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κ-Ga2O3 has been predicted to be a potential ferroelectric material. In this work, undoped Ga2O3 films were grown by either plasma-enhanced atomic layer deposition (PEALD) or metal organic chemical vapor deposition (MOCVD) on platinized sapphire substrates. 50 nm thick PEALD films with a mixture of κ-Ga2O3 and β-Ga2O3 had a relative permittivity of ∼27, a loss tangent below 2%, and high electrical resistivity up to ∼1.5 MV/cm. 700 nm thick MOCVD films with predominantly the κ-Ga2O3 phase had relative permittivities of ∼18 and a loss tangent of 1% at 10 kHz. Neither film showed compelling evidence for ferroelectricity measured at fields up to 1.5 MV/cm, even after hundreds of cycles. Piezoresponse force microscopy measurements on bare κ-Ga2O3 showed a finite piezoelectric response that could not be reoriented for electric fields up to 1.33 MV/cm. [ABSTRACT FROM AUTHOR]

Site- and polarity-controlled core–shell InGaN/GaN nanorod LED structures were grown by metal organic vapor phase epitaxy on Si(111). Scanning transmission electron microscope images reveal uniform multiple quantum wells on polarization-free sidewalls. Spatially resolved photoluminescence mapping on a single nanorod demonstrates that the emission at 3.0 eV stems from the polarization-free m-plane, which is supported by a fast recombination lifetime of ∼490 ps at low temperatures. Quasi-resonant laser excitation demonstrates predominant radiative recombination at low excitation densities, whereas at high excitation densities, the efficiency is lowered by Auger recombination and/or carrier leakage. [ABSTRACT FROM AUTHOR]

The cooling requirement for long-wave infrared detectors still creates significant limitations to their functionality. The phenomenon of minority-carrier exclusion and extraction in narrow-gap semiconductors has been intensively studied for over three decades and used to increase the operating temperatures of devices. Decreasing free carrier concentrations below equilibrium values by a stationary non-equilibrium depletion of the device absorber leads to a suppression of Auger generation. In this paper, we focus on analyzing exclusion and extraction effects separately, based on experimental and theoretical results for a HgCdTe photodiode. To carry out an experiment, the n+-P+-π-N+ heterostructure was grown by metal organic chemical vapor deposition on CdTe-buffered GaAs substrate. In order to separate the extraction and exclusive junctions, three different devices were evaluated: (1) a detector etched through the entire n+-P+-π-N+ heterostructure, (2) a detector made of the P+-π photoconductive junction and (3) a detector made of the π-N+ photodiode junction. For each device, the dark current density–voltage characteristics were measured at a high-temperature range, from 195 K to 300 K. Next, the carrier concentration distribution across the entire heterostructure and individual junctions was calculated using the APSYS simulation program. It was shown that when the n+-P+-π-N+ photodiode is reverse biased, the electron concentration in the π absorber drops below its thermal equilibrium value, due to the exclusion effect at the P+-π junction and the extraction effect at the π-N+ junction. To maintain the charge neutrality, the hole concentration is also reduced below the equilibrium value and reaches the absorber doping level (NA), leading to the Auger generation rate's reduction by a factor of 2ni/NA, where ni is the intrinsic carrier concentration. Our experiment conducted for three separate detectors showed that the exclusion P+-π photoconductive junction has the most significant effect on the Auger suppression—the majority of the hole concentration drops to the doping level not only at the P+-π interface but also deep inside the π absorber. [ABSTRACT FROM AUTHOR]

We investigate experimentally and theoretically the impact of valence band mixing and spectrum of confined states on the polarization of light emitted from or absorbed by GaAs/AlGaAs semiconductor quantum dots and quantum wires with tailored heterostructure potential. In particular, such nanostructures with parabolic-profile confinement potentials, realized by organometallic vapor phase epitaxy inside pyramidal pits, served as model systems for the study. Different degrees of linear polarization (DOLP) of emitted light, depending on the confinement potential profile, the specific excitonic transition, and the level of excitation, are observed. A theoretical model shows that, besides the impact of valence band mixing, the overlap of conduction and valence band wavefunctions as well as state occupation probability and broadening of transitions determine the DOLP. The conclusions are useful for the design of quantum light emitters with controlled polarization properties. [ABSTRACT FROM AUTHOR]

The large polarization barriers between the quantum wells and quantum barriers in long-wavelength GaN-based light-emitting diodes (LEDs) inhibit their performance by requiring excess driving voltages to reach standard operating current densities. Lateral injection of carriers directly into quantum wells is required to circumvent this issue. V-defects are naturally occurring inverted hexagonal defects with semipolar 10 1 ¯ 1 -plane sidewalls generated on surface depressions from threading dislocations. LEDs engineered to intentionally generate V-defects below the active region of the LED can achieve lateral carrier injection through the V-defect sidewalls and have already been able to demonstrate world record wall-plug efficiencies for LEDs in the green-red wavelengths. V-defects can be enlarged during kinetically limited growth where the growth rate of the c-plane GaN is faster than that of their sidewalls, leaving them unfilled. We report on the metal organic chemical vapor deposition growth conditions required to fill in V-defects with p-GaN during epitaxial growth of the LED post the active region. Circular transmission length measurements of Pd/Au contacts processed on p-GaN surfaces with various amounts of unfilled V-defects showed no significant difference in their sheet resistance and specific contact resistance. J–V measurements of LEDs grown with varying unfilled V-defect densities showed no significant difference in the forward bias regime. However, in the reverse bias regime, catastrophic breakdown occurred at markedly lower voltages for samples with larger unfilled V-defect densities. This suggests that unfilled V-defects may act as hotspots for device failure, and planarizing LED surfaces may help prevent early degradation of LED devices. [ABSTRACT FROM AUTHOR]

This document provides a calendar of events for May, June, July, and August 2024. The events listed include conferences, workshops, symposiums, and fairs related to various topics such as metal and metallurgy, corrosion protection, nuclear security, non-destructive testing, and materials science. The events are taking place in different countries around the world, including China, Qatar, Germany, Belgium, Austria, Portugal, USA, South Korea, Turkey, Italy, Bulgaria, and Canada. These conferences offer opportunities for researchers and professionals to exchange knowledge and discuss advancements in their respective fields. [Extracted from the article]

