Market for SiC and GaN in power applications heating up

Several recent announcements indicate that adoption of silicon carbide (SiC) and gallium nitride (GaN) in power converter systems is accelerating. SiC and GaN are replacing silicon as the semiconductor material of choice in many applications in the electric vehicle and wider electronic markets.

ST Microelectronics and Onsemi each announced plans to invest US$1billion in their SiC capacity this year - Onsemi also signed a SiC deal with Volkswagen. Infineon is expanding SiC production in Austria. Semiconductor systems builder Veeco last month acquired Epiluvac, a Swedish startup that develops chemical vapour deposition (CVD) epitaxy systems for advanced SiC applications in the EV market.

Wolfspeed last month announced plans to build the world’s largest SiC plant in Saarland, Germany, with an investment of US$3 billion. The fab will produce 200mm silicon carbide chips for electric vehicles. Last October Wolfspeed had already announced total investments of US$6.5 billion at its North Carolina plant. Automotive supplier BorgWarner recently announced a half billion investment in Wolfspeed.

‘Silicon carbide has become very, very important,’ says Larry Rinehart, Senior Power Electronics Specialist at BorgWarner. He was not directly involved in the deal with Wolfspeed, but mentions that BorgWarner produces power modules for propulsion and needs to secure the supply of bare dice. ‘You will see other suppliers get similar investments from either OEMs or Tier 1s,’ he says.

Rinehart believes SiC ‘will be dominant, certainly in all of the luxury cars, EVs and most of the heavy duty and medium duty vehicles’. Legacy silicon IGBT will continue to lead in the lower cost, 350 volt battery pack end of the market, like the higher volume EVs of BYD in China.

Silicon carbide (SiC) and gallium nitride (GaN) are compound ceramic materials with a wider band gap than legacy silicon. Band gap is the energy needed for electrons to move from the valence band to the conduction band measured in electron volts. Silicon has a band gap is 1.12 eV; for SiC and GaN it is 3.26 and 3.4 eV.

Wide band gap (WBG) semiconductors can handle higher voltages and higher frequencies, making them more suitable for power conversion systems such as EV powertrains, charging systems and solar inverters. Higher costs and thermal management challenges have held back adoption, but that is changing fast. Larry Rinehart mentions that GaN-on-GaN has now become available, eliminating some of the design issues of GaN-on-silicon and providing higher performance. GaN prices are coming down as well, but SiC is certainly becoming more affordable with all of the new wafer fab capacity going up.

GaN will remain a hard sell for EV propulsion, until vertical GaN MOSFETs appear. ‘Eventually you will see that device,’ Rinehart believes. ‘Not sure if that’s ten years out, but that will change the game.’ Silicon carbide will dominate the propulsion market for now and even creep into lower cost EVs as manufacturers will seek cost reductions with battery costs otherwise stuck at current levels.

At the Ceramics Expo 2023 conference in Michigan, Adam Schubring, General Manager for the Automotive Components Division at Kyocera International, will discuss other applications of ceramics in automotive.