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Beta-phase gallium oxide (β-Ga2O3) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power electronics and deep ultraviolet optoelectronics. Key advantages of β-Ga2O3 include the availability of large-size single-crystal bulk native substrates produced from melt and the precise control of n-type doping during both bulk growth and thin-film epitaxy. A comprehensive understanding of the fundamental growth processes, control parameters, and underlying mechanisms is essential to enable scalable manufacturing of high-performance epitaxial structures. This review highlights recent advancements in the epitaxial growth of β-Ga2O3 through various techniques, including Molecular Beam Epitaxy (MBE), Metal-Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Mist Chemical Vapor Deposition (Mist CVD), Pulsed Laser Deposition (PLD), and Low-Pressure Chemical Vapor Deposition (LPCVD). This review concentrates on the progress of Ga2O3 growth in achieving high growth rates, low defect densities, excellent crystalline quality, and high carrier mobilities through different approaches. It aims to advance the development of device-grade epitaxial Ga2O3 thin films and serves as a crucial resource for researchers and engineers focused on UWBG semiconductors and the future of power electronics. [ABSTRACT FROM AUTHOR]

2D materials have received a lot of interest over the past decade. Especially van der Waals (vdW) 2D materials, such as transition metal dichalcogenides (TMDCs), and their heterostructures exhibit semiconducting properties that make them highly suitable for novel device applications. Controllable mixing and matching of the 2D materials with different properties and precise control of the in‐plane twist angle in these heterostructures are essential to achieve superior properties and need to be established through large‐scale device fabrication. To gain fundamental insight into the potential control of these twist angles, 2D heterostructures of tungsten disulfide (WS2) and graphene (Gr) grown by bottom‐up synthesis via metal‐organic chemical vapor deposition (MOCVD) are investigated using a scanning transmission electron microscope (STEM). Specifically, the combination of conventional high‐resolution imaging with scanning nanobeam diffraction (SNBD) using advanced 4D STEM techniques is used to analyze moiré structures. The latter technique is used to reveal the epitaxial alignment within the WS2/Gr heterostructure, showing a direct influence of the underlying Gr layers on the moiré structure in the subsequent WS2 layers. In particular, the importance of grain boundaries (GBs) within the underlying WS2 and Gr layers on the structure of moiré patterns with rotation angles below 2° is discussed. [ABSTRACT FROM AUTHOR]

The epitaxial growth technique of InGaAs photodiode structures based on a digital InGaAs/GaAs metamorphic buffer layer by metalorganic chemical vapor deposition has been developed. The spectral dependence of the photocurrent of photodiodes based on the produced structures has a maximum at the 1.24 μm wavelength. The photosensitivity range at 10% of peak is 1.17–1.29 μm at room temperature. The current-voltage characteristics in the temperature range 9–300 K were investigated. It is shown that the dark current consists of generation-recombination and tunneling components. The dark current density at room temperature was 8 × 10–5 A/cm2 with a reverse bias of –5 V. [ABSTRACT FROM AUTHOR]

We demonstrate a broadband second-harmonic generator for the green spectral range based on a periodical polarity GaN waveguide structure. We grew the structure with a periodicity of 4 μ m using an MOCVD (metal-organic chemical vapor deposition) reactor. We tested the structure using femtosecond laser pulse pumping and obtained the second harmonic ( λ SH =512 nm) conversion efficiency 0.79 · 10 - 7 % · W - 1 for the pump peak power of 440 kW inside the waveguide. Based on the theoretical modeling of the dispersion curves of the pump and the second harmonic, we found multiple crossings, including an extended crossing. We relate this fact to the experimentally measured broadened second harmonic spectrum. [ABSTRACT FROM AUTHOR]

High-power quantum cascade lasers (QCLs) have a wide application prospect. In this paper, a high-power high-beam-quality device with a large ridge width is demonstrated. The effect of different ridge widths on mode loss was studied, and the results showed that the mode loss decreased as the ridge width increased. Furthermore, as the width of the ridge increased, the temperature of the active region rose. In the experiment, the wafers were grown by metal–organic chemical vapor deposition (MOCVD), and the ridge width of the device was controlled by wet etching. A laser with a ridge width of 15 µm and a length of 5 mm achieved an output of 2.2 W under 288 K continuous wave (CW) operation, with a maximum slow-axis divergence angle of 27.2° and a device wavelength of 5 μm. The research results of this article promote the industrial production of base transverse mode QCL. [ABSTRACT FROM AUTHOR]

Germanium diselenide (GeSe2) is a 2D semiconductor with air stability, a wide bandgap, and anisotropic optical properties. The absorption and photoluminescence (PL) of single‐crystalline 2D GeSe2 grown by metal‐organic chemical vapor deposition and their dependence on temperature and polarization are studied. The PL spectra exhibit peaks at 2.5 eV (peak A) and 1.8 eV (peak B); peak A displays a strongly polarized emission along the short axis of the crystal, and peak B displays a weak polarization perpendicular to that of peak A. With increasing temperature, peak B shows anomalous behaviors, i.e., an increasing PL energy and intensity. The excitation energy‐dependent PL, time‐resolved PL, and density functional theory calculations suggest that peak A corresponds to the band‐edge transition, whereas peak B originates from the inter‐band mid‐gap states caused by selenium vacancies passivated by oxygen atoms. The comprehensive study on the PL of single‐crystalline GeSe2 sheds light on the origins of light emission in terms of the band structure of anisotropic GeSe2, making it beneficial for the corresponding optoelectronic applications. [ABSTRACT FROM AUTHOR]

The lattice parameter and thermal expansion coefficient mismatch between the silicon substrate and GaN lead to high tensile stress, which makes the GaN epitaxial layer prone to cracking. Effective compensation of tensile stress on GaN to prevent cracking is an important issue in GaN epitaxial growth. In this work, GaN‐on‐silicon materials with different AlGaN buffer layer structures are prepared by metal‐organic chemical vapor deposition (MOCVD). The GaN epitaxial material with a smooth and crack‐free surface is fabricated by inserting 7 AlGaN buffer layers. The crystal quality of GaN is characterized using high resolution X‐ray diffraction (HRXRD). The full‐width half maximum (FWHM) value of GaN(002) and GaN(102) crystal plane is 398 and 780 arcsec, respectively. The surface root mean square (RMS) roughness of GaN material is 0.31 nm, and the vertical breakdown voltage (BV) of the epitaxial wafer reaches 918 V. The results show that high Al content of the AlGaN buffer layer can effectively reduce the tensile stress and dislocation density of the GaN layer when the entire AlGaN layer thickness remains constant. Suppressing the generation of surface cracks and improving the crystal quality can improve the vertical breakdown voltage and two‐dimensional electron gas (2‐DEG) characteristics of GaN epitaxial wafers. [ABSTRACT FROM AUTHOR]