A significant part of the present and future of optoelectronic devices lies on thin multilayer heterostructures. Their optical properties depend strongly on strain, being essential to the knowledge of the stress level to optimize the growth process. Here the structural and microstructural characteristics of sub‐micron a‐ZnO epilayers (12 to 770 nm) grown on r‐sapphire by metal–organic chemical vapour deposition are studied. Morphological and structural studies have been made using scanning electron microscopy and high‐resolution X‐ray diffraction. Plastic unit‐cell distortion and corresponding strain have been determined as a function of film thickness. A critical thickness has been observed as separating the non‐elastic/elastic states with an experimental value of 150–200 nm. This behaviour has been confirmed from ultraviolet photoelectron spectroscopy, X‐ray photoelectron spectroscopy and high‐resolution transmission electron microscopy measurements. An equation that gives the balance of strains is proposed as an interesting method to experimentally determine this critical thickness. It is concluded that in the thinnest films an elongation of the Zn—O bond takes place and that the plastic strained ZnO films relax through nucleation of misfit dislocations, which is a consequence of three‐dimensional surface morphology. [ABSTRACT FROM AUTHOR]

In this study, the effect of implementing island growth in an AlN/Al0.1Ga0.9N superlattice on the structural properties of vertical GaN‐on‐Si(111) PIN‐structures is investigated. It is demonstrated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) that islands are formed on‐top of V‐pits present in the AlN nucleation layer and that the island coalescence height can be controlled by the growth temperature. Defect selective etching analyses confirm a noteworthy reduction in the threading dislocation density (TDD), which diminishes from 1.2 × 109 cm−2 ± 7.5 × 107 cm−2 to 8.5 × 108 cm−2 ± 7.3 ×107 cm−2 as the island coalescence height increases from ≈160 nm to ≈450 nm, achieved by increasing the growth temperature. Cross‐sectional transmission electron microscopy (TEM) shows that island growth is particularly favorable for the reduction of a‐type dislocations. As a consequence of the significant reduction of a‐type dislocations in the buffer, stress relaxation during the GaN film growth is reduced, which is supported by in situ wafer curvature measurements and high‐resolution X‐ray diffraction (XRD). Owing to the optimized island growth conditions, thick and crack‐free GaN layers on Si(111) substrates are obtained with an absolute wafer bow of <50 μm. [ABSTRACT FROM AUTHOR]

High crystalline quality and flat a‐plane aluminum gallium nitride (AlGaN) films are obtained on Si‐doped AlN templates with a moderate silane (SiH4) flow rate by metal‐organic chemical vapor deposition (MOCVD). The effects of the SiH4 flow rate on the surface morphology, crystalline quality, stress state, and optical property of a‐plane AlN templates and AlGaN films are comprehensively investigated. As the SiH4 flow rate increases from 0 to 7.0 nmol min−1, the full width at half maximum of X‐ray rocking curve values along [0001]/[1–100] directions for the AlGaN films are monotonically reduced to 1124/1143 arcsec. Meanwhile, the surface root mean square roughness value is decreased to 0.88 nm. These achievements are attributed to the suppression of the anisotropy degrees and in‐plane stress of AlN templates. In addition, an excess SiH4 flow rate leads to deteriorated surface morphologies and increased basal plane stacking fault (BPSF) densities for both AlN and AlGaN films. This work suggests that doping AlN layers with an appropriate SiH4 flow rate is a promising route to obtain high‐quality a‐plane AlGaN films for efficient nonpolar deep ultraviolet (DUV) devices. [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]

AlGaN-based LEDs are promising for many applications in deep ultraviolet fields, especially for water-purification projects, air sterilization, fluorescence sensing, etc. However, in order to realize these potentials, it is critical to understand the factors that influence the optical and electrical properties of the device. In this work, AlxGa1−xN (x = 0.24, 0.34, 0.47) epilayers grown on c-plane patterned sapphire substrate with GaN template by the metal organic chemical vapor deposition (MOCVD). It is demonstrated that the increase of the aluminum content leads to the deterioration of the surface morphology and crystal quality of the AlGaN epitaxial layer. The dislocation densities of AlxGa1−xN epilayers were determined from symmetric and asymmetric planes of the ω-scan rocking curve and the minimum value is 1.01 × 109 cm−2. The (10 1 ¯ 5) plane reciprocal space mapping was employed to measure the in-plane strain of the AlxGa1−xN layers grown on GaN. The surface barrier heights of the AlxGa1−xN samples derived from XPS are 1.57, 1.65, and 1.75 eV, respectively. The results of the bandgap obtained by PL spectroscopy are in good accordance with those of XRD. The Hall mobility and sheet electron concentration of the samples are successfully determined by preparing simple indium sphere electrodes. [ABSTRACT FROM AUTHOR]

The document is a comprehensive list of upcoming conferences, workshops, and fairs related to materials science and engineering. These events cover a wide range of topics and are held in various countries around the world. They provide opportunities for researchers and professionals to share knowledge and discuss advancements in their respective fields. Some of the topics covered include thin film technologies, paint expo, tube technology, surfaces and coatings technologies, physics of reactors, thermal spray, metal and metallurgy exhibition, corrosion science, nuclear security, precision optics, additive manufacturing, corrosion, sustainable development, and electrochemistry. [Extracted from the article]

Quantum dots are promising candidates for telecom single photon sources due to their tunable emission across the different low-loss telecommunications bands, making them compatible with existing fiber networks. Their suitability for integration into photonic structures allows for enhanced brightness through the Purcell effect, supporting efficient quantum communication technologies. Our work focuses on InAs/InP QDs created via droplet epitaxy MOVPE to operate within the telecoms C-band. We observe a short radiative lifetime of 340 ps, arising from a Purcell factor of 5, owing to integration of the QD within a low-mode-volume photonic crystal cavity. Through in-situ control of the sample temperature, we show both temperature tuning of the QD's emission wavelength and a preserved single photon emission purity at temperatures up to 25K. These findings suggest the viability of QD-based, cryogen-free C-band single photon sources, supporting applicability in quantum communication technologies. [ABSTRACT FROM AUTHOR]

Based on metal organic chemical vapor deposition (MOCVD), growth mechanism and stress modulation of van der Waals (vdW) heteroepitaxial GaN microwave material were studied with few-layer BN as an interlayer on 4-inch sapphire substrates. The influence of AlN nucleate process on growth mechanism of GaN buffer layer and its correlation with crystalline quality, stress, and electrical properties were discussed. A stress modulation scheme based on AlN/ AlGaN composite nucleation process is proposed, achieving stress well in control for large-size vdW heteroepitaxy firstly. The as-grown GaN microwave material possesses a wafer bow of + 20. 4 μm, fullwidth at half maximum of GaN (002) / (102) peaks of 471. 6/933. 5 arcsec, root-mean-square roughness of 0. 52 nm and electron mobility of 2 000 cm² / (V·s). Finally, largesize wafe-scale GaN microwave material was successfully separated from sapphire substrate by a mechanical lift-off process, providing convenience for transfering to high thermal conductivity substrates and creating conditions for fabricating high-power RF devices. [ABSTRACT FROM AUTHOR]

