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The synthesis and characterization of heterostructure por-Ga2O3/GaAs represent a crucial advancement in nanomaterials, particularly in optoelectronic applications. Employing a two-stage electrochemical etching methodology, this research has elucidated the precise conditions required to fabricate such a heterostructure. The initial stage involves etching monocrystalline gallium arsenide (GaAs) using an aqueous nitric acid solution as the electrolyte. This process is governed by the redox reactions at the crystal-electrolyte interface, where GaAs are partially oxidized and selectively etched. The second stage introduces ethanol into the electrolytic solution. This chemical addition serves a dual purpose: Firstly, it modulates the electrochemical environment, allowing for controlling pore morphology in GaAs. Secondly, it facilitates the etching of the resultant oxide layer, which predominantly consists of gallium oxide (Ga2O3). The formation of this oxide layer can be attributed to the oxidation of GaAs, driven by the electrochemical potentials and resulting in the deposition of reaction by-products on the substrate surface. The fabricated nanocomposite was comprehensively characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), and Raman Spectroscopy. SEM imaging revealed a range of agglomerated nanostructures dispersed across the surface, with dimensions ranging from 8–25 μm, 1–1.5 μm, and 70–100 nm. These observations suggest a hierarchical pore structure indicative of a complex etching mechanism modulated by the electrolyte composition. Raman spectroscopic analysis corroborated the presence of various phases in the heterostructure. Signals corresponding to bulk GaAs, serving as the substrate, were distinguishable. In addition, peaks indicative of porous GaAs and porous Ga2O3 were observed. A cubic phase in the Ga2O3 layer was particularly noteworthy, suggesting a higher degree of crystallinity. Notably, the absence of Raman-active modes associated with internal stresses implies that the fabricated heterostructure is of high quality. [ABSTRACT FROM AUTHOR]

Quantum dot (QD)-based solar cells have been the focus of extensive research. One of the critical challenges in this field is optimizing the size and placement of QDs within the cells to enhance light absorption and overall efficiency. This paper theoretically investigates InAs/GaAs QD intermediate band solar cells (QD-IBSC) employing cylindrical QDs. The goal is to explore factors affecting light absorption and efficiency in QD-IBSC, such as the positioning of QDs, their dimensions, and the spacing (pitch) between the centers of adjacent dots. Achieving optimal values to enhance cell efficiency involves modifying and optimizing these QD parameters. This study involves an analysis of more than 500 frequency points to optimize parameters and evaluate efficiency under three distinct conditions: output power optimization, short-circuit current optimization, and generation rate optimization. The results indicate that optimizing the short-circuit current leads to the highest efficiency compared to the other conditions. Under optimized conditions, the efficiency and current density increase to 34.3% and 38.42 mA/cm2, respectively, representing a remarkable improvement of 15% and 22% compared to the reference cell. [ABSTRACT FROM AUTHOR]

The obtaining and study of semiconductor materials have been topics of interest for decades. However, alternatives that allow greater versatility at the time of their application have yet to be explored, such as the inclusion of some transition metals. In this work, we report the obtaining of GaAs and GaAs/Cr/GaAs layers, which were prepared by r.f. magnetron sputtering on a Si (100) substrate by varying the deposition time of the intermediate Cr layer for t = 5 min and 10 min, respectively. Scanning electron microscopy in cross-section was carried out to determine the growth mode of the GaAs and GaAs/Cr/GaAs films. The percentage of the elements in the GaAs/Cr/GaAs thin films was determined through energy dispersive spectroscopy (EDS) in cross-sections along the entire layer thickness. X-ray diffraction and micro-Raman spectroscopy at room temperature were measured to analyze the formation of CrAs and GaCr binary phases by diffusion across interlayers. Finally, we conclude on the possible use of this technique to obtain semiconductor alloys with Cr inclusion. [ABSTRACT FROM AUTHOR]

The surface morphology modification and optical property modification of semi-insulating gallium arsenide sample implanted with 100 keV silicon ions with the fluences ranging between 5 × 10 1 5 and 4 × 10 1 7 ion cm − 2 were analyzed using scanning electron microscopy and UV–Vis–NIR spectroscopy study. Scanning electron microscopy study revealed pore-like structure formation on the surface of gallium arsenide samples after silicon ion implantation. The size of these pore-like structures was found to increase with increasing ion fluence. Energy dispersive X-ray analysis showed an increase in silicon concentration in the gallium arsenide sample after silicon ion implantation with increasing ion fluence. The UV–Vis–NIR spectroscopy study revealed a decrease in optical transmission for silicon ion implanted gallium arsenide sample with increasing ion fluence. An additional absorption band was observed for the gallium arsenide sample implanted with the highest fluence (4 × 10 1 7 ion cm − 2). Urbach tail energy was found to increase with respect to ion fluence. [ABSTRACT FROM AUTHOR]

The graphene-based plasmonic antenna's operating frequency and performance are significantly controlled by the substrate dielectric material. In this article, a plasmonic microstrip antenna is designed and simulated for terahertz applications. The design procedure is performed by testing different dielectric substrate materials of the same thickness, such as RT5800, polyimide, quartz, silicon dioxide (SiO2), FR4, mica, silicon nitride (SiO3N4), and gallium arsenide (GaAs). Generally, the computed results reveal that the quartz substrate maintains suitable radiation performance with a minimum S11 values of − 45.67 dB, efficiency of 92.65%, gain of about 3.15 dB, and bandwidth values of 310 GHz. Furthermore, a modification is done in the antenna by increasing the substrate height to obtain tri-band radiation mode. The results indicate that the proposed antenna operates at tri-band frequencies when the substrate thickness is larger than 6 µm. However, a better antenna radiation performance is observed with a substrate thickness of 7 µm which operates at frequencies of 0.766, 3.285, and 4.510 THz. Additionally, the overall radiation performance obtained for the proposed antennas of a single band frequency with quartz and dual and triple band frequencies with GaAs is compared with previous study results done by other researchers and a reliable agreement with an advancement in present work, especially in terms of antenna size and bandwidth. Finally, it can be said that the implementation of a graphene patch conductor to develop milt-band resonance frequency is an easy technique with low profiles, simple and alternative to the implementing conducting material slots, or extensions along the patch radiating borders techniques. [ABSTRACT FROM AUTHOR]