Germanium diselenide (GeSe2) is a 2D semiconductor with air stability, a wide bandgap, and anisotropic optical properties. The absorption and photoluminescence (PL) of single‐crystalline 2D GeSe2 grown by metal‐organic chemical vapor deposition and their dependence on temperature and polarization are studied. The PL spectra exhibit peaks at 2.5 eV (peak A) and 1.8 eV (peak B); peak A displays a strongly polarized emission along the short axis of the crystal, and peak B displays a weak polarization perpendicular to that of peak A. With increasing temperature, peak B shows anomalous behaviors, i.e., an increasing PL energy and intensity. The excitation energy‐dependent PL, time‐resolved PL, and density functional theory calculations suggest that peak A corresponds to the band‐edge transition, whereas peak B originates from the inter‐band mid‐gap states caused by selenium vacancies passivated by oxygen atoms. The comprehensive study on the PL of single‐crystalline GeSe2 sheds light on the origins of light emission in terms of the band structure of anisotropic GeSe2, making it beneficial for the corresponding optoelectronic applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have emerged as a promising class of materials with unique physical and chemical properties that offer exciting prospects for various applications. Among all the synthesis methods, chemical vapor deposition (CVD) techniques have demonstrated great advantages in the large-scale production of 2D materials with a controlled thickness. One of the main challenges in the growth of 2D materials is the need for high temperatures and crystalline substrates, which restrict the scalability and compatibility of 2D materials with existing manufacturing processes, due to the high thermal budget and the necessity to transfer the 2D films to secondary substrates. Low-temperature growth methods for 2D materials have the potential to overcome this challenge and enable the integration of 2D materials into a wide range of devices and applications. In recent years, there have been substantial efforts to develop low-temperature growth techniques for different 2D materials, including graphene, hexagonal boron nitride and transition metal dichalcogenides. These methods include thermal CVD, plasma-enhanced CVD, atomic layer deposition and metal-organic chemical vapor deposition. This review not only discusses the progress in the growth but also highlights the applications of low-temperature-grown 2D materials in various fields, such as field effect transistors, sensors, photodetectors, catalysts, batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

A method for defects extraction for a mercury cadmium telluride (MCT) multilayer lowbandgap heterostructure is presented. The N+/T/p/T/P+/n+ epitaxial layer was deposited on a GaAs substrate by a metal-organic chemical vapour deposition (MOCVD). The absorber was optimized for a cut-off wavelength of λc= 6 µm at 230 K. Deep-level transient spectroscopy (DLTS) measurements were conducted for the isolated junctions of the N+/T/p/T/P+/n+ heterostructure. Three localised point defects were extracted within the ptype active layer. Two of them were identified as electron traps and one as a hole trap, respectively. [ABSTRACT FROM AUTHOR]

Nanostructured zirconium carbide coatings were deposited on the surface of multi-walled carbon nanotubes (MWCNT) by the metal-organic chemical vapor deposition growth technique using bis(cyclopentadienyl)zirconium dichloride as precursor. The effect of synthesis parameters on the morphology of samples ZrC/MWCNT was studied and the optimal synthesis conditions were selected. The structure and morphology of synthesized hybrid nanomaterials were investigated by X-ray diffraction, scanning and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The surface morphology of a buffer template is an important factor in the heteroepitaxial integration of optoelectronic devices with a significant lattice mismatch. In this work, InP-based long-wave infrared (~8 µm) emitting quantum cascade lasers with active region designs lattice-matched to InP were grown on GaAs and Si substrates employing InAlGaAs step-graded metamorphic buffer layers, as a means to assess the impact of surface roughness on device performance. A room-temperature pulsed-operation lasing with a relatively good device performance was obtained on a Si template, even with a large RMS roughness of 17.1 nm over 100 µm2. Such results demonstrate that intersubband-operating devices are highly tolerant to large RMS surface roughness, even in the presence of a high residual dislocation density. [ABSTRACT FROM AUTHOR]

High-temperature annealing has been regarded as an effective technology to improve the performance of Ga2O3-based solar-blind photodetectors (SBPDs). However, as a metastable phase, ε-Ga2O3 thin film may undergo phase transformation during post-annealing. Therefore, it is necessary to investigate the effect of the phase transition and the defect formation or desorption on the performance of photodetectors during post-annealing. In this work, the ε-Ga2O3 thin films were grown on c-plane sapphire with a two-step method, carried out in a metal-organic chemical vapor deposition (MOCVD) system, and the ε-Ga2O3 metal-semiconductor-metal (MSM)-type SBPDs were fabricated. The effects of post-annealing on ε-Ga2O3 MSM SBPDs were investigated. As a metastable phase, ε-Ga2O3 thin film undergoes phase transition when the annealing temperature is higher than 700 °C. As result, the decreased crystal quality makes an SBPD with high dark current and long response time. In contrast, low-temperature annealing at 640 °C, which is the same as the growth temperature, reduces the oxygen-related defects, as confirmed by X-ray photoelectron spectroscopy (XPS) measurement, while the good crystal quality is maintained. The performance of the SBPD with the post-annealing temperature of 640 °C is overall improved greatly compared with the ones fabricated on the other films. It shows the low dark current of 0.069 pA at 10 V, a rejection ratio (Rpeak/R400) of 2.4 × 104 (Rpeak = 230 nm), a higher photo-to-dark current ratio (PDCR) of 3 × 105, and a better time-dependent photoresponse. These results indicate that, while maintaining no phase transition, post-annealing is an effective method to eliminate point defects such as oxygen vacancies in ε-Ga2O3 thin films and improve the performance of SBPDs. [ABSTRACT FROM AUTHOR]

Acquiring homogeneous and reproducible wafer-scale transition metal dichalcogenide (TMDC) films is crucial for modern electronics. Metal–organic chemical vapor deposition (MOCVD) offers a promising approach for scalable production and large-area integration. However, during MOCVD synthesis, extraneous carbon incorporation due to organosulfur precursor pyrolysis is a persistent concern, and the role of unintentional carbon incorporation remains elusive. Here, we report the large-scale synthesis of molybdenum disulfide (MoS2) thin films, accompanied by the formation of amorphous carbon layers. Using Raman, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM), we confirm how polycrystalline MoS2 combines with extraneous amorphous carbon layers. Furthermore, by fabricating field-effect transistors (FETs) using the carbon-incorporated MoS2 films, we find that traditional n-type MoS2 can transform into p-type semiconductors owing to the incorporation of carbon, a rare occurrence among TMDC materials. This unexpected behavior expands our understanding of TMDC properties and opens up new avenues for exploring novel device applications. [ABSTRACT FROM AUTHOR]

