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Silicon carbide (SiC) offers significant advantages for microwave high power devises due to its unique electrical and thermal properties. This review presents a summary of the current position in the development of silicon carbide diodes operating at microwave frequencies: varactors, Schottky barrier mixer diodes, p-i-n and IMPATT diodes. Simplified theory of device operation is given for each kind of microwave diodes to derive the figures of merit, to estimate the potential silicon carbide performance for fabrication of these diodes and to compare SiC with conventional semiconductors. These analyses are followed by description of diode design, fabrication and measured characteristics.

Results obtained in recent studies of deep centers in 6H-, 4H-, and 3C-SiC are analyzed. The ionization energies and capture cross sections of centers formed by doping of SiC with different types of impurities or by irradiation, as well as the corresponding parameters of intrinsic defects, are presented. The involvement of these centers in radiative and nonradiative recombination is examined. Analysis of published data shows that a strong influence is exerted by intrinsic defects in the SiC crystal lattice both on the formation of deep centers and on the properties of the epitaxial layers themselves, such as their doping level and polytype homogeneity.

The U. S. Army Research Laboratory (ARL) is investigating compact, energy-dense electronic components to realize high-power, vehicle-mounted survivability and lethality systems. These applications require switching components that are low in weight and volume, exhibit reliable performance, and are easy to integrate into the vehicles' systems. The devices reported here are 4 mm × 4 mm silicon carbide GTOs rated for 3000 V blocking. These devices were packaged at ARL for high pulse current capability, high voltage protection, and minimum package inductance. The GTOs were switched in a 1-ms half-sine, single-pulse discharge circuit to determine reliable peak current and recovery time (or T_q). The GTOs were repeatedly switched over 300 A peak (3.3 A/cm² and an action of 60 A²s) with a recovery time of 20 µs. The switches were also evaluated for dV/dt immunity up to an instantaneous slope of 3 kV/ µs.

Bi-directional solid-state circuit breakers (BDSSCBs) can provide performance benefits over mechanical fault protection devices. A common-source configuration of normally ON, junction field effect transistors (JFETs) is favorable for BDSSCB implementations. SiC 0.1-cm² 1200-V JFETs designed for normally-ON operation at a zero-volt gate bias, and having low leakage currents, were used in the fabrication of a 30-A BDSSCB switch module. Operation of the module under continuous current and during turn-OFF transitions was evaluated to verify the parallel scalability of the common-source configuration. A bi-directional snubber connected across the switch module mitigated inductive voltage overshoot during BDSSCB turn-OFF transitions. At turn-OFF, under maximum power tests in both directions, the load current was reduced from 30 A to 0 A in approximately 10 μs, with a supply voltage of 600 V, and a BDSSCB peak voltage of 680 V. These results demonstrate the functionality and current scalability of this BDSSCB topology.

Army applications require power components that are utilized in pulsed power systems to be reliable and durable, compact, have high power and energy density, and lastly, to be easily integrated into combat vehicles. The U.S. Army Research Laboratory (ARL) is currently investigating silicon carbide Super-gate turn-off thyristors (SiC SGTOs) to meet the future pulsed power system requirements for the Army. ARL's methodology is to evaluate the device performance in pulsed power circuits that emulate the electrical stresses that the power devices would encounter in a pulsed power system. Each module being evaluated utilized four 0.6 cm²SiC SGTOs. The packaging design for the module utilizes ThinPak technology. The module has reliably been pulsed over 2000 times at peak currents greater than 8 kA with a pulse width of 170 μs. The module has also been pulsed greater than 3.6 kA at a pulse width of 1 ms, corresponding to an action rate of 7000 A²s and a current density of 2.5 kA/cm² over the cathode mesa area. This work evaluates SiC SGTO modules under various pulsed conditions. This paper includes details on device structure, module package design, and module pulsed switching and reliability.

Power semiconductor devices are important for numerous applications with power conversion being an important one. Wide energy gap semiconductors SiC and GaN have properties that make them attractive for such applications. Among these properties are high thermal conductivity, high breakdown electric field, wide energy gap, low intrinsic carrier concentration, high thermal stability, high saturation velocity and chemical inertness. These lead to low on-resistance, high breakdown voltage, high frequencies, small volume, and small passive inductors and capacitors. These desirable properties are offset by the higher material costs and higher defect densities. Although wide energy gap devices have been in development for many years, only recently have they become available commercially. Their main competition is silicon power devices with breakdown voltages up to 8000 V and very high surge current capacity. However, silicon power devices are approaching their material limits and wide energy gap devices are beginning to have an impact in the power electronics space. SiC has the advantage of substrates with diameters approaching 150 mm and the ability to grow thermal SiO₂. GaN has the heterojunction advantage, but no viable substrate technology. In fact, a large portion of SiC production is used for GaN substrates. GaN material development has also benefited significantly from the development of optical devices, e.g., light-emitting diodes and lasers.