In this work, we have investigated n-ZnO/p-porous GaAs/p++-GaAs heterostructure for low-cost photodetector applications. Solution-based deposition process was used to synthesize ZnO thin film on porous GaAs layer formed by anodic etching. Energy dispersive x-ray spectroscopy (EDX) was used for chemical characterization and revealed that the deposited ZnO film was oxygen rich. Scanning electron microscopy (SEM) analysis demonstrated a porous surface morphology of the ZnO film and the infiltration of a part of the deposited film inside the porous GaAs matrix. The transport mechanisms of the n-ZnO/p-porous_GaAs/p++-GaAs heterostructure were investigated via current–voltage (I–V) measurements in the dark at room temperature. I–V characteristic showed rectification behavior, and the maximum value of the rectification ratio is 53 at ± 1.78 V. A series resistance Rs = 15 Ω and an ideality factor, n = 8, were obtained by using the Cheung function. The Forward I–V curve in Log–Log scales follows a power law dependence characteristic of trap-assisted space charge limited conduction. In the reverse bias voltages, we found that the thermionic emission theory in the presence of an interface layer reproduces the current–voltage characteristic. A potential barrier height of φ B = 580 meV and an ideality factor n = 1.06 were obtained. For more investigations, we carried out impedance spectroscopy measurements. From the Cole–Cole impedance curves of the reverse-biased device, we demonstrated the formation of two depletion regions operating in opposite directions to the applied voltage. Conductance-frequency (G-f) experimental results agree with Jonsher's law, proving that charge transport processes across device interfaces occur by jumping between localized states. The analysis of I–V characteristic under illumination demonstrates that the n-ZnO/p-porous GaAs/p++-GaAs device can be used for photodetection applications. The measured photocurrent reaches a value of 39 mA for an applied voltage of 1.48 V. The photocurrent spectrum showed a signal without applied voltage and confirmed the presence of an internal electric field that self-polarizes the device. [ABSTRACT FROM AUTHOR]

Receiver and transmitter monolithic microwave integrated circuit (MMIC) multifunction chips (MFCs) for active phased‐array antennas for Ka‐band satellite communication (SATCOM) terminals have been designed and fabricated using a 0.15‐μm GaAs pseudomorphic high‐electron mobility transistor (pHEMT) process. The MFCs consist of four‐channel radio frequency (RF) paths and a 4:1 combiner. Each channel provides several functions such as signal amplification, 6‐bit phase shifting, and 5‐bit attenuation with a 44‐bit serial‐to‐parallel converter (SPC). RF pads are implemented on the bottom side of the chip to remove the parasitic inductance induced by wire bonding. The area of the fabricated chips is 5.2 mm × 4.2 mm. The receiver chip exhibits a gain of 18 dB and a noise figure of 2.0 dB over a frequency range from 17 GHz to 21 GHz with a low direct current (DC) power of 0.36 W. The transmitter chip provides a gain of 20 dB and a 1‐dB gain compression point (P1dB) of 18.4 dBm over a frequency range from 28 GHz to 31 GHz with a low DC power of 0.85 W. The P1dB can be increased to 20.6 dBm at a higher bias of +4.5 V. [ABSTRACT FROM AUTHOR]

We studied epitaxial GaAs samples doped with Ge and Sn up to 1 × 10 19 cm   − 3 , which were stored in a dry and dark environment for 26 years. The optical response of the GaAs samples was determined through the photoluminescence and photoreflectance techniques, taken at different times: just after their fabrication in 1995, 2001 and 2021. The evolution of defects formed by the action of O   2 in the samples and their correlation with doping with Ge and Sn impurities were studied. We obtained the result that aging formed defects of type vacancies, mainly As, which produced energy levels of deep traps linked to the L band. The concentration of vacancies over the 26 years could be as large as 10 17 cm   − 3 , and these vacancies form complexes with doping impurities. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to present the fabrication of a flexible double-heterojunction gallium arsenide solar cell and analyse the photoelectric characteristics by experimental and numerical investigations. Remote epitaxy was used in addition to metal–organic chemical vapour deposition (MOCVD) to fabricate the flexible GaAs thin film. The practical power conversion efficiency (PCE) of the fabricated double heterojunction was nearly 20%, as tested by a solar simulator at air mass global condition AM1.5G (1000 W/m2 insolation and 25 °C). The photoelectric characteristics, including the generation and recombination rates, band bending, carrier concentration and electric potential, were numerically investigated by COMSOL Multiphysics/Semiconductor Module. The experimental PCE was compared with the photovoltaic (PV) cell simulation data of 29% PCE using the MATLAB code/Newton–Raphson method. The comparison was not satisfactory, since the practical solar cell was exposed to high series resistance, which affected the PCE of the thin-film solar cell. [ABSTRACT FROM AUTHOR]

The aging dynamics of materials used to build the active part of optoelectronic devices is a topic of current interest. We studied epitaxial samples of GaAs doped with Ge and Sn up to 1 × 10 19 cm−3, which were stored in a dry and dark environment for 26 years. Photoluminescence spectra were taken in three periods: 1995, 2001 and 2021. In the last year, time-resolved photoluminescence, Raman, and X-ray measurements were also performed to study the evolution of defects formed by the action of O2 in the samples and its correlation with the doping with Ge and Sn impurities. We found that oxygen formed oxides that gave off Ga and As atoms, leaving vacancies mainly of As. These vacancies formed complexes with the dopant impurities. The concentration of vacancies over the 26 years could be as large as 1 × 10 18 cm−3. [ABSTRACT FROM AUTHOR]

