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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]

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]

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]

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]

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]

AlScN/GaN heterostructures are worth investigating due to the remarkable high gradients in spontaneous polarization at their interfaces, which brings them into play for a wide field of potential high-power and high-frequency electronic applications. In this work, AlScN/GaN heterostructures for high electron mobility transistor (HEMT) structures were grown by metalorganic chemical vapor deposition. We have investigated the impact of growth parameters on thick AlScN layers and on thin AlScN/GaN heterostructures. Growth parameters, such as temperature, V/III ratio, pressure, and growth mode, were varied with the focus on surface morphology, crystal quality, and incorporation of impurities. High growth temperatures improve the surface quality and reduce impurities incorporation notably. In addition to that, a slight decrease in carbon concentration is obtained by adopting a pulsed supply of metalorganic precursors. V/III ratio and pressure did not influence the layer quality observably. Heterostructures with root mean square surface roughness values as low as 0.38 nm, revealing smooth growth steps, were achieved. The presence of two-dimensional electron gases with sheet carrier densities and mobilities of up to 2 × 1013 cm−2 and close to 900 cm2/(V s), respectively, resulted in channel sheet resistances as low as 337 Ω/sq, very suitable for AlScN/GaN HEMTs. Heterostructures with sheet resistances below 200 Ω/sq and sheet carrier densities of 5 × 1013 cm−2 were also achieved but showed significantly lower mobility. [ABSTRACT FROM AUTHOR]

Compositionally graded channel AlGaN/GaN high electron mobility transistors (HEMTs) offer a promising route to improve device linearity, which is necessary for low-noise radio-frequency amplifiers. In this work, we demonstrate different grading profiles of a 10-nm-thick AlxGa1−xN channel from x = 0 to x = 0.1 using hot-wall metal-organic chemical vapor deposition (MOCVD). The growth process is developed by optimizing the channel grading and the channel-to-barrier transition. For this purpose, the Al-profiles and the interface sharpness, as determined from scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, are correlated with specific MOCVD process parameters. The results are linked to the channel properties (electron density, electron mobility, and sheet resistance) obtained by contactless Hall and terahertz optical Hall effect measurements coupled with simulations from solving self-consistently Poisson and Schrödinger equations. The impact of incorporating a thin AlN interlayer between the graded channel and the barrier layer on the HEMT properties is investigated and discussed. The optimized graded channel HEMT structure is found to have similarly high electron density (∼ 9 × 10 12 cm−2) as the non-graded conventional structure, though the mobility drops from ∼ 2360 cm2/V s in the conventional to ∼ 960 cm2/V s in the graded structure. The transconductance gm of the linearly graded channel HEMTs is shown to be flatter with smaller g m ′ and g m ″ as compared to the conventional non-graded channel HEMT implying improved device linearity. [ABSTRACT FROM AUTHOR]

Semiconductor thin films for electronic devices are usually produced through processes such as chemical vapor deposition, which requires careful control of the gas flow, heat distribution, and concentration distribution over the substrate to ensure a uniform deposition rate and thickness. Herein, a systematic method is proposed for the theoretical adjustment of metalorganic chemical vapor deposition (MOCVD) process parameters. To this end, a GaN-MOCVD reactor with a vertical injection structure was simulated based on computational fluid dynamics to analyze the stable flow under a fixed flow rate. The orthogonal experimental design was used to analyze the influence of process conditions on film quality. A neural network and genetic algorithm were used to optimize the inlet flow under the stable flow state to render the coefficient of variation <3%. Under these conditions, the flow field in the reactor was stabilized to ensure a uniform thickness for the deposited film. This study provides not only an effective solution for high-quality epitaxial growth but also a theoretical basis for subsequent experiments and equipment improvement. [ABSTRACT FROM AUTHOR]

MgxGa2O4 epitaxial films with different Mg component ratios (x = 0.6, 0.8, 1, 1.1, and 1.4) and their metal–semiconductor–metal solar‐blind ultraviolet (SBUV) photodetectors are prepared on c‐face sapphire by metal–organic chemical vapor deposition (MOCVD). The structure, composition, crystalline quality, and optical properties of the MgxGa2O4 thin films have been investigated in detail. It can be found that five MgxGa2O4 thin films have the spinel structure with a similar bandgap of ≈5.15 eV, and the highest crystalline quality is observed in MgxGa2O4 with x = 1. Besides, photodetector based on MgxGa2O4 film with x = 1 has the highest responsivity, the largest UV–visible rejection ratio, and the fastest response speed. As the content of Mg deviates from the stoichiometric ratio of MgGa2O4, the crystalline quality of the MgxGa2O4 thin film is reduced, and their photoelectric response characteristics are deteriorated. This work indicates that MgGa2O4 is a promising candidate for the applications in high‐performance solar‐blind ultraviolet photodetectors. [ABSTRACT FROM AUTHOR]

