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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]

In this work, we investigated the MOCVD conditions to synthesize thin films with the hexagonal P63cm h-LuMnO3 phase as a potential low-band gap ferroelectric material. The main parameters investigated were the ratio of organometallic starting materials, substrate temperature, and annealing effect. Two different substrates were used in the study: fused silica (SiO2) glass and platinized silicon (Pt\Ti\SiO2\Si(100)). In order to investigate the thermodynamic stability and quality of the developed phases, a detailed analysis of the crystal structure, microstructure, morphology, and roughness of the films was performed by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy, and piezoelectric force microscopy (PFM). Molar compositions in the film within 0.93 < |Lu|/|Mn| < 1.33 were found to be suitable for obtaining a single-phase h-LuMnO3. The best films were obtained by depositions at 700 °C, followed by thermal treatments at 800 °C for long periods of up to 12 h. These films exhibited a highly crystalline hexagonal single phase with a relatively narrow direct band gap, around 1.5 eV, which is within the expected values for the h-LuMnO3 system. [ABSTRACT FROM AUTHOR]

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

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]

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

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]

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]

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]

Remote epitaxy is an emerging technology for producing single-crystalline, free-standing thin films and structures. The method uses 2D van der Waals materials as semi-transparent interlayers that enable epitaxy and release of epitaxial layers at the 2D layer interface. The use of single-layer graphene as the interlayer for heterogeneous remote epitaxial GaN nucleation layer and GaN film on the sapphire substrate was studied. The result shows that GaN nucleation island has a good orientation. Through parameter adjustment, a dense GaN nucleation layer was obtained. AFM observation and XRD detection confirm that GaN thin film has lower surface roughness and dislocation density compared with film that grow directly on sapphire substrate under the same conditions. The existence of graphene after growing GaN film was confirmed by Raman spectra. [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]

In this work, we investigated the MOCVD conditions to synthesize thin films with the hexagonal P63cm h-LuMnO3 phase as a potential low-band gap ferroelectric material. The main parameters investigated were the ratio of organometallic starting materials, substrate temperature, and annealing effect. Two different substrates were used in the study: fused silica (SiO2) glass and platinized silicon (Pt\Ti\SiO2\Si(100)). In order to investigate the thermodynamic stability and quality of the developed phases, a detailed analysis of the crystal structure, microstructure, morphology, and roughness of the films was performed by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy, and piezoelectric force microscopy (PFM). Molar compositions in the film within 0.93 < |Lu|/|Mn| < 1.33 were found to be suitable for obtaining a single-phase h-LuMnO3. The best films were obtained by depositions at 700 °C, followed by thermal treatments at 800 °C for long periods of up to 12 h. These films exhibited a highly crystalline hexagonal single phase with a relatively narrow direct band gap, around 1.5 eV, which is within the expected values for the h-LuMnO3 system.

High-quality AlGaN/GaN/AlN heterostructures with thin GaN channel and thick AlN buffer layer were grown by metal organic chemical vapor deposition (MOCVD) on SiC substrate. By analyzing growth modes of GaN films on AlN buffer layers with different thicknesses, it is revealed that film-forming point of GaN grown on AlN buffer increases with the increase in AlN buffer thickness. Accordingly, new growth model of GaN on AlN buffer was proposed, which shows that there is an optimal matching value between Ga source flow rate and AlN thickness when GaN is grown on AlN buffer of different thicknesses. Under optimal conditions, AlGaN/GaN/AlN heterostructures with 120 nm thin GaN channel layer and thick AlN buffer show excellent carrier-limited domain, high crystalline quality, and good transport properties. Results in this work would be useful for preparing high-quality heterostructures on AlN buffer and high electron mobility transistor (HEMT) devices. Moreover, these findings can also be applied to the growth of other hyperfine structures (quantum wells, superlattices, and digital alloys) in the future. [ABSTRACT FROM AUTHOR]

β-Ga2O3 thin films grown on widely available c-plane sapphire substrates typically exhibit structural defects due to significant lattice and thermal expansion mismatch, which hinder the use of such films in electronic devices. In this work, we studied the impact of a nucleation layer on MOCVD-grown β-Ga2O3 thin film structure and morphology on a c-plane sapphire substrate. The structure and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, transmission and scanning electron microscopy, while the composition was confirmed by X-ray photoelectron spectroscopy and micro-Raman spectroscopy. It was observed that the use of a nucleation layer significantly increases the grain size in the films in comparison to the films without, particularly in the samples in which H2O was used alongside O2 as the oxygen source for the nucleation layer growth. Our study demonstrates that a nucleation layer can play a critical role in obtaining high quality β-Ga2O3 thin films on c-plane sapphire. [ABSTRACT FROM AUTHOR]