The document is a comprehensive list of upcoming conferences and events related to materials science, engineering, and technology. It includes conferences in various locations around the world, covering topics such as structural health monitoring, additive manufacturing, corrosion, and sustainable development. The document provides contact information and website links for each conference, allowing library patrons to access further information if desired. [Extracted from the article]

Using gas-phase deposition (Physical Vapor Deposition (PVD) and Metal Organic Chemical Vapor Deposition (MOCVD)) methods, modern implant samples (Ti alloy and CFR-PEEK polymer, 30% carbon fiber) were functionalized with film heterostructures consisting of an iridium or gold sublayer, on the surface of which an antibacterial component (silver) was deposited: Ag/Ir(Au)/Ti(CFR-PEEK). The biocidal effect of the heterostructures was investigated, the effect of the surface relief of the carrier and the metal sublayer on antibacterial activity was established, and the dynamics of silver dissolution was evaluated. It has been shown that the activity of Ag/Ir heterostructures was due to high Ag+ release rates, which led to rapid (2–4 h) inhibition of P. aeruginosa growth. In the case of Ag/Au type heterostructures, the inhibition of the growth of P. aeruginosa and S. aureus occurred more slowly (from 6 h), and the antibacterial activity appeared to be due to the contribution of two agents (Ag+ and Au+ ions). It was found, according to the in vitro cytotoxicity study, that heterostructures did not exhibit toxic effects (cell viability > 95–98%). An in vivo biocompatibility assessment based on the results of a morphohistological study showed that after implantation for a period of 30 days, the samples were characterized by the presence of a thin fibrous capsule without volume thickening and signs of inflammation. [ABSTRACT FROM AUTHOR]

PN junction with p-Si / n-Ga2O3 structure was developed by metal organic chemical vapor deposition (MOCVD) technology on p-type Si (111) substrate. The crystal structure, surface morphology and surface roughness were measured by X-ray diffractometer and atomic force microscope. Then Ti / Au electrodes on these samples were developed by magnet sputtering and evaporation for testing the PN junction characteristics such as I-V curve chart, threshold voltage, on-off current ratio, reverse saturation current, ideal factor, and the barrier height at zero bias voltage. The regulation of PN junction characteristics with growing parameters such as doping concentration and film thickness was studied, and the reasons were given. The crystal quality of β-Ga2O3 thin film and the characteristics of the devices were improved by two-step growing method. A set of PN junction samples were fabricated at three different temperatures when the buffer was developed. Finally, the best conditions of fabricating the PN junction devices was found, and the lattice mismatch and thermal mismatch between Si substrate and β-Ga2O3 thin film were reduced. A high quality n-type β-Ga2O3 thin film with surface roughness of 4. 21 nm and a PN junction with low ideal factor of 42. 1 was obtained. [ABSTRACT FROM AUTHOR]

The document is a comprehensive list of upcoming conferences and events related to materials science, corrosion, and various other topics. These events will be held in different countries around the world, providing opportunities for researchers and professionals to gather and exchange knowledge. The topics covered in these events are diverse, ranging from industrial computed tomography to nuclear security. The document includes contact information and website links for each event, making it easy for library patrons to access further information. [Extracted from the article]

Combining its unique features of ultrawide bandgap (UWBG) and two-dimensional nature, h-BN has been explored for emerging applications such as deep ultraviolet optoelectronic devices and single photon emitters. One of the unusual applications of h-BN is for solid-state neutron detectors by utilizing the property of high thermal neutron capture cross section of B-10 as well as its UWBG properties. Although a record high detection efficiency of 59% has been attained by h-BN detectors, the understanding/minimization of defects and impurities is still needed to further advance the h-BN material and detector technologies. We report metal organic chemical vapor deposition growth and oxygen (O) impurity diffusion in thick h-BN. The diffusion coefficient (D) of O impurities has been measured via the evolution of an oxygen related emission with the etching depth, providing a value of D of ∼ 2 × 10−13 cm2/s at 1450 °C and supporting the interpretation that oxygen in h-BN is a substitutional donor. A multiple-buffer-layer approach was employed to mitigate to a certain degree the issue of oxygen diffusion from sapphire substrate during growth. It was demonstrated that the performance of h-BN neutron detectors fabricated from the wafer incorporating multiple buffer layers was significantly improved, as manifested by the enhanced thermal neutron detection efficiency. The advancement of the crystal growth technology of h-BN semi-bulk crystals creates applications in optoelectronic and power electronic devices utilizing the UWBG semiconductor properties of h-BN, while high efficiency h-BN neutron detectors have the potential to supplant the traditional He-3 gas detectors in various application areas by offering the obvious advantages of UWBG semiconductor technologies. [ABSTRACT FROM AUTHOR]

Large-area epitaxial growth of III–V nanowires and thin films on van der Waals substrates is key to developing flexible optoelectronic devices. In our study, large-area InAs nanowires and planar structures are grown on hexagonal boron nitride templates using metal organic chemical vapor deposition method without any catalyst or pre-treatments. The effect of basic growth parameters on nanowire yield and thin film morphology is investigated. Under optimised growth conditions, a high nanowire density of 2.1 × 109 cm−2 is achieved. A novel growth strategy to achieve uniform InAs thin film on h-BN/SiO2/Si substrate is introduced. The approach involves controlling the growth process to suppress the nucleation and growth of InAs nanowires, while promoting the radial growth of nano-islands formed on the h-BN surface. A uniform polycrystalline InAs thin film is thus obtained over a large area with a dominant zinc-blende phase. The film exhibits near-band-edge emission at room temperature and a relatively high Hall mobility of 399 cm−2/(Vs). This work suggests a promising path for the direct growth of large-area, low-temperature III–V thin films on van der Waals substrates. [ABSTRACT FROM AUTHOR]

Spin polarized photocathodes are key to the future operation of electron accelerators such as the ones at Thomas Jefferson National Accelerator Facility and Brookhaven National Laboratory. Currently, these photocathodes come in short supply due to limited production by molecular beam epitaxy. By developing a process to implement similar structures using metal organic chemical vapor deposition, the availability of these devices can be increased. In this paper, we detail the implementation of recent photocathode advancements via metal organic chemical vapor deposition process and show an improvement in both polarization and quantum efficiency of our devices compared to those fabricated via molecular beam epitaxy, with devices reaching 82% polarization and 2.9% quantum efficiency. [ABSTRACT FROM AUTHOR]