Deep-level transient spectroscopy (DLTS) measurements were performed on HgCdTe heterostructure photodiode grown by metal-organic chemical vapor deposition (MOCVD) on GaAs substrate. In order to extract defects from individual layers of the heterostructure, three consecutive etchings were performed. In the first experiment, the N+/T/p/T/P+/n+ structure was chemically etched to the N+ bottom contact to obtain a mesa-type detector. Six localized defects were extracted across the entire photodiode. In the second experiment, the bottom contact was made to the p-type absorber. Two localized defects were found in the p/T/P+/n+ structure. In the third experiment, the top layers were removed and N+/T/p type detector was made—the cap contact was made to the p-type absorber, the bottom to the N+ layer. Five defect levels were identified, three of which overlap with the first experiment. A deep-trap level located at 183 meV above the top of the valence band was identified within the absorber bandgap. This energy coincides with the activation energy determined from the Arrhenius plot for the dark currents. A defect at the level of ∼0.5Eg suggests that the dark current at low reverse bias voltage is dominated by the Shockley–Read–Hall (SRH) mechanism. [ABSTRACT FROM AUTHOR]

Experimental results are reported for a medium-wavelength infrared (MWIR) HgCdTe photodetector designed in a joint laboratory run by VIGO Photonics S.A. and the Military University of Technology. The parameters of the MWIR detectors fabricated with HgCdTe heterostructures were studied. Advances in the metal–organic chemical vapor deposition (MOCVD) technique enable the growth of HgCdTe epilayers with a wide range of composition and doping, used for uncooled infrared detectors. Device-quality HgCdTe heterostructures were deposited on 2-inch-diameter, low-cost (100) GaAs substrates. The heterostructures obtained were examined measuring the spectral response and current–voltage characteristics in different temperatures. Our intention here was to determine the relationship between electrical and optical results, using thermal analysis of dark current properties and photocurrent and spectral characteristics. The appearance of an additional signal source in certain ranges of reverse voltages was examined. Comparative analysis of the electrical and electro-optical characterization enabled us to isolate the photocurrent originating from different layers of the detector structure. Automated measurement techniques make it possible to correlate current responsivity with current–voltage curves measured as a function of temperature in a range from 10 K to 300 K with ±0.05 K resolution without human exertion. LabVIEW-aided data acquisition enables the averaging of each characteristic several hundred times, eliminates random and human errors, and decreases measurement uncertainty. [ABSTRACT FROM AUTHOR]

Zirconia layers are often used as thermal barriers. In recent years, depositions by chemical vapor deposition methods using a metalorganic precursor (MOCVD) have been primarily investigated. Here, we combine MOCVD with plasma activation ‐ plasma‐enhanced chemical vapor deposition (PECVD]) ‐ of the gas phase and/or the growth surface to lower the growth temperature and to allow for a flexible coating design. PECVD causes the precursor to be transformed into a chemically active species, yielding thin films with a five times higher sticking coefficient compared to MOCVD. This leads to the onset of crystallization at lower surface temperatures. Carbon is incorporated at oxygen sites, so that the crystalline structure of zirconia is preserved, but the electrical conductivity is affected. The thermal conductivity is like that of pure zirconia. [ABSTRACT FROM AUTHOR]

We employed the selective-area-epitaxy technique using metalorganic chemical vapor deposition to fabricate and study samples of semiconductor heterostructures that incorporate highly strained InGaAs quantum wells (980–990 nm emission wavelength). Selective area epitaxy of InGaAs quantum wells was performed on templates that had a patterned periodic structure consisting of a window (where epitaxial growth occurred) and a passive mask (where epitaxial growth was suppressed), each with a width of 100 µm for every element. Additionally, a selectively grown potential barrier layer was included, which was characterized by an almost parabolic curvature profile of the surface. We conducted a study on the influence of the curvature profile of the growth surface on the optical properties of InGaAs quantum wells and the spatial distribution of composition in an ultrawide window. Our results showed that, under fixed selective-area-epitaxy conditions, the composition of the InxGa1−xAs and the wavelength of the quantum-well emission changed across the width of the window. Our study demonstrates that increasing the curvature profile of the growth surface of highly strained quantum wells leads to a transition in the photoluminescence wavelength distribution profile across the window, from quasi-parabolic to inverted parabolic. [ABSTRACT FROM AUTHOR]

Volatile, reactive, and thermally stable organometallic copper and silver complexes are of significant interest as precursors for the metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) of ultra-thin metallic films. Well-established CuI and AgI precursors are commonly stabilized by halogens, phosphorous, silicon, and oxygen, potentially leading to the incorporation of these elements as impurities in the thin films. These precursors are typically stabilized by a neutral and anionic ligand. Recent advancements were established by the stabilization of these complexes using N-heterocyclic carbenes (NHCs) as neutral ligands. To further enhance the reactivity, in this study the anionic ligand is sequentially changed from β-diketonates to β-ketoiminates and β-diketiminates, yielding two new CuI and two new AgI NHC-stabilized complexes in the general form of [M(NHC) (R)] (M = Cu, Ag; R = β-ketoiminate, β-diketiminate). The synthesized complexes were comparatively analyzed in solid, dissolved, and gaseous states. Furthermore, the thermal properties were investigated to assess their potential application in MOCVD or ALD. Among the newly synthesized complexes, the β-diketiminate-based [Cu(tBuNHC) (NacNacMe)] was identified to be the most suitable candidate as a precursor for Cu thin film deposition. The resulting halogen-, oxygen-, and silicon-free CuI and AgI precursors for MOCVD and ALD applications are established for the first time and set a new baseline for coinage metal precursors. [ABSTRACT FROM AUTHOR]

Heavily Si-doped GaN epitaxial layers (n+GaN) have been grown on semi-insulating 6H-SiC substrate by metal–organic chemical vapor deposition at 1030°C using H2 and N2 as carrier gases. Thin film characterization results demonstrated that n+GaN grown in N2 carrier gas has superior morphological and crystalline quality to that grown in H2. The surface morphology of n+GaN grown with N2 carrier gas is insensitive to the growth rate and SiH4 flow with Si doping concentration up to 1.1 × 1020/cm3. Secondary ion mass spectrometry analysis confirmed that C and O impurity levels in n+GaN are one order of magnitude lower with N2 carrier gas than with H2. The results thus indicate that 100% N2 could be a better carrier gas candidate to enable a broader process window for future HEMT S/D n+GaN selective area epitaxial process applications. [ABSTRACT FROM AUTHOR]

AlzGa1−zAs layers of various compositions were grown using metalorganic chemical vapor deposition on a GaAs substrate with a pattern of alternating SiO2 mask/window stripes, each 100 µm wide. Microphotoluminescence maps and thickness profiles of AlzGa1−zAs layers that demonstrated the distribution of the growth rate and z in the window were experimentally studied. It was shown that the layer growth rate and the AlAs mole fraction increased continuously from the center to the edge of the window. It was experimentally shown that for a fixed growth time of 10 min, as z increased from 0 to 0.3, the layer thickness difference between the center of the window and the edge increased from 700 Å to 1100 Å, and the maximum change in z between the center of the window and the edge reached Δz 0.016, respectively. Within the framework of the vapor -phase diffusion model, simulations of the spatial distribution of the layer thickness and z across the window were carried out. It was shown that the simulation results were in good agreement with the experimental results for the effective diffusion length D/k: Ga—85 µm, Al—50 µm. [ABSTRACT FROM AUTHOR]

