The Features Of Silicon Carbide

Thermal conductivity

Thermal conductivity is a measure of how easily heat is transferred through a material. This is a key property of semiconductors, as it indicates the extent to which a material is able to effectively dissipate heat (heat accumulation due to increased power due to increased current), thereby increasing its voltage and current capabilities.

The thermal conductivity of silicon is 130 W/(m⋅K), which is significantly lower than that of silicon carbide (490 W/(m⋅K), allowing silicon carbide semiconductors to dissipate heat more efficiently and withstand higher operating voltages.

Thermal expansion

Thermal expansion is when a material changes shape or size – but does not change phase – due to a change in temperature, such as from a liquid to a gas. A common example is applying hot water to a stuck bottle cap to allow it to swell for easy opening.

Silicon carbide has a very low coefficient of thermal expansion, which means it retains its shape, strength, and performance better at high temperatures (and high voltages), which silicon may not be able to do.

Electric field strength

Two other key and relevant semiconductor properties are the band gap of the material and the maximum electric field strength.

In a semiconductor material molecule, electrons move between different bands: the area they must occupy because there is no energy state between the bands. The band gap (or energy gap) is the energy required for an electron to make the transition from the valence band to the conduction band, allowing electricity to be conducted. When semiconductors receive electrical energy and enter this conductive state, they exhibit unique insulator/conductor hybrid properties.

Silicon carbide semiconductors have a three times higher energy gap than silicon-based semiconductors, which allows them to withstand higher electric field strengths than silicon, allowing them to operate at higher voltages and temperatures.

Silicon carbide semiconductors have a large energy gap and can withstand and dissipate heat better than silicon-based semiconductors. They also have other advantages:

The high energy gap of silicon carbide is very useful in high-power applications because the higher energy gap allows for smaller semiconductor devices with higher operational performance.

For diodes, a common type of semiconductor device, the breakdown voltage is the voltage at which a reversed applied current can flow through the diode. The high breakdown voltage of silicon carbide makes it ideal for MOSFETs.

This leads to another important semiconductor feature in MOSFETs: reverse recovery time. If the MOSFET goes into a reverse bias state, the time it takes to return to the normal state is known as the reverse recovery time. During this time, the current can flow in the opposite direction and the system experiences energy loss. In these cases, SiC devices have extremely fast reverse recovery times and negligible energy losses, which is not the case with Si devices.

Silicon carbide is more flexible than silicon in terms of doping (adding impurities). It can be customized to conduct electricity only under specific conditions, such as light that undergoes a specific intensity (infrared, visible, or ultraviolet), which makes silicon carbide semiconductors more versatile.