Under vacuum environment, an H interstitial must exist when Ga2O3 is prepared by organometallic chemical vapor deposition. However, few first‐principles systematic studies have been conducted on the influences of point vacancies (VGa, Hi) on the photocatalytic performance and magnetism of Ga2O3:(Li or Na or K) systems, and VGa is a challenge in experiments. Therefore, the first‐principles generalized gradient approximation GGA + U theory is adopted in this study. A first‐principles study is conducted on the formation energy (Ef), photocatalytic performance, and magnetism of Ga30MO48 (M = Li or Na or K) and Ga30MHiO48 systems. In the results, it is shown that under Ga‐poor conditions, the Ga30MO48 and Ga30MHiO48 systems are structurally stable and prone to doping. The Ga30MHiO48 system has lower Ef, more structural stability, and easier doping than the Ga30MO48 system. The Ga30KO48 system exhibits magnetism, mainly generated by the O1−‐2p spin‐polarized wandering electrons near VGa. The spin‐polarized O2−‐2p and Ga‐4s states near VGa contribute to the hybrid coupling double‐exchange interaction. Moreover, the visible spectrum of the Ga30LiHiO48 system exhibits a significant redshift, a relatively high carrier activity, carrier separation, and relative maximum lifetime. It is relatively best as a photocatalyst. [ABSTRACT FROM AUTHOR]

In the flexible photovoltaic (PV) industry, increment of the metal‐organic chemical vapor deposition (MOCVD) deposition zone is crucial to reducing the cost of ownership and increasing the power conversion efficiency (PCE). This implies that the larger closed coupled showerhead (CCS) of MOCVD system should be used in the manufacture of flexible gallium arsenide (GaAs) PV thin‐film solar cells. Currently, Aixtron Crius II is the largest commercial CCS reactor for GaAs deposition with 55 × 2 inches circular wafers. As the size of the carrier and showerhead increases, the deposition uniformity and gas flow stability become more difficult to control. To address these issues, previous studies have investigated the effects of geometric and process parameters of MOCVD on the vertical process gas inlet, with either a rotating carrier model represented by Veeco using high‐speed rotating carrier (Turbo Disc), and Aixtron using low‐speed rotating planetary carrier, or a horizontal process gas injector with a rotating carrier. However, these efforts have limited further capacity scale‐up. In this study, numerical simulations and fluid visualization experiments are conducted, based on previous research on thermal uniformity, for design optimization of a gas distribution system in a large square GaAs‐MOCVD reactor. The achieved reactor capacity is 36 × 4 inches square wafers in one process cycle, and the optimal average deposition rate and deposition uniformity of GaAs film are ≈0.430 µm min−1 and 0.93%, respectively. [ABSTRACT FROM AUTHOR]

The trivalent terbium ion (Tb3+) emits ultra-stable visible light consisting of blue, green, yellow, and red. Tb-doped semiconductors are candidates for novel full-color light sources in next-generation displays. Particularly, Tb-doped AlxGa1−xN (AlxGa1−xN:Tb) has attracted much attention for device applications. We present the luminescence properties of AlxGa1−xN:Tb grown by the organometallic vapor phase epitaxy. At 15 K, emission related to the 5D4–7FJ (J = 3, 4, 5, 6) transitions is observed for AlxGa1−xN:Tb with x ≥ 0.03. Thermal quenching of emission originating from the 5D4–7FJ transition is suppressed for higher Al compositions, and the luminescence is clearly observed at room temperature for AlxGa1−xN:Tb with x ≥ 0.06. The small thermal quenching is attributed to the enhanced excitation to the 5D4 level of Tb3+ ions via the 4f–5d transition and not due to the suppression of energy back-transfer paths in excited Tb3+ ions. Although additional emission originating from the 5D3–7FJ transitions is observed at 15 K for AlxGa1−xN:Tb with x ≥ 0.15, it is not observed at room temperature because the excitation to the 5D3 level via the 4f–5d transition is less efficient at high temperature. For Al0.15Ga0.85N:Tb, monochromatic green light is demonstrated using a SiO2/ZrO2 distributed Bragg reflector. [ABSTRACT FROM AUTHOR]

Metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are two versatile growth techniques that can readily produce multilayer structures with atomic-level precision control, which have found broad applications in technology. However, compared to MBE, MOCVD growth involves the surface reaction of metal-organic precursor compounds, which changes during film deposition. Consequently, a thorough investigation on the chemical profile layer-by-layer is critical for optimizing MOCVD film performance. Here, we examine Sb segregation in an MOCVD-grown InAs/InAs1−xSbx superlattice by analyzing composition and lattice strain at atomic resolution using scanning transmission electron microscopy and compare with the previously reported MBE growth results. Our findings show a different Sb profile along the growth direction in MOCVD, with the segregation coefficient being higher at the InAsSb-on-InAs interface (0.807 ± 0.021) than at the InAs-on-InAsSb interface (0.695 ± 0.009), giving rise to asymmetric composition and lattice strain profiles unlike those obtained with MBE. Furthermore, we obtain direct evidence of Sb clusters with size of ∼1–3 nm and Sb ordering within the InAs1−xSbx layer, which is largely absent in the reported MBE growth. These findings demonstrate the concurrent interplay between surface segregation, surface reconstruction, and surface reaction that is unique to MOCVD growth with broad implications on preparing Sb-containing quantum materials. [ABSTRACT FROM AUTHOR]

A high-quality β-Ga2O3 film was grown on a (111) GaAs substrate using the metal organic chemical vapor deposition method. The band alignment of the β-Ga2O3/GaAs heterojunction interface was determined by x-ray photoelectron spectroscopy. The energy-band structure of β-Ga2O3/GaAs was constructed based on the binding energies of Ga 3d and As 3d core levels as well as valence band maximum values. The valence band offset was determined to be 3.50 ± 0.05 eV. As a consequence, a type-ΙΙ heterojunction with a conduction band offset of 0.12 ± 0.05 eV was determined in the present study. The accurate determination of the band alignment of the β-Ga2O3/GaAs heterojunction provided useful information for the application in β-Ga2O3/GaAs-based devices. [ABSTRACT FROM AUTHOR]

