Group III-V Research Articles

112 Gbps CMOS-compatible waveguide germanium photodetector for the 2 μm wavelength band with a 3.64 A/W response

The 2 μm wavelength band emerges as a promising candidate for the next communication window to enhance the transmission capacity of data. A high-responsivity and high-speed photodetector operating at 2 μm is crucial for the 2-μm-wavelength-band communication system. Here, we present an on-chip waveguide-coupled germanium photodetector with remarkably high responsivity and data-receiving rate, employing subbandgap light absorption and avalanche multiplication. The device is designed with an ingenious and simple asymmetric lateral p-i-n junction structure and fabricated through a standard CMOS process by a commercial factory. It has a responsivity of 3.64 A/W and a maximum bandwidth of 50 GHz at 2 μm wavelength. For the first time, to the best of our knowledge, an optical receiving rate of up to 112 Gbps is demonstrated at 2 μm, verifying its feasibility in a high-speed 2-μm-band communication system. To the best of our knowledge, the proposed device stands out as the fastest photodiode with the highest responsivity among all group III-V and group IV photodetectors working in the 2 μm wavelength band.

A machine-learned kinetic energy model for light weight metals and compounds of group III-V elements

Abstract We present a machine-learned (ML) model of kinetic energy for orbital-free density functional theory (OF-DFT) suitable for bulk light weight metals and compounds made of group III–V elements. The functional is machine-learned with Gaussian process regression (GPR) from data computed with Kohn-Sham DFT with plane wave bases and local pseudopotentials. The dataset includes multiple phases of unary, binary, and ternary compounds containing Li, Al, Mg, Si, As, Ga, Sb, Na, Sn, P, and In. A total of 433 materials were used for training, and 18 strained structures were used for each material. Averaged (over the unit cell) kinetic energy density is fitted as a function of averaged terms of the 4th order gradient expansion and the product of the density and effective potential. The kinetic energy predicted by the model allows reproducing energy-volume curves around equilibrium geometry with good accuracy. We show that the GPR model beats linear and polynomial regressions. We also find that unary compounds sample a wider region of the descriptor space than binary and ternary compounds, and it is therefore important to include them in the training set; a GPR model trained on a small number of unary compounds is able to extrapolate relatively well to binary and ternary compounds but not vice versa.

The Time Response of a Uniformly Doped Transmission-Mode NEA AlGaN Photocathode Applied to a Solar-Blind Ultraviolet Detecting System

Due to the excellent quantum conversion and spectral response characteristics of the AlGaN photocathode, it has become the most promising III-V group semiconductor photocathode in solar-blind signal photoconversion devices in the ultraviolet band. Herein, the influence factors of the time-resolved characteristics of the AlGaN photocathode are researched by solving the photoelectron continuity equation and photoelectron flow density equation, such as the AlN/AlGaN interface recombination rate, AlGaN electron diffusion coefficient, and AlGaN activation layer thickness. The results show that the response time of the AlGaN photocathode decreases gradually with the increase in AlGaN photoelectron diffusion coefficient and AlN/AlGaN interface recombination rate, but the response time of the AlGaN photocathode gradually becomes saturated with the further increase in AlN/AlGaN interface recombination rate. When the thickness of the AlGaN photocathode is reduced from 250 nm to 50 nm, the response time of the AlGaN photocathode decreases from 63.28 ps to 9.91 ps, and the response time of AlGaN photocathode greatly improves. This study provides theoretical guidance for the development of a fast response UV detector.

Bending deformation effects on the optoelectronic performance of flexible GaInP/GaAs/InGaAs triple junction solar cells

To achieve genuine carbon neutrality, PV-powered vehicles show promise for future automotive development. However, the impact of curved surfaces on flexible solar cell module performance remains uncertain. This study specifically focuses on newly-designed flexible GaInP/GaAs/InGaAs triple junction solar cells, which have the highest potential output efficiency. A computational model was developed to analyze the electrical performance of curved solar cells, and variations in short-circuit current (Isc) and open-circuit voltage (Voc) with bending angles were determined to closely match experimental data. The effects of incident light intensity, angle, and bending strain on solar cell performance were analyzed to explain the observed Isc and Voc trends. This method can be applied to other III-V group solar cells, providing theoretical support for accurately calculating the performance of curved solar cell modules.

