High-temperature Chemical Vapor Deposition Research Articles

Comparative analysis: CapEx in diamond mining versus diamond growing, based on open data sources and experimental results

The diamond industry has long been associated with environmental and social problems, ranging from mining practices to ethical concerns related to diamond sourcing. In recent years, there has been a growing interest in lab-grown diamonds as a sustainable alternative for diamond consumers. However, the production of lab-grown diamonds has own challenges. This article examines the capital expenditures per annualized carat of rough diamonds obtained through mining and two fabrication methods: high-pressure high-temperature (HPHT) and microwave plasma-assisted chemical vapour deposition (MP CVD). Lab-grown diamonds produced using HPHT and MP CVD methods require significantly higher capital expenditures per annualized carat compare to mined diamonds. HPHT diamonds require on-time CapEx of 500–833 US$ per carat annually, while MP CVD diamonds demand 549–1648 US$ per carat annually. Finding ways to reduce production cost and increase efficiency will be crucial in realizing the potential of lab-grown diamonds as a sustainable alternative to mined diamonds.

Low sheet resistance buried metal bit line realized by high-temperature metal CVD process in vertical channel transistor array

With the continuous evolution of dynamic random access memory (DRAM) devices, there is a growing demand for increased storage density per unit area. In this work, we aim to create a high-density array of vertical channel transistors using advanced DRAM process technology. A thickness of SiO2 (X+3 nm) was determined for the protective layer, which shows the best-protecting effect. We employed CVD to grow thin Ti films on the array’s bottom. To reduce the resistance of the buried bit line (BBL), we formed a high-quality metal silicide using a thermal annealing process combined with self-align technology. Nanoprobe measurement results show an average resistance of approximately 60 Ω of the bit line of each cell transistor, where the low series resistance can improve device performance. Our work involved optimizing the protective layers and achieving high-performance BBLs, paving the way for the development of high-density DRAMs.

Advances in fast 4H–SiC crystal growth and defect reduction by high-temperature gas-source method

This paper reviews recent progress in the development of high-speed 4H–SiC bulk crystal growth technology using the high-temperature gas-source method (high-temperature chemical vapor deposition). Vertical-type reactors capable of growing SiC bulk crystals of 50–75 and 100–150 mm in diameter have been developed, as have reactor configurations and growth conditions to achieve a high growth rate and material quality. Using the reactors, high growth rates up to or exceeding 3 mm/h have been achieved by employing an H2–SiH4–C3H8 gas system with high partial pressures of source gases and high growth temperature of 2500–2550 °C. It is also confirmed that the dislocation densities decline significantly in the direction of growth under proper growth conditions. Key factors for enhancing growth rate and improving crystal quality in the growth process are discussed.

High-throughput thermodynamic study of SiC high-temperature chemical vapor deposition from TMS-H2

A systematic study on the tetramethylsilane-hydorgen (TMS-H2) system by high-throughput thermodynamic method is conducted with a large experimental condition range (500 ∼ 2700 K, 0 ∼ 75 kPa, and H2:TMS ratio of 0.1 to 10000) towards the deposition of pure single-crystal SiC by high-temperature chemical vapor deposition (HTCVD) method. The temperature, pressure and H2:TMS ratio dependence phase diagrams are calculated to describe the deposition condition of single-phase “gas + SiC” region. Due to the etching effect of hydrogen on graphite, the increasing temperature and pressure could suppress the formation of graphite and favor the growth of SiC in the H2:TMS ratio above 1000, however, excessive H2:TMS ratio could reduce the TMS consumption efficiency. TMS consumption efficiency maps focusing on the gas + SiC region based on the phase diagrams have been carried out to balance the deposition parameters, SiC mole fraction and TMS consumption efficiency. When H2:TMS ratio > 1000, an accepted window for preparing single-phase SiC with a high TMS consumption efficiency (>90%) is provided, and this window could expand furtherly with increasing the ratio. TMS consumption efficiency maps offer the theoretic basis and guidance for improving the quality and cost of industrial production of single-crystal SiC by HTCVD method.

In Situ Construction of High-Thermal-Conductivity and Negative-Permittivity Epoxy/Carbon Fiber@Carbon Composites with a 3D Network by High-Temperature Chemical Vapor Deposition.