The dynamic growth of MOCVD-grown ZnO thin films under temperature effect was systematically investigated by a numerical approach using computational fluid dynamics (CFD) technique. A three-dimensional (3D) reactor-scale model was developed to determine the growth rate and uniformity of ZnO thin film in the temperature range of 593 K to 713 K. The mixed-convection flow and heat transfer inside the reactor chamber were assessed. The results showed that as the temperature increased, ZnO thickness increased initially before decreasing. At 673 K, the highest deposition rate with acceptable uniformity was achieved. The admixture of transverse and longitudinal rolls was observed for the flow conditions. Temperature variations were found to directly affect the axial and lateral uniformity of deposition, but had a minor impact on the size and position of transverse rolls. Experimental verification studies were conducted, and high-quality ZnO films were successfully fabricated by using diethylzinc (DEZn) and tertiarybutanol (t-BuOH) as precursors; it was found that the comprehensive thickness and structural properties of ZnO deposited at temperature of 673 K are preferred. Experimental results and numerical simulations exhibited good agreement. [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]

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]

High-quality ε -phase Ga 2 O 3 thin film with a FWHM of 0.68° for the (002) plane in omega scan is grown on Si/AlN composite substrate by MOCVD. The crystal phase evolution and microstructure of Ga 2 O 3 thin films at different temperatures are studied systematically. It is found that Ga 2 O 3 changes from amorphous at 400 °C to ε -phase at 500 °C. As the temperature further rises to 600 °C, it eventually transforms into β -phase. Due to the difference of lattice mismatch, ε -Ga 2 O 3 is crystalline with high crystallinity on the surface of the film, but amorphous at the interface, while β -Ga 2 O 3 is polycrystalline. In addition, ε -Ga 2 O 3 thin films not only have the smoothest surface with roughness of 2.63 nm, but also the content of point defects (such as oxygen vacancies) is significantly reduced compared with that of amorphous and β -Ga 2 O 3 thin films. This work provides important references for the hetero-integration of Si and Ga 2 O 3 by MOCVD, and is beneficial for the development of low cost and high crystal quality Ga 2 O 3 thin films which are suitable for high voltage and ultraviolet optoelectronics. [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]

YBa 2 Cu 3 O 7− δ (YBCO) thin films deposited on LaAlO 3 single-crystal substrates have great potential for application in microwave field due to their low microwave surface resistance (R s). In order to prepare high-performance films and facilitate adjustment of experimental parameters, we designed novel metalorganic chemical vapor deposition system. This system adopts single liquid-source pulse feed that provides facile control over film composition through the adjustment of Y, Ba, and Cu ratios in precursors. Here, we thoroughly study influence of film composition on performance. By conducting energy-dispersive spectroscopy measurements, Y, Ba, and Cu composition ranges of 21–24%, 28–31%, and 46–54%, respectively, are found to optimize YBCO film transport and microwave properties. Composition affects purity of film phase which in turns determines film performance. To confirm this observation, we adjust ratio through input–output relationship to obtain film with composition ratio within abovementioned optimal range. Obtained YBCO film has critical current density of 2.8 MA/cm2 at 77 K and 0 T and R s of 0.285 mΩ at 77 K and 10 GHz. The full width at half maximum of YBCO (005) peak and (103) plane, measured via X-ray diffraction, are 0.235° and 0.762°, respectively. [ABSTRACT FROM AUTHOR]

The authors reported the MOCVD growth of high-quality β-Ga 2 O 3 on c-plane sapphire substrate, resulting in the achievement of high performance solar blind deep UV photodetectors by introducing an ultra-thin AlN buffer seed layer (BSL). Compared with the direct growth of Ga 2 O 3 on the sapphire, the oxygen vacancy of β-Ga 2 O 3 is reduced after introducing an AlN BSL and the full width at half maximum (FWHM) of (-201) diffraction peak becomes narrower. The dark current is reduced by 1000 times and from 10−10 A down to 10−13 A for the metal-semiconductor-metal planner photodetector of β-Ga 2 O 3 thin film with the AlN BSL. And the detectivity reaches 4.65×1015 cm·Hz1/2·W at 5 V bias. This improvement in performance is derived from the improvement of the growth quality of β-Ga 2 O 3 mediated by the AlN BSL due to the decrease of lattice mismatch. The defects in β-Ga 2 O 3 are reduced, the carrier concentration is reduced, the Fermi level is shifted, the depletion region is widened, the probability of electron tunneling in the dark state is reduced, and the dark current is effectively reduced. • Through introduce of AlN buffer seed layer, reduces the lattice mismatch between the sapphire and β-Ga 2 O 3 , and improves the quality of β-Ga 2 O 3. • The β-Ga2O3 thin film photodetector has a low dark current, which is mainly due to the high crystal quality, reduces the intrinsic carrier concentration and broadens the width of the metal-semiconductor interface depletion region. • The high responsivity of the β-Ga 2 O 3 -based photodetector indicates that it is an effective way to optimize the performance of β-Ga 2 O 3 -based devices by lattice engineering. [ABSTRACT FROM AUTHOR]