Tunable optical properties of BAs/ZnO vdW heterostructure

Stacked heterostructures is an effective strategy for physical property modulation and application of novel two-dimensional materials. In this study, a heterostructure consisting of two-dimensional III-V group hexagonal BAs and monolayer of ZnO is presented. The minimum value of binding and cohesive energies screened the BB’ configuration. Phonon spectra and ab initio molecular dynamics (AIMD) simulations further demonstrated the kinetic and thermodynamic stability of the selected model. Most notably, the formation of the heterostructure greatly improves the optical absorption performance of the monolayer, especially in the infrared (IR) regions. At a compressive strain of −6%, the band alignment shifts from type I to type II, while the bandgap becomes dramatically smaller. Refraction and reflection coefficients in the IR region under compressive strain (−2% and −4%) modulation were enhanced significantly. Our results provide theoretical guidance for the design of high-performance photovoltaic devices and solar cells based on BAs/ZnO heterostructures.

The electronic and optical properties of group III-V semiconductors: Arsenides and antimonides

Investigating the structural, electronic, and optical properties of zinc-blende III-V semiconductors, particularly arsenides, and antimonides, which are crucial for optoelectronic devices such as transistors, infrared detectors, and quantum technologies due to their wide range of direct bandgaps. In this work, we have employed a first-principles approach integrating G0W0 with the HSE06 hybrid functional and spin–orbit coupling (SOC) to study their fundamental properties. Traditional Density Functional Theory (DFT) methods, particularly those using Generalized Gradient Approximation (GGA) PBE functionals, tend to underestimate bandgaps, leading to discrepancies with experimental results. To address this, our study corrects the bandgap underestimation and refines the calculation of optical constants, including the dielectric function, refractive index, extinction coefficient, and absorption coefficient. Moreover, the optimized lattice constants and electronic properties derived from our computational model strongly correlate with experimental data, demonstrating the model’s reliability in predicting material properties. The findings suggest that our methods can be applied to arsenides and antimonides, offering a pathway to designing materials with optoelectronic properties involving III-V compounds and their complex heterostructures for advanced device applications.

Modeling Study of Si3N4 Waveguides on a Sapphire Platform for Photonic Integration Applications.

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III-V materials. In parallel with developing active devices for photonics integration applications, in this work, silicon nitride optical waveguides on a sapphire substrate were analyzed using the commercial software Comsol Multiphysics in a spectral window of 800~2400 nm, covering the operating wavelengths of III-V lasers, which could be monolithically or hybridly integrated on the same substrate. A high confinement factor of ~90% near the single-mode limit was obtained, and a low bending loss of ~0.01 dB was effectively achieved with the bending radius reaching 90 μm, 70 μm, and 40 μm for wavelengths of 2000 nm, 1550 nm, and 850 nm, respectively. Furthermore, the use of a pedestal structure or a SiO2 bottom cladding layer has shown potential to further reduce bending losses. The introduction of a SiO2 bottom cladding layer effectively eliminates the influence of the substrate's larger refractive index, resulting in further improvement in waveguide performance. The platform enables tightly built waveguides and small bending radii with high field confinement and low propagation losses, showcasing silicon nitride waveguides on sapphire as promising passive components for the development of high-performance and cost-effective PICs.

