Foreign Substrates Research Articles

A new method for growing epitaxial films on foreign substrates − Bent epitaxy

In recent years, to mitigate the effects of climate change, countries’ transition to the green economy has accelerated, and thereby, the demand of semiconductor industry for wide-gap semiconductors such as SiC and GaN has increased dramatically. These semiconductors are expensive. To reduce the price of the final product, industrial production of thin epitaxial films of sought-after semiconductors on accessible and cheap substrates, such as Si and sapphire, is being developed. When growing epitaxial films on foreign substrates, the resulting heterostructure bends, becomes concave or convex, due to a mismatch between the coefficients of thermal expansion (CTE) of the substrate and the epitaxial film. As a result, the quality of the epitaxial film deteriorates and further processing of the resulting heterostructures in production lines becomes difficult or even impossible. The essence of the proposed new method is that the epitaxial film is grown not on a flat, but on a pre-curved substrate with the expectation that after cooling the fabricated heterostructure to room temperature, the heterostructure will take a flat shape due to the difference in the CTE of the epitaxial film and the substrate. A round bimetallic plate, located under the substrate, bends the substrate in the required direction to the desired value at the growth temperature, and gradually reduces the bend of the fabricated heterostructure during cooling, in proportion to the thermal contraction of the epitaxial film. This allows obtaining qualitative and flat epitaxial films, regardless of the material of the substrate or epitaxial film and the diameter of the substrate or thickness of the epitaxial film, without any buffer layers or carrying out any additional operations and costs.

High-voltage kV-class AlN metal-semiconductor field-effect transistors on single-crystal AlN substrates

This letter reports the demonstration and electrical characterization of high-voltage AlN metal-semiconductor field-effect transistors (MESFETs) on single-crystal AlN substrates. Compared with AlN MESFETs on foreign substrates, the AlN-on-AlN MESFETs showed high breakdown voltages of over 2 kV for drain-to-gate spacing of 15 μm and one of the highest average breakdown fields among reported AlN MESFETs. Additionally, the devices also exhibited decent drain saturation current and on/off ratio without complicated regrown or graded contact layers, which are several times higher than those of reported AlN-on-sapphire MESEFTs. This work is beneficial for the future development of ultrawide bandgap AlN power electronics.

Leakage current in GaN-on-GaN vertical GaN SBDs grown by HVPE on native GaN substrates

This study investigates leakage mechanisms in vertical GaN-on-GaN Schottky barrier diodes (SBDs) and demonstrates effective mitigation strategies. The fabricated devices exhibit low reverse leakage current (1 × 10−5 A/cm2 at −200 V) and a high Ion/Ioff ratio (∼1010), surpassing the performance of GaN SBDs on foreign substrates. We elucidate dominant leakage mechanisms—thermionic emission, Poole–Frenkel emission, and variable-range hopping—and their evolution with temperature and bias. Optimized fabrication processes, including defect etching and a novel dual-layer passivation technique, achieve over a 1000-fold reduction in leakage current.

Novel approach to produce 3D boron-doped diamond for pollutant removal from water

Diamond growth from Chemical Vapor Deposition (CVD) on foreign substrates can require different pretreatment not only to improve the film nucleation but also to assure its adhesion by decreasing the expected film/substrate interface stress. To improve boron-doped film nucleation, growth, and adherence, different substrate pretreatments have been used mainly from the seeding process with diamond powder at various particle sizes. Despite this, the development of diamond growth on a Ti mesh remains difficult because of the requirement of a cohesive film to cover a 3D macroporous sample with varying growth rates based on its distinct network geometry. Then, this work describes a novel approach to growing boron-doped diamond (BDD) and boron-doped ultrananocrystalline diamond (B-UNCD) on titanium dioxide nanotubes (TDNT) produced simultaneously on both sides of Ti mesh by an anodization process. The films were obtained from two-step growth processes by assuring the entire diamond overlay on both TDNT/Ti mesh sides, including their outer/inner surfaces, as a 3D sample. TiO2 - TiC conversion has dominated the renucleation process, facilitating the nanometric scale control. The film morphologies were systematically analyzed by FEG-SEM images at different sample planes and depths for both sample sides at different stages of film growth. The unique morphology of titania nanotubes associated with columnar and/or renucleation development of BDD, considering the film defects and valley, can systematically increase the electrode specific area. Raman spectra showed the film quality and its micro and/or ultrananodiamond structure and the boron doping features. Also, this growth process allowed a dopant-controlled adjustable conductivity. Then, the boron doping levels for both films were evaluated from Mott-Schottky plots at around 1019 Bcm−3, characterizing them with good conductivity. In addition, electrochemical measurements from Cyclic Voltammetry (CV) confirmed the expected diamond response on redox pair following the quasi-reversible criteria as high-performance diamond electrodes and in situ Raman spectroelectrochemical measurements assessed the stability of samples during electrochemical measurements, ensuring structural integrity. Finally, the samples were applied to the degradation of methylene blue, proving to be superior materials for electrochemical applications due to their advantages compared to those of similar 2D electrodes.

