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Abstract In this paper, a 280–300 GHz hybrid‐integrated transmitter is proposed. The advantages of the SiGe and InP chips are fully made use by integrating these two chips. For low cost and high integration, the local oscillator chain and mixer are based on chips in SiGe technology, and the 300‐GHz power amplifier and on‐chip antenna are realised in InP technology for high output power and small die size. The low‐cost bonding wires are introduced for the interconnection between these two chips, and the lens are attached above the on‐chip antenna for further EIRP enhancement. Finally, the proposed transmitter is fabricated and measured, which shows comparable performances with 21.9 dBm EIRP (equivalent isotropic radiated power) and 10 Gbps data rate.

Abstract The authors present continuous wave (CW) high‐power broad area and ridge waveguide lasers with laser emission at 626 nm at room temperature. For this, the authors employ GaAs‐based diode lasers in the AlGaInP system for laser emission at 626 nm at room temperature. The laser structure is grown on three‐inch wafers by metal organic vapour phase epitaxy. Broad area and ridge waveguide lasers are fabricated. Pulsed broad area laser characterisation on bar level shows laser operation at 20 C heat sink temperature. The authors measured peak lasing wavelengths as short as 625 nm and total maximum output power of both facets up to 1.4 W at an injection current of 2 A. Both, broad area and ridge waveguide lasers show laser operation and CW excitation at room temperature. The ridge waveguide lasers emit output powers of over 90 mW at 626 nm at a maximum injection current of 200 mA with a nearly diffraction‐limited beam profile.

III‐V semiconductors, known for their optoelectronic properties and versatile engineering capabilities, play a crucial role in the fabrication of Micro light‐emitting diodes (Micro‐LEDs). Recent advances in research underscore that the optoelectronic performance of Micro‐LEDs can be significantly enhanced using various strategies, such as passivation and distributed Bragg reflectors (DBRs), the incorporation of metamaterials and plasmonics, and the integration of 2D materials. By implementing these diverse integration strategies, Micro‐LEDs based on III‐V semiconductors have demonstrated remarkably high External Quantum Efficiency (EQE) spanning orders of magnitude across the spectrum, from deep‐ultraviolet (DUV) to the long‐wavelength infrared (LWIR) regions. In this review, the main III‐V semiconductors used in Micro‐LEDs are discussed. Additionally, an overview of the fabrication processes and integration techniques relevant to Micro‐LED‐based technologies is provided. Furthermore, the factors that influence the figure of merit in a wide range of Micro‐LEDs based on III‐V semiconductors, taking into account quantum efficiency, emission wavelength, and electrical injection, are examined. Finally, the discussion highlights several applications of Micro‐LEDs, provides a summary, and outlines future directions for the development of Micro‐LEDs based on III‐V semiconductors. [ABSTRACT FROM AUTHOR]

A colloidal synthesis protocol is demonstrated for InAs@InP core@shell quantum dots (QDs) with a tunable InP shell thickness (ranging from 3 to 8 monolayers), utilizing tris(diethylamino)‐arsine and ‐phosphine. Structural analysis reveals that the InP shell preferentially grows onto the tetrahedral InAs cores along the <‐1‐1‐1> directions, forming tetrapodal‐shaped InAs@InP QDs. Growth of the InP shell causes a red shift in the absorption spectrum of the QDs. This is explained by considering that electrons are delocalized throughout the whole core@shell QDs, while holes preferentially leak along the <‐1‐1‐1> directions, as indicated by the density functional theory calculations. This means such heterostructures cannot be described as type‐I or quasi type‐II, contrary to earlier assumptions. The overlap of carrier wavefunctions throughout the entire InAs@InP QD structure results in no significant reduction of the Auger recombination rate, which remains as fast as in InAs QDs. However, the InP shell enhances photoluminescence (PL) efficiency (up to ≈13%) by passivating surface trap states of the InAs QDs (mainly located close to the top of the valence band). The overgrowth of a ZnSe shell endows the QDs with a high PL efficiency (≈55%) and good stability upon air exposure (≈80% PL intensity retention after 14 days). [ABSTRACT FROM AUTHOR]

In this paper, a 280–300 GHz hybrid‐integrated transmitter is proposed. The advantages of the SiGe and InP chips are fully made use by integrating these two chips. For low cost and high integration, the local oscillator chain and mixer are based on chips in SiGe technology, and the 300‐GHz power amplifier and on‐chip antenna are realised in InP technology for high output power and small die size. The low‐cost bonding wires are introduced for the interconnection between these two chips, and the lens are attached above the on‐chip antenna for further EIRP enhancement. Finally, the proposed transmitter is fabricated and measured, which shows comparable performances with 21.9 dBm EIRP (equivalent isotropic radiated power) and 10 Gbps data rate. [ABSTRACT FROM AUTHOR]

Rising demands on environmentally benign materials lead to the development of heavy-metal-free NCs for light-emitting applications. Tremendous efforts to solve the challenges of heavy-metal-free NCs have been focused on the discovery of synthetic chemistry and photophysical properties of the NCs. This review provides a comprehensive overview of the progress in the synthesis of heavy-metal-free semiconductor NCs, mainly focusing on III–V, I–III–VI2, and II–VI groups. The progress details the discovery of their precursor chemistry and the formation of heterostructures to fit their chemical nature and photophysical properties. The continuous efforts on the structural design and synthetic chemistry reveal how exceptional properties of the NCs materialized. The remarkable progress in photophysical properties and synthetic chemistry on the NCs supports the potential of these NCs in optoelectronic applications, including light-emitting diode (LED) and solar cell, demonstrating their suitability as strong alternatives to Cd and Pb-based NCs. This review offers insights into the remaining challenges of the NCs, directing the future perspectives of the NCs. [ABSTRACT FROM AUTHOR]