Unveiling Novel Direct Bandgap Allotropes of Germanium: A Computational Exploration

Germanium crystallizes in a cubic diamond structure, which restricts its applications in optoelectronics due to its indirect band gap. However, the slight energy difference between the direct and indirect band gaps in germanium presents a promising opportunity to engineer its structure into a direct band gap material, with the hexagonal diamond (lonsdaleite) phase being a notable example. In this study, we conducted an extensive computational search to find germanium allotropes with a direct band gap and low energy using a sensible random structure search approach informed by data-derived interatomic potentials. Among the predicted allotropes, we identified a hexagonal 8H structure with the lowest energy compared to all known germanium allotropes and only 5 meV/atom above the ground state cubic diamond structure. Compared to the cubic diamond phase, which has complete cubicity, the 8H phase consists of 3/4 cubicity and 1/4 hexagonality. This structural motif, coupled with band structure back folding in the hexagonal Brillouin zone, results in a direct band gap of 0.25 eV. Given the prior experimental discovery of 2H and 4H polytypes, the experimental synthesis of the 8H allotrope in germanium is highly feasible. Future research could explore alloying 8H germanium with silicon to optimize the bandgap energy and optical transitions, potentially achieving lifetimes comparable to those of group III-V semiconductors like GaAs.

(Invited) Shape Engineering of Nanostructured III-V Semiconductor Lasers

Group III-V semiconductors have revolutionised electronics and optoelectronics due to their superior physical and optoelectronic properties including high carrier mobility, direct bandgap and band structure engineering capability. Reducing the device size to nanoscale brings many unique properties, such as large surface-area-to-volume ratio, high aspect ratio, carriers and photons confinement effect. These nanostructures have already been demonstrated for potential applications in light emitters, photodetectors, solar cells and for photoelectrochemical water splitting. However, to date most efforts on the growth of these nanostructures have been limited to nanowires.In this talk, we demonstrate selective area growth of III-V nanostructures, showing the possibility of obtaining other functional nanostructures, beyond the limitation of rod-like geometry. We demonstrate that by changing the pattern design on the mask and growth conditions, we are able to grow and control the shapes to form nanostructures such as membranes, flowers, rings, spirals, stars, ellipses etc. These shape-engineered nanostructures open up possibilities of new applications based on devices with novel geometries.In particular, we will show the results of our InP micro-ring lasers which have excellent cavity due to the atomically flat facets. Micro-disk and micro-ring lasers are light emitting devices that operate in the whispering gallery mode. They are important components for integrated photonics applications as light from can these devices can be efficiently coupled to on-chip waveguides. By coupling the micro-ring laser to a nanowire antenna, we further demonstrate that we can tune the emission directionality to the device.

Photoelectrocatalytic Hydrogen Generation: Current Advances in Materials and Operando Characterization.

Photoelectrochemical (PEC) hydrogen generation is a promising technology for green hydrogen production yet faces difficulties in achieving stability and efficiency. The scientific community is pushing toward the development of new electrode materials and a better understanding of the underlying reactions and degradation mechanisms. Advances in photocatalytic materials are being pursued through the development of heterojunctions, tailored crystal nanostructures, doping, and modification of solid-solid and solid-electrolyte interfaces. Operando and in situ techniques are utilized to deconvolute the charge transfer mechanisms and degradation pathways. In this review, both materials development and Operando characterization are covered for advancing PEC technologies. The recent advances made in the PEC materials are first reviewed including the applied improvement strategies for transition metal oxides, nitrites, chalcogenides, Si, and group III-V semiconductor materials. The efficiency, stability, scalability, and electrical conductivity of the aforementioned materials along with the improvement strategies are compared. Next, the Operando characterization methods and cite selected studies applied for PEC electrodes are described. Operando studies are very successful in elucidating the reaction mechanisms, degradation pathways, and charge transfer phenomena in PEC electrodes. Finally, the standing challenges and the potential opportunities are discussed by providing recommendations for designing more efficient and electrochemically stable PEC electrodes.

