven by free-running lasers. The investigation covers a total of two mixers, including narrow-band GaAs and InGaAs. The results reveal that, despite InGaAs mixers exhibiting higher conversion loss, the bit error rate (BER) can be as low as that with GaAs. This is attributed to the purity of optically generated LO signals in the receiver. This work positions InGaAs Schottky technology as a compelling candidate for terahertz reception in the context of optical wireless communication systems. Full article

This work constitutes Part II of a comprehensive three-part study critically reviewing techniques for the indirect extraction of the thermal resistance in bipolar transistors using simple DC current/voltage measurements. While Part I focused on thermometer-based methods, this study examines techniques that rely on intersection points between electrical characteristics. The accuracy of these methods is assessed by applying them to DC curves obtained through PSPICE simulations of an in-house transistor model incorporating nonlinear thermal effects, and comparing the extracted thermal resistance data with the thermal resistance formulation embedded in the model. An InGaP/GaAs HBT and a Si/SiGe HBT for high-frequency applications are considered as case-studies. The analysis highlights key drawbacks affecting the methods, including theoretical approximations and sensitivity to the selection of intersection points. Among the techniques examined, only one adequately accounts for the nonlinear thermal behavior, though its original formulation presents practical limitations. To tackle this problem, we propose an improved and refined version of the approach that offers enhanced accuracy at the cost of increased complexity. Full article

This paper presents two cryogenic low-noise amplifiers (LNAs) based on the WIN’s 0.18 $\mathrm{\mu }$m gate length gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process designed for radio telescope receivers. Discrete transistors with gate peripheries spanning 50–600 $\mathrm{\mu }$m were DC-characterized at 290 K and 15 K, respectively. The LNAs underwent on-chip noise characterization under 15 K using a Y-factor measurement setup, which integrated a calibrated noise source and a noise figure analyzer. This approach directly quantified the noise temperature—critical metrics for radio telescope receiver front-ends. The top-performing LNA variant identified through on-chip characterization was packaged and evaluated in a cryogenic test-bed. This LNA, spanning a bandwidth of 0.3–15 GHz, demonstrated a gain of 26 dB and a minimum noise temperature of 6 K when operated at an ambient temperature of 15 K. In contrast, a second LNA architecture, tested solely on-chip, demonstrated a gain of 30 dB and a minimum noise temperature of 15 K across the 0.3–7 GHz range. Full article

With the advancement of the semiconductor industry into the sub-10 nm regime, high-performance, low-energy transistors have become important, and gate-all-around junctionless field-effect transistors (GAA-JLFETs) have been developed to meet the demands. Silicon (Si) is still the dominant semiconductor material, but other potential alternatives, such as gallium arsenide (GaAs), provide much higher electron mobility, improving the drive current and switching speed. In this study, our contributions include a comparative analysis of Si and GaAs-based cylindrical GAA-JLFETs, using threshold voltage behavior, electrostatic control, short channel effects, subthreshold slope, drain-induced barrier lowering, and leakage current as the metrics for performance evaluation. A comprehensive analytical modeling approach is employed, solving Poisson’s equation and utilizing numerical simulations to assess device characteristics using the ATLAS SILVACO tool under varying channel lengths and gate biases. Comparisons between Si and GaAs-based devices show what trade-offs exist and what the material engineering strategies are to use the advantages of GaAs while minimizing some disadvantages. The results of the study are a valuable contribution to the design and optimization of next-generation FET architectures, pointing the direction for enabling next-generation beyond CMOS technology. Full article

In this work, a cylindrical gate-all-around junctionless field effect transistor (JLFET) was investigated. Junctions and doping concentration gradients are unavailable in JLFET. According to the results, the suggested device has a novel architecture that significantly enhances transistor performance while exhibiting a decreased vulnerability to short-channel effects (SCEs). The Atlas 3D device simulator has been used to analyze the proposed JLFET’s performance, especially for low-power applications for different channel lengths ranging from 10 nm to 60 nm with Al_0.30Ga_0.60As as III-V materials. The comparative simulated study has been based on various performance parameters, including subthreshold slope (SS), drain-induced barrier lowering (DIBL), transconductance, threshold voltage, and I_ON to I_OFF ratio. The results of the simulations demonstrated that the III-V JLFET exhibited a favorable SS and decreased DIBL compared to other circuit topologies. In the suggested study, gallium arsenide (GaAs) and its compound materials have demonstrated a strong correlation between the SS and DIBL values. The SS is approximately 63 mV/dec, extremely near the ideal 60 mV/dec value. Gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) exhibit DIBL of approximately 30 mV/V and an SS value of around 64 mV/dec. Full article

Gallium arsenide photoconductive semiconductor switches (GaAs PCSSs) have attracted much attention in pulsed power systems and high-power microwave sources. The quality of ohmic contact has a significant impact on their switching performance. In this article, a 100 nm p-type epitaxial layer and Ti/Pt/Au metal electrodes were introduced into a GaAs PCSS to enhance ohmic contact, resulting in a specific contact resistivity of 3 × 10⁻⁴ Ω·cm². The optimized device exhibited a reduction in dark current from 32.2 μA to 11.7 μA and achieved a peak pulse output of 4 kV under a bias of 8.1 kV. This work provides a new feasible approach for high-power miniaturized solid switches. Full article