In the paper, non-porous and smooth gadolinium oxide layers were synthesized on the inner surfaces of quartz glass tubes using MOCVD (Metalorganic Chemical Vapour Deposition) in the temperature range of 580–800 °C. Commercial Gd(tmhd) 3 (Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium(III), 99% (99.9%-Gd)) was a basic reactant. Pure argon (99.999%) was used as a carrier gas. Air was applied to eliminate the carbon. It also was a carrier gas. The magnitude of the extended Gr x /Re x 2 criterion did not exceed the value of 0.01. Other synthesis conditions were established in such a way that this condition was maintained. The evaporation temperature of Gd(tmhd) 3 varied in the range of 170–270 °C.The influence of the synthesis conditions on microstructure, structure and transparency of the deposited layers was investigated. Oval-shaped Gd 2 O 3 aggregates and fine crystallites were formed regardless of the synthesis conditions. The conducted research also shows that the lower deposition temperature and the higher evaporation temperature of reactant, causes smaller crystallite sizes and smaller their number. [ABSTRACT FROM AUTHOR]

A comparative study of figure-of-merit fiber sensors of the mass concentration of NaCl solutions based on single-mode and multi-mode fibers was carried out. Lossy mode resonance is realized on chemically thinned sections of optical fibers to various diameters (from 26 to 100 μm) coated with ZnTe. Thin-film coatings were applied using the method of metalorganic chemical vapor deposition (MOCVD). Samples of single-mode and multi-mode fiber sensors were created in such a way that the depth and spectral position of resonances in aqueous NaCl solutions coincided. Sensors implemented on a single-mode fiber have a higher sensitivity (5930 nm/refractive index unit (RIU)) compared to those on a multi-mode fiber (4860 nm/RIU) and a smaller half-width of the resonance in the transmission spectrum. According to the results of experiments, figure-of-merit sensors are in the range of refractive indices of 1.33–1.35 for: multi-mode fiber—25 RIU−1, single-mode fiber—75 RIU−1. The sensitivity of the resulting sensors depends on the surface roughness of the ZnTe coating. The roughness of films synthesized on a single-mode fiber is four times higher than this parameter for a coating on a multi-mode fiber. For the first time, in the transmission spectrum during the synthesis of a thin-film coating on a multi-mode fiber, the possibility of separating the first nine orders of resonances into electric and magnetic transverse components has been demonstrated. The characteristics of sensors with the operating wavelength range in the visible (500–750 nm) and infrared (1350–1550 nm) regions of the spectrum are compared. The characteristics of multi-mode lossy mode resonance sensors are demonstrated, which make them more promising for use in applied devices than for laboratory research. [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]

InGaN red light emitting diode (LED) is one of the crucial bottlenecks that must be broken through to realize high‐resolution full‐color mini/micro‐LED displays. The efficiency of InGaN LEDs drops rapidly as the emission spectra go from blue/green to red range due to the poor quality of high‐indium‐content InGaN materials. Here, high‐performance InGaN red LEDs on sapphire grown by metal–organic chemical vapor deposition through strain modulation are reported. A composite buffer layer is proposed to increase the surface lattice constant of GaN and hence successfully enhances the indium incorporation efficiency of the following InGaN active layers. Consequently, a high‐efficiency InGaN red mini‐LED chip (mesa area: 100 × 200 µm2) with a peak wavelength of 629 nm and an external quantum efficiency of 7.4% is realized. Finally, a full‐color nitride mini‐LED display panel with 74.1% coverage of Rec.2020 color gamut by using the InGaN red mini‐LED chips is fabricated. The study signifies the great potentials of full‐nitrides high‐resolution full‐color mini/micro‐LED displays. [ABSTRACT FROM AUTHOR]

β-Ga2O3 thin films with both a 45 nm Si-doped conductive epilayer and unintentionally doped epilayer were grown on c-plane sapphire substrate by metalorganic chemical vapor deposition. β-Ga2O3 based metal–oxide–semiconductor field-effect transistors (MOSFETs) were fabricated with gate recess depths of 20 nm and 40 nm (it indicated gate depth with 70 nm and 50 nm, respective), respectively, and without said recessing process. The conductivity of β-Ga2O3 epilayers was improved through low in situ doping using a tetraethoxysilane precursor to increase MOSFET forward current density. After recessing, MOSFET operation was transferred from depletion to enhanced mode. In this study, the maximum breakdown voltage of the recessed 40 nm transistor was 770 V. The etching depth of a recessed-gate device demonstrates its influence on device electrical performance. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown on sapphire substrates using metal–organic chemical vapor deposition (MOCVD) with trimethylgallium (TMG) and bis(cyclopentadienyl)magnesium (Cp2Mg) as the precursors for Ga and Mg, respectively. The Mg-doped GaN layer, with a [Mg]/[TMG] ratio of 0.33, was systematically analyzed to compare its mechanical properties and creep behavior to those of the undoped GaN thin film, marking the first investigation into the creep behavior of both GaN and Mg-doped GaN thin films. The results show that the incorporated [Mg]/[TMG] ratio was sufficient for the transition from n-type to p-type conductivity with higher hole concentration around 4.6 × 10 17 cm−3. Additionally, it was observed that Mg doping impacted the hardness and Young's modulus, leading to an approximately 20% increase in these mechanical properties. The creep exponent is also affected due to the introduction of Mg atoms. This, in turn, contributes to an increase in pre-existing dislocation density from 2 × 108 cm−2 for undoped GaN to 5 × 109 cm−2 for the Mg-doped GaN layer. The assessment of the creep behavior of GaN and Mg-doped GaN thin films reveals an inherent creep mechanism governed by dislocation glides and climbs, highlighting the significance of Mg doping concentration in GaN thin films and its potential impact on various technological applications. [ABSTRACT FROM AUTHOR]

In this work, we demonstrated Ga2O3-based power MOSFETs grown on c-plane sapphire substrates using in-situ TEOS doping for the first time. The β-Ga2O3:Si epitaxial layers were formed by the metalorganic chemical vapor deposition (MOCVD) with a TEOS as a dopant source. The depletion-mode Ga2O3 power MOSFETs are fabricated and characterized, showing the increase of the current, transconductance, and breakdown voltage at 150 °C. In addition, the sample with the TEOS flow rate of 20 sccm exhibited a breakdown voltage of more than 400 V at RT and 150 °C, indicating that the in-situ Si doping by TEOS in MOCVD is a promising method for Ga2O3 power MOSFETs. [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]