The In x Ga 1 − x A s y Sb 1 − y alloy was studied in epilayers and photodiodes grown lattice matched to GaSb across a comprehensive composition range, 0 ⩽ x ⩽ 0.3 , as a promising technology to support the extended short-wave infrared region ∼ 1.7 − 3 µ m. Low background carrier concentrations between 6 × 10 14 and 1 × 10 15 cm − 3 were achieved in all samples, reducing with In fraction. Both the absorption coefficient and external quantum efficiency were found to increase with indium fraction, up to ∼ 10 4 cm − 1 and 70% without an AR coating, respectively. Counter to the fundamental bandgap dependence, leakage current density initially reduced with the addition of low In and As fractions, before rising as the fractions increased and the bandgap reduced further. These properties resulted in specific detectivity reaching a maximum in the sample with x = 0.043, before decreasing towards higher alloy fractions. It is concluded that for moderate In fractions, the InGaAsSb alloy offers clear potential to improve on the disappointing material and photodiode properties of GaSb and support emerging SWIR sensing applications. However, development of fabrication and passivation technology is required to fully exploit this potential. [ABSTRACT FROM AUTHOR]

N-polar GaN film was obtained by using a high-temperature AlN buffer layer. It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer. Continuing to increase the V/III ratio of the low-temperature AlN interlayer, the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated. Finally, we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy (XPS), which provides a new direction for the control of GaN polarity. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN)‐based semiconductor laser diodes (LDs) have garnered significant attention due to their promising applications. However, high‐power LDs face serious degradation issues that limit their practical use. This study investigates the degradation factors of 437 nm and 6.3 W LDs by comparing light–current–voltage (L–I–V) characteristics, transmission electron microscopy (TEM), cathodoluminescence (CL), and secondary ion mass spectroscopy (SIMS) before and after 1000‐h aging. The diffusion of mirror coating from the resonant cavity surface is identified as a key factor contributing to high‐power LD degradation, which has not been reported in milliwatt‐level LDs. Meanwhile, the mechanisms behind the LD degradation are profiled and summarized together with the diffusion and other factors. On basis of the mechanism exploration, an anti‐aging technology for high‐power GaN‐based LDs is developed by using aluminum nitride for passivation layer and sapphire materials for mirror film. This anti‐aging technology has been verified, and a nearly ten‐time degradation suppression is achieved from 1000 h. This study elucidates the degradation mechanisms of high‐power GaN LDs and provides an effective technology to extend their lifespan, thereby prompting the practical applications of high‐power LDs. [ABSTRACT FROM AUTHOR]

Multi‐junction photonic power converters (PPCs) are photovoltaic cells used in photonic power transmission systems that convert monochromatic light to electricity at enhanced output voltages. The junctions of a multi‐junction PPC have overlapping spectral responsivity, which poses a unique challenge for spectrally resolved external quantum efficiency (EQE) measurements. In this work, we present a novel EQE measurement technique based on a wavelength‐tunable laser system and characterize the differential multi‐junction device‐level EQE (dEQEMJ) as a function of the monochromatic irradiance over seven orders of magnitude. The irradiance‐dependent measurements reveal three distinct irradiance regimes with different dEQEMJ. For the experimentally studied 2‐junction GaAs‐based device, at medium irradiance with photocurrent densities between 0.3 and 90 mA/cm2, dEQEMJ is independent of irradiance and follows the expected EQE of the current‐limiting subcell across all wavelengths. At higher irradiance, nonlinear device response is observed and attributed to luminescent coupling between the subcells. At lower irradiances, namely, in the range of conventional EQE measurement systems, nonlinear effects appear, which mimic luminescent coupling behavior but are instead attributed to finite shunt resistance artifacts that artificially inflate dEQEMJ. The results demonstrate the importance of measuring the device‐level dEQEMJ in the relevant irradiance regime. We propose that device‐level measurements in the finite shunt artifact regime at low monochromatic irradiance should be avoided. [ABSTRACT FROM AUTHOR]

Air quality is deteriorating due to continuing urbanization and industrialization. In particular, nitrogen dioxide (NO2) is a biologically and environmentally hazardous byproduct from fuel combustion that is ubiquitous in urban life. To address this issue, we report a high‐performance flexible indium phosphide nanomembrane NO2 sensor for real‐time air quality monitoring. An ultralow limit of detection of ~200 ppt and a fast response have been achieved with this device by optimizing the film thickness and doping concentration during indium phosphide epitaxy. By varying the film thickness, a dynamic range of values for NO2 detection from parts per trillion (ppt) to parts per million (ppm) level have also been demonstrated under low bias voltage and at room temperature without additional light activation. Flexibility measurements show an adequately stable response after repeated bending. On‐site testing of the sensor in a residential kitchen shows that NO2 concentration from the gas stove emission could exceed the NO2 Time Weighted Average limit, i.e., 200 ppb, highlighting the significance of real‐time monitoring. Critically, the indium phosphide nanomembrane sensor element cost is estimated at <0.1 US$ due to the miniatured size, nanoscale thickness, and ease of fabrication. With these superior performance characteristics, low cost, and real‐world applicability, our indium phosphide nanomembrane sensors offer a promising solution for a variety of air quality monitoring applications. [ABSTRACT FROM AUTHOR]