MOCVD processes of the deposition of PtxIr(1–x) films in the presence of H2 and O2 in the temperature range 260-300 °C on Si and Ti substrates using a combination of precursors Me3Pt(acac)Py and Ir(CO)2(acac) (acac = acetylacetonato(-), Py = pyridine) are studied. According to the powder XRD data, the films are usually solid solutions with the PtxIr(1–x) composition. The samples prepared in the presence of O2 show the minimal contents of impurities, homogeneous composition, and the Pt:Ir ratio close to the one experimentally specified. In the presence of H2, Ir-enriched PtxIr(1–x) layers with a non-uniform distribution of metals over the thickness are formed in the temperature range 280-300 °C. The surface of PtxIr(1–x) film structures prepared in the presence of hydrogen is formed by small (up to 10 nm in size) particles or 20-32 nm large particle agglomerates prepared in the presence of oxygen. The PtxIr(1–x) layers have a predominantly columnar structure. The structure of films deposited in an oxygen atmosphere is less dense than that of the layers synthesized under similar conditions in a hydrogen atmosphere. The thickness of the films prepared in H2 or O2 falls within intervals 300-450 nm and 750-800 nm, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of the oxygen precursor flow supplied during metalorganic chemical vapor deposition (MOCVD) of Al2O3 films on the forward bias behavior of Al2O3/GaN metal-oxide-semiconductor capacitors. The low oxygen flow (100 sccm) delivered during the in situ growth of Al2O3 on GaN resulted in films that exhibited a stable capacitance under forward stress, a lower density of stress-generated negative fixed charges, and a higher dielectric breakdown strength compared to Al2O3 films grown under high oxygen flow (480 sccm). The low oxygen grown Al2O3 dielectrics exhibited lower gate current transients in stress/recovery measurements, providing evidence of a reduced density of trap states near the GaN conduction band and an enhanced robustness under accumulated gate stress. This work reveals oxygen flow variance in MOCVD to be a strategy for controlling the dielectric properties and performance. [ABSTRACT FROM AUTHOR]

Three-dimensional GaN island growth without any masks was first introduced under high pressure in metalorganic chemical vapor deposition after the growth of AlN and AlGaN buffer layers on Si (111) substrate, followed by two-dimensional GaN growth to form a continuous GaN film with improvement of the crystalline quality and surface smoothness. X-ray diffraction and crosssectional scanning transmission electron microscopy analyses show that a high-quality GaN film can be achieved by bending of edge threading dislocations (TDs) and the formation of dislocation half-loops. It is observed that most of edge TDs bend 90° from the growth direction along c-axis, whereas mixed TDs bend about 30° towards the inclined sidewall facets of the islands. Consequently, a 1.2 μm thick GaN epitaxial film with a low threading dislocation density of 2.5 × 108 cm-2 and a smooth surface of 0. 38 nm roughness can be achieved on Si substrate. [ABSTRACT FROM AUTHOR]

Graphene is an excellent material for Hall sensors due to its atomically thin structure, high carrier mobility, and low carrier density. However, graphene devices need to be protected from the environment for reliable and durable performance in different environmental conditions. Here we present magnetic Hall sensors fabricated on large area commercially available chemical vapor deposited (CVD) graphene protected by exfoliated hexagonal boron nitride (h-BN). To connect the graphene active regions of Hall samples to the outputs, 1D edge contacts were utilized which show reliable and stable electrical properties. The operation of the Hall sensors shows the current-related sensitivity up to 345 V/(AT). By changing the carrier concentration and type in graphene by the application of gate voltage, we are able to tune the Hall sensitivity. [ABSTRACT FROM AUTHOR]

MOCVD processes for the fabrication of PtxIr(1–x) films (x < 0.3, thickness 1.5-1.8 µm) on the contacts of diagnostic electrodes and titanium discs are developed using a combination of Pt(II) and Ir(I) acetylacetonate (acac) derivatives (Pt(acac)2, Ir(cod)(acac) (cod = cyclooctadiene-1,5) and oxygen as a gas reagent. It is shown that the ratios of metals in the films prepared on different types of supports are similar within the same experiment. The films contain phases of solid solution PtxIr(1–x) without admixtures of metallic and oxide phases; the ratio of metals in the sample volume corresponds to the one experimentally specified. EDS and XPS methods determine a lower iridium content after the formation of PtxIr(1–x) films in the subsurface layers (10 nm) than the XRD method. The surface of PtxIr(1–x) films consists of agglomerates formed by small particles. When the Pt content decreases from x = 0.3 to x = 0.2, the average size of these particles decreases from 29 nm to 24–25 nm and then remains virtually constant. The capacitance values of contacts with PtxIr(1–x) films vary within 62.6-84.5 mC/cm2. [ABSTRACT FROM AUTHOR]

GaN-based high electron mobility transistors (HEMT) on Si (111) substrates have large potential for applications in the 5G telecommunication field. However, for this potential to be fully realized, all loss mechanisms need to be minimized. It is known that typical metal-organic chemical vapor deposition (MOCVD) processes used to grow the GaN epitaxial layers can cause considerable parasitic conductivity at the interface of the AlN nucleation layer to the high-resistivity Si substrate, leading to reduced gain and power added efficiency in amplifiers. Reducing this parasitic conductivity is hence of utmost importance to render GaN-on-Si a significant contributor to next-generation 5G power amplifier technology. In this work, we employ secondary ion mass spectroscopy, spreading resistance profiling and insertion loss measurements up to 28 GHz using coplanar waveguides fabricated on the epitaxial layer stacks to study the origin and characterize the parasitic conductivity. While a single heat-up process in an AIXTRON G5+ reactor chamber cleaned using Cl2 does not introduce any extra dopants in the Si substrate, the epitaxial growth of (Al,Ga)N-based HEMT buffer layer stacks leads to the diffusion of Al and, to a lower extent, Ga acceptors into the Si substrate. Optimization of the MOCVD process towards lower growth temperatures leads to a strong reduction of density of diffused acceptors. This reduction goes in line with a significant decrease of the insertion loss from 0.45 dB mm−1 to only 0.20 dB mm−1 at a frequency of 28 GHz. [ABSTRACT FROM AUTHOR]