Electrical Properties of N‐Polar GaN/AlGaN/AlN Grown via Metal‐Organic Vapor Phase Epitaxy

The metal‐organic vapor phase epitaxy (MOVPE) method faces several challenges when used for the growth of N‐polar GaN on foreign substrates, including the presence of a rough surface morphology characterized by step bunching or hexagonal hillocks. In this study, it is aimed to address these issues by establishing optimal growth conditions for the MOVPE method, enabling the growth of N‐polar GaN/Al0.9Ga0.1N/AlN heterostructures with a smooth surface morphology on a vicinal sapphire substrate. The formation of 2D electron gas (2DEG) in N‐polar GaN/AlGaN/AlN prepared using MOVPE is discussed. Additionally, in the study, the impact of growth conditions, such as temperature and V/III ratio, on the electrical properties of N‐polar GaN is investigated. In the results, it is revealed that growth at lower temperatures and a V/III ratio of 30 000 effectively suppresses 3D growth. Moreover, an increase in the V/III ratio correlates with a decrease in residual impurity concentrations (C and H); hence, electron mobility improves. Moreover, the N‐polar GaN/AlGaN/AlN field‐effect transistor, grown under optimized conditions, exhibits a higher maximum drain–source current (IDmax). In these results, possibilities are broadened for the high performance of N‐polar GaN channel high‐electron‐mobility transistors through MOVPE.

Thermodynamics of Ga2O3 Heteroepitaxy and Material Growth Via Metal Organic Chemical Vapor Deposition.

Heteroepitaxy of gallium oxide (Ga2O3) is gaining popularity to address the absence of p-type doping, limited thermal conductivity of Ga2O3 epilayers, and toward realizing high-quality p-n heterojunction. During the growth of β-Ga2O3 on 4H-SiC (0001) substrates using metal-organic chemical vapor deposition, we observed formation of incomplete, misoriented particles when the layer was grown at a temperature between 650 °C and 750 °C. We propose a thermodynamic model for Ga2O3 heteroepitaxy on foreign substrates which shows that the energy cost of growing β-Ga2O3 on 4H-SiC is slightly lower as compared to sapphire substrates, suggesting similar high-temperature growth as sapphire, typically in the range of 850 °C-950 °C, that can be used for the growth of β-Ga2O3 on SiC. A two-step modified growth method was developed where the nucleation layer was grown at 750 °C followed by a buffer layer grown at various temperatures from 920 °C to 950 °C. 2θ-ω scan of X-ray diffraction (XRD) and transmission electron microscope images confirm the β-polymorph of Ga2O3 with dominant peaks in the (-201) direction. The buffer layer grown at 950 °C using a "ramp-growth" technique exhibits root-mean-square surface roughness of 3 nm and full width of half maxima of XRD rocking curve as low as 0.79°, comparable to the most mature β-Ga2O3 heteroepitaxy on sapphire, as predicted by the thermodynamic model. Finally, the interface energy of an average Ga2O3 island grown on 4H-SiC is calculated to be 0.2 J/m2 from the cross-section scanning transmission electron microscope image, following the Wulff-Kaishew theorem of the equilibrium island shape.

Growth and impact of intrinsic interlayers in high temperature vapor phase epitaxy of GaN

Structural quality of GaN layers grown on foreign substrates is usually improved by applying masks or interlayers, which interact with the crystal structure defects, mainly with threading dislocations, and consequently reduce their density. In this work, GaN interlayers with intrinsic defect structures were employed as barriers impeding the propagation of threading dislocations. The GaN samples were produced in a multistage deposition process by high-temperature vapor phase epitaxy (HTVPE). They consisted of GaN seed layers deposited on 15 × 15 mm2 (001)-oriented sapphire substrates, structured GaN interlayers and GaN top layers. The structuring of the interlayers was facilitated by changing the substrate temperature and the V/III ratio during the growth. The optical and scanning electron microscopies revealed that the structured interlayers contain pyramidal facets, vertical trenches and elongated voids. The results of X-ray diffraction and Raman spectroscopy have shown that these microstructure features are able to reduce the density of threading dislocations in the top layer and the tensile residual stress that develops in the top layer during the deposition process. These results demonstrate the potential of the intrinsic interlayer concept for the in-line defect and stress engineering in HTVPE GaN layer stacks.