A series of (In 1- x Al x) 2 O 3 (0.1 ≤ x ≤ 0.6) films with tunable bandgap were grown on MgO (100) substrates by MOCVD. The influences of chemical compositions and growth temperatures on the film properties were studied systematically. XRD analyses indicated that the film quality degraded from crystalline to amorphous structure as Al concentration (x) increased. The (In 1- x Al x) 2 O 3 films prepared at 700 °C exhibited better film crystallinity than those of the ones grown at 600 °C. The films prepared at 700 °C with x = 0.1–0.3 showed an epitaxial In 2 O 3 <111> orientation with the corresponding growth relationship of In 2 O 3 (111)∥MgO (100). The film with x = 0.2 exhibited the best crystallinity and the largest grain size of 25.9 nm. The Hall mobilities and resistivities of the films were influenced evidently by Al concentrations. The Hall mobility showed a monotonous decrease from 12 to 1.1 cm2V−1s−1 as x increased from 0.1 to 0.6. The lowest resistivity of 9.2 × 10−3 Ω cm was acquired for the film with x = 0.2. The average transmittances in the visible region for all the films were beyond 83%. The bandgap of the (In 1- x Al x) 2 O 3 films can be regulated in the range of 3.85–4.88 eV by changing Al concentrations from 0.1 to 0.6. [ABSTRACT FROM AUTHOR]

In this work, a solar-blind ultraviolet (UV) photodetector based on a three-terminal enhancement-mode (E-mode) Si-doped β -Ga2O3 (β -Ga2O3:Si) metal-semiconductor field-effect transistor structure is demonstrated, whose threshold voltage (V th) and subthreshold swing are 4.04 V and 1.4 V decâˆ'1, respectively. A 400 nm thick β -Ga2O3:Si thin film is prepared on sapphire substrate by using metal-organic chemical vapor deposition method. Controlling the channel currents by the Schottky gate voltage in the dark and under illuminations, the photodetector shows dark current (I dark) as low as 13.4 pA, photo-to-dark current ratio of 4.85 Ă— 104 and linear dynamic range of 29.6 dB, illuminated by 254 nm UV light of 245 ÎĽ W cmâˆ'2. As the UV light is turned on and off, the output current rise and decay time (Ď„ r and Ď„ d) are 420 ms and 350 ms. Moreover, at drain voltage (V ds) of 5 V and gate voltage (V gs) of 0 V, the responsivity (R), specific detectivity (D*) and external quantum efficiency are achieved as 74 A Wâˆ'1, 2.15 Ă— 1014 cm Hz1/2 Wâˆ'1 (Jones) and 3.6 Ă— 104%, respectively. [ABSTRACT FROM AUTHOR]

The structurally related cobalt β‐diketonate complexes Co(acac)2, Co(acac)2 ⋅ TMEDA, Co(tfac)2 ⋅ TMEDA, and Co(hfac)2 ⋅ TMEDA (acac=2,4‐pentanedionate, tfac=1,1,1‐trifluoro‐2,4‐pentane‐dionate, hfac=1,1,1,5,5,5‐hexafluoro‐2,4‐pentane‐dionate, TMEDA=N,N,N′,N′‐tetramethylethylenediamine) were thermochemically (thermogravimetric analysis, differential scanning calorimetry) and spectroscopically (infrared, UV‐VIS and electron resonance spectroscopy) characterised and used as precursor for the MOCVD growth of cobalt monoxide (CoO) thin films. The influence of the degree of fluorination of the cobalt precursors on the morphology (scanning electron microscopy) and phase composition (X‐ray diffraction) of the CoO films is demonstrated. Carbon, nitrogen and fluorine impurities as a result of the thermal decomposition of the 2,4‐pentanedionate and tetraamine ligands in the films were identified by X‐ray photoelectron spectroscopy, time‐of‐flight secondary ion mass spectrometry, Rutherford backscattering spectrometry and nuclear reaction analysis. In addition, the influence of these contaminants on the electrocatalytically activity for the oxygen evolution reaction (OER) in alkaline media of the MOCVD grown CoO films is shown. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD), which involves chemical reactions in gases for deposition on a heated surface, is an extensively used manufacturing technique for obtaining thin films of materials like silicon, graphene, silicon carbide, aluminum nitride, and gallium nitride (GaN). The process is driven by heat and mass transfer, fluid flow, and chemical reactions in the gases and at the surface. GaN is one of the most promising materials for manufacturing optical and electronic devices. However, the reliability and durability of the GaN-based devices depend on the crystalline quality of the thin films used. In this study, the epitaxial growth of GaN thin films on sapphire (Al2O3) wafers is carried out in a vertical rotating disk metalorganic chemical vapor deposition (MOCVD) system. Epitaxial growth refers to the process of growing a crystal of a particular orientation on the top of another crystal, with the orientation being determined by the underlying crystal. MOCVD reactors are CVD systems that use metalorganic compounds that consist of metal and organic ligands, leading to materials like GaAs, AlN, InN, and GaN. The quality of the thin films is largely determined by the choice of operating conditions such as the flowrate, surface temperature, and concentration of the metalorganic precursors that decompose due to heat in the reactor, react, and deposit the desired material on the surface of a wafer or a heated susceptor. In this experimental study, the crystalline quality and surface morphology of GaN thin films are evaluated using atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. The correlation between the crystalline quality of GaN thin films and the flowrate of the precursors is examined in detail on the basis of an evaluation of the dislocation density. The results indicate that a low concentration (V/III) ratio, where V and III refer to elements in the fifth and third groups of the periodic table, is beneficial for obtaining a high deposition rate since a low value of this ratio implies a high precursor concentration. However, it negatively affects the crystalline quality of the thin film. Similarly, high V/III ratios lead to low deposition rates and better crystalline quality, indicating the need to optimize the process. [ABSTRACT FROM AUTHOR]