We present a new approach for synthesis of GaN nanowires and microwires by metal organic chemical vapor deposition via a thin titanium film evaporated onto sapphire substrate prior to growth. Titanium etches a two-dimensional GaN layer deposited at the initial stage and GaN nanowires subsequently emerge at the boundaries of the etched grains. These wires grow at an exceptional elongation rate of 18 μm/min and extend radially at a rate of 0.14 μm/min. The GaN layer between the wires grows at a rate of 0.1 μm/min. High material quality of these structures is confirmed by micro-photoluminescence spectroscopy. We investigate the initial nucleation stage, the time evolution of the wire length and diameter, the length and diameter distributions and speculate about a mechanism that yields the observed growth behavior. [ABSTRACT FROM AUTHOR]

This Letter reports the polarization induced hole conduction in composition-graded AlInN epitaxial layers grown by metalorganic chemical vapor deposition. First, the composition-graded AlInN layer with an InN mole fraction from 0.12 to 0.20 was formed on c-plane GaN on sapphire, and they were confirmed to show the p-type hole conduction with a less temperature dependence, which is a feature of polarization-induced carriers. Then, blue light-emitting diodes (LEDs) with the composition-graded AlInN layers inserted in the p-type side were fabricated and their vertical current injection was investigated. The electroluminescence (EL) spectra confirmed that the fabricated LEDs exhibited a single-peak blue-light emission with the help of the impurity Mg doping. The LED simulation indicated that the impurity and polarization co-doping effectively compensated and overcame the residual oxygen donors in the AlInN layer and promoted the carrier recombination at the light-emitting layers. Finally, LEDs with the Mg-doped and composition-graded AlInN insertion layer exhibited good current–voltage characteristics with a low forward voltage drop of approximately 3 V in addition to the good EL spectra. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the detailed optimization of metalorganic chemical vapor deposition (MOCVD)-grown tunnel junctions (TJs) utilizing selective area growth (SAG) for regular size (0.1 mm2) and micro-size InGaN light-emitting diodes (LEDs and µLEDs). Finite-difference time-domain simulations show that the SAG apertures result in a more directional light emission of far-field radiation pattern for the SAG TJ LEDs grown on patterned sapphire substrate. Moreover, it is noted that the n-InGaN insertion layer and Si-doped concentration in the n+GaN TJs layer is essential to realize a low forward voltage (Vf) in TJs LEDs. For both 0.1 mm2 LEDs and µLEDs, the Vf is independent on the SAG aperture space varied from 3 to 8 µm when the Si-doping level in the n+GaN layer is as high as 1.7 × 1020 cm−3. The optimized TJ LEDs exhibit a comparable differential resistance of 1.0 × 10−2 Ω cm2 at 100 A cm−2 and a very small voltage penalty of 0.2–0.3 V compared to the conventional indium tin oxide contact LEDs. The low Vf penalty is caused by a higher turn on voltage, which is the smallest one among the MOCVD-grown TJs LEDs and comparable to the best molecular beam epitaxy-grown TJs LEDs. [ABSTRACT FROM AUTHOR]

We have proposed a MOCVD process for producing thin yttria-stabilized zirconia (YSZ) interface coatings on Tyranno-SAK SiC fiber. Optimization of deposition parameters, such as the temperature, time, and gas flow rate, has made it possible to obtain uniform coatings. Optimization of experimental parameters has shown that uniform YSZ coatings with good adhesion to SiC fiber can be produced at a temperature of 600°C in a time as short as 1 h without impairing the tensile strength of the fiber. [ABSTRACT FROM AUTHOR]

• WTe 2 thin films grown on sapphire by Metal Organic Chemical Vapor Deposition MOCVD. • Diethyl tellurium (DETe) and tungsten hexacarbonyl (W(CO) 6) precursors. • 1 T' phase WTe 2 forms in temperature window between 350 and 500 °C. • Carbon deposition from DETe dominates at higher growth temperatures and pressures. • Nanocrystalline films are largely c-axis oriented with additional twist and tilt. The growth of tungsten ditelluride (WTe 2) thin films on c-plane sapphire substrates was demonstrated by metalorganic chemical vapor deposition (MOCVD) using tungsten hexacarbonyl (W(CO) 6) and diethyltelluride (DETe) as precursors for W and Te, respectively, in a H 2 carrier gas. The effects of substrate temperature, reactor pressure, precursor and carrier gas flow rates, and chalcogen-to-metal ratio on the WTe 2 growth rate and film properties were determined. Substrate temperatures less than 500 °C were required to deposit WTe 2 which was found to be beneficial to suppress simultaneous carbon deposition from the DETe precursor. The films exhibited a fine-grained morphology independent of growth temperature. The layered crystalline 1 T' phase of WTe 2 was confirmed using high resolution X-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (TEM) which revealed that the films were predominantly c-axis oriented with in-plane twist. X-ray photoelectron spectroscopy (XPS) demonstrated that the WTe 2 films were stable in air for a few days but eventually exhibited oxidation. [ABSTRACT FROM AUTHOR]

The ultra-wide bandgap semiconductor gallium oxide (Ga2O3) offers substantial promise to significantly advance power electronic devices as a result of its high breakdown electric field and maturing substrate technology. A key remaining challenge is the ability to grow electronic-grade epitaxial layers at rates consistent with 20–40 μm thick drift regions needed for 20 kV and above technologies. This work reports on extensive characterization of epitaxial layers grown in a novel metalorganic chemical vapor deposition tool that permits growth rates of 1.0–4.0 μm h−1. Specifically, optical, structural and electrical properties of epilayers grown at ∼1 μm h−1 are reported, including employment in an operating MOSFET. The films demonstrate relatively smooth surfaces with a high degree of structural order, limited point defectivity (Nd − Na ≈ 5 × 1015 cm−3) and an optical bandgap of 4.50 eV. Further, when employed in a MOSFET test structure with an n+ doped channel, a record high mobility for a transistor structure with a doped channel of 170 cm2 V−1 s−1 was measured via the Hall technique at room temperature. This work reports for the first time a β-Ga2O3 MOSFET grown using Agnitron Technology's high growth rate MOCVD homoepitaxial process. These results clearly establish a significant improvement in epilayer quality at growth rates that can support future high voltage power device technologies. [ABSTRACT FROM AUTHOR]