Inverted metamorphic Ga0.3In0.7As photovoltaic converters with sub‐0.60 eV bandgaps grown on InP and GaAs are presented. Threading dislocation densities are 1.3 ± 0.6 × 106 and 8.9 ± 1.7 × 106 cm−2 on InP and GaAs, respectively. The devices generate open‐circuit voltages of 0.386 and 0.383 V, respectively, under irradiance producing a short‐circuit current density of ≈10 A cm−2, yielding bandgap‐voltage offsets of 0.20 and 0.21 V. Power and broadband reflectance measurements are used to estimate thermophotovoltaic (TPV) efficiency. The InP‐based cell is estimated to yield 1.09 W cm−2 at 1100 °C versus 0.92 W cm−2 for the GaAs‐based cell, with efficiencies of 16.8 versus 9.2%. The efficiencies of both devices are limited by sub‐bandgap absorption, with power weighted sub‐bandgap reflectances of 81% and 58%, respectively, the majority of which is assumed to occur in the graded buffers. The 1100 °C TPV efficiencies are estimated to increase to 24.0% and 20.7% in structures with the graded buffer removed, if previously demonstrated reflectance is achieved. These devices also have application to laser power conversion in the 2.0–2.3 µm atmospheric window. Peak laser power converter efficiencies of 36.8% and 32.5% are estimated under 2.0 µm irradiances of 1.86 and 2.81 W cm−2, respectively. [ABSTRACT FROM AUTHOR]

Initial stage of precipitate formation during post-growth annealing of nonstoichiometric GaAs and GaAs0.97Sb0.03 grown by low-temperature (150°C) MBE on GaAs (001) substrate with intermediate growth interruption and simultaneous heating up to 250°C was studied by transmission electron microscopy. Short-term intermediate heating despite the low temperature was revealed to result in the precipitation of larger particles during subsequent post-growth annealing compared to the material not subjected to such heating. This effect is explained by the huge concentration of excess arsenic in LT-GaAs and LT-GaAs0.97Sb0.03 grown at 150°C, enhanced diffusion due to the high concentration of nonequilibrium gallium vacancies, and non-threshold nucleation. [ABSTRACT FROM AUTHOR]

A series of low-voltage thyristor current switches based on (Al)GaAs/GaAs homo- and heterostructures with a volume charge region formed in the lightly doped p-GaAs base layer have been developed. The transient processes characteristics in pulse generation mode of nanosecond duration have been studied. It has been shown that the use of a wide-bandgap barrier based on AlGaAs at the n‑emitter/p-base junction allows reducing the minimum control current amplitude from 30 to 3 mA, and the turn-on delay time can be shortened to 6 ns. For the developed thyristor switches, a minimum transition time of 3.7–3.9 ns was demonstrated when operating in a circuit with a 1 nF capacitive load. In a circuit with a nominal 1 Ω resistive load, the thyristor switches provided a peak current of 17.5 A with a pulse duration of 3.7 ns. [ABSTRACT FROM AUTHOR]

The influence of AlGaAsP, GaAsP and AlGaAs/GaAsP compensating layers on the optical quality of the active area based on InGaAs/GaAs quantum wells for LEDs emitting at a wavelength of 940 nm has been studied. Heterostructures with multiple quantum wells have been grown by MOVPE technique using various approaches to compensating structural stresses. An increase in photoluminescence intensity by more than 32% was demonstrated when using AlGaAs/GaAsP compensating layers. [ABSTRACT FROM AUTHOR]

It is shown that when using a standard electrochemical profiling recipe that applies intensive illumination by halogen lamp with power up to 250 W of n+/n GaAs structure to generate the holes necessary for etching, the resulting electron distribution profile differs from that set during growth for an electron concentration in the n+-layer > 4 × 1018 cm–3 when using EDTA electrolyte. This difference is due to the appearance and development of etching pits caused by the increase in the degree of defectivity of GaAs layers with increasing concentration of the donor impurity—silicon. To obtain adequate electron distribution profiles in n+/n GaAs structures it is necessary to limit the illumination up to 25 W. [ABSTRACT FROM AUTHOR]

We calculate a universal shift in work function of 59.4 meV per decade of dopant concentration change that applies to all doped semiconductors and from this use Monte Carlo simulations to simulate the resulting change in secondary electron yield for doped GaAs. We then compare experimental images of doped GaAs layers from scanning electron microscopy and conductive atomic force microscopy. Kelvin probe force microscopy allows to directly measure and map local work function changes, but values measured are often smaller, typically only around half, of what theory predicts for perfectly clean surfaces. LAY DESCRIPTION: Doping means the intentional contamination of a semiconductor by foreign atoms that are integrated as ions into the crystal lattice after either donating (as donors) additional electrons or (as acceptors) electronic holes and thereby change the local electric properties. The resulting material is called n‐ or p‐doped, and pn‐junctions are used in all diodes and transistors that form the basic units of more complicated electronic devices such as computers or solar cells. We calculate how doping changes the energy needed to extract an electron from the semiconductor (called its work function) and how this influences the secondary electron yield in scanning electron microscopy and resistive or Kelvin probe measurements in conductive atomic force microscopy. Both microscopy methods can be used to directly map the spatial distribution of dopants in doped nanostructures but quantitative measurements are difficult due to the influence of surface effects. [ABSTRACT FROM AUTHOR]

We report on a passively Q-switched 2 μm Ho :YAG ceramic laser, using pure GaAs as a saturable absorber. At an absorbed pump power of 1.28 W, the highest pulse repetition rate, shortest pulse width, largest single pulse energy, and highest peak power are measured to be 295 kHz, 83 ns, 1.49 μJ and 17.95 W, respectively. To the best of our knowledge, this is the first 2 μm passively Q-switched laser with a pure GaAs absorber, the three-photon absorption is believed to play an important role in the saturable absorption process. [ABSTRACT FROM AUTHOR]

