Optics and Passivation Properties of Silicon Carbide (SiC) Films

Silicon Carbide (SiC) has rapidly emerged as an ideal material for monolithically integrated photonics applications, due to its combination of high refractive index, wide bandgap, low thermal expansion coefficient, and excellent rigidity properties. SiC is also an excellent material choice for making mirrors in astronomical telescopes.

Ellipsometric results illustrate that transmittance and refractive index of SiC films increase with increasing deposition temperature due to variations in roughness layer thickness.

Refractive index

Silicon carbide is an extremely useful material, for several reasons. With a Mohs hardness rating of 9, it offers incredible durability – making it perfect for grinding wheels. Furthermore, its exceptional fracture characteristics and resistance to chemical reactions makes it suitable for chemical resistance while its thermal conductivity allows it to operate at high temperatures without losing effectiveness.

Erbium’s excellent transparency in the terahertz (THz) region combined with its low optical bandgap and high refractive index make it an attractive substrate material for telecom systems. Its properties are comparable to silicon nitride and sapphire; however, its power absorption rate at THz frequencies exceeds both materials; furthermore, transmission efficiency exceeds most materials as well.

Silicon carbide crystalline structures come in various forms known as polytypes. Each polytype is composed of multiple layers arranged close-packed along one direction; each layer is composed of carbon and silicon atoms bonded to four of their opposite type in a tetrahedral bonding configuration for close packing purposes. Depending on its stacking sequence, crystal structures may take different shapes such as cubic, hexagonal or rhombohedral.

As a result, 2H SiC index values vary with thickness and shape of film thickness and shape, creating noticeable variations in refractive index and extinction coefficient values. Oxidizing environments where silicon carbide forms leave behind an oxide layer on its surface which must be taken into account when measuring optical parameters.

The XRR technique can be used to extract electron density profiles of these films’ surfaces, producing EDPs which closely reflect surface and interface roughness calculated from SE data.

Silicon carbide can be doped with impurities to alter its electrical properties. Pure SiC acts like an electrical insulator; by adding certain impurities such as aluminum, gallium or boron impurities it becomes a semiconductor and can then be made into devices for a wide variety of uses.

Extinction coefficient

Silicon Carbide (SiC) is an electrical semiconductor material with a wide band gap and low thermo-optic coefficient, making it a good candidate for monolithically integrated photonics. Furthermore, SiC’s high radiation hardness and Young’s modulus also make it suitable as MEMS pressure sensors. However, due to their complex chemistry and structure, a-Si1-xCx films are difficult to create and characterize. This study seeks to investigate both optical and passivating properties of SiC:H films prepared using reactive magnetron sputtering technology for use in c-Si solar cell applications. These films were deposited onto glass substrates and tested using X-ray reflectometry and UV-visible spectroscopy, yielding measurements using high transmission transmittance spectra from visible through near infrared with an extinction coefficient below 0.009 at 630nm; thickness, density, and roughness remained constant at elevated temperatures.

DIBSD-deposited SiC films exhibit amorphous properties that prevent formation of dense layers, thus limiting variations in their optical properties and decreasing variation with increased thickness (see Fig 9 for trend of increasing SE and XRR with thickness increase), as is demonstrated in their optical property changes with C:Si ratio changes ( Fig 9(b) and 9(c) respectively).

SiC has both an extinction coefficient and energy loss due to its large electron scattering time and broad electronic bandgap, leading to lower optical losses than its crystalline counterparts. Unfortunately, its amorphous nature prevents its use for MEMS or tunable optic applications.

A-SiC can be found in two polymorphs: alpha and beta. Each form features its own specific crystal structures and melting points: alpha has hexagonal crystal structure similar to Wurtzite while beta forms feature zinc blende structures similar to diamond. Both forms have been widely utilized in semiconductor electronics devices with most commercially available silicon carbide being in alpha form; additionally it’s the main constituent in moissanite jewelry, made of synthetic rubies.