For the production of nitride‐based optical and power devices, it is known that metal organics chemical vapor deposition (MOCVD) is an industrial method which is used worldwide. However, MOCVD has disadvantages: 1) a lot of ammonia gas is consumed; 2) the sublimation of GaN is not negligible at growth temperature and these increase the production cost; 3) the growth of in‐containing nitrides is difficult because the growth temperature is too high; and 4) using large Si substrates of 150–300 mm diameter for industrial production, wafer breakage and bowing occur. It is therefore important to develop novel epitaxial growth methods that can replace the MOCVD method. Recently, high‐density radical source (HDRS) is developed by combining inductively coupled plasma (ICP) and capacitively coupled plasma (CCP) which can be applied to molecular beam epitaxy (MBE) in order to increase the growth rate of nitrides. Another novel method, the radical enhanced MOCVD (REMOCVD) method with using very high frequency (VHF) plasma, has also been developed. This REMOCVD allows the low growth temperature without using any ammonia gas. These novel methods are promising for replacing the MOCVD method from the viewpoint of production cost without ammonia gas usage. [ABSTRACT FROM AUTHOR]

The purpose of the study is to investigate the effect of a new type of compliant substrate based on an AlGaAs superstructure layer (SL) and a protoporous Si (proto-Si) layer formed on a crystal Si (c-Si) layer on the practical implementation and specific features of the epitaxial growth of GaAs layers by metal–organic chemical vapor deposition. It is for the first time shown that the low-temperature growth of high-crystal-quality epitaxial GaAs films can be implemented due to the use of compliant SL/proto-Si substrates. The introduction of a SL into the composition of a compliant substrate in addition to proto-Si makes it possible to neutralize a number of negative effects of low-temperature growth, to reduce the level of stresses in the epitaxial layer, to protect it from self-doping with Si atoms, to reduce the number of technological operations of the growth of transition buffer layers, and to improve the structural and morphological characteristics of the epitaxial layer. [ABSTRACT FROM AUTHOR]

High performance GaN-based micro-light-emitting diodes (µLEDs) with epitaxial n-InGaN/n-GaN tunnel junctions (InGaN TJs) were grown by metalorganic chemical vapor deposition (MOCVD). The InGaN TJs µLEDs show a significant reduction of forward voltage (Vf) by ∼0.6 V compared to the common TJs µLEDs. The Vf at 20 A cm−2 is very low varied from 3.15 V to 3.19 V in small InGaN TJ µLEDs with a size less than 40 × 40 µm2, and then significantly increases in large LEDs. Selective area growth (SAG) of TJs can overcome such size limitation by vertical out diffusion of hydrogen through the apertures on top of p-GaN. The InGaN TJ µLEDs overgrown by SAG show a size-independent low Vf ranged from 3.08 V to 3.25 V. The external quantum efficiency (EQE) of the packaged TJ µLEDs was improved by 6% compared to the common µLEDs with indium tin oxide (ITO) contact. This work solves the key challenges of MOCVD-grown TJs. [ABSTRACT FROM AUTHOR]

Herein, the optical properties of aluminum nitride (AlN) epitaxial layers grown on sapphire substrates by metal‐organic chemical vapor deposition (MOCVD) are reported. The structures investigated in this study are grown at highly different degrees of supersaturation in the MOCVD process. In addition, both pulsed and continuous growth conditions are employed and AlN is deposited on nucleation layers favoring different polarities. The samples are investigated by photoluminescence (PL), photoluminescence excitation (PLE), and absorption spectroscopy and are found to vary significantly in absorption and emission characteristics. Two distinct absorption bands in the UV‐C spectral range are observed and examined in greater detail, with either giving rise to a significant absorption coefficient of around 1000 cm−1. The corresponding defect transitions are identified by PL spectroscopy. Combined with secondary‐ion mass spectrometry (SIMS) measurements, these absorption bands are allocated to the incorporation of carbon and oxygen impurities, depending on the applied growth conditions. Furthermore, similarities with other epitaxial growth techniques serving as basis for UV‐C applications are highlighted. These results are highly relevant for a better understanding of absorption issues in AlN templates grown by various deposition techniques. In addition, consequences for the growth of efficient UV‐C devices by MOCVD on sapphire substrates are outlined. [ABSTRACT FROM AUTHOR]

Clay‐bonded SiC supported cobalt oxide catalysts were produced by the aerosol‐assisted metal organic chemical vapor deposition method (AA‐MOCVD) using Co(acac)2 as precursor. Deposition temperatures 270 and 300 °C were the most appropriate for the synthesis of a composite catalyst of high activity for the CO conversion reaction. A cone‐shaped crystal habit is the dominant morphology. The catalysts were decorated with Au nanoparticles (NPs) of sizes in the range of 5–10 nm. This substantially improved the activity of the catalysts, lowering the onset temperature of activity by about 50 °C. Ambient‐pressure X‐ray photoelectron spectroscopy (APXPS) was used to investigate in situ the electronic state of cobalt and gold during CO oxidation. APXPS results show that while Au remains in the metallic state during the reaction, it enhances the reduction of Co3+ to Co2+. Au NPs adsorb CO molecules from the gas phase and supply them to the neighbor cobalt oxide particles. [ABSTRACT FROM AUTHOR]