Reduction in the size, weight, and power (SWaP) consumption of an infrared (IR) detection system is one of the critical challenges lying ahead for the development of IR detector technology, especially for mid-/long-wavelength IR wave bands, which calls for high operating temperature (HOT) IR photodetectors (PDs) with good sensitivity that would ease the burden for cooling systems. Emerging as strong competitors to HgCdTe detectors, antimonide (Sb)-based IR PDs and focal plane array (FPA) imagers have gradually stepped into real-world applications after decades of development thanks to their outstanding material properties, tunability of cutoff wavelengths, feasibility of device designs, and great potential for mass production with low costs. Meanwhile, the emerging demands of versatile applications seek fast, compact, and smart IR detection systems, in which the integration of Sb-based IR PDs on a Si platform enables direct information readout and processing with Si-based microelectronics. This paper reviews recent progress in Sb-based HOT IR PDs and FPAs, including the fundamental material properties and device designs based on bulk InAsSb, InAs/GaSb, and InAs/InAsSb type-II superlattices, together with the cutting-edge performance achieved. This work also covers new trends of development in Sb-based IR PDs, such as optical engineering for signal harvesting, photonic integration techniques, as well as metal organic chemical vapor deposition growth of antimonides. Finally, challenges and possible solutions for future studies are provided from the perspectives of material growth, device design, and imaging systems. New advances in response to these existing challenges may cast light on designs and strategies for achieving HOT devices at thermoelectric cooling temperatures (yet with lower costs), and more extensive emerging applications may be found. [ABSTRACT FROM AUTHOR]

We report high-quality Ga2O3 grown on an AlGaN/AlN/Sapphire in a single growth run in the same Metal Organic Chemical Vapor Deposition reactor with an AlOx interlayer at the Ga2O3/AlGaN interface. AlOx interlayer was found to enable the growth of single crystalline Ga2O3 on AlGaN in spite of the high lattice mismatch between the two material systems. The resulting nitride/oxide heterogenous heterostructures showed superior material qualities, which were characterized by structural, electrical, and optical characterization techniques. In particular, a significant enhancement of the electron mobility of the nitride/oxide heterogenous heterostructure is reported when compared to the individual electron mobilities of the Ga2O3 epilayer on the sapphire substrate and the AlGaN/AlN heterostructure on the sapphire substrate. This enhanced mobility marks a significant step in realizing the next generation of power electronic devices and transistors. [ABSTRACT FROM AUTHOR]

Spray parameters were fixed to depositing a MCrAlY coating by HVOF process on IN-708 substrate. The deposited coatings exhibited a microstructure with characteristic splats and β and γ phases. An MOCVD process was subsequently carried out to deposit a thin alumina layer on the sprayed MCrAlY coating. Cyclic oxidation tests were conducted at high temperature on the alumina/MCrAlY coating system. Both SEM and XRD analyses were used to characterize the thermally grown oxide after cyclic oxidation. A kinetic analysis was done to determinate the behaviour of the alumina/MCrAlY coating system during oxidation. [ABSTRACT FROM AUTHOR]

Among semiconductor metal oxides, that are an important class of sensing materials, titanium dioxide (TiO2) thin films are widely employed as sensors because of their high chemical and mechanical stability in harsh environments, non-toxicity, eco-compatibility, and photocatalytic properties. TiO2-based chemical oxygen demand (COD) sensors exploit the photocatalytic properties of TiO2 in inducing the oxidation of organic compounds to CO2. In this work, we discuss nanostructured TiO2 thin films grown via low-pressure metal organic chemical vapor deposition (MOCVD) on metallic AISI 316 mesh. To increase the surface sensing area, different inorganic acid-based chemical etching protocols have been developed, determining the optimal experimental conditions for adequate substrate roughness. Both chemically etched pristine meshes and the MOCVD-coated ones have been studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) microanalysis, and X-ray photoelectron spectroscopy (XPS). We demonstrate that etching by HCl/H2SO4 at 55 °C provides the most suitable surface morphology. To investigate the behavior of the developed high surface area TiO2 thin films as COD sensors, photocatalytic degradation of functional model pollutants based on ISO 10678:2010 has been tested, showing for the best performing acid-etched mesh coated with polycrystalline TiO2 an increase of 60% in activity, and degrading 66 µmol of MB per square meter per hour. [ABSTRACT FROM AUTHOR]

In this paper, we report light ion (H+) implantation-induced effect on a-plane GaN epitaxial layer on the sapphire substrate. Non-polar (NP) a-plane GaN (11–20) epitaxial layer is grown on an r-plane sapphire substrate by the metal–organic chemical vapour deposition (MOCVD) technique. The H+ ion-implanted NP (11–20) GaN epitaxial layer (dose 1 × 1017 cm−2 and 170 keV energy) is annealed by the rapid thermal annealing (RTA) process. The un-implanted a-GaN, H+ ion-implanted and annealed samples are investigated structurally and optically by High-resolution X-ray diffraction (HRXRD), Atomic force microscopy (AFM), Raman spectroscopy and Emission characterisation techniques. HRXRD analysis infers that implanted GaN sample is hydrostatically strained up to implanted depth. Raman scattering study by green laser excitation found defect-activated Raman scattering (DARS) due to lattice distortion by ion implantation in the implanted sample and annealed out partially after annealing. The Raman peak intensity ratio between the E2 (high) and LO peak of the above bandgap excited laser (~ 266 nm) was around 3.92 in the un-implanted GaN layer whilst after implantation, the ratio was reduced to ~ 0.97 because implantation induces the defect-activated centre which increased the LO peak intensity. After annealing, the ratio between E2 (high) and LO peak was increased by ~ 2.5. After annealing due to partial recovery and reduction in the implantation-induced defected activated centre, the a-plane GaN thin layer can be transferred to the other substrate easily by exfoliation or ion-cutting process and can be used in electronics and optoelectronic devices. [ABSTRACT FROM AUTHOR]

- 7.3.New Orleans, LA (USA)AMPP Annual Conference + Expo 2024Association for Materials Protection and PerformanceHouston, TexasUSALesley.Martinez@ampp.org12. + 27.2.Oberhof(Germany)& online6th European Symposium on Friction, Wear and Wear ProtectionFriction 2024German Materials Society (DGM):Sankt AugustinGermanydgm@dgm.deMarch 20246. Beijing (China)Third World Congress on Condition Monitoring (3rd WCCM)China Special Equipment Inspection and Research InstituteBeijingChina3rdwccm@csei.org.cn15. [Extracted from the article]