InSb colloid quantum dots (CQDs) are liquid “green” semiconductor materials. Their band gaps can be readily adjusted by controlling their particle size. Their excellent photoelectric properties and non‐toxic properties render them highly suitable for the fabrication of low‐cost infrared photodetectors and image sensors in industrial and consumer electronics applications. Despite the concept and preparation of InSb CQDs having been reported for decades, the performance of InSb CQDs‐based photodetectors still lags behind that of their toxic PbS CQDs‐based counterparts. This is mainly due to the immature synthesis process and the lack of sufficient device research. Fortunately, significant advances have been made in the synthesis of InSb CQDs and ligand exchange strategies over the past three years, resulting in notable enhancements in device performance. This review presents a summary of the recent advances in InSb CQDs and their applications in photodetectors. A particular focus is placed on the development of controllable synthesis routes for high‐quality InSb CQDs, which represents a significant challenge due to the high valence nature of InSb. Furthermore, the performance of these devices is discussed in detail, with a particular focus on ligand exchange and surface treatment strategies. Finally, a brief summary and outlook on InSb CQDs‐based photodetectors is presented. [ABSTRACT FROM AUTHOR]

The authors present continuous wave (CW) high‐power broad area and ridge waveguide lasers with laser emission at 626 nm at room temperature. For this, the authors employ GaAs‐based diode lasers in the AlGaInP system for laser emission at 626 nm at room temperature. The laser structure is grown on three‐inch wafers by metal organic vapour phase epitaxy. Broad area and ridge waveguide lasers are fabricated. Pulsed broad area laser characterisation on bar level shows laser operation at 20 C heat sink temperature. The authors measured peak lasing wavelengths as short as 625 nm and total maximum output power of both facets up to 1.4 W at an injection current of 2 A. Both, broad area and ridge waveguide lasers show laser operation and CW excitation at room temperature. The ridge waveguide lasers emit output powers of over 90 mW at 626 nm at a maximum injection current of 200 mA with a nearly diffraction‐limited beam profile. [ABSTRACT FROM AUTHOR]

Abstract This review aims to provide a comprehensive overview of the development and current understanding of GaAs and InAs heterostructures, with a special emphasis on achieving high material quality and high-mobility two-dimensional electron gases (2DEGs). The review discusses the evolution of structural designs that have significantly contributed to the enhancement of electron mobility, highlighting the critical considerations of scattering mechanisms of the 2DEGs. In addition, this review examines the substantial contributions of Molecular Beam Epitaxy (MBE) to these developments, particularly through advancements in vacuum technology, source material purification, and precision control of growth conditions. The intent of this review is to serve as a useful reference for researchers and practitioners in the field, offering insights into the historical progression and technical details of these semiconductor systems.

Highlights In-depth review assesses III–V materials for efficient hydrogen generation and CO2 reduction in renewable energy technologies. Exploration of strategies for broad light absorption and increased efficiency in water splitting processes and CO2 reduction. Innovative electrode designs conclude the path for stable, large-scale implementation of clean energy systems.

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. [ABSTRACT FROM AUTHOR]

Variable‐angle spectroscopic ellipsometry is used to determine the room temperature complex refractive index (n˜=n+ik)$\left(\right. \overset{&amp;amp;amp;amp;amp;amp;amp;tilde;}{n} &amp;amp;amp;amp;amp;amp;amp;equals; n &amp;amp;amp;amp;amp;amp;amp;plus; i k \left.\right)$ of molecular beam epitaxy grown GaSb1−xBix films with x ≤ 4.25% over a spectral range of 0.47–6.2 eV. By correlating to critical points in the extinction coefficient k, the energies of several interband transitions are extracted as functions of Bi content. The observed change in the fundamental bandgap energy (E0, −36.5 meV per %Bi) agrees well with previously published values; however, the samples examined here show a much more rapid increase in the spin‐orbit splitting energy (Δ0, +30.1 meV per Bi) than previous calculations have predicted. As in the related GaAsBi, the energy of transitions involving the top of the valence band are observed to have a much stronger dependence on Bi content than those that do not, suggesting the valence band maximum is most sensitive to Bi alloying. Finally, the effects of surface droplets on both the complex refractive index and the critical point energies are examined. [ABSTRACT FROM AUTHOR]

This review aims to provide a comprehensive overview of the development and current understanding of GaAs and InAs heterostructures, with a special emphasis on achieving high material quality and high-mobility two-dimensional electron gases (2DEGs). The review discusses the evolution of structural designs that have significantly contributed to the enhancement of electron mobility, highlighting the critical considerations of scattering mechanisms of the 2DEGs. In addition, this review examines the substantial contributions of Molecular Beam Epitaxy (MBE) to these developments, particularly through advancements in vacuum technology, source material purification, and precision control of growth conditions. The intent of this review is to serve as a useful reference for researchers and practitioners in the field, offering insights into the historical progression and technical details of these semiconductor systems. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN)‐based semiconductor laser diodes (LDs) have garnered significant attention due to their promising applications. However, high‐power LDs face serious degradation issues that limit their practical use. This study investigates the degradation factors of 437 nm and 6.3 W LDs by comparing light–current–voltage (L–I–V) characteristics, transmission electron microscopy (TEM), cathodoluminescence (CL), and secondary ion mass spectroscopy (SIMS) before and after 1000‐h aging. The diffusion of mirror coating from the resonant cavity surface is identified as a key factor contributing to high‐power LD degradation, which has not been reported in milliwatt‐level LDs. Meanwhile, the mechanisms behind the LD degradation are profiled and summarized together with the diffusion and other factors. On basis of the mechanism exploration, an anti‐aging technology for high‐power GaN‐based LDs is developed by using aluminum nitride for passivation layer and sapphire materials for mirror film. This anti‐aging technology has been verified, and a nearly ten‐time degradation suppression is achieved from 1000 h. This study elucidates the degradation mechanisms of high‐power GaN LDs and provides an effective technology to extend their lifespan, thereby prompting the practical applications of high‐power LDs.