Modern highly integrated microelectronic devices are unable to dissipate heat over time, which greatly affects the operating efficiency and service life of electronic equipment. Constructing high-thermal-conductivity composites with 3D network structures is a hot research topic. In this article, carbon fiber felt (CFF) was prepared by airflow netting forming technology and needle punching combined with stepped heat treatment. Then, carbon-coated carbon fiber felt (C@CFF) with a three-dimensional network structure was constructed in situ by high-temperature chemical vapor deposition (CVD). Finally, high-temperature treatment was used to improve the degree of crystallinity of C@CFF and further enhance its graphitization. The epoxy (EP) composites were prepared by simple vacuum infiltration-molding curing. The test results showed that the in-plane thermal conductivity (K∥) and through-plane thermal conductivity (K⊥) of EP/C@CFF-2300 °C could reach up to 13.08 and 2.78 W/mK, respectively, where the deposited carbon content was 11.76 vol %. The in-plane thermal conductivity enhancement (TCE) of EP/C@CFF-2300 °C was improved by 6440 and 808% compared to those of pure EP and EP/CFF, respectively. The high-temperature treatment greatly provides an improvement in thermal conductivity for the in-plane and the through-plane. Infrared imaging showed excellent thermal management properties of the prepared epoxy composites. EP/C@CFF-2300 °C owned an in-plane AC conductivity of up to 0.035 S/cm at 10 kHz, and Lorentz-Drude-type negative permittivity behaviors were observed at the tested frequency region. The CFF thermally conductive composites prepared by the above method have a broad application prospect in the field of advanced thermal management and electromagnetics.

Sliding friction behaviors of TiCN/Cr3C2-NiCr and TiCN/WC-CoCr duplex coatings fabricated by combining HVOF and HT-CVD procedures

Hard films play essential roles in the wear protection of metal moving components. In this study, the TiCN/Cr3C2-NiCr and TiCN/WC-CoCr duplex coatings were designed and fabricated by utilizing the high-velocity oxygen fuel and the high-temperature chemical vapor deposition processes. The effects of two cermet interlayers on the microstructure, mechanical characteristics, stress distribution, and sliding wear behavior of the top TiCN films were thoroughly explored. Results evidenced that the TiCN/WC-CoCr duplex coating had a smoother surface than the TiCN/Cr3C2-NiCr duplex coating. The load-bearing capacity and fracture toughness of TiCN/WC-CoCr duplex coating were superior to TiCN/Cr3C2-NiCr duplex coating due to WC-CoCr coating possessing higher hardness, elastic modulus and high-temperature stability. The TiCN/WC-CoCr duplex coating also exhibited lower Von Mises stress compared to TiCN/Cr3C2-NiCr duplex coating, and the stress concentration zone was further away from the interface between the TiCN film and the cermet interlayer. The wear resistance of TiCN/WC-CoCr duplex coating was approximately 2 and 1.5 times that of the single TiCN film and TiCN/Cr3C2-NiCr duplex coating under 20 N load. Moreover, the wear mechanisms of the duplex coatings involved abrasive wear, adhesive wear and oxidative wear. This work significantly enhanced the wear resistance of TiCN films, which will broaden the application of TiCN film in non-load-bearing metal moving components.

Effect of crystal orientation of AlN coatings on its high temperature oxidation in wet air

Aluminum nitride is discussed for different high temperature applications, due to its unique properties. Lately it also received attention as a coating for different substrate materials. Within the present study oriented AlN-coatings with two different crystal orientations were produced via reactive magnetron sputtering and a high temperature CVD process on SiC-based substrates. The oxidation resistance of these coatings in comparison to bulk AlN was investigated in wet synthetic air at 1200 °C. Both, the bulk AlN and (101¯0)-oriented AlN-coating formed a porous Al2O3-scale, which was not protective and resulted in high oxidation rates. In contrast, the (0001)-oriented coatings were able to form a thin oxide scale and remained protective for the total exposure time of up to 200 h at 1200 °C. The underlying mechanism of the oxidation of AlN in wet air was discussed, considering the strong influence of the crystal orientation.