Flexible nanoimprint lithography enables high-throughput manufacturing of bioinspired microstructures on warped substrates for efficient III-nitride optoelectronic devices

III-nitride materials are of great importance in the development of modern optoelectronics, but they have been limited over years by low light utilization rate and high dislocation densities in heteroepitaxial films grown on foreign substrate with limited refractive index contrast and large lattice mismatches. Here, we demonstrate a paradigm of high-throughput manufacturing bioinspired microstructures on warped substrates by flexible nanoimprint lithography for promoting the light extraction capability. We design a flexible nanoimprinting mold of copolymer and a two-step etching process that enable high-efficiency fabrication of nanoimprinted compound-eye-like Al2O3 microstructure (NCAM) and nanoimprinted compound-eye-like SiO2 microstructure (NCSM) template, achieving a 6.4-fold increase in throughput and 25% savings in economic costs over stepper projection lithography. Compared to NCAM template, we find that the NCSM template can not only improve the light extraction capability, but also modulate the morphology of AlN nucleation layer and reduce the formation of misoriented GaN grains on the inclined sidewall of microstructures, which suppresses the dislocations generated during coalescence, resulting in 40% reduction in dislocation density. This study provides a low-cost, high-quality, and high-throughput solution for manufacturing microstructures on warped surfaces of III-nitride optoelectronic devices.

Using machine learning with atomistic surface and local water features to predict heterogeneous ice nucleation.

Heterogeneous ice nucleation (HIN) has applications in climate science, nanotechnology, and cryopreservation. Ice nucleation on the earth's surface or in the atmosphere usually occurs heterogeneously involving foreign substrates, known as ice nucleating particles (INPs). Experiments identify good INPs but lack sufficient microscopic resolution to answer the basic question: What makes a good INP? We employ molecular dynamics (MD) simulations in combination with machine learning (ML) to address this question. Often, the large amount of computational cost required to cross the nucleation barrier and observe HIN in MD simulations is a practical limitation. We use information obtained from short MD simulations of atomistic surface and water models to predict the likelihood of HIN. We consider 153 atomistic substrates with some surfaces differing in elemental composition and others only in terms of lattice parameters, surface morphology, or surface charges. A range of water features near the surface (local) are extracted from short MD simulations over a time interval (≤300 ns) where ice nucleation has not initiated. Three ML classification models, Random Forest (RF), support vector machine, and Gaussian process classification are considered, and the accuracies achieved by all three approaches lie within their statistical uncertainties. Including local water features is essential for accurate prediction. The accuracy of our best RF classification model obtained including both surface and local water features is 0.89 ± 0.05. A similar accuracy can be achieved including only local water features, suggesting that the important surface properties are largely captured by the local water features. Some important features identified by ML analysis are local icelike structures, water density and polarization profiles perpendicular to the surface, and the two-dimensional lattice match to ice. We expect that this work, with its strong focus on realistic surface models, will serve as a guide to the identification or design of substrates that can promote or discourage ice nucleation.

Strain modulation of epitaxial h-BN on sapphire: the role of wrinkle formation for large-area two-dimensional materials.

Strain built-in electronic and optoelectronic devices can influence their properties and lifetime. This effect is particularly significant at the interface between two-dimensional materials and substrates. One such material is epitaxial hexagonal boron nitride (h-BN), which is grown at temperatures often exceeding 1000 °C. Due to the high growth temperature, h-BN based devices operating at room temperature can be strongly affected by strain generated during cooling due to the differences in lattice thermal expansion of h-BN and the substrate. Here, we present results of temperature-dependent Raman studies of the in-plane E2ghighphonon mode in the temperature range of 300-1100 K measured for h-BN grown by metalorganic vapor phase epitaxy. We observe a change, by an order of magnitude, in the rate of the temperature-induced frequency shift for temperatures below 900 K, indicating a strong reduction of the effective h-BN/substrate interaction. We attribute this behavior to the creation of h-BN wrinkles which results in strain relaxation. This interpretation is supported by the observation that no change of layer/substrate interaction and no wrinkles are observed for delaminated h-BN films transferred onto silicon. Our findings demonstrate that wrinkle formation is an inherent process for two-dimensional materials on foreign substrates that has to be understood to allow for the successful engineering of devices based on epitaxially grown van der Waals heterostructures.