β-Ga2O3 thin films grown on widely available c-plane sapphire substrates typically exhibit structural defects due to significant lattice and thermal expansion mismatch, which hinder the use of such films in electronic devices. In this work, we studied the impact of a nucleation layer on MOCVD-grown β-Ga2O3 thin film structure and morphology on a c-plane sapphire substrate. The structure and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, transmission and scanning electron microscopy, while the composition was confirmed by X-ray photoelectron spectroscopy and micro-Raman spectroscopy. It was observed that the use of a nucleation layer significantly increases the grain size in the films in comparison to the films without, particularly in the samples in which H2O was used alongside O2 as the oxygen source for the nucleation layer growth. Our study demonstrates that a nucleation layer can play a critical role in obtaining high quality β-Ga2O3 thin films on c-plane sapphire.

This paper details 3 years of cadmium telluride (CdTe) photovoltaic performance onboard the AlSat‐1N CubeSat in low earth orbit. These are the first CdTe solar cells to yield I–V measurements from space and help to strengthen the argument for further development of this technology for space application. The data have been collected over some 17 000 orbits by the CubeSat with the cells showing no signs of delamination, no deterioration in short circuit current or series resistance. The latter indicating that the aluminium‐doped zinc oxide transparent front electrode performance remained stable over the duration. Effects of temperature on open circuit voltage (Voc) were observed with a calculated temperature coefficient for Voc of −0.19%/°C. Light soaking effects were also observed to increase the Voc. The fill factor decreased over the duration of the mission with a major contribution being a decrease in shunt resistance of all four of the cells. The decrease in shunt resistance is speculated to result from gold diffusion from the rear contacts into the absorber and through to the front interface. This has likely resulted in the formation of a deep trap state within the CdTe and micro shunts formed between the rear and front contact. Further development of this technology should therefore utilise more stable back contacting methodologies more commonly employed for terrestrial CdTe modules. [ABSTRACT FROM AUTHOR]

A new principle for supplying volatile precursors to MOCVD gas-phase chemical deposition systems is proposed, based on a two-stage evaporation of an organic solution of precursors from a soaked cotton thread, which passes sequentially through the zones of evaporation of the solvent and precursors. The technological capabilities of TSF-MOCVD (Thread-Solution Feed MOCVD) are demonstrated based on examples of obtaining thin epitaxial films of СеО2, h-LuFeO3 and thin-film heterostructures β-Fe2O3/h-LuFeO3. The results of studying the obtained films by X-ray diffraction, energy dispersive X-ray analysis, and high- and low-resolution transmission microscopy are presented. Using the TSF module, one can finely vary the crystallisation conditions, obtaining coatings of the required degree of crystallinity, as evidenced by the obtained dependences of the integral width of the h-LuFeO3 reflection on the film growth rate. Based on the TEM and XRD data, it was concluded that β-Fe2O3 grows epitaxially over the h-LuFeO3 layer. Thus, using TSF-MOCVD, one can flexibly change the composition of layered heterostructures and obtain highly crystalline epitaxial films with a clear interface in a continuous deposition process

Iron oxide thin films were grown directly on three‐dimensional nickel foam via metalorganic chemical vapor deposition (MOCVD) in the temperature range of 250–450 °C using Fe(CO)5 as precursor. Iron oxide (α‐Fe2O3) films were formed at low substrate temperatures (250–350 °C), whereas the additional growth of an underlying NiO film occurred at substrate temperatures above 350 °C. The electrochemical activities of the as‐formed binder‐free and noble metal‐free electrodes were tested for the oxygen evolution reaction (OER) in alkaline media. An overpotential reduced by 250 mV at a current density of 50 mA cm−2 and a lower Tafel slope of 55 mV dec−1 compared to bare nickel foam were found for the best‐performing electrocatalyst, while the long‐term stability of the as‐formed electrodes was proven by chronopotentiometry. The surface morphology of the iron oxide films was characterized by scanning electron microscopy, whereas the crystallographic phase as well as the elemental composition were determined by X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and time‐of‐flight secondary ion mass spectrometry in the pre‐ and the post‐catalytic state. [ABSTRACT FROM AUTHOR]