The development of tunable photonic devices is strategic for miniaturized optical instrumentation and sensing systems. Exploiting the birefringence variation of liquid crystals (LCs) instead of MEMS actuation in such devices could bring better spectral stability and lower power consumption. However, aligning LCs inside a III–V semiconductor device is tricky. We demonstrate that self-assembled gallium arsenide (GaAs) quantum dashes (QDHs) could serve as direct planar aligners for LC nematic molecules. The alignment quality and birefringence variation of a LC-microcell embedding QDHs are shown to be similar to those of a polymer nanograting-based reference, with the added advantage of better electrical performance.

Many III–V semiconductors possess direct bandgaps and are thus widely applied in optoelectronics. Although GaN (either in wurtzite phase or zinc blende phase), GaAs, and GaSb are well‐known direct‐gap semiconductors, GaP exhibits an indirect bandgap nevertheless. In this work, the generic rule of energy gaps in GaN, GaP, and GaAs of the zinc blende phase is analyzed, and the trends of gap variation are studied concerning the lattice constant and anion electronegativity. It turns out that GaP actually manifests a normal behavior, the reason why GaN surprisingly has a direct gap is analyzed through examining and perturbing its valence band as well as conduction band (CB). The CB electron shows a non‐negligible probability to emerge near the N cores. The attractive nucleus potential pulls down the CB more strongly at Γ, which is in principle further supported through an analysis of the Kronig–Penney model. The difference between GaP and GaN in this respect is also analyzed in detail. [ABSTRACT FROM AUTHOR]

In this study, we introduce a new extended-mid-wavelength InAsSb-based pBn architecture infrared barrier photodetector with an InAlSb compositional step-graded barrier (SGB), referred to as SGB-pBn-PD, designed specifically to detect a biomarker of bone marrow cancer. Our device outperforms conventional design by replacing the compositional uniform barrier with a step-graded barrier, resulting in improved alignment of the valence band in the barrier and absorber interface, and reduced dark current density via suppression of the Shockley–Read–Hall process. Our simulations show that the dark current density of this detector reaches ~ 2.07 × 10–7 A/cm2 under -400 mV at 150 K. Furthermore, our optical examination reveals that the detector's response peak is around Amide I band, making it highly capable of detecting the Amide I band, a known as biomarkers of bone marrow cancer, particularly acute lymphoblastic leukemia. At -500 mV, the detector's merit criteria, including current responsivity, shot-thermal-limited specific detectivity and noise equivalent power are ~ 1.9 A/W, ~ 2.77 × 1012 cmHz1/2/W and ~ 3.60 × 10–13 W/Hz1/2, respectively. Results indicate that our proposed detector performs exceptionally well and has distinct electrical and optical properties, making it an excellent candidate for optical diagnostics in modern infrared biosensor applications. [ABSTRACT FROM AUTHOR]

InAs/AlSb quantum cascade detectors (QCDs) grown strain-balanced on GaSb substrates are presented. This material system offers intrinsic performance-improving properties, like a low effective electron mass of the well material of 0.026 m0, enhancing the optical transition strength, and a high conduction band offset of 2.28 eV, reducing the noise and allowing for high optical transition energies. InAs and AlSb strain balance each other on GaSb with an InAs:AlSb ratio of 0.96:1. To regain the freedom of a lattice-matched material system regarding the optimization of a QCD design, submonolayer InSb layers are introduced. With strain engineering, four different active regions between 3.65 and 5.5 µm were designed with InAs:AlSb thickness ratios of up to 2.8:1, and subsequently grown and characterized. This includes an optimized QCD design at 4.3 µm, with a room-temperature peak responsivity of 26.12 mA/W and a detectivity of 1.41 × 108 Jones. Additionally, all QCD designs exhibit higher-energy interband signals in the mid- to near-infrared, stemming from the InAs/AlSb type-II alignment and the narrow InAs band gap. [ABSTRACT FROM AUTHOR]

Herein, the crystal phase switching between the cubic zinc‐blende and hexagonal wurtzite phases in self‐catalyzed GaAs nanowires (NWs) is theoretically studied, considering the dependence of the droplet contact angle on the position at the triple‐phase line. This dependence is calculated for the droplets resting on the NW top facet, which has the shape of truncated hexagon. The nucleation of c and h islands, corresponding to the cubic and hexagonal crystal phases, at the triple‐phase line and in the center of the catalyst–NW interface, is considered within the classical nucleation theory. As a result, the probability of h‐island nucleation as a function of the average contact angle is obtained. It is found that the maximum of this probability shifts to the region of large contact angles when the length of narrow edges of the NW top facet decreases. Also, it is shown that the GaAs island nucleation at the triple‐phase line occurs preferentially in the vicinity of the top facet corners. [ABSTRACT FROM AUTHOR]

Abstract The authors report a novel structure to improve the high‐frequency performance of nitrogen‐polar GaN deep‐recess high electron mobility transistors (HEMTs) wherein a timed plasma etch was used to tailor the profile of the gate dielectric. A favourable trade‐off between gate fringing capacitance and transconductance was established, resulting in an improved current gain cutoff frequency times gate length (ft·LG) figure of merit compared to standard Schottky‐gate and metal‐insulator‐semiconductor (MIS) HEMTs. The etched gate dielectric MISHEMT demonstrated a maximum ft·LG of 15.0 GHz·µm for an LG of 100 nm.