Electronic properties modulation for two-dimensional materials of boron phosphorus monolayer and derived single atom catalysts for the hydrogen evolution reaction

Electrocatalytic hydrogen evolution reaction (HER) is the core of the future renewable energy field and an important part of clean energy technology. It is urgent to find a noble metal free catalyst with high stability, good conductivity and economic efficiency for HER. Two-dimensional (2D) materials such as hexagonal boron nitride formed by the combination of B and N atoms of group III-V elements have been substantiated with significant electronic properties. We predict that 2D materials composed of B and P atoms of the same main group also have good electronic properties. This paper reports for the first time the application of two recent 2D boron phosphorus monolayer compounds (BS-B1P1 and PH-B1P1) as excellent single-atom catalysts (SACs) for HER. We have demonstrated that boron phosphorus compounds can obviously improve its electrical conductivity through single-atom transition metal (TM) doping through the density of state (DOS) calculations, which promises their applications in HER. Hence, an electrocatalyst is computer-aided designed with isolated TM single atom of 3d, 4d, and 5d supported on BS-B1P1 and PH-B1P1 to construct SACs with excellent HER performance. Interestingly, we find that the these SACs can show high HER activity in a wide pH-range. Among all SACs studied, Sc-, Ti-, Nb-, Ag-,and Hf-embedded BS-B1P1 have excellent catalytic activity in acidic conditions while Mn-, Ta-, Re-, Os-, Ir-, and Au-embedded BS-B1P1 show high catalytic activity in alkaline conditions. Mn@PH-B1P1 shows high catalytic activity only in acidic conditions. Especially, Tc@BS-B1P1 system exhibits promising catalytic activity, which owns high active in either neutral, acidic and alkaline conditions. Our work provides a highly active HER catalyst with pH regulation, providing a cost-effective alternative to traditional Pt-based catalysts for sustainable hydrogen extraction.

Theoretical investigation on electronic, optical and phonon properties of compound semiconductors suitable for photovoltaic device applications

The III-V group semiconductors have extensive technological applications in the solar cells and light-emitting diodes. The electronic, dynamical, and optical properties of GaSb, GaP, InAs, GaAs, AlSb and AlAs semiconductors are comprehensively analysed using first-principle calculations of the density functional theory. The GGA computed band gaps are in the solar spectrum and found to be low effective charge due to high dispersion in the band structures. The acoustic phonons and optical phonons are obtained in the energy range of 0–33 meV and 21–55 meV, respectively. These phonon results have suggested that all the crystal structures are dynamically stable. Above electronic and phonon results are used to analyse the optical properties. Generally, optical properties are affected by electron-phonon interaction via inter-bond transitions. The phonon influenced dielectric function could effectively enhance the light absorption by electron-phonon coupling which is useful to improve the efficiency of solar cell. Particularly, the phonon role in the shaping of optical absorption has been analysed based on the electron-phonon interaction. The optical absorption shows significant optical absorption (>105 cm−1) for all the semiconductors useful in solar cell applications.

Recent progress of group III-V materials-based nanostructures for photodetection.

Due to the suitable bandgap structure, efficient conversion rates of photon to electron, adjustable optical bandgap, high electron mobility/aspect ratio, low defects, and outstanding optical and electrical properties for device design, III-V semiconductors have shown excellent properties for optoelectronic applications, including photodiodes, photodetectors, solar cells, photocatalysis, etc. In particular, III-V nanostructures have attracted considerable interest as a promising photodetector platform, where high-performance photodetectors can be achieved based on the geometry-related light absorption and carrier transport properties of III-V materials. However, the detection ranges from Ultraviolet to Terahertz including broadband photodetectors of III-V semiconductors still have not been more broadly development despite significant efforts to obtain the high performance of III-V semiconductors. Therefore, the recent development of III-V photodetectors in a broad detection range from Ultraviolet to Terahertz, and future requirements are highly desired. In this review, the recent development of photodetectors based on III-V semiconductor with different detection range is discussed. First, the bandgap of III-V materials and synthesis methods of III-V nanostructures are explored, subsequently, the detection mechanism and key figures-of-merit for the photodetectors are introduced, and then the device performance and emerging applications of photodetectors are provided. Lastly, the challenges and future research directions of III-V materials for photodetectors are presented.