We investigated the properties of indium-doped zinc oxide layers grown by metalorganic chemical vapor deposition on semi-insulating GaN(0001) templates. Specular and transparent films were grown with n-type carrier concentrations up to 1.82 × 1019 cm−3 as determined by Hall measurements, and all In-doped films had carrier concentrations significantly higher than that of a comparable undoped film. For low In flows, the carrier concentration increased accordingly with trimethyl-indium (TMIn) flow until a maximum carrier concentration of 1.82 × 1019 cm−3 was realized. For higher In flows, the carrier concentration decreased with increasing TMIn flow rate. Sheet resistance as low as 185 Ω/sq was achieved for the In-doped films, which is a significant decrease from that of a comparable undoped ZnO film. Our n-type doping studies show that In is an effective dopant for controlling the n-type conductivity of ZnO.

Gallium oxide (Ga2O3) thin films of various thicknesses were grown on sapphire (0001) substrates by metal organic chemical vapor deposition (MOCVD) using trimethylgallium (TMGa), high purity deionized water, and silane (SiH4) as gallium, oxygen, and silicon precursors, respectively. N2 was used as carrier gas. Hall measurements revealed that films grown with a lower VI/III ratio had a dominant p-type conduction with room temperature mobilities up to 7 cm2/Vs and carrier concentrations up to ~1020 cm−3 for thinner layers. High resolution transmission electron microscopy suggested that the layers were mainly κ phase. Microstrip field-effect transistors (FETs) were fabricated using 2D p-type Ga2O3:Si, channels. They achieved a maximum drain current of 2.19 mA and an on/off ratio as high as ~108. A phenomenological model for the p-type conduction was also presented. As the first demonstration of a p-type Ga2O3, this work represents a significant advance which is state of the art, which would allow the fabrication of p-n junction based devices which could be smaller/thinner and bring both cost (more devices/wafer and less growth time) and operating speed (due to miniaturization) advantages. Moreover, the first scaling down to 2D device channels opens the prospect of faster devices and improved heat evacuation.

Bis-(morpholinodithiato-s,s′)-Cu-Zn was synthesized as a single solid source precursor and characterized using particle-induced x-ray emission (PIXE), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Cu-Zn-S thin film was deposited on sodalime glass substrate using metal organic chemical vapor deposition (MOCVD) technique at temperatures ranging from 360°C to 450°C. The thin films were characterized using Rutherford backscattering spectroscopy (RBS), x-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy and four-point probe technique. PIXE of the precursor confirmed the presence of the expected elements that can lead to deposition of Cu-Zn-S thin film while FTIR confirmed that the organic ligands were attached to the metals. DSC showed that the precursor is thermally stable and can pyrolyze at temperature between 340°C and 460°C. RBS analysis of the films showed that there was no substantial deposition at 360°C while other films showed various stoichiometry and thickness. XRD analysis of the films showed that films deposited at 360°C and 380°C are amorphous, while those deposited between 400°C and 450°C showed peaks, in which the crystal size decreased as the deposition temperature increased. The SEM micrographs showed that the morphology of the films is temperature dependent and as deposition temperature increased larger secondary grains dissociated into smaller grains that are closely packed, without cracks and holes. Optical characterization showed that the films exhibited high transmittance, which fairly increased as the deposition temperature increased. A direct band gap value between 2.49 eV and 2.92 eV was obtained as deposition temperature increased. Urbach energy also increased from 0.87 eV to 1.51 eV, while the steepness parameter decreased as the deposition temperature increased. The electrical characterization showed that the resistivity of the films decreased as the deposition temperature increased while the I–V plot showed a rectifying character. [ABSTRACT FROM AUTHOR]

Green H 2 production by solar water splitting relies entirely on the intrinsic properties of the photocatalyst. In this study the impact of these intrinsic properties on the photocatalytic activity of anatase TiO 2 , the quintessential component of state of the art photocatalytic systems was explored at the nanoscale. The exploration involved a holistic microstructural and optical characterization of fully crystallized anatase thin films synthetized by metalorganic chemical vapor deposition. A combination of electron microscopy, spectroscopic ellipsometry, and infrared spectroscopy revealed that when the deposition temperature increased, the morphology evolved from dense to porous and columnar nanostructures. Interestingly, the columns with a complex, tree-like nanostructure photogenerated 18 times more H 2 than the densest sample. This result shows that the beneficial effect of the morphological nano-complexification and crystallographic diversification of the exchange facets on the photocatalytic performance outweighs the detrimental aspects inherent to this evolution, namely the drop of the charge carrier transport and the increase of residual stress. Unlabelled Image • Nanotree-like columnar TiO 2 films present high porosity and specific surface area. • They present 〈110〉 growth direction and various crystallographic exposed facets. • They present low optical absorption and high residual compressive stress • Strong morphological complexity of TiO 2 films improves solar water splitting. [ABSTRACT FROM AUTHOR]

