The diverging worlds of SiC and GaN semiconductors

Gallium nitride (GaN) and silicon carbide (SiC) semiconductors are now in mass production and rapidly gaining market share. According to market research firm Yole, by the end of 2027, GaN and SiC devices will capture 30% of the power semiconductors market, replacing silicon MOSFETs and IGBTs. That’s a huge ramp, and it calls for greater clarity on where these wide bandgap (WBG) cousins stand in terms of the underlying design technology, manufacturing practices, and target applications.

Stephen Oliver, VP of corporate marketing at Navitas Semiconductor, acknowledged that today, it’s mostly SiC, which has been ahead of GaN in production by a decade or even longer. “That means power design engineers are more familiar with it,” he said. “Additionally, it’s more of a single component, which means you can replace one for another.”

Oliver added that most SiC devices are available in three-pin packages, which makes them highly suitable for high-power, high-voltage applications. As a result, they are being widely used in wind turbines, solar inverters, railway locomotives, and trucks and buses. On the other hand, for GaN semiconductors, he sees 650-V and 700-V devices catering to anything ranging from 20-W cellphone chargers to 20-kW power supply applications. “Beyond that, SiC is the right choice.”

Figure 1 The GaN-based Dell Alienware 240-W charger is nearly the same size as the old 90-W chargers, boasting 2.7x more power packed into the same volume. Source: GaN Systems

Sweet spots for SiC and GaN

GaN Systems CEO Jim Witham also categorized the SiC and GaN worlds as catering to high-power, high-voltage and medium-power, medium-voltage applications, respectively. “GaN semiconductors usually span 50 V to 900 V while SiC devices serve applications above 1,000 V.” He also noted that silicon is still a viable choice for low-power, low-voltage applications, serving power designs below 40 V to 50 V.

While explaining areas where each semiconductor technology matches with requirements, Witham said that in terms of power levels, silicon serves applications at 20 W and below, GaN for 20 W to 100 kW, and SiC for 100 kW to 300 kW and above. “There are sweet spots for silicon, GaN and SiC, respectively, and there is some fight at the edges.”

He also recognized SiC as prominent in serving automotive—especially traction inverters for electric vehicles (EVs)—as well as high-energy grids and wind and solar energy. For GaN transistors, he added, mobile chargers for cellphones and laptops have already happened while data center power supplies are just midstream. For the future, Witham sees GaN semiconductors taking off in automotive areas like onboard chargers (OBCs) and DC-DC converters for EVs.

Figure 2 The GaN-based DC-DC converters are becoming popular in electric and hybrid vehicles to bridge the high-voltage battery pack with the low-voltage auxiliary circuits. Source: GaN Systems

At CES 2023 in Las Vegas, GaN Systems demonstrated GaN inside a 7.2 kW OBC from Canoo, the EV company that supplies vehicles for Walmart and the United States Army. The Ottawa, Canada-based supplier of GaN semiconductor solutions also displayed a GaN-based DC-DC converter from Vitesco that operates in 800-V battery bus architectures. It takes battery voltage and changes it to the appropriate voltage for low-voltage auxiliary circuits like windshield wipers and door locks.

Contrast in manufacturing worlds

When it comes to wafer buildup, we see a lot of activities on the SiC side. Take the case of Wolfspeed, which is spending nearly $10 billion on its new 200-mm SiC fab in Marcy, New York. Oliver says that such SiC players want control of their destiny. “If you go back four years, Wolfspeed, then Cree, was the only company making SiC wafers, and it was $3,000 just for wafer,” he said. “Today, we estimate that there are eight qualified suppliers of SiC wafers, and the price has come down to about $1,000.”

Oliver anticipates that the price may be $400 in another four years. “So, SiC wafer will become a commodity, and once it’s a commodity, manufacturing will not be a strength anymore,” he added. “In other words, vertical consolidation of supply process won’t be the strength, and the strength will be in the design of the chip.”

On the other hand, while GaN is an advanced material, you can use an old process for GaN semiconductors, Oliver pointed out. “So, while silicon designers are talking about 12 nm and smaller manufacturing nodes, we are using 500-nm processing equipment for GaN devices.” For GaN semiconductors, Navitas uses TSMC’s Fab No. 2, the oldest fab they still have running. “It uses equipment that is completely written down financially, and still, it offers very high quality and good capacity,” Oliver said.

Figure 3 The GaN fabrication can retrofit old fabs, so GaN suppliers don’t need to spend billions on building new fabs. Source: Navitas Semiconductor

“The good thing about GaN is that you don’t need to spend billions on building new fabs and can retrofit old fabs,” he added. “We estimate that there are 40 old fabs in the United States doing old silicon that can be retrofitted for GaN or SiC semiconductors.” So, there is a lot of capacity out there for both GaN and SiC manufacturing.

Witham’s views about GaN fabrication resonated with Oliver’s stand. Witham said that while wafer capacity could be a problem for SiC devices, it’s not a problem for GaN semiconductors, where a capacity addition costs a few million dollars. “If you go the China, Taiwan and Korea, you will see factories with a couple of millions of dollar machines fabricating GaN devices,” he said. “With these machines of the size of a minivan, we need only a couple of million dollars to add capacity, though people usually don’t talk about it.”

Contest between GaN and SiC

In the summer of 2022, Navitas acquired SiC developer GenSic, and there is an interesting rationale behind this deal. According to Oliver, there is a $13 billion market for GaN devices, but the top $4 to $5 billion are contested. “Sometimes it’s GaN, and sometimes it’s SiC, so if we have SiC as well, it extends the market to $22 billion,” he said. “We don’t mind if a customer chooses one or the other in this $22 billion market.”

In fact, the automotive design engineers at Navitas were very happy when GenSic was acquired, Oliver added. “Now they don’t have to push GaN designs too far.”

Both GaN and SiC are new technologies, and they are rapidly diversifying in terms of applications as well as design innovations. As Witham puts it, specific markets are shaping up for GaN and SiC devices, and there is some market overlap between these WBG technologies.

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