The low contact resistivity with the median value of 3.1 × 10#8722;9Ω ⋅ cm2 (the lowest value of 1.1 × 10#8722;9Ω ⋅ cm2) is achieved by Ti metal contact to in-situ B-doped GeSn with B segregation at Ti/GeSn:B interface. The newly developed two-sheet-resistance model is used to extract the contact resistivity, considering the different sheet resistance of GeSn:B in the gap regions and under the metal layers. Sn incorporation into Ge lowers the Schottky barrier height of holes, and the heavy B doping at the Ti/GeSn:B interface reduces the hole tunneling distance. Fully compressively strained GeSn:B epitaxial layer with the bulk active [B] of 1.9 × 1020 cm−3 and [Sn] of 4.7% on the Ge-buffered Si substrate is successfully grown by chemical vapor deposition. The effects of B2H6 precursor on growth rate and [Sn] are investigated. Low contact resistivity is obtained using conventional B-doping in GeSn grown at a temperature as low as 305 °C and submitted to a post epitaxy thermal budget of 400 °C for 30 s. [ABSTRACT FROM AUTHOR]

In this work, a dual-sided buffer template, which allows the deposition of YB 2 Cu 3 O 7-δ (YBCO) coated conductors on both sides, has been proposed and investigated. Theoretically, in contrast to traditional YBCO structure on one side, the performance of critical current in YBCO films has been improved by two times. In this buffer structure, the dual-sided Y 2 O 3 films were grown on a flexible metal template by a home-made reel-to-reel dynamic direct current sputtering system and the film growth parameters were systematically investigated. The microstructure were characterized by in situ reflection high-energy electron diffraction monitoring in real time during the deposition stage. X-ray diffraction, and atomic force microscopy were used to detect the biaxial texture and surface morphology, respectively. What's more, by the application of stopping and range of ions in matter software, it helped us to understand the influence of deposition parameter to the growth rate of Y 2 O 3 films. Finally, the biaxial texture of dual-sided Y 2 O 3 film yielded out-of-plane texture of Δ ω = 4.2° and in-plane texture of Δ Φ = 5.2° for one side, as well as Δ ω = 5° and Δ Φ = 5.3° for the second side. Subsequently, the dual-sided YBCO superconducting films were coated on the above Y 2 O 3 buffer layer by low-cost metal-organic chemical vapor deposition method with critical current of 30 A/cm and 60 A/cm for each side. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is known for its versatile properties and hence is promising for a wide range of applications. The fabrication of high quality MoS2 either as homogeneous films or as two-dimensional layers on large areas is thus the objective of intense research. Since industry requirements on MoS2 thin films can hardly be matched by established exfoliation fabrication methods, there is an enhanced need for developing new chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes where a rational precursor selection is a crucial step. In this study, a new molybdenum precursor, namely 1,4-di-tert-butyl-1,4-diazabutadienyl-bis(tert-butylimido)molybdenum(VI) [Mo(NtBu)2(tBu2DAD)], is identified as a potential candidate. The combination of imido and chelating 1,4-diazadieneyl ligand moieties around the molybdenum metal center results in a monomeric compound possessing adequate thermal characteristics relevant for vapor phase deposition applications. Hexagonal MoS2 layers are fabricated in a metalorganic CVD (MOCVD) process with elemental sulfur as the co-reactant at temperatures between 600 °C and 800 °C. The structure and composition of the films are investigated by X-ray diffraction, high resolution transmission electron microscopy, synchrotron X-ray photoelectron spectroscopy and Raman spectroscopy revealing crystalline and stoichiometric MoS2 films. The new MOCVD process developed for MoS2 is highly promising due to its moderate process conditions, scalability and controlled targeted composition. [ABSTRACT FROM AUTHOR]

A detailed optical characterization by means of micro Raman and cathodoluminescence spectroscopy of catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition has been carried out. This characterization has allowed correlating the growth conditions, in particular the precursors partial-pressures and growth time, with the optical properties of nanorods. It has been shown that a high Zn supersaturation can favor the incorporation of nonradiative recombination centers, which can tentatively be associated with ZnI-related defects. Characterization of individual nanorods has evidenced that ZnI-related defects have a tendency to accumulate in the tip part of the nanorods, which present dark cathodoluminescence contrast with respect to the nanorods bottom. The effect of a ZnO buffer layer on the properties of the nanorods has been also investigated, showing that the buffer layer improves the luminescence efficiency of the ZnO nanorods, revealing a significant reduction of the concentration of nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

Mid-wavelength infrared planar photodiodes were demonstrated, in which both the epitaxy growth of InAs/GaSb superlattices and the thermal diffusion of p-type dopant were performed in production-scale metal–organic chemical vapor deposition reactors. The formation of a planar homojunction was confirmed by secondary ion mass spectroscopy and its I–V characteristics. A cut-off wavelength around 5 μm was determined in 77 K optical characterization, and photo-current as high as 600 nA was collected from a reverse-biased planar diode of 640 μm diameter. These preliminary results were obtained despite the structural degradation revealed by x-ray diffraction, and we attribute the degradation to the concert of thermal annealing and high Zn concentration behind the diffusion front. [ABSTRACT FROM AUTHOR]