The growth of hexagonal boron nitride (h‐BN) and van der Waals (vdW) epitaxy of blue multi‐quantum well (MQW) GaN‐based LED heterostructures on 6‐inch sapphire substrates using metal‐organic chemical vapour deposition (MOCVD) is demonstrated. Challenges associated with the growth of large surface h‐BN and the subsequent vdW epitaxy of GaN‐based LED heterostructures are discussed. To overcome these challenges, the spatial uniformity is controlled of the growth temperature, optimizes the slope of temperature variations during the growth and cooling process, and manages the surface temperature during switching of gas flows. With these adaptations, high quality GaN‐based LED heterostructures are grown on h‐BN without any spontaneous delamination. The GaN‐based LED devices are then fabricated on a 6‐inch sapphire wafer, which are lifted off as a membrane and transferred to a flexible copper support. These GaN‐based LED devices emitt bright blue illumination with an electroluminescence peak at 437 nm. This scaling up of growth, lift‐off, and transfer can lead to the commercialization of GaN‐based LEDs on h‐BN template on 6‐inch sapphire substrates, with a process compatible with current modern equipment for the fabrication of LEDs and electronic devices. [ABSTRACT FROM AUTHOR]

- 1.5.Cascais (Portugal)SMST (Shape Memory and Superelastic Technologies) Conference and Exposition 2024ASM InternationalMateriakls ParkUSAmemberservicecenter@asminternational.org26. - 1.5.Milan (Italy)The International Thermal Spray Conference and Exposition (ITSC 2024)ASM InternationalMateriakls ParkUSAmemberservicecenter@asminternational.orgMay 202412. - 7.3.Orlando (USA)TMS 2024 Annual Meeting & ExhibitionTMSPittsburghUSAmembership@tms.org3. [Extracted from the article]

The AlGaN photocathode with a superlattice emission layer was grown by metal organic chemical vapor deposition. The existence of the superlattice structure was confirmed using a transmission electron microscope, and its optical and electrical properties were measured. The results showed that the introduction of a superlattice emission layer can reduce the transmittance and reflectance at 275 nm and improve the absorption of incident light. In particular, the Hall measurement results indicate that the introduction of a superlattice structure can significantly increase the concentration of holes in the AlGaN photocathode material. The activation experiment demonstrated that the photocurrent of the AlGaN photocathode subassembly with a superlattice structure increased significantly after Cs/O activation and that it showed better photoemission performance. The increase in the incident light absorption to produce more photoelectrons, the enhancement of photoelectron transport capacity by the polarized electric field generated by the superlattice structure, and the reduction in the surface barrier caused by the higher hole concentration were responsible for the significant improvement in photoemission performance. [ABSTRACT FROM AUTHOR]

Research on the semiconductors available for thermal neutron detection is of great significance for the development of thermal neutron detection technology and alleviating the dependence on rare 3 He resources. Hexagonal boron nitride (h- 10 BN) materials have attracted wide attention in the thermal neutron detection field because of their higher 10 B content and unique two-dimensional layered lattice structure. Based on the metal organic chemical vapor deposition (MOCVD) method, a 70 μ m h- 10 BN semiconductor detector was fabricated and experimentally studied. The product of the carrier mobility and lifetime ( μ τ ) of the semiconductor was 1.62 × 10 - 7 cm 2 /V. The time response of the detector was less than 12 ns, and the charge collection efficiency (CCE) was more than 90%. The effects on detection performance of the electric field distribution were studied. At 700 V, the maximum depth at which charges were able to be collected was approximately 50 μ m . The energy spectrum of the h- 10 BN to thermal neutrons was observed with distinct peaks. The results indicate that h- 10 BN has great potential in thermal neutron detection due to its high reaction section, compact volume and short trapping distance. [ABSTRACT FROM AUTHOR]

AlScN films are produced in a commercial metal–organic chemical vapor deposition (MOCVD) system modified to low‐vapor‐pressure Sc metal–organic precursors. Growth conditions are optimized for surface morphology, film stress, and piezoelectric coefficient across a range of compositions. Epitaxial structures are designed to eliminate internal tensile stresses that develop during the film growth as well as prevent surface adatom interactions unique to the MOCVD process. From these films, wide‐bandwidth resonators and filters are manufactured using a novel microelectromechanical‐based bulk acoustic wave (BAW) transfer process. When tested on‐wafer, resonators exhibit a keff2$k_{\text{eff}}^{2}$ of 10.5%, and a Qmax$Q_{\text{max}}$ value of 1400. Ladder‐type RF filters using these resonators are fabricated at 6.2 GHz and show improved performance over filters fabricated using physical vapor deposition‐deposited AlScN. [ABSTRACT FROM AUTHOR]

Accurate detection of gases such as hydrogen sulfide in the exhaled human breath is of great interest for medical professionals as it can possibly help in the early detection of organ malfunction and other diseases. GaInN heterostructure sensors are sensitive to the changes in the surface potential caused by the adsorption of gas molecules. A quantum well (QW) placed close to the surface experiences a change in the quantum‐confined Stark effect and as a result shifts its photoluminescence signal. Several parameters of the GaInN sensors grown by metal organic vapor phase epitaxy are optimized such as the GaN cap layer, QW thickness, and doping concentration. Moreover, how various metal functionalization layers can improve its sensitivity and selectivity is investigated. Gold (Au) and Silver (Ag) shows sensitivity to hydrogen sulfide in the 10–100 parts per billion (ppb) range. Ammonia gas is also detected in the 5–10 range (ppm) with a sensor structure covered with a thin gold layer. [ABSTRACT FROM AUTHOR]

The monoclinic structures of vanadium dioxide are widely studied as appealing systems due to a plethora of functional properties in several technological fields. In particular, the possibility to obtain the VO2 material in the form of thin film with a high control of structure and morphology represents a key issue for their use in THz devices and sensors. Herein, a fine control of the crystal habit has been addressed through an in-depth study of the metal organic chemical vapor deposition (MOCVD) synthetic approach. The focus is devoted to the key operative parameters such as deposition temperature inside the reactor in order to stabilize the P21/c or the C2/m monoclinic VO2 structures. Furthermore, the compositional purity, the morphology and the thickness of the VO2 films have been assessed through energy dispersive X-ray (EDX) analyses and field-emission scanning electron microscopy (FE-SEM), respectively. THz time domain spectroscopy is used to validate at very high frequency the functional properties of the as-prepared VO2 films. [ABSTRACT FROM AUTHOR]