Effect of graphene coatings on the morphology of submillimeter thin copper wires after salt spray aging

Unprotected copper conductors are prone to oxidation and corrosion, especially when in contact with salt water or at high temperature. In this study, we compared commercially available coating with graphene oxide and plasma-enhanced chemical vapor deposition (PECVD) graphene coated wires in terms of antioxidation and anticorrosion protection. Samples were subjected to aging tests in a salt spray chamber. Thereafter, both the degree of coverage and surface protection were assessed by X-ray photoelectron spectroscopy measurements and scanning electron microscope images, which showed significant surface protection for both graphene coatings. Raman spectra obtained from the transferred coatings revealed their structural stability, which shows that it is possible to successfully use few atomic-layers-thick coatings to protect commercially available wires. Wire resistance tests performed at temperatures up to 320°C showed similar or better results for graphene coatings than for commercially coated wires. Additionally, images of the wires after high temperature tests showed high antioxidation protection for graphene coatings, especially for PECVD. The results of this study can be applied for further research on mechanical suitability of the coatings and wires themselves, especially after high-temperature CVD processes. Such studies may lead to novel Cu wire processing technologies.Graphical abstract

Quality Evaluation of 150 mm 4H-SiC Grown at over 1.5 mm/h by High-Temperature Chemical Vapor Deposition Method

To reduce manufacturing costs, high-quality 150 mm 4H-SiC wafers were grown at over 1.5 mm/h by high-temperature chemical vapor deposition. The dislocations in the initial growth stage did not increase compared with those in the seed crystal. The dislocation densities decreased during crystal growth, and the densities of threading dislocations and basal plane dislocations at the growth thickness of 7.1 mm were 1186 and 211 /cm2, respectively. The resolved shear stress, which is the cause of the increase in dislocations during growth, was calculated based on thermal fluid simulations; the shear stress of the grown crystal with a flat surface was small compared with that of the convex-shaped crystal. The dislocations did not increase likely because the crystals grown at high speeds were relatively flat. In addition, the decrease in dislocations was attributed to the frequent annihilation of dislocations due to the growth at a high temperature (2490 °C).

C+ ion implanted single crystal diamond with amorphous surface for efficient oxygen evolution catalysis

Oxygen evolution reaction (OER) is critical in water splitting for green hydrogen gas production due to its sluggish kinetics; however, commercial OER catalysts commonly suffer from high cost, low catalytic activity and poor stability. Herein, we developed a C+ ion implantation method to modify single crystal diamond, and the resultant surface amorphous layer not only raised the active site number but also increased the content of the C=O group, thus significantly improving the OER activity. The C+ ion implanted high-temperature and high-pressure (C+-HTHP) and chemical vapor deposition (C+-CVD) diamonds both exhibit low OER overpotential with η10 of 317 mV and 325 mV respectively, superior to those of HTHP diamond (360 mV), CVD diamond (395 mV) and RuO2 (364 mV). The potentiostatic testing shows that the C+ implanted diamonds almost didn't undergo the rise of OER overpotential upon catalysis for more than 12 h at a current density of 10 mA cm−2, suggesting a high catalytic stability, owing to the strong bonding between single crystal diamond and amorphous carbon layer. For the first time, we utilized carbon ion implantation to prepare diamond-based high-performance OER catalyst, which broadens the understanding of carbon-based materials in OER catalysis.

Effect of H Plasma Treatment of the Nucleation Layer on AlN Epitaxy in Microwave Plasma Chemical Vapor Deposition

The crystallinity of nucleation layers has significant influence on the crystallinity of aluminum nitride (AlN) epilayers. In this work, the etching effect of hydrogen (H) plasma was used to improve the nucleation-layer crystallinity. AlN nucleation layers were first cooled in a H-plasma atmosphere; then, AlN films were deposited on the processed nucleation layers, and the whole epitaxial process was carried out in high-temperature microwave plasma chemical vapor deposition (MPCVD) without the participation of ammonia. X-ray rocking curves (XRCs) showed that the cooling process obviously improved the crystal quality of AlN films, which was attributed to the preferential etching effect of H plasma on low-crystallinity nucleation islands. When a H2 flow rate of 135 sccm was used to process the nucleation layer, the AlN film with the narrowest (002) XRC full width at half-maximum (FWHM) of 86 arcsec was obtained. Possible growth mechanisms were suggested for the observations.

Coaxial heterostructure formation of highly crystalline graphene flakes on boron nitride nanotubes by high-temperature chemical vapor deposition

We develop a high-temperature chemical vapor deposition of highly crystalline graphene on the surface of boron nitride nanotubes (BNNTs). The growth of few-layer graphene flakes on BNNT templates was confirmed by scanning transmission electron microscopy. Based on an investigation of the effect of growth temperature and growth time on defect density, graphene with relatively high crystallinity was obtained at 1350 °C. The absence of undesirable alterations in the BNNT lattice during graphene growth was verified by multiple analyses. The high-temperature growth of heterolayers would assist in the advancement of nanodevices that coaxially combine graphene and boron nitride.