Heteroepitaxial κ‐Ga2O3 films grown by metal–organic chemical vapor deposition (MOCVD) are found to have superior materials and electrical properties thanks to the interfacing with a β‐Ga2O3 template layer. κ‐Ga2O3 grown on sapphire has not been able to demonstrate its full potential due to materials imperfections created by strain induced by the lattice mismatch at the interface between the epilayer and the substrate. By adopting a β‐Ga2O3 template on a c‐sapphire substrate, higher quality κ‐Ga2O3 thin films are obtained, as evidenced by a smoother surface morphology, narrower X‐ray diffraction (XRD) peaks, and superior electrical performance. The implications of this phenomenon, caused by β‐Ga2O3 buffer layer, are already very encouraging for both boosting current device performance and opening up the perspective of novel applications for Ga2O3. [ABSTRACT FROM AUTHOR]

We report that, for the first time, a low-temperature GaN (LT-GaN) layer prepared by metal–organic chemical vapor deposition (MOCVD) regrowth was used as a Mg stopping layer (MSL) for a GaN trench current–aperture vertical electron transistor (CAVET) with p-GaN as a carrier blocking layer (CBL). Inserting LT-GaN on top of the p-GaN effectively suppresses Mg out-diffusion into the regrown AlGaN/GaN channel, contributing to the high current capability of GaN vertical devices with a p-GaN CBL. With different MOCVD growth conditions, MSLs inserted in trench CAVETs were comprehensively investigated for the influence of MSL regrowth temperature and thickness on device performance. With the best on-state current performance obtained in this study, the trench CAVET with a 100 nm thick MSL regrown at 750 °C shows a high drain current of 3.2 kA/cm2 and a low on-state resistance of 1.2 mΩ∙cm2. The secondary ion mass spectrometry (SIMS) depth profiles show that the trench CAVET with the 100 nm thick MSL regrown at 750 °C has a dramatically decreased Mg diffusion decay rate (~39 nm/decade) in AlGaN/GaN channel, compared to that of the CAVET without a MSL (~104 nm/decade). In developing GaN vertical devices embedded with a Mg-doped p-type layer, the LT-GaN as the MSL demonstrates a promising approach to effectively isolate Mg from the subsequently grown layers. [ABSTRACT FROM AUTHOR]

The effects of pre-metallization of the growth surface on film stress and structural properties of undoped and Ge-doped AlxGa1−xN (x ~ 0.5–0.6) epilayers grown by metal–organic chemical vapor deposition (MOCVD) on 500 nm-thick hydride vapor-phase epitaxy (HVPE) AlN/sapphire templates were investigated. AlxGa1−xN typically grows under compressive stress on the AlN templates due to its larger lattice parameter, which can lead to increased surface roughness and V-pits in undoped and Ge-doped AlxGa1−xN. The introduction of the group III sources in the growth ambient for a short period of time (5 s) prior to the addition of NH3 induced a tensile growth stress in the AlxGa1−xN, as measured by in situ wafer curvature measurements, which correlated with an improvement in the surface morphology. However, the pre-metallization was also observed to result in the deposition of a carbon-rich layer at the AlxGa1−xN/AlN interface and an increased density of screw-type dislocations as measured by post-growth x-ray diffraction. By utilizing a pre-metallization step with a lower AlxGa1−xN growth rate, it was possible to eliminate the carbon interfacial layer and maintain low surface v-pitting and threading dislocation density in Ge-doped AlxGa1−xN. The results provide insight into the impact of pre-metallization on the AlxGa1−xN/AlN interface and the structural properties of the layers. [ABSTRACT FROM AUTHOR]

The spectral sensitivity change of a silicon photodiode with its temperature is analyzed in the article. This research area is relevant because silicon photodiodes are used as sensitive elements in temperature control systems of the vapour-phase epitaxy process. Technical characteristics of the obtained semiconductor devices are mostly determined by the quality of heterostructures used for their manufacture. The optical pyrometry method is used for the surface temperature precise control of the A3B5 solid solutions active layers during metalorganic chemical vapour deposition (MOCVD). Since the surface relief and parameters during deposition change significantly, classical pyrometry leads to significant measurement errors, so the pyrometry method with radiation compensation is used. This method combines the wafer surface radiation measurement and its reflectivity. This allows to determine the surface temperature true value, the layer thickness and the heat distribution uniformity on the wafer in real time. However, for high precision, it is necessary to take into account the temperature coefficient of the silicon photodiode ampere-watt sensitivity change. The basics of MOCVD technology are discussed in this article. The features of the epitaxy process in the reactor with high-precision temperature control are highlighted. The analytical and empirical study of change in silicon photodiode ampere-watt sensitivity and its effect on measurement accuracy are given. The research results improve the accuracy of real temperature measurement using pyrometric parameter control systems in MOCVD technology and help to understand and to take into account the influence of temperature factors on measurement accuracy to improve this technology. [ABSTRACT FROM AUTHOR]

We report the electrical properties of Al0.3Ga0.7N/GaN heterojunction field effect transistor (HFET) structures with a Ga2O3 passivation layer grown by metal–organic chemical vapor deposition (MOCVD). In this study, three different thicknesses of β-Ga2O3 dielectric layers were grown on Al0.3Ga0.7N/GaN structures leading to metal-oxide-semiconductor-HFET or MOSHFET structures. X-ray diffraction (XRD) showed the ( 2 ¯ 01) orientation peaks of β-Ga2O3 in the device structure. The van der Pauw and Hall measurements yield the electron density of ~ 4 × 1018 cm−3 and mobility of ~770 cm2V−1s−1 in the 2-dimensional electron gas (2DEG) channel at room temperature. Capacitance–voltage (C-V) measurement for the on-state 2DEG density for the MOSHFET structure was found to be of the order of ~1.5 × 1013 cm−2. The thickness of the Ga2O3 layer was inversely related to the threshold voltage and the on-state capacitance. The interface charge density between the oxide and Al0.3Ga0.7N barrier layer was found to be of the order of ~1012 cm2eV−1. A significant reduction in leakage current from ~10−4 A/cm2 for HFET to ~10−6 A/cm2 for MOSHFET was observed well beyond pinch-off in the off-stage at -20 V applied gate voltage. The annealing at 900° C of the MOSHFET structures revealed that the Ga2O3 layer was thermally stable at high temperatures resulting in insignificant threshold voltage shifts for annealed samples with respect to as-deposited (unannealed) structures. Our results show that the MOCVD-gown Ga2O3 dielectric layers can be a strong candidate for stable high-power devices. [ABSTRACT FROM AUTHOR]