Synthesis and Tuning of Electronic, Optical, and Photoelectrochemical Properties of Copper Metavanadate Alloys via Alkaline Earth Metal Substitution

Unlike the well-studied and technologically advanced Group III-V and Group II-VI compound semiconductor alloys, alloys of ternary metal oxide semiconductors have only recently begun to receive widespread attention. Here, we describe the effect of alkaline earth metal substitution on the optical, electronic, and photoelectrochemical (PEC) properties of copper metavanadate (CuV2O6). As a host, the Cu-V-O compound family presents a versatile framework to develop such composition-property correlations. Alloy compositions of A0.1Cu0.9V2O6 (A = Mg, Ca) photoanodes were synthesized via a time and energy-efficient solution combustion synthesis (SCS) method. The effect of introducing alkaline earth metals (Mg, Ca) on the crystal structure, microstructure, electronic, and optical properties of copper metavanadates was investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), and Raman spectroscopy. The PXRD, TEM, and Raman spectroscopy data demonstrated the polycrystalline powder samples to be mutually soluble, solid solutions of copper and alkaline earth metal metavanadates and not simple mixtures of these compounds. The DRS data showed a systematic decrease in the optical bandgap with Cu incorporation. These trends were corroborated by electronic band structure calculations. Finally, the PEC properties exhibited a strong dependence on the alloy composition, pointing to possible applicability in solar water splitting, heterogeneous photocatalysis, phosphor lighting/displays, and photovoltaic devices.

Enable strong electrical coupling between the InZnP@PbS collodial quantum dots in films via the two-step ligand exchange method

Colloidal quantum dots (CQDs) are promising materials for building next-generation solution-processed, high-performance, and low-cost optoelectronic devices. The photoelectric properties of the resulting films are not only determined by the intrinsic characteristics of the CQDs but are also significantly affected by the electrical coupling between them. However, enhancing the electrical coupling in CQD-based films is still a big challenge. In this work, a two-step ligand exchange strategy has been conducted to solve the above issue, where the InZnP@PbS CQDs have been used as the case. First, the Meerwein salt (Et3OBF4) solution in N, N-dimethylformamide (DMF) has been employed to peel off the native ligands that are strongly capped on the surface of oil-soluble CQDs, resulting in a neat surface. Second, iodide ions are linked to the neat surface of the CQDs to narrow the distance between them and passivate their defects, establishing strong electrical coupling. Transient surface photovoltage (TSPV) and photo-conductance tests confirm that the resulting InZnP@PbS–I CQDs films possess good photoelectric properties and stability. In the fabricated solid-state solar cells, 3.1 % of the photoelectric conversion efficiency (PCE) has been achieved under 1 sun. The current results are outstanding for III-V group CQD-based all solid-state solar cells.

GaN HEMT for High-performance Applications: A Revolutionary Technology

Background: The upsurge in the field of radio frequency power electronics has led to the involvement of wide bandgap semiconductor materials because of their potential characteristics in achieving high breakdown voltage, output power density, and frequency. III-V group materials of the periodic table have proven to be the best candidates for achieving this goal. Among all the available combinations of group III-V semiconductor materials, gallium nitride (GaN), having a band gap of 3.4eV, has gradually started gaining the confidence to become the next-generation material to fulfill these requirements. Objective: Considering the various advantages provided by GaN, it is widely used in AlGaN/GaN HEMTs (High Electron Mobility Transistors) as their fundamental materials. This work aimed to review the structure, operation, and polarization mechanisms influencing the HEMT device, different types of GaN HEMT, and the various process technologies for developing the device. Methods: Various available methods to obtain an enhancement type GaN HEMT are discussed in the study. It also covers the recent developments and various techniques to improve the performance and device linearity of GaN HEMT. Conclusion: Despite the advantages and continuous improvement exhibited by the GaN HEMT technology, it faces several reliability issues, leading to degradation of device performance. In this study, we review various reliability issues and ways to mitigate them. Moreover, several application domains are also discussed, where GaN HEMTs have proven their capability. It also focuses on reviewing and compiling the various aspects related to the GaN HEMT, thus providing all necessary information.

