Silicon carbide (
SiC), as a third-generation wide bandgap semiconductor material composed of silicon (Si) and carbon (C) bonded by strong covalent bonds, has been gradually discovered and valued for its excellent properties since its artificial synthesis in the late 19th century. Compared to traditional semiconductor materials such as silicon (Si) and first generation gallium arsenide (GaAs), SiC exhibits a series of revolutionary advantages in physical, chemical, and electrical properties, making it a key core material supporting modern high-tech industries, especially in the fields of power electronics, RF communication, and extreme environmental applications.
Firstly, the most notable characteristics of silicon carbide are its extremely high physical hardness and outstanding mechanical properties. Its Mohs hardness is as high as 9.2-9.3, second only to diamond (10), making it one of the hardest materials known. Therefore, it was widely used as a superhard coating for abrasives (such as sandpaper, grinding wheels) and cutting tools in the early days, demonstrating excellent wear resistance and mechanical stability. This inherent high-strength characteristic also enables the devices made from it to withstand harsh mechanical stress and vibration environments.
Secondly, silicon carbide has excellent thermal stability. Its melting point is extremely high, exceeding 2700 ° C, far higher than the 1414 ° C of silicon. More importantly, its thermal conductivity is very high, even up to three times that of silicon. This means that the heat generated by SiC devices during operation can be quickly and effectively conducted and dissipated, avoiding the accumulation of heat inside the chip. This feature is crucial for high power density electronic devices, as it can significantly reduce the operating temperature of the device, improve system reliability and lifespan, simplify the design of the heat dissipation system, and achieve miniaturization and lightweighting of the device.
Thirdly, it is also its core advantage as a semiconductor material, namely its extraordinary electrical properties. This is mainly reflected in the following aspects:
1. Wide Bandgap: The bandgap width of SiC (approximately 3.2 eV for 4H SiC) is nearly three times that of silicon (1.12 eV). The wide bandgap brings many benefits: firstly, it makes the intrinsic carrier concentration of SiC devices extremely low, which means that even at very high temperatures (theoretically able to operate above 600 ° C), the device can maintain stable electrical performance and will not generate excessive leakage current due to thermal excitation. Its high-temperature operating capability is far superior to that of silicon devices. Secondly, the wide bandgap endows the material with an extremely high critical breakdown electric field, approximately 10 times that of silicon. This allows SiC devices to operate at higher voltages, while the drift layer of the device can be made thinner and doped at higher concentrations, greatly reducing the on resistance and switching losses of the device.
2. High saturation electron drift rate: The saturation drift rate of electrons in SiC is very high, which means that the movement speed of carriers in the device is faster, allowing SiC devices to operate at higher frequencies, making them very suitable for high-frequency applications.
3. Excellent radiation resistance: Its sturdy crystal structure provides strong resistance to the bombardment of cosmic rays and high-energy particles, making it less prone to lattice defects. Therefore, it has irreplaceable advantages in radiation environments such as aerospace and nuclear energy.
In addition, silicon carbide also has excellent chemical inertness. It does not react with any known strong acids (including aqua regia) or strong bases at room temperature, and has extremely strong antioxidant properties. Even at high temperatures, a dense layer of silicon dioxide (SiO ₂) protective layer forms on its surface, preventing further oxidation inside. This strong chemical stability enables it to be applied in corrosive environments or scenarios that require long-term stable operation.
However, outstanding features also come with challenges. The preparation process of SiC single crystal is extremely difficult, with slow growth rate, harsh conditions (requiring high temperature above 2000 ° C), and easy generation of various lattice defects, resulting in high costs. This was once the main bottleneck restricting its large-scale application. In addition, it is more difficult to grow a high-quality, low interface state gate oxide layer (SiO ₂) on its surface than on silicon, which poses a challenge for manufacturing high-performance MOSFET devices.
In summary, silicon carbide (SiC) combines excellent properties such as high hardness, high thermal conductivity, high thermal stability, high breakdown electric field, high frequency, high temperature, radiation resistance, and chemical corrosion resistance. These features perfectly meet the urgent needs of modern power electronic systems for "higher efficiency, smaller size, higher temperature resistance, and higher voltage". It is gradually replacing traditional silicon-based devices and widely used in electric drive control systems for new energy vehicles, vehicle chargers, DC/DC converters, charging piles, photovoltaic inverters, wind power converters, industrial motor drives, rail transit, smart grids, and infrastructure for 5G communication base stations. It has become a key material leading the new round of industrial upgrading and energy revolution.
