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The generation of high-voltage ultrafast electrical pulses has significant potential for application in ultrawideband microwave sources, terahertz technology, and inertial confinement fusion. However, there is still a lack of the generation of high-voltage ultrafast electrical pulses with greater peak amplitudes and faster pulse widths and ultrafast characteristics. In this paper, a linear low-temperature gallium arsenide photoconductive semiconductor switch (LT-GaAs PCSS) is developed using the ps-scale carrier lifetime of low-temperature gallium arsenide (LT-GaAs). The generation of ultrafast electrical pulses with a pulse width of 0.5 ns and a voltage amplitude of 1 kV is achieved by triggering a pulsed laser with a wavelength of 1064 nm, a single pulse energy of 70 μJ, and a pulse width of 30 ps. The impact of parameters, such as bias electric field, laser pulse energy, and transmission line length, on the ultrafast characteristics of the output electric pulse of the LT-GaAs PCSS is investigated through a synthesis of experimental and simulation approaches. The results show that (1) in linear conditions, the output pulse amplitude is mainly determined by the bias voltage and laser pulse energy, and the output pulse amplitude is also affected by conductor and dielectric attenuation in the transmission line; (2) the falling edge is determined by the carrier lifetime. Because of the absorption depth at 1064 nm and the carrier lifetime of semi-insulating gallium arsenide material, the output electrical pulse has a trailing edge; (3) the bias voltage and laser pulse energy can improve voltage transmission efficiency, and the saturation of voltage transmission efficiency is caused by the saturation of photon absorption in LT-GaAs material. [ABSTRACT FROM AUTHOR]

X-ray-induced carrier dynamics in silicon and gallium arsenide were investigated through intensity variations of transmitted terahertz (THz) pulses in the pico- to microsecond timescale with x-ray free-electron laser and synchrotron radiation. We observed a steep reduction in THz transmission with a picosecond scale due to the x-ray-induced carrier generation, followed by a recovery on a nano- to microsecond scale caused by the recombination of carriers. The rapid response in the former process is applicable to a direct determination of temporal overlap between THz and x-ray pulses for THz pump–x-ray probe experiments with an accuracy of a few picoseconds. [ABSTRACT FROM AUTHOR]

This work reports the concept of a shunt negative feedback technique for implementing a millimeter-wave wideband low-noise amplifier. The proposed shunt negative feedback network consists of a resistor–capacitor–inductor configuration. The proposed feedback network can achieve simultaneous noise and input matching (SNIM) over a wide frequency range by adjusting the values of the resistor–capacitor–inductor configuration based on numerical analysis. By adopting the SNIM-based gain core as the first stage of the amplifier, the simulation results of the three-stage low-noise amplifier in a 150-nm GaAs pHEMT process achieve a gain of 15.6–18.6 dB and a noise figure of 1.05–2.8 dB in the frequency range of 13–33 GHz, respectively, while dissipating 99 mW. [ABSTRACT FROM AUTHOR]

In this paper, we propose a sub-terahertz PAM4 modulator based on transmission characteristic reconstruction by combining meta-unit, GaAs Schottky diode, and fan branch lines. This method combined the significant electromagnetic resonant characteristics of meta-unit, the high-speed controllability of GaAs Schottky diode, and the high integration of on-chip transmission line together to realize high-speed modulation. Then, we achieve transmission characteristic reconstruction by adjusting the resonance strength under different applied voltages through fan branch lines, enabling high-order amplitude modulation of sub-terahertz waves. The experimental results show that the PAM4 modulation of sub-terahertz waves is achieved with a nearly linear variation of the transmission coefficient in the whole voltage range and a maximum modulation rate of 21 Gbps, providing a promising prospect for the development and application of integrated sub-terahertz direct high-order modulation technology. [ABSTRACT FROM AUTHOR]

Unipolar (sub-cycle) electromagnetic fields are a subject of current interest as a possible useful tool for light–matter interaction studies and applications. We propose, numerically simulate, and experimentally prove a method to produce unipolar terahertz fields by optical gating of conventional bipolar terahertz pulses in a GaAs wafer. In particular, picosecond long unipolar pulses with the electric field strength of ∼ 1 kV/cm were detected by electro-optic sampling at the output of the wafer. [ABSTRACT FROM AUTHOR]