Recently, the doping‐less tunnel FET has gained popularity due to its lower process complexity than conventional TFETs with heavily doped source and drain regions. In this literature, we have introduced a symmetric gate Ge/GaAs heterojunction doping‐less TFET(SG HJ DL TFET) using 4.6 eV work function for both the top gate and bottom gate and an asymmetric gate Ge/GaAs heterojunction doping‐less TFET (AG HJ DL TFET) using 3.9 eV work function as top gate and 4.6 eV work function as a bottom gate. A comparative study has been performed between these two devices. The back gate misalignment engineering in the AG HJ DL TFET induces higher charge plasma near the source‐channel junction which will enhance the drain current. Due to a larger drain current, an improved ION/IOFF ratio (11.8 times), and steeper SS (37%) are achieved in optimized AG HJ DL TFET than SG HJ DL TFET. Furthermore, the Analog/Radio Frequency and linearity performance parameters have been examined, and a significant improvement is noticed in the optimized AG HJ DL TFET. The impact of different interface trap charges (ITCs) on device performances is also investigated and it is found that AG HJ DL TFET shows more immunity to ITCs than SG HJ DL TFET. Finally, the Verilog‐A‐based model has been developed for the AG HJ DL TFET to utilize its circuit‐level behavior. The optimized device‐based Common Source amplifier (CS amplifier) has been simulated in the Cadence Virtuoso tool. The AG HJ DL TFET‐based CS amplifier offers a 6.83% improvement in voltage gain over the other reported work. [ABSTRACT FROM AUTHOR]

For the first time, a novel source extension heterojunction gate‐all‐around tunnel FET (SE‐GAA‐TFET) is proposed and examined using Synopsys TCAD simulator in this manuscript. SE‐GAA‐TFET is found to exhibit improved performance in terms of various analog/RF and DC parameters. As channel/source (C/S) interface and electric field exerted by gate are perpendicular to each other, radius of channel is downscaled to enhance electric filed, without reducing area of the tunneling. Furthermore, the presence of GaSb/GaAs heterojunction at C/S interface leads to reduction in the effective band overlap, which helps a great number of mobile charges to tunnel through C/S boundary at ON‐state. The consequences of variation in different geometrical metrics are evaluated to optimize the device performance. SE‐GAA‐TFET is found to offer a current switching ratio (CSR) of ~1013 along with 32.2 mV dec−1 of average sub‐threshold swing (SSAVG). Furthermore, improvement in transconductance and parasitic capacitance boost the cut‐off frequency of SE‐GAA‐TFET up to 37 GHz. Next, both positive and negative traps are introduced at S/C interface and the study reveals that there is no much deviation in parameters of the transfer characteristics like ION, SSAVG, and IOFF of SE‐GAA‐TFET. Next, proper benchmarking is done to compare the performance of the SE‐GAA‐TFET with similar devices available in literature and it is found that proposed SE‐GAA‐TFET exhibits better DC performance due to improved electrostatic behavior. Finally, SE‐GAA‐TFET is found to offer better fall time along with full‐voltage swing when deployed in a resistive load inverter. [ABSTRACT FROM AUTHOR]

As the key component of transceiver, power amplifier (PA) plays an extremely important role in wireless communication system. In order to accurately characterize the performance variation of PA at any temperature, the temperature behavior of a gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) high gain monolithic microwave integrated circuit (MMIC) PA is modeled in this paper. In this modeling, the resilient back propagation neural network (BPNN) is utilized to do the temperature behavior modeling for this PA. The investigation shows that the minimum mean square error (MSE) of the prediction results is 4.9607 × 10−4, which implies that it is feasible to use this modeling method to characterize the temperature behavior of PA. This modeling not only theoretically overcomes the problem of slow convergence speed of BPNN, but also solves the limitation of experimental devices and time setting. It will provide a more convenient guidance for test engineers. [ABSTRACT FROM AUTHOR]

The direct growth of III–V semiconductors on silicon holds tremendous potential for photonics applications. However, the inherent differences in their properties lead to defects in the epitaxial layer, including threading dislocations (TDs), antiphase boundaries (APBs), and thermal cracks, significantly impacting device performance. Current processes struggle to suppress these defects simultaneously, necessitating the development of methods to inhibit TDs and APBs in a thin buffer on silicon. This study introduces a GaSb buffer layer during GaAs epitaxy on a silicon (001) substrate. This approach successfully suppresses defect formation by promoting the formation of interfacial misfit dislocation arrays at both the AlSb/Si and GaAs/GaSb interfaces. The resulting GaAs layer exhibits a step-flow surface with a rough mean square of ∼3.8 nm and a full width at half maximum of 158 arcsec. Remarkably, the growth is achieved without any observable interfacial intermixing. Building on this platform, InAs/GaAs quantum dots are grown with a density of 3.8 × 1010 cm−2, emitting at a wavelength of 1288 nm. This breakthrough holds immense promise for developing high-quality GaAs films with reduced defect densities on silicon for O band lasers, laying the foundation for the mass production of silicon-based integrated circuits. [ABSTRACT FROM AUTHOR]

In this paper, we show and analyse the results of morphological characterisations of Dy2O3 layer deposited on an n-type GaAs substrate using atomic force microscopy (AFM). For structural measurement, the surface morphology of the elaborated layer was revealed as a nano-conical event. The global experimental ellipsometric results Ψ and Δ versus emission wavelength of the Dy2O3/n-GaAs structure have been presented and discussed. Using these results and a Matlab code in which we assumed the structure had three layers, we have calculated several linear and nonlinear optical constants of the Dy2O3 thin layer. Dysprosium oxide has high optical conductivity and a noticeable increase in nonlinear optical parameters, making it a promising candidate for various applications. This is especially true in the field of optoelectronics. [ABSTRACT FROM AUTHOR]

