The importance of SiC semiconductors for energy efficiency

By Maurizio Di Paolo Emilio for EETIMES Europe – The development of new technologies in power electronics has directed the industrial market towards other resources to optimize energy efficiency. Silicon and germanium are two of the main materials used today to produce semiconductors. The limited development in terms of losses and switching speed has directed technology towards new wide-bandgap resources such as silicon carbide (SiC)…

SiC offers a higher efficiency level than silicon, mainly due to significantly lower energy loss and reverse charge. This leads to more switching power and less energy required in the switch-on and switch-off phase. Lower heat loss also makes it possible to remove cooling systems, thus reducing space, weight and infrastructure cost. With the growing deployment of IoT and AI applications and the migration to the cloud, a higher level of efficiency in the management of energy-intensive IT infrastructure will become increasingly important.

Silicon carbide has a wider bandwidth than pure silicon, this allows technology to be used even at high operating temperatures… 

SiC diodes

Silicon carbide diodes are mostly Schottky diodes. Classical silicon diodes are based on a P-N junction. In Schottky diodes, metal is substituted with the p-type semiconductor, creating a metal-semiconductor (m-s) junction or Schottky barrier. This offers a low conduction drop, high switching speed, and low noise. The Schottky diode is used to control the direction of current flow within a circuit, allowing it to only pass from the anode to the cathode. When a Schottky diode is in an unbiased state, the free electrons will move from the n-type semiconductor to the metal forming a barrier. In the case of a forward-biased state, electrons can cross the barrier if the voltage is greater than 0.2 V.  

The leakage current of a silicon carbide diode is much lower than that of a normal diode. As a WBG semiconductor, silicon carbide has a much lower leakage current and can be doped much higher than silicon. In addition, the forward voltage of the SiC diode is higher than that of the silicon diode due to the wider bandgap of silicon carbide. 

In an interview with Amine Allouche, member of System Plus Consulting’s Power Electronics and Compound Semiconductors team, we highlighted some features of SiC diodes.

Unlike normal PiN diodes, Schottky diodes do not have recovery current because they are unipolar components with majority charge carriers. However, they do exhibit some recovery effects caused by the parasitic capabilities and inductances of the package and circuit. The main applications for SiC diodes are in power supply circuits but especially in PFC (Power Factor Correction) circuits in CCM (Continuous Conduction Mode). Silicon carbide (SiC) gives the diode a higher fault voltage and higher current capacity, thus finding room in industrial charging.

“According to Yole Développement, the power SiC bare diode die market was worth $160M in 2019. This includes various different market segments, such as automotive, energy, industrial… In fact, SiC diodes are mainly used in medium-voltage applications (automotive, PV, motor control…) to high-voltage applications (smart power grid…). In automotive applications, SiC devices, and particularly SiC diodes, are currently adopted in On-Board Chargers (OBC),” said Allouche… Full article

Headline image – Courtesy of System Plus Consulting, 2020