This study investigates Beam Line Absorbers (BLAs) for the Hefei Advanced Light Facility (HALF). A ferrite-based BLA prototype was developed, demonstrating high-power handling capacity up to 10kW, ultra-high vacuum performance better than $6.5\times 10^{-10}$ mbar, and high absorption efficiency in critical frequency ranges. Subsequently, more compact designs with reduced longitudinal length were explored, investigating ferrite-only, silicon carbide (SiC)-only, and hybrid configurations through RF simulations. Based on preferred absorption efficiency, ferrite-only and hybrid BLA structures were further analyzed under high-power conditions. Referencing test results, multiphysics simulations were conducted under 3kW absorbed power. The hybrid design, comprising two rings of ferrite tiles and one ring of SiC tiles, improved the temperature distribution of the absorbing materials. Extrapolating to 11kW absorbed power, this design reduced the maximum temperatures on absorbing tiles by up to 40$°$C compared to the ferrite-only design. The hybrid design offers a balanced solution that combines effective HOM damping with enhanced thermal performance, improving the long-term operational stability of BLAs.

Magneto- and piezo-spectroscopy of high quality bulk samples have been used to clarify the origin of the characteristic, V1, V2 and V3 luminescence lines observed in 6H-SiC polytypes, correspondingly, at 1.433, 1.398, and 1.368 eV. The uniaxial stress, up to 500 MPa, was applied along [11-20] and [10-10] directions, perpendicular to the c-axis of the investigated 6H-SiC crystals. Magnetic field was applied in different directions with respect to the c-axis. The obtained results allow us to analyze in detail the symmetry of the initial and final states responsible for the V2 emission line. This analysis leads to a conclusion which contradicts the existing identification of the defect responsible for this characteristic emission.

The effect of post-deposition annealing in forming gas on the structural and electrical properties of sol–gel derived SiO₂ thick film on n-type 4H–SiC has been systematically investigated. Tetraethylorthosilicate-based precursor with H₂SO₄ as catalyst was prepared and prior to film deposition, substrate surface was treated by hexamethyldisilizane. The spin-coated film was annealed at 750–950°C for 30 min with an approximately 185-nm thick film. It was found that oxide annealed at the highest temperature revealed the densest film, lowest oxide defects, and lowest total interface trap density. As a result, this oxide had demonstrated the lowest leakage current density if compared with other oxides.

The long-range aim of this research is to develop porous ceramics with high strength, excellent thermal resistance and chemical stability at high temperature in environmental industry. The C_f/SiC was made by hot pressing method with SiC powder whose particle size is 50nm and less on the average also Al₂O₃, Y₂O₃ and SiO₂ as additive. The carbon fibers of oxidation property are investigated by TGA for finding out decarburization point. As a result, decarburization point selected the specific temperature of TGA curve and the C_f/SiC composites occurred perfectly decarburization at carbon fibers so the clearly porous SiC ceramics were formed many holes of 3-5µm diameters through length direction by its reaction.

The use of silicon-based ceramics and composites as combustor liners and turbine vanes provides the potential of improving next-generation turbine engine performance, through lower emissions and higher cycle efficiency, relative to today's use of super alloy hot-section components. As a series of research for FOD resistant, a particle erosion wear test was carried out for continuous Pre-SiC fiber-reinforced SiC matrix composites with a new concept of lab. scale fabrication by LPS process. The result shows that aperture (some form of porosity) between fiber and interface has a deleterious effect on erosion resistance. Aperture along the fiber interfaces consequently causes a severe wear in the form of fiber detachment. Wear rate increase proportional as contents of open porosity increases. For nearly full dense composite materials of about 0.5 % porosity, are about 200 % more wear-resistant than about 5 % porous composites. Grain growth and consolidate condition of matrix which directly affects to FOD resistant are also discussed.

Molecular dynamics simulations of crystal growth of SiC in the reduced temperature range of 0.51–1.02 have been carried out. In particular, the relationship between the growth rate and the reduced temperature has been investigated by the simulations. The results show that the growth rate increases first with the temperature and then decreases dramatically after passing through a maximum. Calculations of the growth rate according to the Wilson–Frenkel model have been applied to the present system, with the required parameters of the activation energy for atomic diffusion and the free energy changes calculated by molecular dynamics simulations. The temperature dependence of the growth rate, calculated by molecular dynamics, agrees with the prediction of Wilson–Frenkel model, indicating that the crystal growth of SiC is a kind of diffusion limited growth.

The first-principles Projector-Augmented Wave method (PAW) is used to investigate the electronic, phonon band structure and dielectric properties of four bulk silicon carbide (SiC) polytypes. We employ PAW pseudopotential density functional theory with Perdew, Burke and Ernzerhof (PBE) and hybrid HSE06 approximations of the exchange-correlation functional. Many-body effects are incorporated using the GW approximation of the self-interaction to study SiC properties. GW method in its single-shot variant, which is based on the many-body perturbation theory (MBPT), is used to calculate the quasi-particle (QP) energies of the band structure and the dielectric properties for different polytypes. The electronic band structure determination within GW method uses the Wannier procedure where a basis set of maximally localized Wannier function (MLWF) is constructed to interpolate the QP energies of few regular mesh k-points to the high-symmetry lines in Brillouin zone. As a consequence of QP correction to the Kohn–Sham energies, bandgap is increased by upto 3 eV in case of 4H–SiC, as compared to PBE bandgap. GW results are comparable to those of hybrid functionals and are in good agreement with the experimental results. The optical properties are then studied within PBE, HSE06 and include many-body effects. In addition, the phonon band structure has been investigated within HSE06 and compared to previous PBE results. We found good agreement with the previous theoretical results and the experimental available data.

