In summary, for power electronics systems, GaN offers unprecedented
advantages over Si and SiC. Operating at high voltage operation with both significantly higher frequencies and extremely low conduction losses results in:
• Increased efficiency,
• Reduction in size of passive components at higher frequency and thus,
• Reduction in overall power conversion system size, weight and cost.
below is comparison:
Wide Bandgap Semiconductor:
GaN and SiC are relatively similar in both their bandgap and breakdown field. Gallium nitride has a bandgap of 3.2 eV, while silicon carbide has a bandgap of 3.4 eV. While these values appear similar, they are markedly higher than silicon's bandgap. At just 1.1 eV, silicon's bandgap is three times smaller than both gallium and silicon carbide. The compounds' higher bandgap allows gallium nitride and silicon carbide to support higher voltage circuits comfortably, but they cannot support lower voltage circuitry as well as silicon.
Breakdown field Strength:
Gallium nitride and silicon carbide's breakdown fields are relatively similar to each other, with gallium nitride boasting a breakdown field of 3.3 MV/cm, while silicon carbide has a breakdown field of 3.5 MV/cm. When compared to plain silicon, these breakdown fields make the compounds significantly better equipped to handle higher voltages. Silicon has a breakdown field of 0.3 MV/cm, which means that gallium nitride and silicon carbide are nearly ten times more capable of maintaining higher voltages. They are also able to support lower voltages using significantly smaller devices.
High Electron mobility Transistor (HEMT)
The most significant difference between gallium nitride and silicon carbide lies in their electron mobility, which indicates how quickly electrons can move through the semiconductor material. For starters, silicon has an electron mobility of 1500 cm^2/Vs. Gallium nitride has an electron mobility of 2000 cm^2/Vs, meaning electrons can move over 30% faster than silicon's electrons. Silicon carbide, however, has an electron mobility of 650 cm^2/Vs, which means that silicon carbide's electrons are slower moving than both GaN and silicon's. With such elevated electron mobility, GaN is nearly three times more suitable for high-frequency applications. Electrons can move through a gallium nitride semiconductor much faster than SiC.
GaN and SiC Thermal conductivity
A material's thermal conductivity is its ability to transfer heat through itself. Thermal conductivity directly influences the material's temperature, given the circumstances of its use. In high-power applications, inefficiencies in materials will create heat, thus increasing the temperature of the material, and subsequently changing its electrical characteristics. Gallium nitride has a thermal conductivity of 1.3 W/cmK, which is actually worse than that of silicon, which sits at 1.5 W/cmK. However, silicon carbide boasts a thermal conductivity of 5 W/cmK, making it nearly three times better at transferring thermal loads. This feature makes silicon carbide highly advantageous in high-power, high-temperature applications.