With their exceptional strength-to-weight ratio, titanium alloys find applications in numerous key enabling technologies. However, their implementation in harsh environments comes up against their limited resistance to high-temperature oxidation. To face this problem, in this work dense, amorphous alumina, Al2O3 coatings are applied on the surface of Ti6242S alloy by metalorganic chemical vapor deposition, MOCVD, from aluminum triisopropoxide, ATI and from dimethylaluminum isopropoxide, DMAI. Isothermal oxidation tests show that the parabolic rate constants of the mass gain of the coated Ti6242S coupons are reduced up to two orders of magnitude compared with the bare material. 5000 h long oxidation of DMAI Al2O3 coated alloy at 600 °C results in 0.180 mg cm−2 weight gain to be compared with 1.143 mg cm−2 for the bare alloy. In these conditions, an interfacial layer is formed, containing the complex Ti3(Al0.5Sn0.5) (or (Ti,Sn)2N) phase. Cyclic oxidation consisting of eighty, 1 h cycles between 50 and 600 °C show null mass gain of the coated sample. Finally, the hardness profiles determined on cross sections of oxidized coupons reveal a very limited oxygen dissolution for the coated alloy. MOCVD coatings of amorphous Al2O3 have great potential for efficient, durable protection against oxidation of Ti6242S alloys. [ABSTRACT FROM AUTHOR]

Herein, the potential of reformed GaN nanowires (NWs) fabricated by metalorganic chemical vapor deposition (MOCVD) for device‐quality low‐defect density templates and low‐cost alternative to bulk GaN substrates is demonstrated. The effects of epilayer thickness and NW reformation conditions on the crystalline quality and thermal conductivity of the subsequent GaN epilayers are investigated. Smooth surfaces with atomically step‐like morphologies with no spirals are achieved for GaN epilayers on the reformed NW templates, indicating step‐flow growth mode. It is further found that annealing of the NWs at a temperature of 1030 °C in the presence of NH3 and H2, followed by a coalescence done at the same temperature under planar growth conditions, leads to the most efficient screw dislocation density reduction by nearly an order of magnitude. At these optimized conditions, the growth takes place in a layer‐by‐layer fashion, producing a smooth surface with a root mean square (RMS) roughness of 0.12 nm. The highest thermal conductivity of k = 206 W m−1 K−1, approaching the respective value of bulk GaN, is obtained for the optimized 2 μm‐thick GaN layer. The thermal conductivity results are further discussed in terms of the phonon‐dislocation and the phonon‐boundary scattering. [ABSTRACT FROM AUTHOR]

Herein, the fabrication of MoS2/p‐GaN heterostructures via direct chemical vapor deposition (CVD) and transfer methods are demonstrated. The molybdenum disulfide (MoS2) layers are grown on p‐GaN and sapphire substrates via CVD under the same growth conditions. Subsequently, in the case of sapphire substrate, MoS2 from the sapphire substrate is transferred onto the p‐GaN substrates to produce a vertically stacked heterostructure. Atomic force microscopy (AFM) images indicate that the MoS2 that is directly grown on the GaN substrate exhibits granular structure, whereas the transferred MoS2 exhibits triangle‐shaped grains. In the current–voltage measurement of the heterostructures, similar I–V curves are obtained for the direct CVD and transfer methods. However, the results indicate higher current in the transfer‐produced heterostructure than in the CVD‐produced heterostructure. The difference in resistance in both heterostructures is attributed to the density of the grain boundary of MoS2. The results suggest that the type of substrate is crucial and the quality of the MoS2 layers depends on them. [ABSTRACT FROM AUTHOR]

Despite exhibiting their attractive properties and performances, the interlayer interaction in two-dimensional van der Waals epitaxy heterostructures is not well understood. Here, we demonstrate the growth of two dimensional vertically stacked multilayer β-In2Se3/monolayer WS2 heterostructures via the chemical vapor deposition method. Despite a large lattice misfit (29.9%), the vertically stacked β-In2Se3/WS2 heterostructures exhibit van der Waals epitaxy with well-aligned lattice orientation of WS2(100)[001]//In2Se3(100)[001], forming a periodic superlattice. Interestingly, a reversible phase transformation of epitaxial β-In2Se3 has been observed by temperature-dependent Raman spectroscopy and electron diffraction conducted from liquid N2 to room temperature. Notably, the phase transformation of epitaxial β-In2Se3 can only be observed when its layer number is larger than 4 and the transformation temperature increases with the increase in the layer number, indicating a layer number dependent phase transformation of epitaxial β-In2Se3. These results indicate that the confinement effect exists between monolayer WS2 and epitaxial β-In2Se3, strongly constraining the lattice change of adjacent few layers of β-In2Se3. [ABSTRACT FROM AUTHOR]

• Core-shell structured CeO 2 @Fe composites were synthesized using a MOCVD method. • Composite with 80 wt% CeO 2 @Fe exhibits the optimal microwave absorption properties. • Minimum RL values of −23.88 dB is achieved with thickness of 1.1 mm. • An effective absorption bandwidth of 4.24 GHz is obtained at thickness of 1.24 mm. • Microwave absorption mechanisms of the composites are systematically analyzed. Core–shell structured CeO 2 @Fe composites composed of a dielectric CeO 2 core and ferromagnetic Fe shell were synthesized via a metal organic chemical vapor deposition (MOCVD) method. The phase structure, morphology, magnetic, and electromagnetic (EM) properties of the composites were characterized with modern measurement techniques. According to the results, the rough α-Fe shell is homogeneously deposited on the CeO 2 surface. The saturation magnetization (M s) and coercivity (H c) of the CeO 2 @Fe composites are 45.1 emu/g and 274.3 Oe, respectively. The EM properties of the composites containing 60, 70, and 80 wt% CeO 2 @Fe and paraffin wax (PW) were investigated in the frequency range 2–18 GHz. The CeO 2 @Fe–PW composite with 70 wt% CeO 2 @Fe exhibits a minimal reflection loss (RL) of − 17 dB at 9.6 GHz (thickness of 2.54 mm). The composite with 80 wt% CeO 2 @Fe shows a broad effective absorption bandwidth (RL ≤ −10 dB) at 4.24 GHz (thickness of 1.24 mm) and can be exploited for practical applications at 3.12–18.0 GHz by tuning its thickness from 0.97 to 4.0 mm. The excellent microwave absorption performance of the composites is attributed to the synergistic effects of a dielectric loss due to Debye relaxation and interface polarization and a magnetic loss due to natural resonances and exchange resonances. Moreover, the balance between the impedance matching and attenuation constants are benefits for the microwave absorption. [ABSTRACT FROM AUTHOR]

