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Herein, the effect of intermediate layers for high‐speed InGaN growth using trihalide vapor‐phase epitaxy (THVPE) on ScAlMgO4 (SAM) is investigated. The coverage and thickness of the intermediate layer have a significant impact on both composition and crystalline quality. Herein, InGaN is successfully fabricated with 17% of indium on SAM in a lattice‐matched state employing THVPE, showing the X‐ray rocking curve full width at half maximum values less than 1000 arcsec, in a two‐step growth. THVPE is used to indicate the possibility of fabricating high‐quality InGaN quasi‐substrate with high indium composition. [ABSTRACT FROM AUTHOR]

The detection of ultraviolet (UV) radiation with effective performance and robust stability is essential to practical applications. Metal halide single‐crystal perovskites (ABX3) are promising next‐generation materials for UV detection. The device performance of all‐inorganic CsPbCl3 photodetectors (PDs) is still limited by inner imperfection of crystals grown in solution. Here wafer‐scale single‐crystal CsPbCl3 thin films are successfully grown by vapor‐phase epitaxy method, and the as‐constructed PDs under UV light illumination exhibit an ultralow dark current of 7.18 pA, ultrahigh ON/OFF ratio of ≈5.22 × 105, competitive responsivity of 32.8 A W−1, external quantum efficiency of 10867% and specific detectivity of 4.22 × 1012 Jones. More importantly, they feature superb long‐term stability toward moisture and oxygen within twenty‐one months, good temperature tolerances at low and high temperatures. The ability of the photodetector arrays for excellent UV light imaging is further demonstrated. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) semiconductors have attracted much interest due to their unique structures and unusual properties. The direct vapor growth of high-quality 1D nanowires remains a significant challenge. In this study, high-quality Sb2Se3 nanowires are directly grown on insulating SiO2/Si substrate by improved vapor-phase epitaxy. The x-ray diffraction pattern and Raman spectrum demonstrate the composition of the as-prepared samples. Transmission electron microscopy characterization confirms high crystallization quality of Sb2Se3 nanowires. The electrical transport results show that Sb2Se3 nanowires exhibit electrical properties of a p-type semiconductor and have a current on/off ratio (Ion/Ioff) of ~ 102. The photoelectric test data indicate that Sb2Se3 nanowires have a good optical detection capability. The photoresponsivity is 4.12 A/W for Sb2Se3 nanowires with a diameter of 17 nm and up to 270 A/W for Sb2Se3 nanowires with a diameter of 55 nm, and the fast photoresponse time is less than 8 ms. Together, the as-grown Sb2Se3 nanowires with high quality have potential applications in electronics and optoelectronics. [ABSTRACT FROM AUTHOR]

In this study, we propose large-scale CsPbBr 3 (CPB) single-crystalline films (SCFs) grown by a one-step vapor-phase epitaxy (VPE) method for application in optoelectronic devices. After optimizing the transport speed of the precursor and cooling rate, we obtained continuous CPB films with a lateral size exceeding 2 cm 2 , and the thickness could be controlled from several micrometers to hundreds of nanometers. Crystallography and optoelectronic characterization proved the excellent crystallinity and very low trap density (2.14 × 10 11 ) of the SCFs. Furthermore, we demonstrate a transfer-assembly strategy for fabricating perovskite SCF-based heterostructures for visible photodetectors. The high-quality SCF films in the active layer suppress the leakage current, leading to a low dark current of 5 × 10 -10 A at -0.6 V. Therefore, the self-biased photodetector based on the vertical CsPbBr 3 SCF-SnO 2 heterostructure showed a high responsivity of 1.9 A/W, a detectivity of 4.65 × 10 12 Jones, and a large on/off ratio of 4.63 × 10 3 under a 1 mW/cm 2 450 nm light illumination. Our study not only demonstrates the excellent performance of single-crystalline perovskite-based photodiodes but also provides a universal assembly method for the integration of monocrystalline perovskite films in optoelectronic devices.