GaAs remains one of the crucial materials for solar cell applications as it boasts the world's highest efficiency single‐junction solar cells. However, their high cost limits their widespread terrestrial applications. Traditional GaAs solar cells require a complex stack of doped junctions, which can only be grown using epitaxy, which is a very costly technique. Herein, a nonepitaxial bilayer of ZnO and TiO2 as electron‐selective contact is studied. It is shown that a bilayer selective contact can achieve very high performance through interface band engineering and a reduction of the barrier for electron transfer. 21.2% efficient solar cells is achieved, with Voc of 1.04 V, Jsc of 26.13 mA cm−2, and a fill factor of 77.8%. The Voc reported in the article is comparable to the highest Voc reported for substrate‐based GaAs solar cells of 1.075 V. An experimental loss analysis shows that the device is mainly limited by series and shunt resistance and reflection losses, both of which can further be minimized by optimization of the fabrication process. The results presented will be very useful for the further development of cheaper GaAs solar cells, whereas the bilayer selective contact concept can be implemented for other kinds of solar cells. [ABSTRACT FROM AUTHOR]

This work proposes a microwave resonator built from gallium arsenide using integrated passive device (IPD) technology. It consists of a three-layered interlaced spiral structure with airbridges and inner interdigital structures. For integrated systems, IPD technology demonstrated outstanding performance, robustness, and a tiny size at a low cost. The airbridges were made more compact, with overall dimensions of 1590 × 800 µm2 (0.038 × 0.019 λg2). The designed microwave resonator operated at 1.99 GHz with a return loss of 39 dB, an insertion loss of 0.07 dB, and a quality factor of 1.15. Additionally, an experiment was conducted on the properties of the airbridge and how they affected resistance, inductance, and S-parameters in the construction of the resonator. To investigate the impact of airbridges on the structure, E- and H-field distributions of the resonator were simulated. Furthermore, its use in sensing applications was explored. Various concentrations of glucose solutions were used in the experiment. The proposed device featured a minimum detectable concentration of 0.2 mg/mL; high sensitivity, namely, 14.58 MHz/mg·mL−1, with a linear response; and a short response time. Thus, this work proposes a structure that exhibits potential in integrated systems and real-time sensing systems with high sensitivity. [ABSTRACT FROM AUTHOR]

The formation mechanism of a highly adherent silicon dioxide (SiO2) film on gallium arsenide (GaAs) substrate by plasma enhanced chemical vapor deposition (PECVD) is proposed. Ar, N2, and NH3 were used as pre-treatment gas to improve the interfacial adhesion. The interfacial adhesion was measured by the cross-cut tape test. By the measurement of spectroscopic ellipsometry and x-ray photoelectron spectroscopy (XPS), it is revealed that nitrogen plasma pre-treatment had formed a very thin GaN transition layer on the surface, which was responsible for the improvement of interfacial adhesion. XPS depth-profiling further confirmed various pre-treatment gases generate plasma mixtures and form thin film layers with different compositions on the GaAs surface. These layers have a significant impact on the adhesion of the subsequently prepared SiO2 film. The primary mechanism for improving interfacial adhesion is the renovation of the substrate composition via plasma pre-treatment by PECVD, which forms a transition layer of nitrides that eliminates the negative effects of oxides on adhesion. This study reveals the mechanism of interfacial adhesion enhancement between SiO2 film and GaAs substrate, which is of significant importance in fabricating high-performance and reliable semiconductor devices. [ABSTRACT FROM AUTHOR]

Professor Joseph "Joe" Greene taught me a great deal about research, leadership, and how to succeed. He was a mentor and a tireless advocate for me over the course of my career. This article summarizes some of the work that my research group carried out, inspired by Prof. Greene but not in direct collaboration with him. Three examples of these efforts are provided, epitaxial growth of Cu(In,Ga)Se2 (CIGS) on GaAs by sputter deposition, synthesis of Cu-Mo metastable alloys by sputter deposition, and recrystallization of CIGS deposited at high rates by treatment with metal halides. These works were carried out with many collaborators who are acknowledged in the description of the research carried out by them and in the references where full details can be found. [ABSTRACT FROM AUTHOR]

The aim of this review paper is to summarize a decade of research focused on enhancing metalorganic vapor-phase epitaxy (MOVPE) growth rates of GaAs, driven by the imperative for most cost-effective and energy-efficient III–V compounds' production. While MOVPE is renowned for producing high-quality devices, it has been constrained by production cost. For example, MOVPE was traditionally thought to have moderate growth rates that limit the throughput of the cost-intensive reactors. Recent research endeavors, however, have demonstrated ultrafast growth rates, exceeding 280 μm/h, with a remarkable group III precursor utilization efficiency of over 50%. It is worth noting that even with increased growth rates, the surface quality remains unaffected in terms of roughness and morphology. Nonetheless, optoelectronic properties, such as minority carrier lifetime, deteriorate for both p- and n-doped materials under constant growth conditions. This is attributed to an increase in the defect density of arsenic antisites, particularly EL2 and HM1 defects, as revealed by deep-level transient spectroscopy investigations. Some of these losses can be mitigated by optimizing growth conditions, such as elevating the temperature and reducing the V/III ratio. The latter not only restores some of the material quality but also increases the growth rate and reduces precursor consumption. Still, fully recovering the original reference lifetimes remains a challenge. Solar cell results indicate that structures with predominantly n-type absorbers are less affected by reduced minority carrier lifetimes. A remarkable 24.5% efficiency was achieved in a GaAs single-junction solar cell grown at 120 μm/h, representing less than 1 min of growth time for the absorber layers. [ABSTRACT FROM AUTHOR]