Quantum Cascade Lasers Grown by Metalorganic Chemical Vapor Deposition on Foreign Substrates with Large Surface Roughness

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

Pulsed-Mode Metalorganic Vapor-Phase Epitaxy of GaN on Graphene-Coated c-Sapphire for Freestanding GaN Thin Films.

We report the growth of high-quality GaN epitaxial thin films on graphene-coated c-sapphire substrates using pulsed-mode metalorganic vapor-phase epitaxy, together with the fabrication of freestanding GaN films by simple mechanical exfoliation for transferable light-emitting diodes (LEDs). High-quality GaN films grown on the graphene-coated sapphire substrates were easily lifted off by using thermal release tape and transferred onto foreign substrates. Furthermore, we revealed that the pulsed operation of ammonia flow during GaN growth was a critical factor for the fabrication of high-quality freestanding GaN films. These films, exhibiting excellent single crystallinity, were utilized to fabricate transferable GaN LEDs by heteroepitaxially growing InxGa1-xN/GaN multiple quantum wells and a p-GaN layer on the GaN films, showing their potential application in advanced optoelectronic devices.

(Invited) Application of Synchrotron X-Ray Topography Techniques to the Analysis of Defect Microstructures in Bulk GaN Substrates and Epilayers for Power Devices

Wide bandgap semiconductor gallium nitride (GaN), along with silicon carbide (SiC) are replacing silicon materials in the applications for power electronic devices. While SiC-based power technologies are based on bulk SiC substrates, GaN-based power technologies have until recently been based on GaN layers grown on foreign substrates such as sapphire, SiC and Si substrates. To achieve the full potential of GaN power devices, devices on bulk GaN substrates are desirable. In this review, the use of synchrotron X-ray topography techniques to evaluate defects and strain in bulk GaN substrates for vertical device development is presented. Ray tracing simulations is shown to effectively identify the Burgers vectors of all dislocations on X-ray topographs from GaN materials. Ammonothermal-grown GaN substrate wafers show the best quality among all the wafers. These wafers, which are free of basal plane dislocations (BPDs), have low curvature and threading mixed dislocations (TMDs) dominant among the TDs. However, certain ammonothermal substrates contain growth sectors with different impurity concentrations that are likely inherited from prior seed expansion growth runs. Patterned hydride vapor phase epitaxy (HVPE) GaN reveal a starkly heterogeneous distribution of dislocations with large areas containing low threading dislocation densities in between a grid of strain centers with higher threading dislocation densities and BPDs. These substrates also contain growth sector boundaries separating core regions growing in <11-22> directions and surrounding regions growing along [0001]. HVPE GaN substrates are characterized by high lattice distortion and dislocation densities of the order of 105-106 cm-2, which is much higher than 103-104 cm-2 of ammonothermal samples and dislocation-free areas in the patterned HVPE samples. Epitaxial growth and other processes involving heat treatment (including annealing) does not nucleate new defects but can result in interactions of dislocations (threading screw dislocations(TSDs)/threading mixed dislocations (TMDs)/threading edge dislocations (TEDs)) with point defects leading to changes in dislocation configurations. Mg-ion implantation for p-type doping does not change the distribution of dislocation but introduces lattice damage. By Rocking curve Analysis by Dynamical Simulation (RADS) analysis of X-ray rocking curves, the depth profile of strain can be obtained and correlated with doping profile. During annealing the implanted samples to heal lattice damage and activate the Mg ions, proper capping is necessary to limit loss of matter and introduction of additional lattice distortion. However, high pressure annealing has been shown to eliminate the need for capping. The effect on microstructure from other selectively area doping techniques such as etch and regrowth, diffusion and neutron transmutation will also be discussed.