Heteroatomic stitching of broken WS2 monolayer with enhanced surface potential.

Sub-nanometre thick two-dimensional (2D) materials suffer from severe cracking during the high temperature chemical vapour deposition growth process. The cracking can be utilised to generate more active edges. These active edges can be stitched with a homo- or hetero-material. While the direct growth of 2D-heterostructures is mostly limited to a small fraction of outer edges of monolayer flakes, the cracked monolayers can be utilised to produce a large fraction of heterostructures. Heterostructures are important for developing multifunctional components for nanoscale electronics and optoelectronics. In this work, we demonstrate the formation of WS2-MoS2 heterostructures in large fractions by atomic stitching of cracked WS2 monolayers with the sequential growth of MoS2. Aberration-corrected scanning transmission electron microscopy and Raman spectroscopy have been utillised to probe fine details on the stitched interface between WS2 and MoS2. Growth of MoS2 domains were observed to take place at the terminating edge of cracked WS2, which then merged to form MoS2 multilayers at the cracked site. Growth of MoS2 at the opposite edges of WS2 eventually results in a MoS2-MoS2 junction with a Σ = 7 tilt boundary. Kelvin probe force microscope (KPFM) measurement from the stitched region revealed that the work function of WS2 is ∼32.46 meV higher than that of MoS2, which also closely matches with the Fermi energy difference between these two materials. With the aid of an atomic force microscope and KPFM, the surface potential width at the stitched region was found to be ∼5 times higher than the actual width of the interface, confirming the modulation of properties near the interface.

Microstructure and integrity of multilayer ceramic coating with alumina top coat on silicon carbide by laser chemical vapor deposition

Thin double-layer coatings comprising an alumina top coat and mullite bond coat were deposited on SiC substrates by laser chemical vapor deposition (CVD). The effect of the presence of mullite bond coat and the phases of alumina top coat on the structural integrity against the thermal residual stress loaded by the high-temperature CVD process was examined by microstructural characterization and simulative consideration. A laminated layered structure having a dense γ-alumina top surface with a cone-like morphology are grown at a deposition temperature of 1323 K, whereas an α-alumina top layer comprising densely packed faceted grains was grown at 1473 K. The interfaces between the SiC and mullite layers were coherent owing to the formation of a thin transition layer. The γ-alumina layer formed an adhesive interface bordering the mullite layer, whereas small residual defects were formed in the α-alumina layer bordering the mullite layer. Spacings of surface cracking induced by the high-temperature deposition process in the double-layer coatings were approximately half of those in the coatings without mullite layers. As simulative results by finite element method suggested, the double-layer coatings were experimentally verified to be more tolerant to the formation of surface cracks and interfacial delamination, compared to single-layer coatings without the mullite bond layers.

Chemical Vapor Deposition of Graphene on Self-Limited SiC Interfacial Layers Formed on Silicon Substrates for Heterojunction Devices

Direct chemical vapor deposition (CVD) of graphene on any desired substrate is always required to manufacture high-quality heterojunctions with excellent interfacial properties. Herein, the growth of graphene on cubic-silicon carbide (3C-SiC) surfaces using conventional high-temperature direct thermal CVD and plasma-enhanced CVD (PECVD) is explored, which is hardly reported to date. Since 3C-SiC substrates are not available, the controlled self-limited 3C-SiC layers on the Si(100) substrates were grown at different temperatures (900–1200 °C) via thermal-CVD technique to obtain virtual 3C-SiC substrates. The direct production of graphene via thermal CVD could not be achieved on such 3C-SiC surfaces. The density functional theory and molecular dynamics simulations confirm that the carbon atom diffusion over the 3C-SiC surface is extremely low, like over the Si surface, which leads to no graphene growth. A similar growth mechanism may be attributed to their similar crystal structure viz diamond cubic for Si and zinc blend for 3C-SiC. However, graphene nanowalls (GNWs) were successfully grown on both Si and 3C-SiC/Si surfaces at 700 °C via the PECVD technique, where similar surface morphologies were observed because the growth mechanism of GNWs is independent of substrate type. Moreover, I–V characterization was performed for different SiC/Si heterostructures and their corresponding GNWs/SiC/Si heterostructures, respectively. The current conduction improved considerably more for GNW/SiC/Si heterostructures as compared to SiC/Si heterostructures, but the creation of a SiC interfacial layer as well as its quality affected the conductivity of GNWs/SiC/Si heterostructures. The inevitable formation of an interfacial SiC layer during the direct graphene growth via thermal CVD on Si substrates can seriously affect the performance of graphene/Si heterojunction devices. Hence, PECVD growth of graphene is an ideal option to fabricate graphene/Si heterojunction devices with excellent interfacial properties or graphene/3C-SiC/Si heterojunction devices for various electronic/optoelectronic applications such as gas sensors and photovoltaic devices.

