Wide bandgap semiconductors are reshaping the transportation world
Property
SI
SIC
GAN
Bandgap energy (eV)
1.1
3.2
3.4
Breakdown electric field (MV/cm²)
0.3
3.5
3.3
Electron mobility (cm²/V•s)
1500
900
900-2000
Electron saturation velocity (cm/s)
1 • 107
2.2 • 107 2.5 • 107
Thermal conductivity (W/cm•K)
1.5
5.0
1.3
Dielectric constant
11.8
10
8.9
Table 1: Comparison of the properties of Si, SiC, and GaN.
Table 1 lists the main properties of silicon carbide (SiC) and gallium nitride (GaN), the two most popular WBG materials, compared to silicon. The main advantages of SiC power devices, compared to silicon-based counterparts, are the following: ■ Low switching losses: SiC MOSFETs are unipolar devices that exhibit very low turn- on and turn-off switching losses. This property enables higher switching frequencies with lower losses, allowing the reduction of passive components and magnetics ■ Low conduction losses: due to the absence of a bipolar junction, SiC devices can also reduce losses during light-load or partial-load operation
■ High operating temperatures: silicon carbide offers superior thermal properties compared to silicon. SiC exhibits low leakage currents over a wide range of temperatures, allowing operation beyond 200°C. Simplified cooling and excellent thermal management are a consequence of this property ■ Intrinsic body diode: thanks to this characteristic, SiC MOSFETs can operate in diode mode in the third quadrant providing excellent performance in power applications Combining the above properties allows obtaining SiC devices with higher power density, efficiency, operational frequencies, and smaller footprint.
Properties of WBG materials
Wide bandgap materials are quickly transforming the power electronics area due to their advantages over commonly used silicon (Si). While silicon has a bandgap of 1.1 electronvolts (eV), WBG materials have a bandgap of 2 to 4 eV. Additionally, the breakdown electric field of most WBG semiconductors is substantially higher than silicon. That means they can operate at significantly higher temperatures and voltages, providing higher power levels and lower losses.
The entire transportation sector is undergoing a radical transformation, with internal combustion engine (ICE) vehicles gradually giving way to less polluting electric and hybrid cars and cleaner mass transportation solutions (trains, aircraft, and ships). Solutions capable of maximizing efficiency and reducing environmental impact are needed to contain greenhouse gases (GHG) emissions and mitigate global warming. Wide bandgap (WBG) semiconductors exhibit several properties that make them attractive for transportation applications. Their usage can result in more efficient, faster, and lightweight vehicles with improved range and reduced environmental impact.
By Rolf Horn Contributed By DigiKey's North American Editors
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