• This study summarized and compared the kinetic parameters of gas-phase reactions during InN MOCVD growth. • The results show that with varying kinetic parameters, the gas reaction path is likely to be dominated by the addition or trimethylindium pyrolysis path, or to proceed through both reaction paths. • Although the reaction path changes with varying kinetic parameters, the predicted growth rates do not vary substantially, because the total rate of transport of In-containing substances to the substrate changes little with the reaction path. • The contribution of pyrolytic products to the growth rate is greater than that of amine. During simulation of the growth of indium nitride (InN) thin films in metal–organic chemical vapor deposition (MOCVD), different choices of kinetic parameters (activation energy E a and pre-exponential factor A) for gas-phase reactions give rise to many uncertainties in the gas reaction path and growth rate. This study summarized and compared the kinetic parameters of gas-phase reactions during InN MOCVD growth. The InN MOCVD growth in a close-coupled showerhead reactor was simulated with varying kinetic parameters of gas-phase reactions. The effects of kinetic parameters on the gas reaction path were determined by comparing molar concentrations and growth rates of primary In-containing substances. The results show that with varying kinetic parameters, the gas reaction path is likely to be dominated by the addition or trimethylindium pyrolysis path, or to proceed through both reaction paths. Although the reaction path changes with varying kinetic parameters, the predicted growth rates do not vary substantially, because the total rate of transport of In-containing substances to the substrate changes little with the reaction path. The results also indicate that the contribution of pyrolytic products to the growth rate is greater than that of amine, whereas H radicals have minimal effect on the gas reaction path in InN MOCVD growth. [ABSTRACT FROM AUTHOR]

Monoclinic gallium oxide (β-Ga 2 O 3) has attracted wide attention due to its low-cost single crystal and excellent optoelectronic properties. However, the low specific surface area and high defect density of β-Ga 2 O 3 thin films result in weak light-matter interaction and poor crystal quality, seriously hindering their applications. In this article, the growth of high light-trapping β-Ga 2 O 3 nanorod (NR) film on GaAs substrates by metal-organic chemical vapor deposition (MOCVD) is demonstrated. The GaAs substrates were pre-treated by thermal oxidation (TO) to produce a β-Ga 2 O 3 seed layer. The effect of MOCVD growth conditions on the morphology of β-Ga 2 O 3 NR films is investigated. The growth mechanism of β-Ga 2 O 3 NR films is studied in detail. X-ray diffraction, Raman, and photoluminescence were employed to study the crystal and optical properties of β-Ga 2 O 3 NR films. A significant light-trapping effect with a 40 % reduction in optical reflectance at the wavelength of 254 nm is observed. The results show that the β-Ga 2 O 3 NR films exhibit strong light-matter interaction and have potential in optoelectronic applications. [ABSTRACT FROM AUTHOR]

A single solid source precursor, tetraamminebis-(hexamethylenetetrammine) Manganese (II) Chloride [Mn (HMTA) 2 (NH 3) 4 ] Cl 2 was prepared and thin films of manganese nitride Mn x N y were grown on soda-lime glass substrates at varied temperature using Metal Organic Chemical Vapor deposition (MOCVD) technique. The Energy Dispersive X-ray (EDX) spectra showcased the thin film constituent's elements as Mn and N in weight ratios which further confirmed absolute stoichiometry. The Fourier Transform Infra-Red (FTIR) spectrometry carried out on the precursors revealed the presence of functional groups between 1600 and 3200 cm−1 in the precursors, and ligands were mostly removed by pyrolysis process of the MOCVD at a temperature range of 300–340 °C. Due to the thermal deposition technique employed, FTIR spectrographs of MnN thin films exhibit coalescences between grains and a clear bond disintegration. Structural characterization using X-ray diffraction (XRD) revealed that the synthesized MnN thin film possesses a simple cubic structure with crystallite sizes estimated by employing Scherer's formula and Hall–Williamson plots. The scanning electron microscopy (SEM) showed columnar pattern and mesopores with the substrate covered by smaller, spherical grain particles having an estimated size of 3–4 nm, and large, structured particles with an estimated size of 10.0–20.0 nm placed on top of the smaller grain size particles. The indirect optical bandgap value of the MnN thin film was confirmed by optical absorbance analysis to be 2.75 eV and 3.0 eV at temperatures of 300 and 340 °C, respectively. • High-quality MnxNy thin films have been grown at relatively high temperatures using a novel precursor Mn(HMTA)2(H2O). The MOCVD deposited MnN thin films were nearly stoichiometric and were found to be free of additional impurity elements, according to the EDAX analysis. Analysis revealed that based on this precursor (Mn(HMTA)2(H2O)) and varied deposition temperatures, the films' estimated Mn/N ratio is 3:4. • The MnxNy films are texturized, with surface roughness and mesoporous growths under the varied temperature conditions. • The MnCl-HMTA precursors exhibited stretching vibrations in the characteristic absorption range which indicate that the medium CN nitride functional groups co-exist with a weak two band N-O nitro functional groups. • The optical energy bandgap of MnN films is 2.75 eV for films deposited at 300 oC and 3.0 eV for films deposited at 340 oC on sodalime glass substrates. These differences are primarily explained by structural changes at high temperatures. • The XRD analysis of the MnN thin film revealed that the film has simple cubic structure,which is a good fit with the results that have been provided in previous research work.The films predominantly X-ray crystalline, although certain broad peaks caused by the crystalline Mn3N2phase show signs of amorphous development. • The SEM images of MOCVD deposited MnN thin film clearly reveals that the film surface is mostly homogenous considering the spherical core grain particles. [ABSTRACT FROM AUTHOR]