High-Temperature Performance of the 4H-SiC n-p-n Bipolar UV Phototransistor

Excellent high-temperature performance (298–523 K) of the 4H-SiC n-p-n bipolar phototransistor detector (PTD) was explored. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition (HTCVD). The static and dynamic properties of the device were tested and analyzed. The results show that the device still has an optical gain of up to 103, a wide linear response range, and good repeatability at the high temperatures up to 523 K under a 3-V bias with a wavelength of 360 nm. The temperature coefficient of the optical gain is extracted, the value of which is 1.02/K. Although the response time of the device increases with the temperature, the increased percentage in responsivity is significantly greater than that of the response time. The results provide an important experimental reference for the application of high-temperature detection and suggest that the PTD has the potential to be used in ultraviolet (UV) detecting systems at high temperatures.

Structural characteristics of 3C–SiC thin films grown on Si-face and C-face 4H–SiC substrates by high temperature chemical vapor deposition

Hetero-epitaxy of 3C–SiC on Si-face and C-face 4H–SiC is experimentally investigated and corresponding growth model is identified. This study of polytypes of SiC will be useful for band-gap engineering, optical, electrical, and electronic applications of SiC. 3C–SiC was epitaxially deposited on 4H–SiC using a high temperature chemical vapor deposition. The primary factor affecting the epi-quality on Si-face SiC is double positioning boundary (DPB) defect. An adatom migration model elucidates the formation of the V-shaped DPB defect structures. On C-terminated 4H–SiC, super-V-shaped-structure (SVSS) defects and polycrystalline complexes in 3C–SiC are formed. These characteristics of 3C–SiC are measured and analyzed using transmission electron microscopy, X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. A model considering adatoms' migration in step-flow direction and anti-step-flow direction explains the SVSS defects. Effects of both step-flow and anti-step-flow growth mode on the atom adsorption near the step edge are discussed.

High temperature oxidation of SiC-coated Fe-Cr-Al-Mo alloys in muffle and concentrated solar furnaces

The maximal temperature of a solar receiver is limited by its resistance to oxidation, thermal cycling and mechanical stresses as it is a key component of solar power plant with a central tower. Currently used Ni-based alloys cannot heat the air coolant at temperatures beyond 1000 K due to the severe oxidation that may affect the surfaces exposed to air at high temperatures, affecting the solar absorptivity of the receiver. A SiC coating should protect a high temperature metallic alloy from oxidation and improve its solar absorptivity, only if the accommodation between the metallic substrate and the ceramic coating is optimized to prevent the coating from cracking and peeling due to the thermal expansion of the assemblage. To reduce the interfacial stresses, SiC was deposited using High Temperature Chemical Vapor Deposition on a pre-oxidized Fe-Cr-Al-Mo alloy, so that a 2µm-thick alumina layer could work as an accommodation layer. The oxidations performed in muffle and solar furnaces (associated to ex situ characterizations using scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping, X-ray diffraction, and room-temperature normal spectral emissivity measurements) have demonstrated that this multilayer structure could support long-term oxidation and thermal stresses up to1400 K without significant changes regarding the spectral emissivity, but the coating peels if the sample is treated at 1600 K. The multilayer structure can therefore work beyond the current working point of solar receivers, nevertheless the accommodation still has to be improved in case of accidental exposures to higher solar fluxes.