All-AlGaN based high electron mobility transistors (HEMTs) are promising for increasing the power density in both RF and power devices, improving overall efficiency. Nitrogen (N) polar GaN/AlGaN HEMTs offer lower contact resistance compared to its metal-polar counterpart. In this work, we report the metal organic chemical vapor deposition (MOCVD)-based growth of N-polar AlGaN channel HEMT structures with a varying Al mole fraction in the AlxGa1−xN channel (x = 20%, 30%, 59%, and 73%). We confirmed the high-quality morphology and the Al composition of the grown structures using atomic force microscopy and x-ray diffraction spectra, respectively. We measured a mobility of ∼160 cm2/(V.s) in our N-polar AlGaN HEMT stack (20% Al in the channel) structure and found an alloy-scattering dominated transport with increasing Al mole fraction, further supported by our simulations that consider both alloy-scattering and optical phonon-scattering mechanisms. From 20% to 59% Al composition, we found a decreasing trend in mobility while for 59%–73% Al composition in the channel, both the simulated and the experimental mobility showed a nearly saturating trend. The structures were then fabricated into HEMTs with Al0.20Ga0.80N (channel)/Al0.59Ga0.41N (barrier), showing 320 mA/mm drain current for a 4 μm long-channel device. [ABSTRACT FROM AUTHOR]

The structure of trimethylplatinum(IV) iodide [(CH3)3PtI]4 (I) (CIF file CCDC no. 22330007) is refined. The structure of the synthesized for the first time trimethylplatinum(IV) complex with tridentate N,N,O-iminoketonate [(CH3)3Pt(C9H17N2O)] (II) is determined by X-ray diffraction (XRD) (CIF file CCDC no. 22330008). The purity of the isolated phases is confirmed by elemental analysis and IR and NMR spectroscopy. The thermal behavior of complex II is studied by thermogravimetry. The energies of ionization and fragmentation of the molecules of complex II leading to the formation of the most stable fragment [(CH3)3Pt]+ are estimated by quantum-chemical calculations. Complex II is tested in the MOCVD processes. The Pt films with the pronounced (111) texture and particle sizes about 100 nm are prepared on Si plates in the presence of oxygen. [ABSTRACT FROM AUTHOR]

β-Ga 2 O 3 nanowire films were prepared on Si(111) substrate by selective area growth (SAG) using metal-organic chemical vapor deposition (MOCVD). A large-area periodic nano-hole array TiN mask was fabricated. The effects of MOCVD process parameters on SAG were discussed by calculating Ga supersaturation. It was found that the SAG is closely related to the selective area nucleation and inhibition of lateral growth. Transmission electron microscopy confirmed that β-Ga 2 O 3 nanowires have a preferential orientation of the (002) crystal plane. The sample after in-situ O 2 annealing showed an x-ray diffraction intensity increase of (400), (002), and (-111) crystal planes. On this basis, P–Si/β‐Ga 2 O 3 nanowire heterojunctions were fabricated and presented high resistance of the films. At a bias voltage of 20 V, the current decreased from 6.14 × 10−6 to 2.25 × 10−6 A. The MOCVD-based SAG paves a novel way to fabricate β-Ga 2 O 3 nanowire films with high surface-to-volume ratio and homogeneity. [ABSTRACT FROM AUTHOR]

We report on the controllable nitrogen doping of β-Ga2O3 as a deep acceptor dopant using ammonia diluted in nitrogen (NH3/N2) as a source of active nitrogen in the metal organic chemical vapor deposition epitaxy. The effects of the NH3/N2 flow rate and substrate temperature on the incorporation efficiency, reproducibility, and controllability of N doping into Ga2O3 were studied using secondary ion mass spectrometry measurements. With the increase in the NH3/N2 molar flow rate from ∼2 × 10−8 to ∼2 × 10−6 mol/min, the N impurities incorporated into the β-Ga2O3 increased linearly from ∼1 × 1018 to ∼2 × 1020 cm−3. At low substrate temperatures (<800 °C), hydrogen was incorporated into the film accompanying nitrogen with comparable concentrations. Despite this, the current–voltage measurements showed that the N and H co-doped films were resistive with a measured resistance of >70 MΩ for a film grown with [N] ≈ [H] of ∼8 × 1018 cm−3. X-ray on-axis (020) and off-axis (111) rocking curve ω-scans and atomic force microscopy measurements show no influence of NH3/N2 dopant on the structural and surface quality of the films. However, the presence of H promoted the growth of (110) and ( 1 ¯ 10) facets elongated along the [001] direction. At high growth temperatures (≥950 °C), the H concentration in the films was reduced by nearly ∼10×, but with a slight increase in the concentration of N. The results show that controllable and repeatable nitrogen doping into β-Ga2O3 can be achieved using ammonia to obtain deep acceptor doping or compensation needed for device engineering in β-Ga2O3-based power electronic devices. [ABSTRACT FROM AUTHOR]

Growing a thick high-quality epitaxial layer on the β-Ga2O3 substrate is crucial in commercializing β-Ga2O3 devices. Metal organic chemical vapor deposition (MOCVD) is also well-established for the large-scale commercial growth of β-Ga2O3 and related heterostructures. This paper presents a systematic study of the Schottky barrier diodes fabricated on two different Si-doped homoepitaxial β-Ga2O3 thin films grown on Sn-doped (001) and (010) β-Ga2O3 substrates by MOCVD. X-ray diffraction analysis of the MOCVD-grown sample, room temperature current density–voltage data for different Schottky diodes, and C–V measurements are presented. Diode characteristics, such as ideality factor, barrier height, specific on-resistance, and breakdown voltage, are studied. Temperature dependence (170–360 K) of the ideality factor, barrier height, and Poole–Frenkel reverse leakage mechanism are also analyzed from the J–V–T characteristics of the fabricated Schottky diodes. [ABSTRACT FROM AUTHOR]

In this article, an AlN epitaxial layer with a step bunching surface morphology was grown on 0. 2° to 1. 0° offcut angle c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD), and the evolution regularity of the surface morphology during high-temperature annealing ( HTA) was systematically studied. The underlying physical mechanisms were further uncovered through first-principles calculations. It is revealed that as the annealing temperature gradually increase, thermal etching pits with hexagonal structure characteristics first appear on step edges, and then polygonal pits with regular edges formed on the step terraces. The main reason is that the energy of Al-N pairs decomposed from AlN surface at the step-bunching edges (10.72 eV) is smaller than that of Al-N pairs decomposed from the step terraces (12.12 eV), which leads to the phenomenon that the morphology of step edges will change firstly during HTA. In addition, because the width of the step becomes narrower with the increase of the miscut angle, the pits of the step terraces tend to merge with the pits of the step edges during the expansion process to form a V-shaped edge, resulting in step terraces with large miscut angle hardly appearing pits. This study clarifies the evolution mechanism of step-bunching morphology of AlN grown on sapphire substrates with various offcut angles during high-temperature annealing, and provides theoretical support for the preparation of high-quality AlN templates. This template can be used for AlGaN in-plane composition modulation to obtain high-efficiency deep ultraviolet light-emitting diodes (DUV-LEDs). [ABSTRACT FROM AUTHOR]