Abstract Semiconductor wafer manufacturing relies on the precise control of various performance metrics to ensure the quality and reliability of integrated circuits. In particular, GaN has properties that are advantageous for high voltage and high frequency power devices; however, defects in the substrate growth and manufacturing are preventing vertical devices from performing optimally. This paper explores the application of machine learning techniques utilizing data obtained from optical profilometry as input variables to predict the probability of a wafer meeting performance metrics, specifically the breakdown voltage (Vbk). By incorporating machine learning techniques, it is possible to reliably predict performance metrics that cause devices to fail at low voltage. For diodes that fail at a higher (but still below theoretical) breakdown voltage, alternative inspection methods or a combination of several experimental techniques may be necessary.

Density-functional theory calculations on P-rich InP(001):H surfaces are presented. Depending on temperature, pressure and substrate doping, hydrogen desorption or adsorption will occur and influence the surface electronic properties. For p-doped samples, the charge transition levels of the P dangling bond defects resulting from H desorption will lead to Fermi level pinning in the lower half of the band gap. This explains recent experimental data. For n-doped substrates, H-deficient surfaces are the ground-state structure. This will lead to Fermi level pinning below the bulk conduction band minimum. Surface defects resulting from the adsorption of additional hydrogen can be expected as well, but affect the surface electronic properties less than H desorption.

The authors report a novel structure to improve the high‐frequency performance of nitrogen‐polar GaN deep‐recess high electron mobility transistors (HEMTs) wherein a timed plasma etch was used to tailor the profile of the gate dielectric. A favourable trade‐off between gate fringing capacitance and transconductance was established, resulting in an improved current gain cutoff frequency times gate length (ft·LG) figure of merit compared to standard Schottky‐gate and metal‐insulator‐semiconductor (MIS) HEMTs. The etched gate dielectric MISHEMT demonstrated a maximum ft·LG of 15.0 GHz·µm for an LG of 100 nm. [ABSTRACT FROM AUTHOR]

Semiconductor wafer manufacturing relies on the precise control of various performance metrics to ensure the quality and reliability of integrated circuits. In particular, GaN has properties that are advantageous for high voltage and high frequency power devices; however, defects in the substrate growth and manufacturing are preventing vertical devices from performing optimally. This paper explores the application of machine learning techniques utilizing data obtained from optical profilometry as input variables to predict the probability of a wafer meeting performance metrics, specifically the breakdown voltage (Vbk). By incorporating machine learning techniques, it is possible to reliably predict performance metrics that cause devices to fail at low voltage. For diodes that fail at a higher (but still below theoretical) breakdown voltage, alternative inspection methods or a combination of several experimental techniques may be necessary. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the structural, electronic, and optical characteristics of boron phosphide (BP) as well as Ga and In doped BP. The study employs two different density functional approximations namely, Perdew Burke Ernzerhof generalized gradient approximation (PBE-GGA) and Tran-Blaha modified Becke Johnson (TB-mBJ) approximations. The present investigation revealed that on doping, band gap of BP changes abruptly and decreases with increasing concentration of Ga and In dopants. The analysis of energy bands and density of states provides insights into the electronic structure of pure and doped boron phosphide (BP). Moreover, we have evaluated the dielectric constants, absorption coefficient, conductivity, refractive index, reflection spectra, absorbance, and transmittance spectra of pure and doped BP. Considering the close agreement between the estimated properties namely, energy gaps and optical variables with the available data, these compounds are recommended as promising candidates for optoelectronic devices. Their favourable electronic and optical characteristics make them potentially suitable for various applications in optoelectronics. [ABSTRACT FROM AUTHOR]

Au nanoparticles (NPs) were designed to be embedded into III-V semiconductors to form Au/GaAs Schottky heterostructures, which were used as top-modified cover layers for quantum dot semiconductor saturable absorption mirrors (QD-SESAMs). By harnessing the distinctive localized surface plasmon resonance (LSPR) effect exhibited by Au NPs, a remarkable enhancement in photogenerated carrier concentration is achieved at the heterojunction interface. Consequently, this leads to a significant improvement in the nonlinear optical characteristics of the device. The modulation depth (MD) and saturation fluence of the device are optimized from the initial 2.2% and 16.1 MW/cm2 to 2.8% and 8.3 MW/cm2, respectively. Based on the optimized device, a Q-switched laser has been developed with an impressive output power of 17.61 mW and a single pulse energy of 274.9 nJ. These results unequivocally showcase the exceptional advantages offered by utilizing Au NPs to optimize the nonlinear optical characteristics of III-V semiconductor devices, thereby highlighting its immense potential for practical applications in various fields. [ABSTRACT FROM AUTHOR]