Low-Temperature Self-Limiting Growth of Cubic Boron Nitride Via Hollow-Cathode Plasma-Enhanced Atomic Layer Deposition

The two main polymorphs of boron nitride are hexagonal (h-BN) and cubic (c-BN) phases and both show attractive material properties to be employed under extreme environments. h-BN is also known as “white graphene” due to the matching hexagonal crystal symmetry and shows a layered structure which provides advantages as a lubricant material and as gate dielectrics for two-dimensional (2D) transistor channels. On the other hand, c-BN is analogous to another important elemental carbon material, diamond. While the mechanical strength of c-BN is lower than diamond, the thermal and chemical stability is even superior. Both h-BN and c-BN films are therefore strong candidates for applications under harsh ambient, including high-temperature, high-pressure, and corroding factors.BN films and coatings are conventionally grown using high-temperature CVD methods with typical substrate temperatures over 1000 oC. To reduce the deposition temperatures of this material while preserving the attractive crystal properties, alternative lower temperature physical and chemical vapor deposition strategies have been offered in the literature. Plasma-enhanced atomic layer deposition (PEALD) provides significant advantages over other methods such as precision thickness control, ultimate conformality, while reducing the growth temperature substantially. In our previous work, we had demonstrated the crystalline synthesis of h-BN films at substrate temperatures as low as 350 oC, while no growth was observed at lower substrate temperatures.In this work, we aim to demonstrate the feasibility of growing c-BN at substrate temperatures reaching 200 oC via a customized PEALD reactor featuring a large-diameter capacitively-coupled hollow-cathode plasma source with a relatively short source-to-substrate distance. We used Si(100), sapphire, and glass as the substrates to deposit the films. The growth temperature is kept between 150 and 250 °C, 10 sccm of N2 flow is used as a carrier gas and Ar-purging gas flow was kept at 50 sccm. The triethylboron (TEB) precursor and various nitrogen plasma chemistries including different compositions of N2, H2, and Ar gases are utilized. The optimized growth condition is determined from in-situ monitored saturation studies, where the growth-per-cycle (GPC) parameter is noted for different precursor pulse time (15 and 30 ms), rf-plasma power (100 W to 250 W) and plasma-gas chemistries (N2-only, N2/H2, Ar/N2, Ar/N2/H2 at varying ratios). While the 200 °C as-grown BN films exhibited nanocrystalline c-BN with relatively weak crystal peaks as verified by XRD measurements, vacuum annealing at 5 mTorr N2 flow and 700 °C transformed the film structure into single-phase polycrystalline c-BN. The spectroscopic ellipsometer, x-ray reflectivity (XRR), and x-ray photoelectron spectroscopy (XPS) studies will be presented as well as the influence of post-deposition vacuum annealing to further improve the crystalline structure of c-BN films. Basic electrical properties of the grown BN films will be characterized using metal-insulator-semiconductor (MIS) diode temperature-dependent current-voltage (I-V) measurements.A specific effort will be devoted to enhance the as-grown film crystal properties via implementing novel atomic layer plasma annealing processes, which showed its potential for the ultrawide bandgap Ga2O3 alloy. Another research question to be investigated is whether there is a possibility of tuning the material phase from cubic to hexagonal by carefully adjusting growth and in-situ Ar-plasma annealing conditions.

Van der Waals Epitaxy of c-Oriented Wurtzite AlGaN on Polycrystalline Mo Substrates for Enhanced Heat Dissipation.

The epitaxy of III-nitrides on metallic substrates is competitive due to the advantages of vertical carrier injection, enhanced heat dissipation, and flexible application in various III-nitride-based devices. However, the serious lattice mismatch, atom diffusion, and interface reaction under the rigorous growth conditions have caused enormous obstacles. Based on the thermal and chemical stability of the graphene layer, we propose the van der Waals epitaxy of c-oriented wurtzite AlGaN on the polycrystalline Mo substrate by high-temperature metal-organic chemical vapor deposition. The insertion of a graphene layer interrupts the chaotic epitaxial relationship between the polycrystalline metal and epilayers, resulting in the single-crystalline orientation along the wurtzite (0002) plane and residual stress release in AlGaN because of the weak van der Waals interaction. We also demonstrate that the epitaxy of AlGaN on Mo metal possesses enhanced heat dissipation ability, in which the epilayer temperature is controlled at only 28.7 °C by the heating of a ∼54 °C hot plate. The heat dissipation enhancement for the present epitaxial structures provides a desirable strategy for the fabrication of efficient ultraviolet devices with excellent stability and lifetime.