We report design, growth, and characterization of midwavelength infrared nBn photodetectors based on a type-II InAs/InAs1-xSbx superlattice on a GaSb substrate grown by metal-organic chemical vapor deposition. An InAs/AlAs1-ySby/InAs/InAs1-xSbx superlattice design was used as the large bandgap electron barrier in the photodetectors. At 150 K, the photodetector exhibits a peak responsivity of 1.23 A/W, corresponding to a quantum efficiency of 41% at an applied bias voltage of −100 mV under front-side illumination, with a 50% cut-off wavelength of 4.6 μm. With an R × A of 356 Ω cm2 and a dark current density of 1.6 × 10−4 A/cm2 under an applied bias of −100 mV at 150 K, the photodetector exhibits a specific detectivity of 1.4 × 1011 cm Hz1/2/W. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) is an attractive material for manufacturing light emitting diodes and other electronic devices due to its wide band-gap and superb optoelectronic performance. The quality of GaN thin film determines the reliability and durability of these devices. Metal-organic chemical vapor deposition (MOCVD) is a common technique used to fabricate high-quality GaN thin films. In this paper, GaN growth rate and uniformity in a vertical rotating disk MOCVD reactor are investigated on the basis of a three-dimensional computational fluid dynamics (CFD) model. GaN growth rate is investigated under the influence of reactor pressure, precursor concentration ratio, and composition of the carrier gas mixture. The numerical simulation shows that the carrier gas mixture and the reactor pressure have significant effects on growth rate and uniformity of GaN thin films. It is also found that an appropriate mixture of N2 and H2 may be employed as the carrier gas to improve the flow field characteristic in the reactor. This results in an improved crystal growth of GaN thin films. [ABSTRACT FROM AUTHOR]

Abstract We report promising results regarding the possible use of AlN or Al 2 O 3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN films are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al 2 O 3 films are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al 2 O 3 /4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric field across the AlN or Al 2 O 3 is ∼ 3 MV/cm or ∼ 5 MV/cm respectively. By depositing an additional SiO 2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al 2 O 3 layers, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC or Al 2 O 3 /SiC interfaces. [ABSTRACT FROM AUTHOR]

Oblique incidence polarized IR reflectivity measurements of Metal Organic Chemical Vapor Deposition (MOCVD) grown GaN epitaxial layers on sapphire are discussed in the context of recent literature on Berreman effect. The dependence of the p-polarized reflectivity spectrum on incidence angle and thickness of the GaN films is analyzed theoretically and the results are compared with experiment. The 'Berreman minimum' that is the reflectivity minimum near the longitudinal-optical (LO) phonon frequency is shown to be due to optical interference. Our calculations show that in GaN layers with thickness greater than 0.1 μm and for high incidence angles, the frequency of 'Berreman minimum' does not correspond to the A1 LO phonon frequency. [ABSTRACT FROM AUTHOR]

This study reports on the fabrication of metal-organic chemical vapor deposited (MOCVD) YBa2Cu3O6+δ (YBCO) films doped with varying amounts of Ce and Ho and the characterization of their electrical, microstructural, and chemical properties. The films are prepared by vapor phase deposition of a Y-Ba-Cu precursor mix containing controlled amounts of Ce and Ho onto buffered metal strip templates. The comprehensive characterization of these films by critical current measurement, transmission electron microscopy, x-ray diffraction, Raman microspectroscopy, and x-ray absorption spectroscopy provides detailed information about the structure/chemistry/performance relationships and how they vary with varying amounts of Ce and Ho in the YBCO films. The microstructure exhibited by both the Ce-doped and the Ho-doped films contains a high density of crystal basal-plane aligned, fluoritelike precipitates within the YBCO matrix. For optimally doped samples, the influence of these nanocrystalline phases on the flux pinning properties manifests itself as a significant improvement in the critical current density (Jc) for magnetic field orientations that approach being parallel to the ab planes of the YBCO, while no appreciable change is observed in either self-field Jc or applied-field Jc performance in the vicinity of field orientations parallel to the YBCO c-axis. The Ce is almost exclusively concentrated in the fluoritelike nanoprecipitates, while the Ho incorporates into both the planar arrays of nanoprecipitates and the superconducting matrix, where it substitutes for Y in the YBCO lattice. The present findings for Ce and Ho doping are in interesting contrast with our prior findings for Zr-doped MOCVD films due to the fact that the Zr-doped films exhibit columnar precipitate arrays that produce a substantial improvement in Jc for magnetic field orientations parallel to the YBCO c-axis, while no appreciable change is observed in either self-field or applied-field Jc performance for field orientations parallel to the ab planes. These results suggest that improvement of the in-field Jc of YBCO films over an extended range of field angles could be achieved by doping strategies that simultaneously produce both ab-plane aligned and c-axis aligned precipitate arrays. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm’s have been synthesized. Structural characterizations by atomic force microscopy, scanning tunneling microscopy, cross-sectional transmission electron microscopy (XTEM), and Raman spectroscopy confirm that such large-scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few-layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth and buckling processes of the GTF. Measurements on mm-scale back-gated transistor devices fabricated from the transferred GTF show ambipolar field effect with resistance modulation ∼50% and carrier mobilities reaching ∼2000 cm2/V s. We also demonstrate quantum transport of carriers with phase coherence length over 0.2 μm from the observation of two-dimensional weak localization in low temperature magnetotransport measurements. Our results show that despite the nonuniformity and surface roughness, such large-scale, flexible thin films can have electronic properties promising for device applications. [ABSTRACT FROM AUTHOR]