Density-functional theory calculations on P-rich InP(001):H surfaces are presented. Depending on temperature, pressure and substrate doping, hydrogen desorption or adsorption will occur and influence the surface electronic properties. For p-doped samples, the charge transition levels of the P dangling bond defects resulting from H desorption will lead to Fermi level pinning in the lower half of the band gap. This explains recent experimental data. For n-doped substrates, H-deficient surfaces are the ground-state structure. This will lead to Fermi level pinning below the bulk conduction band minimum. Surface defects resulting from the adsorption of additional hydrogen can be expected as well, but affect the surface electronic properties less than H desorption. [ABSTRACT FROM AUTHOR]

The pursuit for enhanced light‐matter interactions using ever more suitable plasmonic materials has led to the development of novel bulk materials, such as ϵ‐near‐zero (ENZ) media. The ability to control the free carrier density gives semiconductors a significant advantage over traditionally used noble metals and phonon‐based materials as ENZ media for infrared applications. A metal‐ENZ‐metal structure is designed of epitaxially‐grown III‐V semiconductors and patterned into nanoantennas by electron‐beam lithography (from 200 up to 1800 nm) and demonstrates plasmonic resonances tuned from the terahertz up to the near‐infrared, according to the ENZ doping level (1 × 1016, 1 × 1019, and 2 × 1019 cm‐3). Experimental results, corroborated by numerical simulations, show that the designed metal‐ENZ‐metal structure is a promising vehicle to provide additional insights regarding ENZ‐based phenomena including the resonance pinning, the near‐constant phase, and the dispersive nature of ENZ materials. It is believed that III‐V semiconductors within a metal‐ENZ‐metal structure address the problem of weak light‐matter interactions and shall greatly benefit infrared applications, e.g., sensing and communication, as they can be engineered to take advantage of both plasmon and ENZ effects and integrated onto modern photonics devices. [ABSTRACT FROM AUTHOR]

The collection of single‐photon emission from a quantum dot (QD) in a Bragg waveguide through a photonic wire bond (PWB) via free‐space resonant frequency pumping at 1.6 K is demonstrated. The in‐fiber single photons show a small multiphoton contribution, quantified by a low second order photon autocorrelation value of gcorr(2)(0)=(5.9±0.8)×10−3$g_{{\mathrm{corr}}}^{(2)}\;(0) = ({5.9 \pm 0.8})\; \times {10^{ - 3}}$ (background‐corrected) or graw(2)(0)=(9.5±1.4)×10−2$g_{{\mathrm{raw}}}^{(2)}(0)\; = ({9.5 \pm 1.4})\; \times {10^{ - 2}}{\mathrm{\;}}$(raw data). The decay time of the QD is measured to be τ=440${\mathrm{\tau \;}} = {\mathrm{\;}}440$ ps. The PWB obviates the need for in‐cryostat alignment of the single‐photon source with an optical fiber and thus offers a route to scalable integration of quantum photonic devices in a cryogenic environment. Uniquely, the approach combines the QD‐waveguide technique, enabling resonant driving of individual QDs without the need for cross‐polarization filtering, and the PWB for deterministic, alignment‐free coupling of single‐photon sources to optical fibers. [ABSTRACT FROM AUTHOR]

Purcell‐enhanced quantum dot single‐photon emission in the telecom C‐band from InAs quantum dots inside circular Bragg grating cavities is shown. The InAs quantum dots are grown by means of molecular beam epitaxy on an InP substrate and are embedded into a quaternary In0.53Al0.23Ga0.24As membrane structure. In a post‐growth flip‐chip process with subsequent substrate removal and electron beam‐lithography, circular Bragg grating ("bullseye") resonators are defined. Micro‐photoluminescence studies of the devices at cryogenic temperatures of T=5$T = 5$ K reveal individual quantum dot emission lines into a pronounced cavity mode. Time‐correlated single‐photon counting measurements under above‐band gap excitation yield Purcell‐enhanced excitonic decay times of τ=(180±3)$\tau =(180\pm 3)$ ps corresponding to a Purcell factor of FP=(6.7±0.6)${F}_{P}=(6.7\pm 0.6)$. Pronounced photon antibunching with a background limited g(2)(0)=(0.057±0.004)${g}^{(2)}(0)=(0.057\pm 0.004)$ is observed, which demonstrates that the light originated mostly from one single quantum dot. [ABSTRACT FROM AUTHOR]

Herein, it is demonstrated that optical excitation of InAs quantum dots (QDs) embedded directly in an InP matrix can be mediated via states in a quaternary compound constituting an InP/InGaAlAs bottom distributed Bragg reflector (DBR) and native defects in the InP matrix. It does not only change the carrier relaxation in the structure but could also lead to the imbalanced occupation of QDs with charge carriers, because the band structure favors the transfer of holes. Thermal activation of carrier transfer can be observed as an increase in the emission intensity versus temperature for excitation powers below saturation on the level of both an inhomogeneously broadened QD ensemble and single QD transitions. That increase in the QD emission is accompanied by a decrease in the emission from the InGaAlAs layer at low temperatures. Finally, carrier transfer between the InGaAlAs layer of the DBR and the InAs/InP QDs is directly proven by the photoluminescence excitation spectrum of the QD ensemble. The reported carrier transfer can increase the relaxation time of carriers into the QDs and thus be detrimental to the coherence properties of single and entangled photons. It is important to take it into account while designing QD‐based devices. [ABSTRACT FROM AUTHOR]