Abstract Doping of CdTe using Group-V elements (As, P, and Sb) has gained interest in pursuit of increasing the cell voltage of CdTe thin film solar devices. Studies on bulk CdTe crystals have shown that much higher acceptor concentration than the traditional copper treatment is possible with As, P or Sb, enabled by high process temperature and/or rapid thermal quenching under Cd overpressure. We report a comprehensive study on in-situ As doping of poly-crystalline CdTe solar cells by MOCVD, whereby high acceptor densities, approaching 3 × 1016 cm−3 were achieved at low growth temperature of 390 °C. No As segregation could be detected at grain boundaries, even for 1019 As cm−3. A shallow acceptor level (+0.1 eV) due to As Te substitutional doping and deep-level defects were observed at elevated As concentrations. Devices with variable As doping were analysed. Narrowing of the depletion layer, enhancement of bulk recombination, and reduction in device current and red response, albeit a small near infrared gain due to optical gap reduction, were observed at high concentrations. Device modelling indicated that the properties of the n-type window layer and associated interfacial recombination velocity are highly critical when the absorber doping is relatively high, demonstrating a route for obtaining high cell voltage. Graphical abstract The acceptor concentration of the CdTe absorber layer in CdZnS/CdTe thin film solar cells tuned up to 3 × 1016/cm3 via in-situ arsenic doping, and its influence on photovoltaic properties and the defect structure established. No grain-boundary segregation observed even at the highest arsenic concentrations. Devices become sensitive to window layer properties at high acceptor concentrations. Modelling suggests ways to suppress the interfacial recombination to achieve remarkable V oc values. fx1 Highlights • In-situ As doping of poly-crystalline CdTe films by MOCVD resulted in high acceptor densities up to 3 × 1016 cm−3. • The photovoltaic properties and defect structure of CdTe:As absorbers identified. • J sc reduces slightly due to bulk recombination due to narrowing of depletion layer. • V oc increases but becomes sensitive to interface recombination at high As concentrations. • Modelling shows ways to suppress interface recombination and boost the V oc. [ABSTRACT FROM AUTHOR]

Ga-doped Zn0.7-xMg0.3O thin films were deposited on glass substrates at 350 °C by metal-organic chemical vapor deposition using an ultrasonic nebulization technique to transport the source precursors, and the effects of the Ga-doping concentration were investigated. The films with Ga-doping concentrations less than 5 mol% grew with [001] preferred orientation perpendicular to the substrate surface and were composed of large crystallites. At Ga content greater than 5 mol%, the films grew with random orientation and very small crystallite size. The charge carrier concentration in the films increased rapidly up to 4 mol% Ga and then decreased gradually with further increases in the Ga-content. The film resistivity decreased with increasing Ga-content up to 4 mol% due mainly to the increase in charge carrier concentration. Then, the resistivity increased gradually with increasing Ga-content due to the decrease in mobility. The lowest resistivity of the Ga-doped Zn0.7-xMg0.3O thin film was 3.8 × 10−1 Ωcm at the Ga doping concentration of 4 mol%. The mean transmittance in the visible range was more than 85% in all films. The optical band gap of the films increased with increasing Ga-doping concentration up to 5 mol% due to the Burstein-Moss effect. [ABSTRACT FROM AUTHOR]

We report the post-growth thermal annealing and the subsequent phase transition of Ga2O3 grown on c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). We demonstrated the post-growth thermal annealing at temperatures higher than 900 °C under N2 ambience, by either in situ or ex situ thermal annealing, can induce phase transition from nominally metastable κ- to thermodynamically stable β-phase. This was analyzed by structural characterizations such as high-resolution scanning transmission electron microscopy and x-ray diffraction. The highly resistive as-grown Ga2O3 epitaxial layer becomes conductive after annealing at 1000 °C. Furthermore, we demonstrate that in situ annealing can lead to a crack-free β-Ga2O3.