Perovskite monocrystalline films are regarded as desirable candidates for the integration of high-performance optoelectronics due to their unique photophysical properties. However, the heterogeneous integration of a perovskite monocrystalline film with other semiconductors is fundamentally limited by the lattice mismatch, which hinders direct epitaxy. Herein, the van der Waals (vdW) integration strategy for 3D perovskites is developed, where perovskite monocrystalline films are epitaxially grown on the mother substrate, followed by its peeling off and transferring to arbitrary semiconductors, forming monocrystalline heterojunctions. The as-achieved CsPbBr 3 -Nb-doped SrTiO 3 (Nb:STO) vdW p-n heterojunction exhibited comparable performance to their directly epitaxial counterpart, demonstrating the feasibility of vdW integration for 3D perovskites. Furthermore, the vdW integration could be extended to silicon substrates, rendering the CsPbBr 3 -n-Si and CsPbCl 3 -p-Si p-n heterojunction with apparent rectification behaviors and photoresponse. The vdW integration significantly enriches the selections of semiconductors hybridizing with perovskites and provides opportunities for monocrystalline perovskite optoelectronics with complex configurations and multiple functionalities.

Chloride-hydride epitaxy is the main vapor-phase technique for forming layers of functional homostructures and heterostructures for microelectronics and optoelectronics. At present, nanoheterostructures are obtained by MOS-hydride and molecular epitaxy; the molecular-layering technique is currently being perfected. The occurrence of new materials requires long-term development of the optimal technological conditions for their fabrication and the mathematical, physical, and other principles for modeling these processes. The chloride-hydride method continues to be perfected for forming relatively thick layers of functional heterostructures. The work outlines the fundamentals of physicochemical modeling by the example of chloride-hydride epitaxy. A physicochemical model of the variation in the technological modes of the vapor-phase epitaxy of different compounds under the corresponding conditions, which facilitate the formation of compounds with the same degree of disorder, is discussed. Equations for predicting the conditions for the epitaxy of other materials of the same group by the well-developed technology of a material have been derived. The obtained regularities can be used to optimize the chloride-hydride epitaxy of gallium phosphide and solid solutions based on it. The calculated conditions for gallium-nitride epitaxy are shown to be in good agreement with the conditions of real technological developments made by other authors. [ABSTRACT FROM AUTHOR]

The results of studies of nominally undoped epitaxial p-GaSb layers grown by metal–organic vapor-phase epitaxy at a ratio TMSb/TEGa in the range from 1 to 50 are reported. At the ratio TMSb/TEGa = 50, GaSb epitaxial layers, whose resistivity is 400 Ω cm, are produced. It is shown that, for such layers, the crystal quality assessed by several methods remains comparable to the quality of n-GaSb substrates used for the growth of nominally undoped GaSb layers. [ABSTRACT FROM AUTHOR]

GaInPAs/InP heterostructures grown by metalorganic chemical vapor-phase deposition at a temperature of 600°C and pressure of 0.1 bar are investigated. The thicknesses of the grown GaInAsP layers amount to about 1 μm. For Ga1 –xInxP1 –yAsy solid solutions with average compositions of x = 0.77–0.87 and y = 0.07–0.42, the variation in the content y of V-group atoms over the epitaxial-layer thickness by a value of Δy up to 0.1 atomic fractions in the sublattice of the V-group elements is revealed by secondary ion mass spectrometry. In most cases, a change in y occurs in the GaInAsP layer over a length to 200 nm from the InP heterointerface. In certain cases, y varies throughout the entire GaInPAs-layer thickness. For the epitaxial layers with satisfactory crystalline perfection, the value of Δy is less in the case of better lattice-matching between the GaInPAs epitaxial layer and the substrate. For GaInPAs layers strongly lattice-mismatched with the substrate and characterized by a low degree of crystalline perfection, the value of Δy is close to zero. All these facts enable us to assume that it is elastic deformations arising in the forming monolayer lattice-mismatched with the growing surface that affect the incorporation of V-group atoms into the forming crystalline lattice. [ABSTRACT FROM AUTHOR]