In this work, single-crystal gallium oxide (β-Ga2O3 ) thin films were epitaxially grown on different off-cut angled c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD), and the effect of off-cut angles on the crystal quality and surface roughness of the epitaxial films were investigated. For the β-Ga2O3 epilayer grown on the 6° off-cut angled sapphire substrate, the full width at half maximum (FWHM) of the rocking curve is reduced to be 1.10°, together with the smallest surface roughness of 7.7 nm. Consequently, the metal-semiconductor-metal structured solar-blind ultraviolet photodetectors were fabricated by lithography, development, electron beam evaporation and lift-off techniques. The photodetector has excellent performances, including photo-dark current ratio of 6. 2 × 106, peak photoresponsivity of 87. 12 A/ W at 248 nm, specific detectivity of 3. 5 ×1015 Jones, UV-visible rejection ratio of 2. 36 ×104, and total response time of 226. 2 μs. [ABSTRACT FROM AUTHOR]

Ga2O3, a fourth-generation ultrawide-bandgap semiconductor material, offers a broad range of potential applications in automotive electronics, electrical devices, and other high-power electronic domains. Metal–organic chemical vapor deposition (MOCVD) is an important technique for growing semiconductor thin films. To obtain high-quality Ga2O3, it is vital to comprehend the chemical vapor deposition process. In this study, the thermal decomposition and adduct formation pathways of triethylgallium (TEGa) with H2O, O2, and N2O molecules were studied using density functional theory. Potential energy scanning was performed and the reaction energy barrier was obtained. Further, the kinetic parameters were calculated, and the entire reaction mechanism, including the gas-phase and surface reactions, was presented. To investigate and compare the growth rates under various oxygen sources with experimental results, the chemical mechanisms were also employed in conjunction with the computational fluid dynamics method. In addition, the growth process, reaction source distribution, and intermediate product dispersion in MOCVD are discussed. The results indicate that the adduct formation pathway is the main route for the growth of Ga2O3 in MOCVD. The Ga(OH)3 polymer is the source of nanoparticles in the gas-phase reaction, which is ultimately hydrolyzed to Ga2O3 nanoparticles. Ga(OH)3 can be produced using TEGa and H2O/O2/N2O. The reaction temperature of TEGa with H2O was the lowest, followed by those of TEGa with N2O and O2. This study could facilitate the understanding of the MOCVD process for growing Ga2O3 films. [ABSTRACT FROM AUTHOR]

Structural defects in transition metal dichalcogenide (TMDC) monolayers (ML) play a significant role in determining their (opto)electronic properties, triggering numerous efforts to control defect densities during material growth or by post-growth treatments. Various types of TMDC have been successfully deposited by MOCVD (metal-organic chemical vapor deposition), which is a wafer-scale deposition technique with excellent uniformity and controllability. However, so far there are no findings on the extent to which the incorporation of defects can be controlled by growth parameters during MOCVD processes of TMDC. In this work, we investigate the effect of growth temperature and precursor ratio during MOCVD of tungsten diselenide (WSe2) on the growth of ML domains and their impact on the density of defects. The aim is to find parameter windows that enable the deposition of WSe2 ML with high crystal quality, i.e. a low density of defects. Our findings confirm that the growth temperature has a large influence on the crystal quality of TMDC, significantly stronger than found for the W to Se precursor ratio. Raising the growth temperatures in the range of 688 °C to 791 °C leads to an increase of the number of defects, dominating photoluminescence (PL) at low temperatures (5.6 K). In contrast, an increase of the molar precursor ratio (DiPSe/WCO) from 1000 up to 100 000 leads to less defect-related PL at low temperatures. [ABSTRACT FROM AUTHOR]

2D semiconductors, especially 2D transition metal dichalcogenides (TMDCs), have attracted ever‐growing attention toward extending Moore's law beyond silicon. Metal–organic chemical vapor deposition (MOCVD) has been widely considered as a scalable technique to achieve wafer‐scale TMDC films for applications. However, current MOCVD process usually suffers from small domain size with only hundreds of nanometers, in which dense grain boundary defects degrade the crystalline quality of the films. Here, a periodical varying‐temperature ripening (PVTR) process is demonstrated to grow wafer‐scale high crystalline TMDC films by MOCVD. It is found that the high‐temperature ripening significantly reduces the nucleation density and therefore enables single‐crystal domain size over 20 µm. In this process, no additives or etchants are involved, which facilitates low impurity concentration in the grown films. Atom‐resolved electron microscopy imaging, variable temperature photoluminescence (PL) spectroscopy, and electrical transport results further confirm comparable crystalline quality to those observed in mechanically exfoliated TMDC films. The research provides a scalable route to produce high‐quality 2D semiconducting films for applications in electronics and optoelectronics. [ABSTRACT FROM AUTHOR]

This Letter reports a high performance β -Ga2O3 thin channel MOSFET with T gate and degenerately doped (n++) source/drain contacts regrown by metal organic chemical vapor deposition. Highly scaled T-gate with a gate length of 160–200 nm was fabricated to achieve enhanced RF performance and passivated with 200 nm silicon nitride. Peak drain current (ID,MAX) of 285 mA/mm and peak transconductance (gm) of 52 mS/mm were measured at 10 V drain bias with 23.5 Ω mm on resistance (RON). Metal/n++ contact resistance of 0.078 Ω mm was extracted from transfer length measurements. RON is possibly dominated by interface resistance between channel and highly doped n++ regrown layer. A gate-to-drain breakdown voltage of 192 V is measured for LGD = 355 nm resulting in average breakdown field (EAVG) of 5.4 MV/cm. This EAVG is the highest reported among all sub-micron gate length lateral FETs. Current gain cut off frequency (fT) of 11 GHz and record power gain cut off frequency (fMAX) of approximately 48 GHz were extracted from small signal measurements. fT is limited by DC-RF dispersion due to interface traps which needs further investigation. The fT·VBR product is 2.112 THz V for 192 V breakdown voltage. Device surpasses the switching figure of merit of Silicon and competitive with mature wide bandgap devices. [ABSTRACT FROM AUTHOR]