Carrier relaxation dynamics in tin nitride (SnxNy) nanowires have been investigated using femtosecond transient absorption spectroscopy. The nanowires were grown directly on quartz using chemical vapor deposition and had diameters ≤200 nm and lengths up to 2 μm. Steady state optical transmission measurements suggest that the band gap is ∼2.9 eV while time resolved measurements reveal that free carrier absorption dominates the carrier dynamics and overcomes state filling within 0.5 ps of the incoming excitation pulse even when probing above the band edge. This is a unique and markedly different behavior compared to what we have observed in other semiconductor nanowires and it is attributed to fast scattering of the photogenerated carriers out of the excitation energy region and possible rise in the lattice temperature due to energy relaxation. Carrier relaxation occurs through two channels with a fast time constants of ≈200 ps and a slow time constant ranging between 5 and 8 ns while intensity measurements reveal negligible contribution from nonlinear effects such as Auger recombination. [ABSTRACT FROM AUTHOR]

Te-doped and ZnTe-doped diluted ZnSeTe samples were grown by using metal-organic chemical vapor deposition. The green lights emitted from these two samples in the photoluminescence (PL) measurement have different peak emission energies and can be attributed to different emission mechanisms. For the Te-doped sample, the PL emission band is excitation laser power independent, the lifetime of the PL emission is short, and the PL emission could be attributed to the emission originated from Te isoelectronic centers. For the ZnTe-doped sample, the energy of the green emission band is laser power dependent, the PL lifetime is much longer than the Te-doped sample, and the PL emission could be attributed to the emission from type-II ZnTe/ZnSe quantum dots. The results demonstrate that there are two different mechanisms responsible for the green PL emission in ZnSeTe system and our growth methods provide a way of selecting one of the two mechanisms for the green light emission in this system. [ABSTRACT FROM AUTHOR]

(111)-textured Pb(Zr0.4Ti0.6)O3 films (thickness of ∼120 nm) were deposited on (111)-oriented SrRuO3 bottom electrodes by pulse metal organic chemical vapor deposition (MOCVD). PZT single phase was evidenced over a large range of Pb precursor input rate into the MOCVD chamber. In this process window, the good control of the (111) texture of PZT films was confirmed. It is shown that the control of both the composition and orientation of PZT films leads to reproducible electric properties (Pr, Vc, resistance to fatigue) across the process window. Furthermore, the impact of the top electrode chemical nature, elaboration process, and annealing process upon the electric properties was studied systematically. [ABSTRACT FROM AUTHOR]

We report on the electrical and structural characterization of Mg-doped Al-rich p-type Al0.69Ga0.31N alloys on SiC substrate grown by metal organic chemical vapor deposition. The impact of growth conditions and dopant activation annealing conditions on the electrical conductivity was investigated. The most efficient activation was achieved by annealing in N2 gas at 1000 °C for 3 min in the presence of a SiO2 cap. The impact of p-GaN contact layer thickness was also studied. Higher growth temperature resulted in lower Mg incorporation, and for constant Mg concentration the resistivity increased with the increase in the growth temperature. Mg incorporation increased linearly with Mg effective flow. Transmission electron microscopy revealed the generation of vertical spike-like defects with increasing Mg doping. The resistivity also increased with the increase in Mg doping. A minimum resistivity of 10 Ω cm was achieved at 670 K. [ABSTRACT FROM AUTHOR]

Aluminum (Al) incorporation in AlxGa1-xN films grown by low-pressure metal organic vapor phase epitaxy using trimethylaluminum (TMAl) and trimethylgallium as group III precursors has been systematically studied. The solid phase Al composition of the AlxGa1-xN films varied nonlinearly with the Al gas phase composition. The incorporation kinetics of AlxGa1-xN alloy has been analyzed by using an adsorption-trapping model. Two parameters were used to characterize the properties of Al incorporation, i.e., the capture radius and the adsorption time of Al atoms. An exponential function of the Al composition of the AlxGa1-xN films versus the TMAl gas flow rate was obtained. It was demonstrated that the adsorption time of the Al atom was larger than the growth time of one atomic layer. The effects of ammonia flow rate, crystal growth rate, and growth temperature on the adsorption parameters were also discussed. [ABSTRACT FROM AUTHOR]

This paper describes the structural and electronic characterization of lanthanum hafnium oxide thin films deposited by metal organic chemical vapor deposition using a novel precursor mixture. Structural characterization is obtained using x-ray diffraction and cross-sectional transmission electron microscopy and indicates that the as-deposited films and films annealed up to 900 °C remain effectively amorphous. Capacitance voltage and current voltage measurements on metal-oxide-semiconductor capacitors made using the films as a gate dielectric show the films exhibit good electrical integrity following post deposition annealing at temperatures up to 950 °C. A dielectric constant, k for the films of 20±1.5 is determined and a density of interface states (at midgap) Dit of 3.9×1011 cm-2 eV-1 was measured. [ABSTRACT FROM AUTHOR]