Influence of the Crystallographic Texture of ITO on the Electrodeposition of Silver Nanoparticles

Metal nanoparticles exhibit physical and chemical properties that differ significantly from macroscopic metal phases. In particular, silver nanoparticles (NPs) had have extensive attention since it has a strong interaction with light due to their high quality localized surface plasmon resonances, which can be tuned all across the visible to the NIR regime. These strong and tuneable interaction of visible light with silver NPs have found many applications, in sensing, surface enhanced Raman spectroscopy, photo(electro)catalysis, and more.Polycrystalline indium tin oxide (ITO) films are highly desired substrates for many of these optoelectronic applications. In many of these applications, it is essential to reliably and precisely control the size and density of silver NPs. Even though it is well known that the electrochemical control over nucleation and growth of silver NPs on foreign substrates highly depends on the surface properties of the substrate, yet, the only parameter that is often specified for these ITO substrates is a bulk property: sheet resistance. As a result, nucleation and growth on ITO is highly irreproducible.In this work, we show that ITO substrates with same technical specifications (i.e. sheet resistance, light transmittance and roughness) and supplier may still have different surface properties such as the crystalline texture. We find that these differences in the surface properties has a strong impact on the nucleation and growth. Even though we used seemingly equal ITO substrates, XRD and EBSD scans clearly differentiate between two types of films based on the ratio between the (222) and (400) related peaks. We controlled the density and size of the silver NPs by making use of the double pulse technique. In this method, where the high overpotential nucleation pulse controls the nucleation density. Previous studies have reported an empirical exponential relationship between island density and nucleation pulse overpotential, where the slope is a measure for the electron kinetics.We find that the preferential presence of lower index surfaces (e.g. (100)) leads to few orders of magnitude lower particle density compared to the preferential presence of higher index surfaces (e.g. (111)). Furthermore, the density on the lower index surface is strongly dependent on the nucleation pulse overpotential, while the higher index surface is barely affected. We find that this difference in the relationship is caused by mass transport limited nucleation. We have verified this through a spatial correlation analysis using the nearest-neighbour distance. For higher index surfaces, the nucleation density is already large compared to the Nernst diffusion length at low nucleation pulse overpotentials, such that the limiting mechanism becomes mass transport instead of electron kinetics. We therefore elucidate that the empirical exponential relationship between island density and nucleation pulse overpotential is not enough to draw conclusions on electrode kinetics, where additional validation of the growth process is essential.Beyond careful control of electrochemical parameters, here we show that neglecting the macroscopic surface characteristics of polycrystalline substrates can lead to major ambiguity in nucleation and growth dynamics of metal nanoparticles. We show here that XRD characterization prior to deposition is a simple additional measure to tailor metal nanoparticle electrochemical growth on ITO.

Wafer-scale heteroepitaxy GaN film free of high-density dislocation region with hexagonal 3D serpentine mask

GaN-based III-Nitride compound semiconductors are fundamental materials for high-performance optoelectronic and electronic devices. Low-defect-density substrate has been a major bottleneck in achieving high internal quantum efficiency and high breakdown voltage in those devices. However, a large-scale and uniform low dislocation density GaN film is still hard to obtain on foreign substrates, which is the mainstream economical method in scientific research and industrial production. Here, we present a 3D serpentine mask method of growing high-quality GaN film on foreign substrates without high dislocation density (HDD) areas by designing both sectional and planar shapes of stacked masks. The serpentine channel in the cross-section mechanically blocks the extended dislocations and the hexagonal planar pattern reduces the dimension of coalescence geometry. A wafer-scale GaN epilayer, free of HDD zone, with the overall threading dislocation density of 1.7 × 107 cm−2 estimated by plan-view cathode luminescence, is achieved in the metal-organic chemical vapor deposition system. Then, an array of light-emitting diodes based on this substrate with low forward voltages and high light output powers are fabricated, which introduces a practical method to provide high-quality GaN films for high-performance optoelectronic devices.

Progress in Ammonothermal Crystal Growth of Gallium Nitride from 2017–2023: Process, Defects and Devices

Gallium nitride continues to be a material of intense interest for the ongoing advancement of electronic and optoelectronic devices. While the bulk of today’s markets for low-performance devices is still met with silicon and blue/UV LEDs derived from metal–organic chemical vapor deposition gallium nitride grown on foreign substrates such as sapphire and silicon carbide, the best performance values consistently come from devices built on bulk-grown gallium nitride from native seeds. The most prominent and promising of the bulk growth methods is the ammonothermal method of high-pressure solution growth. The state-of-the-art from the last five years in ammonothermal gallium nitride technology is herein reviewed within the general categories of growth technology, characterization and defects as well as device performance.