In this work, we studied the electrical behavior of radial p-n junctions based on submicron Silicon (Si) and Gallium Arsenide (GaAs) structures, with a focus on the implications of incomplete ionization of atoms below 800 K. By solving the Poisson equation in a cylindrical coordinate system, we derived solutions for radial structures with a core radius of R = 0.5 μm. An analytical solution was obtained, providing the probability of ionization P(T) of dopant atoms in the range 0–800 K, as well as the variation of space charge density ρ(T), with temperature. [ABSTRACT FROM AUTHOR]

This paper presents a W-band power amplifier monolithic microwave integrated circuit (MMIC) that is designed for high-precision millimeter-wave systems and fabricated using a 0.1 µm GaAs pHEMT process. The amplifier's stability was evaluated using the network determinant function, ensuring robust performance under both linear and nonlinear conditions. Simultaneous matching for gain and output power was achieved with minimal passive elements. The developed power amplifier MMIC exhibits a linear gain exceeding 20 dB and an input return loss greater than 6 dB across the 88–98 GHz range. It delivers an output power of 23.8–24.1 dBm with a power gain of 17.3–17.9 dB in the 88–97 GHz range and achieves a maximum power-added efficiency (PAE) of 24% at 94 GHz. [ABSTRACT FROM AUTHOR]

Abstract A solar cell's internal quantum efficiency (IQE) measurement reveals critical information about the device's performance. This information can be obtained using a qualitative analysis of the shape of the curve, identifying and attributing current losses such as at the front and rear interfaces, and extracting key electrical and optical performance parameters. However, conventional methods to extract the performance parameters from IQE measurements are often time‐consuming and require manual fitting approaches. While several methodologies exist to extract those parameters from silicon solar cells, there is a lack of accessible approaches for non‐silicon cell technologies, like gallium arsenide cells, typically limiting the analysis to only the qualitative level. Therefore, this study proposes using a deep learning method to automatically predict multiple key parameters from IQE measurements of gallium arsenide cells. The proposed method is demonstrated to achieve a very high level of prediction accuracy across the entire range of parameter values and exhibits a high resilience for noisy measurements. By enhancing the quantitative analysis of IQE measurements, the method will unlock the full potential of quantum efficiency measurements as a powerful characterization tool for diverse solar cell technologies.

Abstract The monolithic integration of III‐Vs on Silicon (Si) is of great interest for the development of active photonic integrated circuits (PICs). The main challenge is to achieve a high‐quality epitaxy of the III‐V on the Si substrate, as the differences between the materials are responsible for the formation of crystal defects, in particular threading dislocations (TDs) and antiphase domains (APDs) delineated by antiphase boundaries (APBs), which degrade the device's performance. A new technique is demonstrated to achieve thin APBs‐free GaSb buffer layers grown on Si substrates. The original idea presented in this paper is to introduce a GaAs layer into the buffer to promote faster burial of APDs. Two strategies are compared; the first one involves the complete APDs burying in GaAs before growing GaSb, while the second one uses a thin GaAs layer before burying the APDs in the GaSb layer. APB‐free buffer layers as thin as 215/400 nm have been obtained using the first method, which represents a factor of 2/4 thickness reduction compared to the previous results for both 0.5° and 0.2° miscut angles.

The article "A 1 kV sub-nanosecond electrical pulse generated by a linear GaAs photoconductive semiconductor switch and its characterization" in the Journal of Applied Physics contained errors in Eqs. (4), (5), (7), and (12) as well as a typo on page 4, which were corrected in the online version on 13 January 2025. The corrected equations are provided in the article, authored by Hongqi Wang, Wei Shi, Cheng Ma, Meilin Wu, Jiang Tao, and Kaipeng Chen. AIP Publishing issued an apology for the errors in the original publication. [Extracted from the article]

• InGaAs QDs grown in pyramidal pits are excellent single-photon sources. • However, they suffer from low photon extraction efficiency. • Growing GaAs nanowire antennas above them improves efficiency by up to x36. • This improvement is related to Purcell effect and increased acceptance angle. InGaAs/GaAs quantum dots (QDs) embedded in a GaAs substrate are very useful photon sources, including single and entangled photons, due to their unperturbed environment. Contrary to self-formed QDs, those grown in pyramidal pits can be well controlled in position and energy, important properties for scaling. However, photon extraction efficiency from these QDs is limited due to the GaAs/Air index mismatch and non-directionality of the emission. GaAs nanowires grown vertically on top of these QDs can serve as resonant antennas, thus enhancing their emission and increasing their usefulness as sources. Such structures were fabricated and their photon emission was studied by micro-photoluminescence as function of excitation power and temperature. The structures showed an intensity increase by up to x36 over quantum dots without nanowire antennas. [ABSTRACT FROM AUTHOR]

