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Silicon Carbide: From Abrasive Material to Next-Generation Semiconductor

When we talk about silicon carbide, the first thing that may come to mind is the familiar carborundum grinding wheel—the kind often used for sharpening kitchen knives. Thanks to its excellent wear resistance, high hardness, and outstanding high-temperature stability, silicon carbide has long been widely used in abrasives, grinding tools, refractory materials, and functional ceramics.

In our previous article, we discussed the story of silicon carbide crystals as “love gemstones.” In this article, we will focus on silicon carbide as a semiconductor material.

Semiconductors are essential components in almost every electronic circuit we encounter. A semiconductor is a special type of material whose electrical conductivity lies between that of a conductor, such as a metal, and an insulator, such as ceramic or plastic. The conductivity of a semiconductor can also change depending on its operating temperature or the impurities introduced during the manufacturing process.

Strictly speaking, however, electrical conductivity is determined by the material’s energy band structure. Therefore, a more precise definition of a semiconductor should be based on its band structure.

As shown in the diagram below, conductors, semiconductors, and insulators have different energy band structures. In conductors, the conduction band and valence band overlap, or the energy difference between them is very small. As a result, only a small amount of energy, such as an external electric field, is needed to excite electrons into the conduction band and generate directional current flow.

In semiconductors, there is a forbidden band, also known as the band gap, between the conduction band and the valence band. Electrons can only be excited into the conduction band when they absorb energy greater than the band gap. In general, semiconductor band gaps range from approximately 0 to 6.5 eV.

In insulators, the band gap is much larger, typically on the order of more than 10 eV, making it very difficult for electrons to be excited into the conduction band. As a result, electrical conduction does not easily occur.

Therefore, the unique electrical conductivity of semiconductors—between conductors and insulators—is fundamentally determined by their energy band structure.

Energy band structure diagram

From Silicon to Silicon Carbide

Semiconductors can be made from pure elements, with silicon and germanium being the most common examples. They can also be made from compound materials such as silicon carbide (SiC) and gallium arsenide (GaAs).

Early semiconductor devices were mainly made from germanium. Later, silicon became the most widely used semiconductor material. However, as silicon-based device technology has continued to develop, device performance has gradually approached the physical limits of silicon itself.

This has created new opportunities for advanced semiconductor materials. Among them, silicon carbide, or SiC, has become one of the most promising competitors to traditional silicon.

Let us take a closer look at the advantages of SiC compared with Si.

The Unique Structure of SiC Gives It Superior Performance

Silicon carbide is a compound semiconductor material composed of carbon and silicon atoms in a 1:1 stoichiometric ratio. The basic structural unit of a SiC crystal is a tetrahedral structure, such as SiC₄ or CSi₄. In this structure, one atom is located at the center of a tetrahedron formed by four surrounding atoms.

Atomic structure of SiC

The structure of a material determines its properties, and its properties determine its applications. It is precisely the unique atomic structure of SiC that gives it excellent physical and chemical performance.

Let us look at several key properties of SiC, including breakdown strength, band gap, and thermal conductivity.

1. High Critical Breakdown Strength

SiC has a very high critical breakdown strength. This means that SiC devices can withstand higher voltages while maintaining the same package size. It also allows for reduced insulation requirements in packaging while keeping the same voltage rating.

As a result, SiC can be used to manufacture components with blocking voltages that may be an order of magnitude higher than those achievable with silicon.

One of the most important characteristics of a semiconductor is its energy gap, or band gap. The band gap is measured in electron volts, or eV, where 1 eV is approximately equal to 1.602 × 10⁻¹⁹ joules.

The band gap of SiC is approximately 3.26 eV, while that of Si is about 1.12 eV. Compared with traditional semiconductor materials such as Si and GaAs, third-generation wide-bandgap semiconductors represented by SiC enable electronic devices—especially power electronic devices—to operate at higher voltages, higher temperatures, and higher frequencies.

This makes SiC-based devices faster, smaller, and more reliable.

3. High Thermal Conductivity

Thermal conductivity is another important property of semiconductor materials. The higher the thermal conductivity, the more effectively the material can dissipate the heat generated during operation.

This allows components made from high-thermal-conductivity semiconductors to be smaller and helps improve the thermal management of the overall system.

The thermal conductivity of SiC is approximately 430 W/m·K, while that of Si is about 150 W/m·K. This gives SiC a clear advantage in high-power and high-temperature applications.

Silicon Carbide as a Semiconductor Material

We have already discussed many traditional applications of SiC, including refractory materials, abrasives, and functional ceramics. However, the most exciting potential of SiC lies in its performance as a power semiconductor material used in devices such as MOSFETs and Schottky barrier diodes.

Thanks to its high breakdown strength, wide band gap, and excellent thermal conductivity, SiC can outperform traditional semiconductor materials such as Si, Ge, and GaAs in many demanding applications.

As manufacturing technologies continue to mature, silicon carbide is becoming a rising star in the field of semiconductor materials.