The combination of III–V compound semiconductor materials and organic semiconductor materials to construct hybrid solar cells is a potential pathway to resolve the problems of conventional doped p–n junction solar cells, such as complexities in fabrication process and high costs. This review presents the recent progress of organic–inorganic hybrid solar cells based on polymers and III–V semiconductors, from materials to devices. The available growth process for planar/nanostructured III–V semiconductor materials, along with patterning and etching processes for nanostructured materials, are reviewed. As an emphasis of this review, advanced device structure designs are reviewed for facilitation of carrier collection and high efficiency, at planar structure level and nanowire structure level, respectively. Optimization pathways for efficiency enhancement are discussed with respect to polymer layers and surface/interface passivation, respectively. Finally, perspectives on the future development of such hybrid cells are presented. [ABSTRACT FROM AUTHOR]

In this work, 1 eV Ga0.7In0.3As inverted metamorphic (IMM) solar cells were analyzed to achieve a deeper understanding of the mechanism limiting their improvement. For this purpose, high-resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM), high-resolution cross-sectional cathodoluminescence (CL), and transient in situ surface reflectance were carried out. Additionally, the photovoltaic responses of the complete devices were measured using the external quantum efficiency (EQE) and numerically simulated through Silvaco TCAD ATLAS. The combination of structural characterization of the semiconductor layers and measurements of the solar cell photovoltaic behavior, together with device modeling, allows us to conclude that the lifetime of the bulk minority carriers is the limiting factor influencing the PV response since the recombination at the interfaces (GaInP window–GaInAs emitter and GaInAs base–GaInP back surface field (BSF)) does not impact the carrier recombination due to the favorable alignment between the conduction and the valance bands. The advanced characterization using cross-sectional cathodoluminescence, together with transient in situ surface reflectance, allowed the rejection of the formation of traps related to the GaInAs growth conditions as being responsible for the decrement in the minority-carrier lifetime. Conversely, the TEM and HRXRD revealed that the presence of misfit dislocations in the GaInAs layer linked to strain relaxation, which were probably formed due to an excessive tensile strain in the virtual substrate or an incorrect combination of alloy compositions in the topmost layers, was the dominant factor influencing the GaInAs layer's quality. These results allow an understanding of the contributions of each characterization technique in the analysis of multi-junction solar cells. [ABSTRACT FROM AUTHOR]

In recent years, III–V semiconductor nanowires have been widely investigated for infrared photodetector applications due to their direct and suitable bandgap, unique optical and electrical properties, flexibility in device design and to create heterostructures, and/or grow on a foreign substrate such as Si with more effective strain relaxation compared with planar structures. In particular, vertically aligned and ordered nanowire arrays have emerged as a promising photodetector platform, since their geometry‐related light absorption and carrier transport properties can be tailored to achieve high photodetector performance and new functionalities. In this article, the state‐of‐the‐art progress in the development of various types of infrared photodetectors based on III–V semiconductor nanowire arrays is reviewed. The nanowire synthesis/fabrication methods are introduced briefly at first, followed by discussions on the working principle and device performance of various types of nanowire array‐based photodetectors and their emerging applications. Finally, we analyze the challenges and present the perspectives for the development of future low‐cost, large‐scale, high‐performance nanowire array infrared photodetectors for practical applications. [ABSTRACT FROM AUTHOR]

III-V compound semiconductors are widely used for electronic and optoelectronic applications. However, interfacing III-Vs with other materials has been fundamentally limited by the high growth temperatures and lattice-match requirements of traditional deposition processes. Recently, we developed the templated liquid-phase (TLP) crystal growth method for enabling direct growth of shape-controlled single-crystal III-Vs on amorphous substrates. Although in theory, the lowest temperature for TLP growth is that of the melting point of the group III metal (e.g., 156.6 °C for indium), previous experiments required a minimum growth temperature of 500 °C, thus being incompatible with many application-specific substrates. Here, we demonstrate low-temperature TLP (LT-TLP) growth of single-crystalline InP patterns at substrate temperatures down to 220 °C by first activating the precursor, thus enabling the direct growth of InP even on low thermal budget substrates such as plastics and indium-tin-oxide (ITO)-coated glass. Importantly, the material exhibits high electron mobilities and good optoelectronic properties as demonstrated by the fabrication of high-performance transistors and light-emitting devices. Furthermore, this work may enable integration of III-Vs with silicon complementary metal-oxide-semiconductor (CMOS) processing for monolithic 3D integrated circuits and/or back-end electronics.

Abstract Experimental data on analog performance of gate‐all‐around III‐V vertical Tunnel Field‐Effect Transistors (TFETs) and circuits are presented. The individual device shows a minimal subthreshold swing of 44 mV/dec and transconductance efficiency of 50 V−1 for current range of 9 nA/μm to 100 nA/μm and at a drain voltage of 100 mV. This TFET demonstrates translinearity between transconductance and drain current for over a decade of current, paving way for low power current‐mode analog IC design. To explore this design principle, a current conveyor circuit is implemented, which exhibits large‐signal voltage gain of 0.89 mV/mV, current gain of 1nA/nA and an operating frequency of 320 kHz. Furthermore, at higher drain bias of 500 mV, the device shows maximum transconductance of 72 μS/μm and maximum drain current of 26 μA/μm. The device, thereby, can be operated as a current mode device at lower bias voltage and as voltage mode device at higher bias voltage.