Notes on fits of analytic estimations, 2D finite element method (FEM), and 3D FEM simulations to measurements of the cathodoluminescence (CL) and to the degree of polarization (DOP) of the CL from the top surface of a (100) GaAs substrate with a 6.22 μ m wide SiN stripe are presented. Three interesting features are found in the DOP of CL data. Presumably these features are noticeable owing to the spatial resolution of the CL measurement system. Comparisons of both strain and spatial resolutions obtained by CL and photoluminescence (PL) systems are presented. The width of the central feature in the measured DOP is less than the width of the SiN, as measured from the CL. This suggests horizontal cracks or de-laminations into each side of the SiN of about 0.7 μ m. In addition, it appears that deformed regions of widths of ≈1.5 μ m and adjacent to the SiN must exist to explain some of the features. [ABSTRACT FROM AUTHOR]

Further development of information technologies hinges on innovations in the electronic components sector, particularly in enhancing electronic communication devices. This involves creating dynamic interconnects—electrically conductive channels that can be configured on-demand within chip circuitry to overcome the "tyranny of interconnects," which limits electronic systems due to the fixed nature of conventional interconnects. This paper presents experimental verification of transmitting information through photoconductive channels formed on a photosensitive cadmium sulfide (CdS) semiconductor single crystal using optical irradiation. By directing a focused light beam to specific areas of the CdS crystal, localized conductivity is induced, allowing for the dynamic formation of conductive channels. This method's efficacy in real-time signal transmission validates the theoretical framework and suggests new possibilities for semiconductor technology. The integration of dynamic interconnects could revolutionize communication systems by enhancing device efficiency and processing capabilities. This technology could lead to more complex electronic architectures needed in high-speed computing and advanced telecommunications. Additionally, this approach has potential applications in optoelectronics, improving device interaction with light. Dynamic interconnects could enhance solar cell efficiency, increase light sensor sensitivity, and aid in developing innovative visual displays. The ability to control material conductivity through light not only advances existing device performance but also opens doors to new electronic designs and operations. This includes fully reconfigurable circuits that adapt in real-time, self-optimizing network components, and smart sensors that respond to environmental changes. In summary, this research not only confirms the practicality of using photoconductive channels for information transmission but also emphasizes the significant implications for electronic and communication system advancements. As this technology evolves, it promises to significantly impact the design and functionality of future electronic devices, paving the way for more adaptable and powerful systems.

Abstract This letter presents a novel millimetre‐wave (mm‐wave) on‐chip substrate integrated waveguide (SIW) filtering crossover using 0.25 µm GaAs pHEMT technology. The design methodology of the proposed crossover is thoroughly illustrated. The proposed filtering crossover employs a dual‐mode cavity with TE102 and TE201 degenerate mode resonances at the intersection, leveraging the degenerate modes for in‐band resonance and inter‐channel isolation. Additionally, four TE101 mode resonant half‐mode SIW cavities are coupled around the dual‐mode cavity to achieve two third‐order bandpass response channels and reduce the overall size. A prototype is designed, analysed, and fabricated to validate the proposed approach, with measured results showing good agreement with simulations. The presented on‐chip SIW filtering crossover offers promising potential for mm‐wave applications, demonstrating the effectiveness of the design methodology and GaAs pHEMT technology integration.

The damage induced in GaAs crystals irradiated with dual-ion beam (low-energy I2+ and high-energy Fe9+), producing simultaneous nuclear (Sn) and electronic (Se) energy depositions, was investigated using several characterization techniques. Analysis of the damage buildup shows that Sn alone (single 900 keV ion beam) leads, in a two-step process, to full amorphization of the irradiated layer (at a fluence of 1.5 nm−2) and to the development of a high (2.2%) elastic strain. Conversely, only one step in the disordering process is observed upon dual-ion beam irradiation (i.e., 900 keV I2+ and 27 MeV Fe9+, Sn&Se); hence, amorphization is prevented and the elastic strain remains very weak (below 0.2%). These results provide a strong evidence that, in GaAs, the electronic energy deposition can induce an efficient dynamic annealing of the damage created in collision cascades formed during nuclear energy deposition. [ABSTRACT FROM AUTHOR]

We propose a non-destructive, all-optical technique to imprint embedded lateral superlattices near semiconductor heterostructures by illuminating the samples with a stable interference pattern generated by a phase diffraction grating. We demonstrate the technique on an ultrahigh mobility GaAs/AlGaAs sample with a Si δ-doping by inducing a persistent charge redistribution at cryogenic temperatures in the doping layer containing DX-centers. Weiss commensurability oscillations in the magnetoresistance of the light-induced superlattice are observed and analyzed to obtain its characteristics. [ABSTRACT FROM AUTHOR]

This experimental study reports the morphological and optical properties of self-organized quaternary InAlGaAs quantum dots (QDs) grown on GaAs substrates. Atomic force microscopy (AFM) revealed the presence of QDs and their geometry across the sample surface, while the optical properties were verified by photoluminescence (PL) spectroscopy. Temperature-dependent PL measurements were performed for a series of samples with different indium compositions. Unlike conventional quantum well materials, the change in PL peak positions in QD structures exhibits a non-monotonic exotic dependence on temperature. Our AFM data confirm a bimodal distribution of dot sizes as corroborated by calculated thermal activation energies. A rapid decrease in the PL signal at elevated temperatures suggests that thermionic emission and interface defects are the two dominant mechanisms of carrier escape and recombination in these QD structures. Such a quaternary QD-based active region is important for realizing next-generation diode lasers with an emission wavelength shorter than 1 μm. [ABSTRACT FROM AUTHOR]

Design strategies for improving terahertz (THz) quantum cascade lasers (QCLs) in the 5–6 THz range are investigated numerically and experimentally, with the goal of overcoming the degradation in performance that occurs as the laser frequency approaches the Reststrahlen band. Two designs aimed at 5.4 THz were selected: one optimized for lower power dissipation and one optimized for better temperature performance. The active regions exhibited broadband gain, with the strongest modes lasing in the 5.3–5.6 THz range, but with other various modes observed ranging from 4.76 to 6.03 THz. Pulsed and continuous-wave (cw) operation is observed up to temperatures of 117 K and 68 K, respectively. In cw mode, the ridge laser has modes up to 5.71 THz – the highest reported frequency for a THz QCL in cw mode. The waveguide loss associated with the doped contact layers and metallization is identified as a critical limitation to performance above 5 THz.