Two different approaches to epitaxy of 4-μm-thick layers of polar GaN(0001) and semipolar GaN(10 1) on a V-shaped nanostructured Si(100) substrate with nanometer-thick SiC and AlN buffer layers have been experimentally demonstrated. The GaN(0001) layers were synthesized by hydride vapor-phase epitaxy, and GaN(10 1) layers, by metal-organic vapor-phase epitaxy, with the growth completed by hydride vapor-phase epitaxy. It was shown that layers of the polar GaN(0002) have a longitudinal elastic stress of –0.45 GPa and the minimum full width at half-maximum of the X-ray diffraction rocking curve ωθ ~ 45 arcmin, whereas for the semipolar GaN(10 1), these values are –0.29 GPa and ωθ ~ 22 arcmin, respectively. A conclusion is drawn that the combined technology of semipolar gallium nitride on a silicon (100) substrate is promising. [ABSTRACT FROM AUTHOR]

Experimental and theoretical studies of the processes of mesoporous-silicon carbonization during the formation of buffer layers for the subsequent epitaxy of 3C-SiC films and related wide-gap semiconductors are performed. Analytical expressions for the effective diffusion factor and diffusion length of carbon atoms in a porous system are obtained. The proposed model takes into account the processes of Knudsen diffusion, coagulation and the overgrowth of pores during the formation of a silicon-carbide layer. [ABSTRACT FROM AUTHOR]

Photovoltaic converters of 520- to 540-nm laser radiation based on GaInP/GaAs heterostructures have been studied. It is established that a decrease in the degree of GaInP layer ordering by introduction of antimony (Sb) atoms leads to a short-wave shift of the absorption edge with simultaneous growth in the open-circuit voltage. An increase in the total thickness of photoactive layers in heterostructures results in increasing spectral responsivity of radiation converters. The proposed optimization allows the efficiency of laser radiation photoconverters to be increased from 39.4 to 44.4%. [ABSTRACT FROM AUTHOR]

We propose a heat-conduction model that takes into account the features of the heat and mass transfer during vapor-phase epitaxy on a curvilinear surface. Using the integro-interpolation method, a difference scheme is constructed and the numerical solution of the stated problem is found. The approximation and the stability of the difference scheme are investigated. Examples of the numerical computation for various materials are presented. [ABSTRACT FROM AUTHOR]

The surface of silicon-on-sapphire (SOS) epitaxial layers is studied by atomic-force microscopy and the UV (ultraviolet) scattering method. X-Ray diffraction analysis of the SOS layers is carried out. The silicon-sapphire transition region is studied by the photovoltage method. The problem of the accumulation of by-products formed during the synthesis of silicon from monosilane is considered and experimentally confirmed. It is found that the addition of chlorine-containing reagents to the epitaxial process makes it possible to exclude the influence exerted by these products on the growing layer and also to modify the surface microprofile. Analysis of the surface and structure of the SOS layers demonstrates that film growth occurs by the Stranski-Krastanov mechanism. It is shown that a combined method in which a 30-60-nm-thick SOS layer is preliminarily grown from pure SiH4 and then a layer is additionally grown at a 2SiH4:1SiC14 ratio of gas component flow rates is the most preferable method for the fabrication of SOS structures with layer thicknesses of 300 nm and more. [ABSTRACT FROM AUTHOR]

This paper presents a method for the analytical calculation of the flow velocity of the gas mixture and the concentration of the growth component during vapor-phase epitaxy in a reaction chamber with a rotating substrate holder disk. The concentration of the growth component is analyzed in relation to some epitaxy process parameters. [ABSTRACT FROM AUTHOR]