The ex situ sputtered AlN buffer and GaN epilayer grown on top of it by metalorganic chemical vapor deposition were studied comprehensively by a variety of techniques including atomic force microscope, high resolution x-ray diffraction, Raman and x-ray photoelectron spectroscopy characterizations. It exhibited that the AlN buffer deposited by using sputtering technique could be oxidized with exposure in atmosphere. Such oxidation phenomenon significantly influences the characteristics of GaN epilayer, for example leading to poor surface morphology, high dislocation density, and large compressive stress. This study demonstrated the effect of oxygen impurities on GaN growth and has an important guiding significance for the growth of high-quality III-nitride related materials. [ABSTRACT FROM AUTHOR]

This letter reports vacuum annealing of lateral field-plated $\beta $ -Ga2O3 MOSFETs with significant current recovery and improvement in the on-state resistance, $\text{R}_{\text {on}}$ , after Reactive Ion Etching (RIE) induced damage. We fabricate and characterize MOSFETs based on Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) grown $\beta $ -Ga2O3 wafers to better understand the effects of vacuum annealing. We see a clear trend of vacuum annealed devices showing no reduction in breakdown voltages, $\text{V}_{\text {br}}$ , as compared to polymer passivated MOSFETs. This trend holds for identical gate-drain separation, $\text{L}_{\text {gd}}$ , varying from $20 ~\mu \text{m}$ to $60 ~\mu \text{m}$. Devices show up to 10 times reduction in $\text{R}_{\text {on}}$ as compared to previously reported $\text{R}_{\text {on}}$ for SU-8 passivated devices. For MBE sample, $\text{V}_{\text {br}}$ of 7.16 kV for a $\text{L}_{\text {gd}}$ = $40 ~\mu \text{m}$ device, with an average field strength of 1.79 MVcm $^{{-{1}}}$ and peak drain current density of 40 mA/mm, is reported. $\text{R}_{\text {on}}$ is $897 \Omega $. mm, giving Baliga’s Figure of Merit (BFOM) as 5.71 MWcm $^{{-{2}}}$. For a $\text{L}_{\text {gd}}$ = $60 ~\mu \text{m}$ device, we report record high breakdown of 8.56 kV with BFoM of 4.9 MWcm $^{{-{2}}}$. For MOCVD grown sample, a $\text{L}_{\text {gd}}$ = $60 ~\mu \text{m}$ device has $\text{V}_{\text {br}}$ of 6.11 kV, $\text{R}_{\text {on}}$ of 1.98 $\text{k}\Omega $. mm and corresponding BFoM of 1.88 MWcm $^{{-{2}}}$. Transfer Length Method (TLM) analysis indicates incomplete post etch current recovery after vacuum annealing. [ABSTRACT FROM AUTHOR]

150 mm Indium Phosphide wafers are now commercially available with crystal quality comparable to wafer of smaller radius. This may pave the way for scaling up the production of a multitude of photonic devices for Datacoms operating in the 1.30- 1. 55 μ m infrared range with a gain in wafer surface of factor 4 and a reduction of roughly 50% in die cost. To achieve this goal, it is of utmost importance to prove that both AlGaInAs and InGaAsP quaternary compound semiconductors can be grown by metal–organic chemical vapor deposition (MOCVD) on wafers of larger sizes with both thickness and composition uniformities comparable to those achievable on 75 mm. In this article, we report pioneering production technology developments based on the Planetary Reactor® design. Both reactor and related inlet geometry have been deeply revisited with the introduction of a novel 4-fold injector, which in combination with Cl 2 In-situ chamber clean, prove to enable such transition in wafer size. Sub-nanometric photoluminescence in-wafer uniformities are demonstrated and historic challenges, such as drift in material composition of highly sensitive InGaAsP alloys during a production campaign, are addressed thanks to this unique combination. Uniformity, tunability and reproducibility results are thus presented for two prototypical case scenarios: a highly strained AlGaInAs multiple quantum well (MQW) and a bulk InGaAsP layer with wavelength emission of 1550 nm and 1100 nm respectively to corroborate reactor flexibility in meeting industry requirements for next device generation. [Display omitted] • MOCVD growth of IIIAsP compound semiconductors on 150 mm Indium Phosphide wafer. • IIIAsP material uniformity tuning by 4-fold gas inlet system. • Cl 2 based in-situ chamber clean for superior system repeatability. [ABSTRACT FROM AUTHOR]

Stable and volatile complexes of composition [Ni(SB)Li(dkt)] are quite suitable template to design SSPs containing lithium and transition metals for LiTMO 2 CVD. Combination of different ligands stabilizes heterometallic complexes delivering stability and volatility. [Display omitted] A series of volatile Li-Ni heteroleptic complexes [Ni(SB)Li(dkt)] were prepared as single-source precursors (SSP) for thin-film lithium ion microbatteries, Ni(SB) = Ni(acacen) (1) or Ni(CH 3 acacen) (2), dkt = beta-diketonate ligand. Crystal structures of heterometallic complexes [Ni(acacen)Li(ptac)] (3), [Ni(CH 3 acacen)Li(ptac)] (4), [Ni(acacen)Li(LF)] (5), [Ni(acacen)Li(tmhd)] (6), [Ni(CH 3 acacen)Li(tmhd)] (7), [Ni(acacen)Li(tmha)] (8) (where acacen = N,N' -ethylenebis (acetylacetoniminate), CH 3 acacen = N,N'- propylenebis(acetylacetoniminate), tmhd = 2,2,6,6-tetramethyl-heptane-3-imino-5-onate, ptac = 1,1,1-trifluoro-5,5-dimethyl-hexane-2,4-dionate, LF = 1,1,1-trifluoro-5-methoxy-5-methyl-hexane-2,4-dionate, tmha = 2,2,6,6-tetramethyl-heptane-3-imino-5-onate) were studied by X-ray diffraction. Structures of 3 – 8 are molecular, the packing motif of binuclear complexes is largely determined by the stacking of Ni(SB) fragments. Li atoms always have a tetrahedral coordination involving donor oxygen atoms of the ligands, while oxygen atoms of SB are bridging. Crystals of 3,5,6 are formed by infinite stacking of binuclear molecules, while centrosymmetric pairs of heterocomplexes are formed in crystals of 4,7,8. The thermal properties of the compounds were studied by vacuum sublimation and TGA. It was established that Ni(CH 3 acacen)-derivatives 2,4,7 are more volatile and have lower melting point compared to Ni(acacen)-ones 1,3,5,6. Li(dkt) moiety in the heterocomplex affects thermal properties as following: fluorine-containing complexes 3,4,5 are less volatile than non-fluorinated ones, and ketoiminate complex 8 is the least thermally stable. Following the obtained results, complexes 6,7 can be recommended as SSP for chemical vapor deposition of mixed oxides films. [ABSTRACT FROM AUTHOR]