This letter presents a novel millimetre‐wave (mm‐wave) on‐chip substrate integrated waveguide (SIW) filtering crossover using 0.25 µm GaAs pHEMT technology. The design methodology of the proposed crossover is thoroughly illustrated. The proposed filtering crossover employs a dual‐mode cavity with TE102 and TE201 degenerate mode resonances at the intersection, leveraging the degenerate modes for in‐band resonance and inter‐channel isolation. Additionally, four TE101 mode resonant half‐mode SIW cavities are coupled around the dual‐mode cavity to achieve two third‐order bandpass response channels and reduce the overall size. A prototype is designed, analysed, and fabricated to validate the proposed approach, with measured results showing good agreement with simulations. The presented on‐chip SIW filtering crossover offers promising potential for mm‐wave applications, demonstrating the effectiveness of the design methodology and GaAs pHEMT technology integration. [ABSTRACT FROM AUTHOR]

In this paper, we present the physics and design-space exploration of a novel pulse compression photoconductive switch (PCPS) using semi-insulating gallium arsenide (GaAs) operating in the negative differential mobility (NDM) regime of electron transport. We systematically quantify the relationship between the PCPS performance and various design options, including contact separation, laser energy and placement, and trap dynamics. Specifically, we report the full-width at half-maximum and the peak output current generated by the PCPS as a function of applied electrical and optical bias. We discuss the optimal spacing between the electrodes and the distance of the laser spot to the anode to achieve higher electron confinement and superior radio-frequency (RF) metrics. Reducing the laser energy is important to prevent the appearance of secondary peaks due to diffusive transport, but there exists a trade-off between the bandwidth and the maximum current of the PCPS. We also compare the PCPS response with and without trap dynamics and find that the electrostatic screening from the trap-induced space charge is time-independent when the trapping time constant is set larger than the recombination lifetime. Overall, trap dynamics are detrimental to performance, unless the compensation doping scheme to achieve semi-insulating GaAs is carefully selected. Results presented in this paper can be used by experimentalists to fine-tune the PCPS design parameters to meet the specifications of various RF applications. Moreover, our results will provide a strong theoretical basis to the measurements of PCPS devices using GaAs and other NDM materials under investigation. [ABSTRACT FROM AUTHOR]

The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. Here, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near-zero magnetic field. Spin blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ∼0.1 found for a magnetic field parallel to the direction [ 1 ¯ 10 ] is approximately a factor of four lower than that for comparable circuits fabricated from a material grown on widely employed standard (001) GaAs substrates and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates. [ABSTRACT FROM AUTHOR]

The emission lines of strongly confined (211)B InAs/GaAs quantum dots (QDs), embedded in short-period GaAs/AlAs superlattices, are thoroughly characterized by a range of single-dot spectroscopy techniques, including cross correlation photon-counting measurements. Contrary to what is expected for a piezoelectric QD system, the single-dot biexciton line is found redshifted with respect to the exciton one by as many as 6 meV. This comes in striking contrast to previous reports on the same QD system, without additional confinement, where the biexciton lines always showed up at higher energies than the exciton, by 4–13 meV. In addition, two charged exciton lines are identified for the first time in a piezoelectric InAs-based QD. A positively charged (Χ+) and a negatively charged (Χ−) trion line are observed 1.5 and 7.5 meV below the neutral exciton line, respectively. Our results pave the way to an enhanced understanding of the excitonic transitions in (211)B QDs and highlight the possible role of strong confinement and accompanying correlation effects as a means to tailor the transition energies of multi-particle states in semiconductor QDs. [ABSTRACT FROM AUTHOR]

A method is proposed for calculating the diffusion length damage coefficient for minority carriers (K L) in GaAs and InGaP solar cells under electron irradiation using the Shockley–Read–Hall (SRH) model for defect-assisted recombination. In the SRH model, the damage coefficient K L is proportional to the product k σ c , where k is the defect introduction rate under particle radiation and σ c is the minority carrier capture cross section of the said defects. The introduction rate k is evaluated using the atomic theory for displacement under electron radiation, and the calculation for σ c is adapted from Henry and Lang's high-temperature multiphonon emission formulation. A linear scaling relationship is observed between k , K L and nonionizing energy loss—validated by bibliographic data in the radiation energy range E ≈ 0.7 –12 MeV. Our model reproduces the increasing trend in K L with doping, as observed in the literature, while also capturing the anisotropy between the p -type and n -type materials, with the p -type exhibiting greater radiation resistance than its n -type counterpart. The calculated K L is fed into the physical model for solar cell operation to obtain the post-irradiated I sc , V oc , P max at a given fluence Φ. The degradation of the electrical quantities is consistent with the measurements recorded in the literature. The findings show that InGaP is more radiation resistant than GaAs. It is demonstrated that calculating k not only aids in determining the degradation of solar cell parameters from first principles, but also in obtaining the empirical function for degradation: a − b log (1 + c k Φ) , used in fitting the experimental measurements. The limitations and potential scope of improvements in the model are also discussed. [ABSTRACT FROM AUTHOR]

We investigate the influence of strain and dislocations on band alignment in GaSb/GaAs quantum dot systems. Composition profiles from cross-sectional scanning tunneling microscopy images are interpolated onto a finite element mesh in order to calculate the distribution of local elastic strain, which is converted to a spatially varying band alignment using deformation potential theory. Our calculations predict that dislocation-induced strain relaxation and charging lead to significant local variations in band alignment. Furthermore, misfit strain induces a transition from a nested (type I) to a staggered (type II) band alignment. Although dislocation-induced strain relaxation prevents the type I to type II transition, electrostatic charging at dislocations induces the staggered band alignment once again. [ABSTRACT FROM AUTHOR]