This research investigates the influence of nanoscale morphology and bandgap on the optical properties of semiconductor nanostructures, with a particular emphasis on surface reflectance and optical absorption across the UV–VIS–NIR wavelength range. Our investigation shows that plasma-etched densely packed silicon (Si) nanotip arrays (NTs) demonstrate significant anti-reflective properties, as revealed by specular and hemispherical reflectance measurements, due to their sub-wavelength spacing and tip lengths exceeding the incident optical wavelength. In contrast, sparsely arranged Si NTs have reflective behaviour that is similar to bare Si substrates. Semiconductor substrates such as gallium phosphide (GaP), Si, gallium arsenide (GaAs), and germanium (Ge), when decorated with NTs, show notable changes in their optical characteristics, with hemispherical reflectance spectra decreasing to 1–3% and absorptance increasing to 97–99 % in the entire spectral region above the bandgap. Below the bandgap, a slight reduction in reflectance and a modest rise in absorptance are observed. These findings offer critical insights for enhancing semiconductor nanostructures to optimize their performance in photonic and optoelectronic applications across various wavelength ranges. [ABSTRACT FROM AUTHOR]

The formation of dotted and lined 2D nano- and microstructures on the surface of GaAs is demonstrated. These surface structures were devised using the vector 1030 nm, 250 fs laser beams of variable polarization (lineal, radial, and orthogonal) polarization. The annular and radial ripples were produced using radial and azimuthal polarizations of the laser pulses. Additionally, the formation of the grooves orthogonally placed with regard to the curved and radial ripples appeared with the increase of the number of laser shots on the same spot. This pattern was also observed when the laser beam was moved across the GaAs surface at a 50 kHz pulse repetition rate. This method of printing the unconventional 2D patterns allow for the formation of the complex surface structures. [ABSTRACT FROM AUTHOR]

Highly granular calorimeters play a crucial role in the precision QED measurement, one of the most important parts of the calorimeter being the sensor. In 2022, two samples of silicon pad sensors and two samples of GaAs sensors were tested in a 5 GeV electron beam at DESY. A technological prototype has been developed to demonstrate the performance of the ECAL sensors. For the readout, a very low-power ASIC called FLAME was used. The raw data is pre-processed and deconvoluted using FPGAs. This article describes the results of the test beam measurements, together with a study of the edge effect and homogeneity of the sensor response. • Two prototypes of pad sensors are studied in a 5 GeV electron beam. • A simulation of the silicon sensor response in is in very good agreement with data. • Measured readout gain agrees between MC simulations and independent lab measurement. • In a GaAs sensor the signal drop is visible, but not in a silicon sensor. • The response homogeneity for the GaAs is 2.0% and for silicon sensors is 2.6%. [ABSTRACT FROM AUTHOR]

This paper presents a high interference-rejection receiver front-end in 0.15- μ m GaAs pHEMT process for 5G applications. We propose a novel architecture to improve the selectivity of the receiver front-end, thereby enhancing its interference-rejection capability. The design strategy of this novel architecture is to split the functions of the high-selectivity filter and distribute them into the individual devices within the receiver front-end, and then employ the more compact zero-pole filtering circuit topology to implement and merge these split functions. This enables us to achieve the equivalent integration of the high-selectivity filter within the receiver front-end while maintaining an optimal balance among its multiple key performance parameters. Simulation results demonstrate that within the relatively low intermediate frequency (IF) range of 2.7–3.3 GHz, this receiver front-end has an equivalent 20-dB shape factor (SF 20) of less than 2.14, which exhibits excellent selectivity. Consequently, it can efficiently suppress various interference signals, featuring an image-rejection ratio (IRR) exceeding 63 dB and a local-oscillator feedthrough rejection ratio (LOFTRR) surpassing 58 dB. Furthermore, this receiver front-end achieves a noise figure (NF) of less than 2.8 dB, a peak conversion gain (CG) ranging from 23.5 to 26.5 dB, and an input 1-dB compression point (IP1dB) greater than −23 dBm. • A novel architecture is proposed to enhance the selectivity of the receiver front-end. • The compact filtering circuit topology is employed to avoid significant increase in area. • Some sensible integration approaches are adopted to mitigate the deterioration of noise figure. [ABSTRACT FROM AUTHOR]