MgO (1 0 0) as an affordable support for heteroepitaxial growth of high-quality β-Ga2O3 thin films and related highly-sensitive solar-blind UV photodetectors

Heteroepitaxial growth of high-quality β-Ga2O3 thin films on foreign substrates is of crucial importance for achieving high-performance power-electronic and optoelectronic devices with affordable prices. Herein, we demonstrate realization of heteroepitaxial growth of high-quality β-Ga2O3 films on MgO(100) via pulsed laser deposition, and achievement of related highly-sensitive solar-blind ultraviolet photodetectors (SBUVPDs). Under optimized oxygen pressure (7 Pa), single-phase, (100)-oriented, and atomically-smooth β-Ga2O3 films were grown epitaxially on MgO(100), consisting of unique 8–12 nm-wide columnar nanodomains. Atomically-resolvable aberration-corrected transmission electron microscopy unveiled initial growth of a cubic γ-phase transition layer of ∼ 8 nm thickness, and directly visualized occurrence and preferable location of oxygen vacancies at domain walls in the further grown β-Ga2O3 film. Density-functional-theory simulations rationalized the formation of columnar nanodomains in terms of energetics, and presumably identified the nanodomains interface orientations as (112¯)/(11¯2¯). The heteroepitaxial β-Ga2O3(100)/MgO(100) film-based photodetector demonstrates excellent performance, featured with exceedingly-low dark current, remarkably-high light-to-dark current ratio, and ultrahigh responsivity and detectivity (Idark = 0.6 pA, Ilight/Idark = 1.47 × 107, R = 191 A/W, D*=3.08 × 1015 Jones) as well as fast response speed towards 255 nm-UV detection. This work highlights MgO(100) as a suited yet affordable foreign substrate for heteroepitaxial growth of high-quality β-Ga2O3 films towards further development of high-performance devices such as SBUVPDs.

AlGaN/GaN heterostructures for high power and high-speed applications

Abstract AlGaN/GaN heterostructures are one of the most promising semiconducting structures for fabricating high-speed and high-power electronic devices such as high electron mobility transistors and heterojunction bipolar transistors. Due to the lack of native substrates, these epitaxial structures are generally grown on foreign substrate materials such as sapphire, SiC and Si by using two-step growth techniques. In this paper, a few test structures along with TLM pads, FET structure, ohmic contacts and Schottky contacts have been fabricated on AlGaN/GaN heterostructure by photolithography, reactive ion etching, and e-beam metallization. Transmission line measurement has been used to calculate the sheet resistivity and contact resistance of ohmic pads. Current voltage measurement is used to test an FET structure of size 1 × 150 µm2 with a gate length of 4 µm and source to drain spacing of 5 µm.

СТРАТЕГИИ ДОМЕСТИЗАЦИИ В ТРАНСЛИНГВАЛЬНОМ ПОДРОСТКОВОМ РОМАНЕ (НА МАТЕРИАЛЕ ПРОИЗВЕДЕНИЯ «ДЕРЕВНЯ У МОРЯ» (1982) А. ДЕСАИ)

Translingual literature is heterogenic; its classification based on structure, form and genre implies distinguishing novels, novelettes, short stories, plays, poems, etc. As well as differentiating among the following genres and subgenres: young adult/youth literature, fantasy novels and stories, science fiction, criminal literature, etc. Foreign linguistic and cultural substrate is verbalized in translingual young adult novels: culture-loaded loanwords, proper names (including precedent names derived from the non-native languages of target readers). Frequently used domestication strategies aimed at decoding foreign linguistic and cultural substrate rank as follows (in descending order): explanatory context, the author’s detailed commentary, one-word translation equivalent, extratextual glossary.

Fabrication of Quasi-Vertical GaN-On-SiC Trench MOSFETs

We demonstrate quasi-vertical GaN MOSFETs fabricated on SiC substrates. The GaN epitaxial layers were grown via MOCVD on 100 mm 4H-SiC wafers, with the device structure consisting of a 2.5 μm drift layer and a Mg doped p-GaN body. The fabricated transistors exhibit normally-off characteristics, with low off-state leakage behavior and an on/off ratio of over . The specific on-resistance was measured to be which compares favorably to devices fabricated on other foreign substrates. Our results demonstrate an alternative substrate for realizing vertical GaN devices, which potentially offers better material quality and thermal properties compared with other foreign substrate choices.