We report the effect of the quantum dot aspect ratio on the sub‐gap absorption properties of GaAs/AlGaAs quantum dot intermediate band solar cells. We have grown AlGaAs solar cells containing GaAs quantum dots made by droplet epitaxy. This technique allows the realization of strain‐free nanostructures with lattice matched materials, enabling the possibility to tune the size, shape, and aspect ratio to engineer the optical and electrical properties of devices. Intermediate band solar cells have been grown with different dot aspect ratio, thus tuning the energy levels of the intermediate band. Here, we show how it is possible to tune the sub‐gap absorption spectrum and the extraction of charge carriers from the intermediate band states by simply changing the aspect ratio of the dots. The tradeoff between thermal and optical extraction is in fact fundamental for the correct functioning of the intermediate band solar cells. The combination of the two effects makes the photonic extraction mechanism from the quantum dots increasingly dominant at room temperature, allowing for a reduction of the open circuit voltage of only 14 mV, compared to the reference cell. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a low‐cost, stable photovoltaic market contributor which is approaching its single‐junction theoretical efficiency limit. To further elevate the efficiency of crystalline Si (c‐Si) afterward, Si solar cells (SCs) need a proper top cell absorber in Si tandem SCs. Herein, the top cell absorber is studied by evaluating their current state of the art, the existing challenges, and possible future solutions which can enhance their efficiency. The progress of perovskite/Si tandem SC both for monolithic and four terminals is exceptional but still many challenges limit their commercialization. In view of these challenges, the relative's solutions are prescribed in detail to make possible their realization. III–V semiconductors being mature candidates still face a growth/fabrication problem, which makes them a costly option for III–V/Si tandem SCs. Effective growth strategies along with technical solutions are discussed in detail. Emerging chalcogenides are considered the future of tandem technology. Recent developments in the chalcogenides/Si tandem SC are highlighted and the possible options are presented. In the end, a short note is given on the near future tandem materials for Si tandem SCs. [ABSTRACT FROM AUTHOR]

A systematic study of spin‐dependent recombination (SDR) under steady‐state optical pumping conditions as a function of nitrogen content, x, in dilute nitride alloys of the form GaAs1−xNx is reported. Use of high‐excitation power densities up to 107 W cm−2 allows measurement of the full SDR versus power curves, even at relatively high nitrogen contents of x = 0.039. Alloy contents for 0.022≤x≤0.039 are determined within δx = ±0.005 by fitting the photoluminescence (PL) spectra using a Roosbroeck–Shockley relation, and values consistent with those obtained by studying the intensity of the GaN‐like LO2 Raman mode are found. PL intensity increases by a factor known as the SDR ratio when switching from linearly to circularly polarized pump excitation. This factor reaches 5 for x = 0.022 and decreases with increasing x, falling to 1.5 for x = 0.039. Moreover, the excitation power required for maximum SDR increases with increasing x, varying from 0.6 mW for x = 0.022 to 15 mW for x = 0.039. These observations indicate an increase in the density of electronically active defects with increasing nitrogen content, both responsible for the SDR and other, standard Shockley–Read–Hall centers. The result demonstrates the importance of including nonspin‐dependent recombination channels in a complete model of SDR. [ABSTRACT FROM AUTHOR]

Reverse biasing triple-junction GaInP/Ga(In)As/Ge solar cells may affect their performance by the formation of permanent shunts even if the reverse breakdown voltage is not reached. In previous works, it was observed that, amid the three components, GaInP subcells are more prone to degrade when reverse biased suffering permanent damage, although they present an initial good performance. The aim of this work is, firstly, to study the characteristics of the defects that cause the catastrophic failure of the devices. For this, GaInP isotype solar cells were analysed by visual inspection and electroluminescence maps and submitted to reverse bias stress test. We find that specific growth defects (i.e. hillocks), when covered with metal, cause the degradation in the cells. SEM cross-section imaging and EDX compositional analysis of these defects reveal their complex structures, which in essence consist of material abnormally grown on and around particles present on the wafer surface before growth. The reverse bias stress test is proposed as a screening method to spot defects hidden under the metal that may not be detected by conventional screening methods. By applying a quick reverse bias stress test, we can detect those defects that cause the degradation of devices at voltages below the breakdown voltage and that may also affect their long-term reliability. • Application of reverse bias stress tests to GaInP isotype solar cells. • Degradation of devices that seem to be healthy according to their initial I-V curve. • Detection of the type of defect responsible for the degradation at reverse bias. • Physical explanation of the possible failure mechanism at the defects. • A reverse bias stress test is proposed as a screening process to spot these defects. [ABSTRACT FROM AUTHOR]

Au nanoparticles (NPs) were designed to be embedded into III-V semiconductors to form Au/GaAs Schottky heterostructures, which were used as top-modified cover layers for quantum dot semiconductor saturable absorption mirrors (QD-SESAMs). By harnessing the distinctive localized surface plasmon resonance (LSPR) effect exhibited by Au NPs, a remarkable enhancement in photogenerated carrier concentration is achieved at the heterojunction interface. Consequently, this leads to a significant improvement in the nonlinear optical characteristics of the device. The modulation depth (MD) and saturation fluence of the device are optimized from the initial 2.2% and 16.1 MW/cm2 to 2.8% and 8.3 MW/cm2, respectively. Based on the optimized device, a Q-switched laser has been developed with an impressive output power of 17.61 mW and a single pulse energy of 274.9 nJ. These results unequivocally showcase the exceptional advantages offered by utilizing Au NPs to optimize the nonlinear optical characteristics of III-V semiconductor devices, thereby highlighting its immense potential for practical applications in various fields.