This study investigates the impact of Mg doping concentration in GaN thin films on their physical and mechanical properties, specifically on their conductivity transition, luminescence, hardness, Young's modulus, and creep behavior. Mg-doped GaN layers were grown on sapphire substrates using the MOCVD technique, with trimethylgallium (TMG) and bis(cyclopentadienyl) magnesium (Cp 2 Mg) as precursors for Ga and Mg, respectively. The TMG flow rate was set at 20 μmol/min, while the Mg flow rate was adjusted by tuning the temperature of the thermostatic bath of Cp 2 Mg. Three different Cp 2 Mg flow rates: 2, 7 and 9 μmol/min were utilized to explore their effects on the physical and mechanical properties of the grown epilayers. The results demonstrate that an increase in the Mg concentration leads to a conductivity transition from n-type to p-type, with the highest hole concentration (4.5 ± 0.2) × 1017 cm−3 and blue luminescence attained with Mg concentration equal to 2.1 × 1019 atoms/cm3. Moreover, the hardness, Young's modulus and the intensity of compressive stress increase with the Cp 2 Mg flow rate due to the evolution of pre-existing dislocation density and point defects incorporation. Additionally, this study evaluates the creep behavior of the Mg-doped GaN thin films. It shows that both the creep stress exponent and the maximal creep depth decrease with the increase of the Cp 2 Mg flow rate. This is attributed to dislocation glides and climbs governing the creep mechanism. Accordingly, this investigation highlights the importance of understanding the relationship between physical properties and mechanical characteristics of Mg-doped GaN thin films, which have potential implications for various technological applications. [Display omitted] • Mg-doped GaN films on sapphire were deposited using MOCVD technique. • Mg-doping effects on physical and mechanical properties of GaN films were systematically studied. • Cp 2 Mg flow rate was found for n to p-type conductivity transition, enhancing LED efficiency. • Mg incorporation impacts Young's modulus, hardness, and creep exponent. • Creep behavior suggests dislocation glides and climbs as governing deformation mechanism. [ABSTRACT FROM AUTHOR]

The potential of gallium oxide (Ga 2 O 3) as a promising semiconductor for advanced electronics and optoelectronics has been propelled by its wide bandgap, high breakdown voltage tolerance, and excellent chemical and thermal stability. To develop it into an industrial-level application, extensive research needs to be conducted to advance wafer-scale and high-quality epitaxy growth techniques. In this work, a close-coupled showerhead (CCS) metal-organic chemical vapor deposition (MOCVD) system was used to grow wafer-scale Ga 2 O 3 films. Through a detailed examination of growth parameters including substrate temperature, oxygen flow rate, precursor proportion, and chamber pressure, as well as their effect on film crystallinity, surface morphology, and optical properties, a comprehensive growth phase diagram and control over the growth rate of 2-inch Ga 2 O 3 thin films were obtained at a wafer-scale. These findings suggest that the CCS-MOCVD system presents a competitive avenue for future industrial high-speed fabrication of single-phase Ga 2 O 3 films. • High quality wafer-scale epitaxial ε- & β-Ga 2 O 3 films were grown by Metal-Organic Chemical Vapor Deposition. • Growth parameters effect on film crystallinity, surface morphology, and optical properties were detailed examined. • A comprehensive growth phase diagram and control over the growth rate of Ga 2 O 3 thin films were obtained at a wafer-scale. [ABSTRACT FROM AUTHOR]

High quality β -Ga 2 O 3 film is grown by using N 2 O as reaction gas for the fabrication of high performance solar-blind-ultraviolet photodetector. Compared with traditional solar-blind-ultraviolet photodetector based on β -Ga 2 O 3 film grown with O 2 , the reported solar-blind-ultraviolet photodetector exhibits higher photoresponsivity of 26.1 A/W, larger on/off ratio (I 255 nm light /I dark ) of 10 4 , and faster response speed (a rise time of 0.48 s and a decay time of 0.18 s at 10 V. The high photoresponsivity and fast response speed of the reported β -Ga 2 O 3 solar-blind-ultraviolet photodetector can be attributed to the reduction of scattering or/and trapped centre of photo-generated carriers formed in the film grown with N 2 O. [ABSTRACT FROM AUTHOR]

We employ a simple two-step growth technique to grow large-area 1550-nm laser structures by direct hetero-epitaxy of III-V compounds on patterned exact-oriented (001) silicon (Si) substrates by metal organic chemical vapor deposition. Densely-packed, highly uniform, flat and millimeter-long indium phosphide (InP) nanowires were grown from Si v-grooves separated by silicon dioxide (SiO) stripes with various widths and pitches. Following removal of the SiO patterns, the InP nanowires were coalesced and, subsequently, 1550-nm laser structures were grown in a single overgrowth without performing any polishing for planarization. X-ray diffraction, photoluminescence, atomic force microscopy and transmission electron microscopy analyses were used to characterize the epitaxial material. PIN diodes were fabricated and diode-rectifying behavior was observed. [ABSTRACT FROM AUTHOR]