This study presents a demonstration of the surface morphology behavior of gallium antimonide (GaSb) layers deposited on gallium arsenide (GaAs) (100) substrates using three different methods: metamorphic, interfacial misfit (IMF) matrix, and a method based on a Polish patent application number P.443805. The first two methods are commonly used, while the third differs in the sequence of successive steps and the presence of Be doping at the initial growth stage. By comparing GaSb layers made by these methods for the same growth parameters, the most favorable procedure for forming a GaSb buffer layer is selected. Using GaAs substrates with a GaSb buffer layer is a cheaper alternative to using GaSb substrates in infrared detector structures based on II-type superlattices T2SL, such as InAs/GaSb. The quality of the GaSb buffer layer determines the quality of the subsequent layers that form the entire T2SL and affects factors such as dark current in terms of application. [Display omitted] • Step-by-step analysis of the evolution of the surface morphology of GaSb layers on GaAs substrates deposited by 3 different procedures. • Innovative use of pyrometric measurements of substrate temperature to determine the moment of formation of a solid GaSb layer. • Use of a innovative procedure for depositing a GaSb buffer layer on a GaAs substrate. [ABSTRACT FROM AUTHOR]

The surface property of GaAs has an important impact on device performance, so how to improve the surface quality in reactive ion etching process is one of the key issues. In this paper, the composition and roughness changes of GaAs surface subjected to Ar plasma bombardment were investigated. It was found that the relative contents of Ga 2 O 3 and As 2 O 3 of the surface decreased with the increase of RF power, and the distribution depths of the compositions were different. In addition, dielectric constant increased with the increase of RF power. It was found that the surface roughness can be reduced after the plasma bombardment. Furthermore, the surface roughness and Ga/As component ratio followed a certain trend with the RF power. When the RF power was lower than 150 W, the surface roughness and Ga/As component ratio had the same trend, and when the RF power was higher than 150 W, they had the opposite trend. These results are helpful for the improvement of GaAs-based wafer-bonding strength and the performance of optoelectronic structures. [ABSTRACT FROM AUTHOR]

III-V thin-film solar cells (SCs) have shown exceptional optoelectronic properties and remarkable power conversion efficiency (PCE), attributed to their outstanding charge transport, efficient photon trapping, adaptability, and recycling of photons. In particular, incorporating anti-reflective coatings (ARCs) made from wide-bandgap oxides has proven effective in reducing optical losses, with reductions as low as 20 % being reported. Furthermore, the use of carrier-selective contacts in these designs not only eliminates the need for complex doped junctions but also simplifies the fabrication process, further enhancing their performance. Despite these advancements, relatively few studies have explored the integration of both ARCs and carrier-selective contacts in gallium arsenide (GaAs)-based thin-film solar cells. This gap represents a significant opportunity for improving the efficiency and performance of these devices. To address this, we present a GaAs thin-film solar cell incorporating an ARC layer for enhanced light-trapping and optimized photon absorption. In addition, we integrate carrier-selective contacts using titanium dioxide (TiO 2) as the electron transport layer and molybdenum oxide (MoO 3) as the hole transport layer, ensuring effective charge separation and collection. Our optical analysis demonstrates that, with an optimized ARC thickness, the optical losses in the 380 nm-thick GaAs absorber layer can be limited to 20 %. Moreover, by maintaining a surface recombination velocity (SRV) of 103 cm/s and a carrier lifetime of 10μs, the proposed design achieves an impressive PCE of approximately 23 %. This study highlights the potential of combining ARCs and carrier-selective contacts to push the performance of GaAs thin-film solar cells to new heights, paving the way for more efficient, and cost-effective photovoltaic technologies. • Anti-Reflection Coatings and Carrier Selective contacts are integrated with GaAs Solar Cell. • An optical J sc of 26.5 mA/cm2 is obtained at an optimal absorber layer thickness. • The optical losses in the SC are reduced by 4 % due to the introduction of surface roughness. • An impressive PCE of ∼23 % is obtained at SRV = 103 cm/s and a carrier lifetime of 10 μs. [ABSTRACT FROM AUTHOR]