Renewable energy is in high demand, with significant contributions from the solar industry encouraging research into more efficient, cost-effective, and versatile solar cell technologies. Anti-reflection coating (ARC) is an important method for improving solar cell efficiency by minimizing light reflectance and maximizing photon absorption. This study investigates the electrical and optical behaviors of single- and double-layer ARCs for gallium arsenide (GaAs) solar cells, using PC1D simulation for single-layer SiO₂, and ZnSe, and double-layer SiO₂/ZnSe configurations. The findings indicate that the double-layer SiO₂/ZnSe ARC structure significantly reduces reflectance and enhances light absorption, leading to a higher current density (J_sc) and overall efficiency. With optimized layer thicknesses of 60 nm (ZnSe) and 100 nm (SiO₂), the efficiency increased from 20.628% to 30.904%, representing a 49.81% improvement. This enhancement is primarily attributed to the increased photon absorption and a higher electron–hole generation rate, confirming the superior performance of double-layer ARCs over single-layer configurations. Full article

The electronic and optical properties of a mesoscopic heterostructure of a two-dimensional quantum ring composed of Gallium Arsenide (GaAs) semiconductors are investigated. Using the confinement potential proposed by Tan and Inkson to describe the system under analysis, we conducted a numerical study of the photoionization cross-section for a 2D quantum ring with and without rotation effects. The interior of the quantum ring is traversed by an Aharonov–Bohm (AB) flux. Our research aims to investigate how this mesoscopic structure’s electronic and optical properties respond to variations in the following parameters: average radius, AB flux, angular velocity, and incident photon energy. Under these conditions, we establish that optical transitions occur from the ground state to the next excited state in the conduction subband, following a specific selection rule. One of the fundamental objectives of this study is to analyze how these rules can influence the general properties of two-dimensional quantum rings. To clarify the influence of rotation on the photoionization process within the system, we offer findings that illuminate the effects of the pertinent physical parameters within the described model. We emphasize that, although this is a review, it provides critical commentary, analysis, and new perspectives on existing research. Some results presented in this paper can be compared with those in the literature; however, new physical parameters and quantum ring configurations are used. Full article

This study investigates the growth of gallium arsenide nanowires, using lead as a catalyst. Typically, nanowires are grown through the vapor–solid–liquid mechanism, where a key factor is the reduction in the nucleation barrier beneath the catalyst droplet. Arsenic exhibits limited solubility in conventional catalysts; however, this research explores an alternative scenario in which lead serves as a solvent for arsenic, while gallium and lead are immiscible liquids. Liquid lead easily dissolves in Si as well as in GaAs. The preservation of the catalyst during the growth process is also addressed. GaAs nanowires have been grown by molecular beam epitaxy on silicon Si (111) substrates at varying temperatures. Observations indicate the spontaneous doping of the GaAs nanowires with both lead and silicon. These findings contribute to a deeper understanding of the VLS mechanism involved in nanowire growth. They are also an important step in the study of GaAs nanowire-doping processes. Full article

Semiconductor photodetectors can work only in specific material-dependent light wavelength ranges, connected with the bandgaps and absorption capabilities of the utilized semiconductors. This limitation has driven the development of hybrid devices that exceed the capabilities of individual materials. In this study, for the first time, a hybrid heterojunction photodetector based on methylammonium lead bromide (MAPbBr₃) polycrystalline film deposited on gallium arsenide (GaAs) was presented, along with comprehensive morphological, structural, optical, and photoelectrical investigations. The MAPbBr₃/GaAs heterojunction photodetector exhibited wide spectral responsivity, from 540 to 900 nm. The fabrication steps of the prototype device, including a new preparation recipe for the MAPbBr₃ solution and spinning, will be disclosed and discussed. It will be shown that extending the soaking time and refining the precursor solution’s stoichiometry may enhance surface coverage, adhesion to the GaAs, and film uniformity, as well as provide a new way to integrate MAPbBr₃ on GaAs. Compared to the pristine MAPbBr₃, the enhanced structural purity of the perovskite on GaAs was confirmed by X-ray Diffraction (XRD) upon optimization compared to the conventional glass substrate. Scanning Electron Microscopy (SEM) revealed the formation of microcube-like structures on the top of an otherwise continuous MAPbBr₃ polycrystalline film, with increased grain size and reduced grain boundary effects pointed by Energy-Dispersive Spectroscopy (EDS) and cathodoluminescence (CL). Enhanced absorption was demonstrated in the visible range and broadened photoluminescence (PL) emission at room temperature, with traces of reduction in the orthorhombic tilting revealed by temperature-dependent PL. A reduced average carrier lifetime was reduced to 13.8 ns, revealed by time-resolved PL (TRPL). The dark current was typically around 8.8 × 10⁻⁸ A. Broad photoresponsivity between 540 and 875 nm reached a maximum of 3 mA/W and 16 mA/W, corresponding to a detectivity of 6 × 10¹⁰ and 1 × 10¹¹ Jones at −1 V and 50 V, respectively. In case of on/off measurements, the rise and fall times were 0.40 s and 0.61 s or 0.62 s and 0.89 s for illumination, with 500 nm or 875 nm photons, respectively. A long-term stability test at room temperature in air confirmed the optical and structural stability of the proposed hybrid structure. This work provides insights into the physical mechanisms of new hybrid junctions for high-performance photodetectors. Full article