Graphene plasmons (GPs) are broadband and electrically tunable mid-infrared (MIR)/terahertz (THz) excitations, exhibiting high confinement factors exceeding two orders of magnitude. Such highly confined modes are extremely attractive for nonlinear frequency conversion owing to the large inherent field enhancement. However, this high confinement is also accompanied by losses, and together with the centrosymmetric nature of graphene practical usage of its properties in second-order nonlinear processes remains hindered. In this paper, we introduce an approach for realizing quasi-phase-matching (QPM) of propagating GPs, by placing the graphene on an orientationally patterned GaAs substrate—a transparent material in the MIR/THz range with a large second-order nonlinear coefficient. We analyze the complete frequency/Fermi-level space for QPMed second-harmonic generation of GPs in the MIR and THz and demonstrate GP amplification and loss compensation. We find that our approach provides extended GP propagation lengths that are more than twice larger than the state-of-the-art cryogenic temperature propagation lengths. The approach is general to all second-order nonlinear processes, such as sum and difference frequency generation, thus opening a path for efficient and electrically tunable QPM nonlinear processes at the atomic scale. [ABSTRACT FROM AUTHOR]

This work examines the role of spatial impurity extension (SIE) on a few nonlinear optical (NLO) properties of impurity-doped GaAs quantum dot (QD). The NLO properties considered are the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG). The study also includes 1 (GWN) which has been incorporated into the doped QD through additive and multiplicative pathways. The study uncovers the delicate interplay between GWN and SIE which ultimately fabricates the said NLO properties. NOR, SHG and THG manifest red-shift with enhancement of SIE both with and without GWN. The study also shows possibilities of attaining maximum NLO response by prudently applying GWN in a particular pathway. Depending upon the particular NLO property concerned, the presence of noise and its mode of application can either deplete or amplify it to different extents with respect to the noise-free situation. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of GaAsBi strain reduction layers (SRLs) on InAs QDs with different Bi fluxes to achieve nanostructures with improved temperature stability. The SRLs are grown at a lower temperature (370 °C) than the usual capping temperature for InAs QDs (510 °C). The study finds that GaAs capping at low temperatures reduces QD decomposition and leads to larger pyramidal dots but also increases the threading dislocation (TD) density. When adding Bi to the capping layer, a significant reduction in TD density is observed, but unexpected structural changes also occur. Increasing the Bi flux does not increase the Bi content but rather the layer thickness. The maximum Bi content for all layers is 2.4%. A higher Bi flux causes earlier Bi incorporation, along with the formation of an additional InGaAs layer above the GaAsBi layer due to In segregation from QD erosion. Additionally, the implementation of GaAsBi SRLs results in smaller dots due to enhanced QD decomposition, which is contrary to the expected function of an SRL. No droplets were detected on the surface of any sample, but we did observe regions of horizontal nanowires within the epilayers for the Bi-rich samples, indicating nanoparticle formation. [ABSTRACT FROM AUTHOR]

Erbium (Er)‐doped III‐V semiconductors are promising for optoelectronic devices due to the unique intra‐4f electronic transitions of Er3+; however, the Er‐related luminescence at room temperature has always been challenging to obtain. In this work, High crystalline quality ErAs:GaAs films are grown with self‐assembled ErAs nanoparticles embedded within the GaAs matrix by molecular beam epitaxy. Rich photoluminescence spectra in a broad wavelength ranging from near‐ultraviolet to near‐infrared are observed at room temperature and confirmed to be Er‐related. A carrier‐mediated energy transfer up‐conversion mechanism is proposed, and the pump power‐dependent photoluminescence results reveal that the excited‐state absorption is governed by a single photonic process. The efficient interaction and energy transfer between the semiconductor matrix and Er3+ ions offered by this unique nanocomposite material provide a promising route to achieve novel optoelectronic devices with the potential to cover a broad wavelength range. [ABSTRACT FROM AUTHOR]

The low-temperature-grown InGaAs (LT-InGaAs) photoconductive antenna has received great attention for the development of highly compact and integrated cheap THz sources. However, the performance of the LT-InGaAs photoconductive antenna is limited by its low resistivity and mobility. The generated radiated power is much weaker compared to the low-temperature-grown GaAs-based photoconductive antennas. This is mainly caused by the low abundance of excess As in LT-InGaAs with the conventional growth mode, which inevitably gives rise to the formation of As precipitate and alloy scattering after annealing. In this paper, the migration-enhanced molecular beam epitaxy technique is developed to grow high-quality (InAs)m/(GaAs)n short-period superlattices with a sharp interface instead of InGaAs on InP substrate. The improved electron mobility and resistivity at room temperature (RT) are found to be 843 cm2/(V·s) and 1648 ohm/sq, respectively, for the (InAs)m/(GaAs)n short-period superlattice. The band-edge photo-excited carrier lifetime is determined to be ~1.2 ps at RT. The calculated photocurrent intensity, obtained by solving the Maxwell wave equation and the coupled drift–diffusion/Poisson equation using the finite element method, is in good agreement with previously reported results. This work may provide a new approach for the material growth towards high-performance THz photoconductive antennas with high radiation power. [ABSTRACT FROM AUTHOR]

Abstract—The growth mechanism of monolayer on the top facet of Ga-catalyzed GaAs and GaP nanowires is investigated. Within the framework of a theoretical model, the maximal monolayer coverage due to the material in the catalyst droplet, the nanowire growth rate and the content of group V atoms in the droplet are found depending on the growth conditions. The estimates of the phosphorus re-evaporation coefficient from neighboring nanowires and substrate are obtained by comparing the theoretical and experimental growth rate of Ga-catalyzed GaP nanowires. [ABSTRACT FROM AUTHOR]