Https://www.texilajournal.com/public-health/article/2527-guardians-of-liver

Glyphosate is used as an herbicide in agriculture. At sub-agriculture concentrations, glyphosate-based herbicide inhibits cell proliferation. Glyphosate is a chelating agent that interferes with the metabolic activities in plants thereby adversely affecting its metabolism. The study aimed to determine the glyphosate-induced detrimental changes in SREBP-1c and PPAR-γ mRNA expression in adipose tissue of adult male rats. Adult male Wistar albino rats were divided into 4 groups, each consisting of 6 animals. Group I served as normal control rats; Group II-IV consisted of rats exposed to glyphosate at different concentrations (50, 100, and 250 mg/kg body weight respectively) orally for 16 weeks. After 16 weeks of treatment, the animals were sacrificed, and adipose tissue was dissected out for the assessment of SREBP-1c and PPAR-γ mRNA by real-time PCR using gene-specific down-regulated primers. The results with the p<0.05 level were considered to be statistically significant. The results showed a significant dose-dependent increase (P <0.05) in the expression of SREBP-1c in all the glyphosate-exposed rats compared to control rats and PPAR-γ mRNA expression was found to be significantly reduced in a concentration-dependent manner (P<0.05) compared to normal control animals. The current findings for the first time report that glyphosate had detrimental changes in the expression of transcription factors such as SREBP-1c and PPAR-γ mRNA in adipose tissue and thereby glyphosate may lead to the development of type-2 diabetes or insulin resistance.

Anodic Reconstructed p+-GaAs/a-InAsN for Stable and Efficient Photoelectrochemical Hydrogen Evolution.

The extremely poor solution stability and massive carrier recombination have seriously prevented III-V semiconductor nanomaterials from efficient and stable hydrogen production. In this work, an anodic reconstruction strategy based on group III-V active semiconductors is proposed for the first time, resulting in 19-times photo-gain. What matters most is that the device after anodic reconstruction shows very superior stability under the protracted photoelectrochemical (PEC) test over 8100s, while the final photocurrent density does not decrease but rather increases by 63.15%. Using the experiment and DFT theoretical calculation, the anodic reconstruction mechanism is elucidated: through the oxidation of indium clusters and the migration of arsenic atoms, the reconstruction formed p+-GaAs/a-InAsN. The hole concentration of the former is increased by 10 times (5.64×1018cm-1 increases up to 5.95×1019cm-1) and the band gap of the latter one is reduced to a semi-metallic state, greatly strengthening the driving force of PEC water splitting. This work turns waste into treasure, transferring the solution instability into better efficiency.

Electronic Transport and Quantum Phenomena in Nanowires.

Nanowires are natural one-dimensional channels and offer new opportunities for advanced electronic quantum transport experiments. We review recent progress on the synthesis of nanowires and methods for the fabrication of hybrid semiconductor/superconductor systems. We discuss methods to characterize their electronic properties in the context of possible future applications such as topological and spin qubits. We focus on group III-V (InAs and InSb) and group IV (Ge/Si) semiconductors, since these are the most developed, and give an outlook on other potential materials.

Defects and Defect Engineering of Two-Dimensional Transition Metal Dichalcogenide (2D TMDC) Materials.

As layered materials, transition metal dichalcogenides (TMDCs) are promising two-dimensional (2D) materials. Interestingly, the characteristics of these materials are transformed from bulk to monolayer. The atomically thin TMDC materials can be a good alternative to group III-V and graphene because of their emerging tunable electrical, optical, and magnetic properties. Although 2D monolayers from natural TMDC materials exhibit the purest form, they have intrinsic defects that limit their application. However, the synthesis of TMDC materials using the existing fabrication tools and techniques is also not immune to defects. Additionally, it is difficult to synthesize wafer-scale TMDC materials for a multitude of factors influencing grain growth mechanisms. While defect engineering techniques may reduce the percentage of defects, the available methods have constraints for healing defects at the desired level. Thus, this holistic review of 2D TMDC materials encapsulates the fundamental structure of TMDC materials, including different types of defects, named zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D). Moreover, the existing defect engineering methods that relate to both formation of and reduction in defects have been discussed. Finally, an attempt has been made to correlate the impact of defects and the properties of these TMDC materials.