The m-plane InN (1 $\bar 1$ 00) epilayers have been grown on a LiAlO (1 0 0) substrate by a two-step growth method using a metal-organic chemical vapor deposition (MOCVD) system. The low temperature InN buffer layer (LT-InN) is introduced to overcome the drawbacks of thermal instability of LiAlO (LAO) and to relieve the strains due to a large thermal mismatch between LAO and InN. Then the high temperature m-plane InN (1 $\bar 1$ 00) epilayers (HT-InN) were grown. The results of X-ray diffraction (XRD) suggest that the m-plane InN (1 $\bar 1$ 00) epilayer is a single crystal. The X-ray rocking curves ( ω scans) (XRC) and atomic force microscopy (AFM) indicate that the m-plane InN (1 $\bar 1$ 00) epilayer has anisotropic crystallographic properties. The PL studies of the materials reveal a remarkable energy band gap structure around 0.70 eV at 15 K. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to explore self-organizational tendencies of transition-metal silicide nanoislands formed by heteroepitaxial self-assembled processes, such as Co x Si y /Si, Ti x Si y /Si, Mn x Si y /Si, etc, which may exhibit a variety of intermediate phases, polymorphs, and shape transitions, with unique physical properties and size effects. Recent scanning tunneling microscopy observations of self-assembled growth of CoSi2 nanoislands have shown self-organization of nanoislands at the step-bunches of the vicinal Si(111) surfaces during solid-phase epitaxial growth, namely room-temperature deposition of sub-monolayer Co followed by elevated-temperature annealing treatments. In the current set of experiments, the specific effects of metal coverage, and of structural mismatch of respective silicide with silicon, were investigated by depositing higher coverage of Co and Ti, respectively, prior to the annealing treatments. Higher Co coverage has drastically modified the process, with flat fractal-type two-dimensional islands covering most of the terraces, though tiny dots were still observed at the step-bunches. The outcome of a higher Ti coverage experiment resembled that of a lower Co coverage with the disc-shaped silicide nanodots preferentially occupying the step-bunch sites; however, with a lesser degree of ordering, quite a few dots were found to populate terrace sites. More importantly, no size-selection took place, i.e., no correlation between the dot size and the parent step-bunch height was observed. [Copyright &y& Elsevier]

Abstract: In this work, shapes and shape transitions of several types of self-assembled heteroepitaxial nanostructures, as observed in in situ scanning tunneling microscopy experiments during growth, are examined in the framework of several equilibrium and kinetic models. In particular, heteroepitaxial TiSi2 and CoSi2 islands on Si(111) are shown to behave in accordance with generalized Wulff–Kaishew theorem of equilibrium strained and supported crystal shapes. More specifically, these silicide nanocrystals exhibit out-of-plane thickening shape transition by increasing their vertical aspect ratio with growth, as long as they are strained, and inverse (flattening) transition upon relaxation by misfit dislocations. On the other hand, heteroepitaxial Ge and CoSi2 islands on Si(001) are well-known for their in-plane anisotropic elongation. Plausible energetic and kinetic reasons for such elongation, based on the unique nucleation features of Ge–hut/Si(001) and non-planar CoSi2–hut/Si(001) interface, are discussed. [Copyright &y& Elsevier]

Abstract: Titanium silicide grows on silicon in a form of discontinuous layers, which is the most serious obstacle to the formation of high-quality epilayers for VLSI applications. At the same time, nanometric dimensions of the epitaxial silicide islands attract interest as quantum nanostructures. However, for this purpose, nanocrystals in a self-assembled array have to be defect-free, and exhibit high shape and size uniformity. In this work titanium silicide was grown on Si(111) substrates by reactive deposition epitaxy and by solid-phase epitaxy. Since the reaction and phase-formation kinetics depend on the growth method, accordingly different lattice matching and facet energies may result in different morphological shapes of the nanocrystals. Nanocrystals from reaction in a solid-state could be characterized as highly non-uniform in both shape and size, and their evolution due to post-deposition anneals increased that non-uniformity even further. Relaxation of epitaxial mismatch strain by misfit dislocations could be inferred from a gradual reduction of the nanocrystal vertical aspect ratio and development of flat top facets out of the initially sharp conical crests, in accord with generalized Wulf–Kaishew theorem. On the other hand, the silicide nanocrystals formed by reactive deposition exhibited high uniformity and thermal stability. Significant strain relaxation, as could be judged by the nanocrystal flattening, took place only at temperatures in excess of 650°C, followed by progressive nanocrystal coalescence. It thus could be inferred, that better titanium silicide nanocrystal arrays (in the sense of uniformity and stability) are more easily obtained by reactive deposition epitaxy than by solid-phase epitaxy. While terminal, stable C54-TiSi2 phase, did eventually form in the epilayers in both methods, different evolution pathways were manifested by different respective morphologies and orientations even in this final state. [Copyright &y& Elsevier]

In this work, ultrathin titanium silicide layers were grown on Si(1 1 1) substrates, with the aim to stimulate spontaneous growth of nanostructures by self-assembly. Scanning tunneling microscopy was used as a primary tool for a close, in situ monitoring of the related surface processes. This method enabled a detailed observation of the formation and subsequent evolution of the silicide nanoislands as a function of deposition parameters and annealing treatments. Nanoisland shape and, possibly, phase transformations were analyzed in real time and space with atomic, or near atomic resolution. The results of these measurements are discussed, and plausible explanations offered. [Copyright &y& Elsevier]