• The regulation of O defects in AlGaN on the HTA-AlN template is revealed. • O defects have limited diffusion distance and concentration in the AlN epilayer. • Increasing V/III ratio or decreasing Al components can decrease O concentration. • The underlying mechanism is the increased formation energy of O defects. The regulation of oxygen (O) point defects in AlGaN-based epilayers grown on high-temperature annealed AlN (HTA-AlN) template by metal–organic chemical vapor deposition (MOCVD) is systematically investigated in this work. The concentration of O impurity in AlN epilayers is restricted to 1 × 1017 cm−3, but decreases by 59 % and 27 % when the AlN layer is replaced by the Al 0.5 Ga 0.5 N interlayer (IL) and AlN/Al 0.5 Ga 0.5 N superlattice (SL), respectively. By analyzing the growth conditions, the O impurity can be inhibited by raising V/III ratio or decreasing Al component, which increases the formation energy of O point defects according to first-principles calculation. This work provides accurate guidance for regulating O point defects in AlGaN-based materials. [ABSTRACT FROM AUTHOR]

This work reports on the fabrication of excellent quality deep ultraviolet photodetectors (DUV PDs) based on metalorganic chemical vapor deposition (MOCVD) grown spinel ZnGa 2 O 4 thin films on c-plane sapphire. Herein, The DUV PDs by exhibiting an ultra-low dark current of 6.69 f A and a high photo-to-dark-current ratio (PDCR) of >108 at a low-power operation of 0.2 V. While PDCR reached more than 109 on applied bias of 10 V having extremely low dark current of 37 fA. The detector revealed an ultra-high responsivity of 185 and 3.53 A/W under the exposure of 107 μW/cm2 of 245 nm wavelength at room temperature (RT) and applied bias of 10 and 0.2 V, respectively, and exhibited the record-high detectivity of the order of 1017 Jones. The temperature-dependent operation remained stable across a wide temperature range, from 27 °C to 125 °C, maintaining ultra-low dark current. The nearly constant growth and decay time of DUV PDs throughout the temperature range emphasizes the robustness and reliability of PD. The ideality factor in both DUV and dark conditions nearing unity proves the dominance of the thermionic emission mechanism. Also shows the stable and slight improved performance after a year. Therefore, these findings suggest that ZnGa 2 O 4 is a strong contender for deep UV detection that shows robustness even at high temperatures. [ABSTRACT FROM AUTHOR]

In the realm of high-power electronics, the potential of gallium oxide (β -Ga 2 O 3) as a front-runner material has garnered significant attention due to its wide bandgap and the capacity to withstand high critical electric fields. To push the boundaries of performance for β -Ga 2 O 3 devices, a meticulous exploration into the effects of silicon (Si) doping on β -Ga 2 O 3 films was carried out using the metalorganic chemical vapor deposition (MOCVD) technique with various tetraethoxysilane (TEOS) flow rates (0–30 sccm). The Si-doped β -Ga 2 O 3 films were systematically studied and characterized using XRD, SEM, and XPS techniques. XRD patterns demonstrated the preservation of the β -Ga 2 O 3 monoclinic structure in the Si-doped β -Ga 2 O 3 films, without any evidence of secondary phases. In addition to this, first-principles calculations were performed to explore the incorporation of Si atoms in Ga 2 O 3 supercells, which revealed the preference of Si atoms to occupy substitutional Ga tetrahedral sites within the Ga 2 O 3 lattice. Through the utilization of Si-doped β -Ga 2 O 3 films, a unique design of donut-shaped Schottky barrier diode (SBD) was successfully engineered. Remarkably, the Si-doped β -Ga 2 O 3 SBD (employed with 20 sccm TEOS flow rate) exhibited the breakdown voltage (V br) of 497 V and Baliga's Figure of Merit (BFOM) value of 1.16 kW/cm2, which is five-order higher BFOM compared to undoped β -Ga 2 O 3 SBD. This substantial improvement in BFOM underscores the significant potential of Si-doped β -Ga 2 O 3 films for high-power electronics, opening avenues for enhanced device efficiency and capabilities. [Display omitted] • Successful growth of Si-doped β -Ga 2 O 3 films on c-plane sapphire substrates using MOCVD is achieved. • XRD analysis confirmed the preservation of the β -Ga 2 O 3 monoclinic structure within Si doped β -Ga 2 O 3 films. • First-principle calculations indicated Si atoms occupy substitutional Ga tetrahedral sites. • Fabrication of donut-shaped SBDs improved the breakdown voltage. • Si-doped β -Ga 2 O 3 SBD exhibited 5 orders higher BFOM than undoped β -Ga 2 O 3 SBDs. [ABSTRACT FROM AUTHOR]

Very few sodium complexes are available as precursors for the syntheses of sodium-based nanostructured materials. Herein, the diglyme, triglyme, and tetraglyme (CH3O(CH2CH2O)nCH3, n = 2–4) adducts of sodium hexafluoroacetylacetonate were synthesized in a single-step reaction and characterized by IR spectroscopy, 1H, and 13C NMR. Single-crystal X-ray diffraction studies provide evidence of the formation of the ionic oligomeric structure [Na4(hfa)6]2−•2[Na(diglyme2]+ when the diglyme is coordinated, while a mononuclear seven-coordinated complex Na(hfa)•tetraglyme is formed with the tetraglyme. Reaction with the monoglyme (CH3OCH2CH2OCH3) does not occur, and the unadducted polymeric structure [Na(hfa)]n forms, while the triglyme gives rise to a liquid adduct, Na(hfa)•triglyme•H2O. Thermal analysis data reveal great potentialities for their applications as precursors in metalorganic chemical vapor deposition (MOCVD) and sol-gel processes. As a proof-of-concept, the Na(hfa)•tetraglyme adduct was successfully applied to both the low-pressure MOCVD and the sol-gel/spin-coating synthesis of NaF films. [ABSTRACT FROM AUTHOR]

Zirconium nitride (ZrN) is a candidate for contact metal and diffusion barrier in ohmic contacts for GaN-based devices due to its superior electrical conductivity and corrosion resistance. This paper reported ZrN films deposited on GaN/Si templates using metal-organic chemical vapor deposition (MOCVD) and analyzed the effect of substrate temperature (T s) on its growth mode, film stress, as well as electrical properties. Firstly, the surface morphology and film roughness of the resultant ZrN epilayers were investigated, which were found to vary dramatically with T s. Then, a temperature-dominated crystal formation process was reasonably proposed, revealing the transfer from the island to layer growth mode and the augmentation of the growth rate of ZrN with elevated T s. Stress information was obtained from the position of XRD diffraction peaks, indicating large in-plane lattice stretching in ZrN film and the presence of compressive stress in the GaN/Si template. The stress states can be related to island merger and thermal mismatch between ZrN and GaN, which proved satisfyingly advantageous in preventing the GaN layer from cracking during the subsequent preparation procedure. In addition, XPS surface and interface investigations were performed to identify the chemical state and the atomic content of the ZrN film, which also implied a relatively clear interface between the ZrN epilayer and GaN/Si template. Furthermore, Hall tests proved the resistivity of ZrN thin film can reach a minimum of 2.28 Ă— 10âˆ'4 Ω cm, owing to the grain boundary chaining and flat film surface at high temperatures. Overall, it appears to have promising prospects for its application in the contact layer and diffusion barrier of ohmic contact in GaN-based devices. [ABSTRACT FROM AUTHOR]