Optical properties

Silicon carbide is an attractive wide-bandgap semiconductor with excellent optical properties. Specifically, its high refractive index, low extinction coefficient and small thermal expansion coefficient make it suitable for photonic applications. Furthermore, fabrication is easy while electrical properties make this material highly appealing compared to traditional materials. With low costs and an expansive application list compared with conventional ones – silicon carbide stands out as an appealing choice as an alternative material choice.

Silicon carbide’s optical properties can be evaluated using X-ray scattering and Raman spectroscopy techniques, providing noninvasive ways of exploring its structure and composition in polycrystalline (crystalline) silicon carbide crystalline form. In contrast to diffraction techniques which limit size constraints when studying samples, these methods enable nanoparticle analysis as part of powder samples which then form samples suitable for various experimental techniques.

One way of producing 3C silicon carbide samples is sputtering organosilanes at high pressures and then using X-ray diffraction analysis to examine its microparticles’ structural features, while Raman spectroscopy can reveal composition and atomic arrangements; its Raman spectrum will show which polytype they belong to by showing peaks related to transverse optical (TO) and longitudinal optical (LO) phonons in Brillouin zones corresponding to transverse optical and longitudinal optical (TO/LO) phonons in Brillouin zones which will give away their composition and composition and compositional arrangements.

These optical properties of silicon carbide depend heavily on its polytype and doping; hence their study is key to understanding its physics. X-ray scattering, Raman spectroscopy and ellipsometry can all provide valuable information.

Figure 1 displays the ellipsometric spectra of SiC-1, SiC-2 and SiC-3 polytypes as illustrated by an ellipsometric fit to their TL fit spectra, whereby real (e1) and imaginary (e2) parts of their dielectric functions were obtained using wavelength-by-wavelength matching of dielectric functions to wavelength values – these fitted values are represented by circles and lines in Figure 1.

Ellipsometric measurements show that the below-band gap birefringence of SiC is much lower than that of silicon, due to polytypism being strongly influential on its extraordinary component of dielectric function while ordinary component influence remains weaker. Polarized light transmission results illustrate this fact further in Figure 2. Absorption also depends on polytype as evidenced by above-band-gap absorption results shown here (see Figure 2).

Composition

Silicon carbide (SiC) is a hard chemical compound composed of silicon and carbon. First synthesized synthetically in the late 19th century, SiC has since become an invaluable material for applications requiring high endurance such as abrasives. Furthermore, bulletproof vest manufacturers utilize ceramic plates made of SiC as bulletproof plates. SiC powder or crystal can also be bonded together into ceramics used in abrasives, industrial furnaces and wear-resistant parts found on pumps and rocket engines as wear resistant parts made of SiC. Furthermore, SiC serves as the basis for high voltage power semiconductor devices as well.

Silicon carbide stands out from other materials because of the strong bonds formed by Si and C atoms, giving rise to unique physical and chemical characteristics. It features exceptionally high hardness, excellent chemical resistance, low thermal expansion rate, and remarkable electrical conductivity resulting from its valence/conduction band overlap with that of carbon atoms, allowing electrons to move easily between them.

Doping silicon carbide with various impurities enables it to display various electronic characteristics. Doping aluminum creates a p-type semiconductor while doping with nitrogen or phosphorus produces an n-type semiconductor; both concentration and spatial distribution of dopants play an integral part in controlling its electrical characteristics. EAG Laboratories offers comprehensive analytical services for silicon carbide including both bulk analysis techniques as well as spatially resolved analysis services.

SiC has a higher breakdown voltage than standard silicon or gallium nitride semiconductors, making it the perfect material choice for power semiconductors. Due to its wide bandgap characteristics and wide voltage tolerance, SiC can withstand high voltages without producing excess heat or increasing resistance – something IGBTs and bipolar transistors cannot do reliably. Furthermore, SiC offers exceptional corrosion and oxidation resistance making it suitable for extreme environments and harsh operating conditions.