Two previously unreported shallow acceptor levels with ionization energies of 25.2 and 43.2 meV, respectively, have been observed in a number of vapor phase epitaxial and metalorganic chemical vapor deposited GaAs samples grown in several different laboratories. The corresponding donor-to-acceptor and conduction band-to-acceptor transitions are identified in low temperature photoluminescence spectra by means of their temperature and excitation intensity-dependence. These levels are present as residual acceptors in high purity material, but their chemical and/or metallurgical nature has not yet been determined. [ABSTRACT FROM AUTHOR]

CVD growth conditions, particularly growth temperature and partial pressures of the reactant gases, strongly affect the growth characteristics and properties of GaAsP epitaxial layers grown on GaAs substrates. For LED's the most important properties of the material are B/J (brightness per unit current density) and surface morphology. This paper presents the results of a systematic study of the effect of temperature and reactant gas partial pressure (at a fixed III/V ratio) on B/J, surface morphology, growth rate, impurity doping and layer composition. Growth conditions which yield the optimum properties for LED's are determined. The results are interpreted on the basis of kinetic and thermodynamic mechanisms controlling the growth process under various growth conditions. At constant temperature and constant III/V ratio, increasing the partial pressures causes the growth process to change from mass transport limited, where the growth rate increases with increasing partial pressures, to kinetically limited, where the growth rate is independent of partial pressures. Good morphology layers are obtained over a range of partial pressures around the transition from mass transport limited to kinetically limited growth. The B/J peaks at a value of partial pressure in the kinetically limited regime at which good morphology layers are obtained. Although B/J increases with increasing growth rate in the mass transport regime, the maximum B/J occurs in the region where growth rate is independent of partial pressures so that growth rate alone is not sufficient to determine B/J. In contrast to the 'parabolic≓ dependence of growth rate on growth temperature, caused by the transition from the mass transport regime to the kinetic regime, the relative incorporation of As, P, and Te varies with temperature in the manner predicted from thermodynamics in both regimes. This behavior is consistent with the growth rate in the kinetic regime being limited by the desorption of chlorine atoms from the growth surface, with the reaction of As, P, and Te with the Ga proceeding thermodynamically at all temperatures. [ABSTRACT FROM AUTHOR]

Silicon carbide light-emitting diodes with emission in the blue range of the spectrum have been produced by vapor growth and liquid-phase epitaxy. The technology of devices with a p-type (Al-doped) luminescent layer is described. Emission spectra and efficiency data are presented for two types of diodes. [ABSTRACT FROM AUTHOR]

InGaAs (x = 0.05 to 0.32) p-n junction structures have been grown on GaAs substrates by vapor-phase epitaxy (VPE) and liquid-phase epitaxy (LPE). It is shown that by step-grading the VPE material, lattice-mismatch strain can be absorbed by dislocations at the grading interfaces, leaving the final constant-composition device layers relatively dislocation free. In contrast, the dislocation density for LPE InGaAs increases with increasing InAs concentration. For both materials, diffusion lengths, electroluminescence efficiencies, and 77°K laser-diode parameters (threshold and efficiency) can be correlated with their dislocation densities. The VPE materials have electrical and luminescence properties that are independent of InAs concentration, and match those of their GaAs counterparts. The LPE materials exhibit properties that degrade with increasing InAs concentration. [ABSTRACT FROM AUTHOR]

Recent advances in materials technology, activation technology, and device technology have brought to fruition practical imaging devices utilizing NEA photoemitters. This paper describes the characteristics of proximity-focused image tubes utilizing large-area semitransparent, single-crystal III-V photocathode structures. Since the spectral response of the photocathode is determined by choice of the material used as the photoemitting layer, specific choices allow optimization for specific applications; e.g., laser illuminators. The material selection criteria and methods of fabricating the photocathode material structure will be discussed. The use of NEA materials allows the separation of the bulk photocathode material from other tube processing variables and has allowed a high degree of reproducibility from device to device. Specific device characteristics to be included in this discussion are resolution, stability of the photocathode during operation, and photocathode spectral data. [ABSTRACT FROM AUTHOR]