Orthorhombic tantalum pentoxide (β -Ta 2 O 5) monocrystalline films were deposited on epi-GaN/α-Al 2 O 3 (0001) substrates using the metal-organic chemical vapor deposition method. The prepared films were grown along the β -Ta 2 O 5 (001) plane. The film deposited at 850 °C exhibited the best crystalline quality and the corresponding FWHM of the XRD ω -rocking curve for β -Ta 2 O 5 (001) plane was 1.81°. The prepared β -Ta 2 O 5 film possessed a domain structure, and the growth mechanism was studied in detail. By the XRD Φ scan and HRTEM analyses, the in-plane epitaxial relationship of the 850 °C-prepared sample was determined as β -Ta 2 O 5 [ 100 ] ‖ GaN [ 1 ‾ 100 ]. The elemental composition and valence states were studied and the band gap of the film prepared at 850 °C was calculated to be 4.34 eV by the analysis of the electron energy loss spectrum. [ABSTRACT FROM AUTHOR]

Semipolar (11 2 ¯ 2) InGaN/GaN superlattice templates with different periodical InGaN layer thicknesses were grown on m-plane sapphire substrates using metal-organic chemical vapor deposition (MOCVD). The strain in the superlattice layers, the relaxation mechanism and the influence of the strain relaxation on the semipolar superlattice template were explored. The results demonstrated that the strain in the (11 2 ¯ 2) InGaN/GaN superlattice templates was anisotropic and increased with increasing InGaN thickness. The strain relaxation in the InGaN/GaN superlattice templates was related to the formation of one-dimension misfit dislocation arrays in the superlattice structure, which caused tilts in the superlattice layer. Whereas, the rate of increase of the strain became slower with increasing InGaN thickness and new misfit dislocations emerged, which damaged the quality of the superlattice relaxed templates. The strain relaxation in the superlattice structure improved the surface microtopography and increased the incorporation of indium in the InGaN epitaxial layers. [ABSTRACT FROM AUTHOR]

Metal–organic chemical vapor deposition (MOCVD) is an important method for growing metal–oxide semiconductor films. However, owing to problems associated with gas-phase parasitic reactions and wall deposition, this method achieves low growth efficiency and affects the film quality. Computational fluid dynamics (CFD) has been widely used in MOCVD research and can be employed to investigate the flow field and the chemical vapor deposition (CVD) process in the reactor. In this study, considering the growth of zinc oxide and indium oxide as examples, a four-step reaction mechanism is proposed based on a combination of the multi-step reaction mechanism and experimental results. The effect of chemical reactions on the film growth rate is studied based on the Arrhenius plot and experimental results. A new flow stability map is proposed, and the flow field stability under different pressures is investigated to explore the influence of the flow field on the film growth rate. Results show that the deposition rate is influenced by both the gas-phase parasitic reactions and the effect of the flow field on the source component distribution. Furthermore, the causes and factors influencing sidewall deposition are revealed. [ABSTRACT FROM AUTHOR]

A 4Ă—4 beta-phase gallium oxide (β -Ga2O3) deep-ultraviolet (DUV) rectangular 10-fingers interdigital metal-semiconductor-metal (MSM) photodetector array of high photo responsivity is introduced. The Ga2O3 thin film is prepared through the metalorganic chemical vapor deposition technique, then used to construct the photodetector array via photolithography, lift-off, and ion beam sputtering methods. The one photodetector cell shows dark current of 1.94 pA, photo-to-dark current ratio of 6Ă—107, photo responsivity of 634.15 Aâ‹...Wâˆ'1, specific detectivity of 5.93Ă—1011 cmâ‹...Hz1/2â‹...Wâˆ'1 (Jones), external quantum efficiency of 310000%, and linear dynamic region of 108.94 dB, indicating high performances for DUV photo detection. Furthermore, the 16-cell photodetector array displays uniform performances with decent deviation of 19.6% for photo responsivity. [ABSTRACT FROM AUTHOR]

The relationship between the purge time and the overall growth rate in pulsed injection metal–organic chemical vapor deposition with different V/III ratios is studied by numerical analysis. The transport behavior of TMAl and TMAlNH3 during the process is studied to understand the effect of the adductive reaction. The results show that, as the V/III ratio increases, there is a significant reduction in the average growth rate per cycle, without the addition of a purging H2 pulse between the III and V pulses, due to stronger adductive reaction. The adductive reaction can be reduced by inserting a purging pulse of pure H2 between the III and V pulses, but there is a decrease in the overall growth rate due to the longer cycle time. At smaller V/III ratios, the growth rate decreases with increasing purge times, since the gain in reducing the adductive reaction is offset by the detrimental effect of extending the cycle time. The degree of reduction in the adductive reaction is higher for larger V/III ratios. When the benefit of reducing the adductive reaction overcomes the deficiency of the extending cycle time, a remarkable enhancement of the growth rate can be obtained at high V/III ratios by inserting a pure H2 purge pulse between the III and V pulses. A higher overall growth rate can be achieved at higher V/III ratios by choosing an appropriate purge time. [ABSTRACT FROM AUTHOR]

Controlling the morphology, orientation, and crystal phase of semiconductor nanowires is crucial for their future applications in nanodevices. In this work, zinc sulfide (ZnS) nanowires have been grown by metalorganic chemical vapor deposition (MOCVD), using gold or gold–gallium alloys as catalyst. At first, basic studies on MOCVD growth regimes (mass-transport, zinc- or sulfur- rich conditions) have been carried out for ZnS thin films. Subsequently, the growth of ZnS nanowires was investigated, as a function of key parameters such as substrate temperature, S/Zn ratio, physical state and composition of the catalyst droplet, and supersaturation. A detailed analysis of the structural properties by transmission electron microscopy (TEM) is given. Depending on the growth conditions, a variety of polytypes is observed: zinc-blende (3C), wurtzite (2H) as well as an uncommon 15R crystal phase. It is demonstrated that twinning superlattices, i.e., 3C structures with periodic twin defects, can be achieved by increasing the Ga concentration of the catalyst. These experimental results are discussed in the light of growth mechanisms reported for semiconductor nanowires. Hence, in this work, the control of ZnS nanowire structural properties appears as a case study for the better understanding of polytypism in semiconductor 1D nanostructures. [ABSTRACT FROM AUTHOR]