The effect of high-energy electron beam on the silicon carbide nanopowder’s structural parameters, strain and powder size was studied. The sample was irradiated with $\sim$2-MeV electron beam energy under different fluencies such as 1.13 ⋅ 10${}^{17}$, 1.89 ⋅ 10${}^{17}$, 2.79 ⋅ 10${}^{17}$ and 3.69 ⋅ 10${}^{17}$ cm${}^{-2}$ at the linear electronic accelerator. Initial and irradiated samples at various doses have been analyzed in the XRD. The nanostructural effects within FullProf are treated using the pseudo-Voigt profile function. The dependences of maximum strain and nanocrystallite size on irradiation dose were obtained and analyzed.

In this paper, a simulation model of $p$ type PiN high voltage pulse open switch is established. The switch operates in “punch through” mode, with a 4 kA/cm² cut-off current density and sub-nanosecond cut-off speed. The cut-off process of switch can be divided into three stages, that is, non-equilibrium carriers extraction stage, majority carriers drift stage and charging stage of junction capacitance by change of internal electric field and carrier concentration. Keeping injection current and cut-off current as 20 A and 40 A, the switch cut-off speed and “pedestal” voltage are reciprocally determined. Thus, optimizing the doping concentration and thickness of $p$ layer is a valid solution for the actual system design.

A series of undoped and p-doped a-SiC:H samples have been made in the framework of a research plan for obtaining high quality p-type window layers by "Plasma Enhanced Chemical Vapor Deposition (PECVD)" technique from the mixtures of silane (SiH₄), methane (CH₄) and diborane (B₂H₆) gases. For the optimization of the window layer, the dependence of the electrical (conductivity) and optical (band gap) properties due to altered ratios of methane and diborane gases were investigated. When the diborane gas ratio was changed from Y = 0.06 to Y = 0.24 with an increase of 0.06 steps at a constant of X = 0.948 methane gas ratio, the dark conductivity and optical band gap values changed from ~ 10^-19 (Ω·cm)^-1 to ~ 10^-10 (Ω·cm)^-1 and 2.542 eV to 2.178 eV, respectively, and between these values, the most appropriate layers can be selected.

In this paper, we present a comparative study of structural and optical properties of polycrystalline p-type 6H-SiC and thin SiC layer growth onto Si. The thin SiC layer was grown on a p-type Si(100) substrate by pulsed laser deposition (PLD) using KrF excimer laser from a 6H-SiC hot pressed target. The properties of polycrystalline 6H-SiC and thin SiC layer were investigated by scanning electronic microscopy (SEM), high resolution X-Ray Diffraction (XRD), secondary ion mass spectrometry (SIMS), FT-IR spectroscopy and photoluminescence spectrometry. XRD analysis showed that the two materials have the same hexagonal structure (6H-SiC) as identified by ASTM 72-0018. In addition, a SIMS analysis gives a ratio Si/C of the thin SiC layer around 1.15 but the ratio Si/C of the target was found equal to 1.06, whereas one should have 1.0. This is due to the higher ionization efficiency of Si by the report of C atoms and in photoluminescence, the two materials exhibit the same emission bands (blue and green). Finally, a crystalline thin SiC layer of 1.6 μm was elaborated using the PLD method at low-temperature indicating that the technique reproduces the same macroscopic property (optical, structural, mechanical, etc.) of the target.

Hydrogenated amorphous SiC films (a-Si_1-xC_x:H) were prepared by DC magnetron sputtering technique on p type Si(100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6H-SiC). The deposited film a-Si_1-xC_x:H was realized under a mixture of argon and hydrogen gases. The (a-Si_1-xC_x:H) films have been investigated by scanning electronic microscopy equipped with EDS system (SEM-EDS), X-rays diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-visible-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure of a-Si_0.81C_0.19:H corresponding to 19 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centered at 463 nm (2.68 eV) and 542 nm (2.29 eV). The structural properties and the origin of the luminescence were discussed.

Electronic structures and optical properties of IV A elements (Ge, Sn and Pb)-doped 3C-SiC are investigated by means of the first-principles calculation. The results reveal that the structure of Ge-doped system is more stable with a lower formation energy of 1.249 eV compared with those of Sn- and Pb-doped 3C-SiC systems of 3.360 eV and 5.476 eV, respectively. Doping of the IV A elements can increase the band gap, and there is an obvious transition from an indirect band gap to a direct band gap. Furthermore, charge difference density analysis proves that the covalent order of bonding between the doping atoms and the C atoms is Ge–C $>$ Sn–C $>$ Pb–C, which is fully verified by population values. Due to the lower static dielectric constant, the service life of 3C-SiC dramatically improved in production practice. Moreover, the lower reflectivity and absorption peak in the visible region, implying its wide application foreground in photoelectric devices.