While gallium nitride (GaN) transistors were once the musings of university research projects 20 years ago, these devices are now widely adopted across the industry—especially in 2020.
GaN transistors are now a popular substitute for silicon-based FETs because they offer extremely high electron mobility. This also gives GaN a leg up with smaller on-resistances and significantly faster switching speeds than silicon-based transistors.
GaN vs. Si transistors. Image used courtesy of EPC
GaN transistors are driven in the same way as conventional MOSFETs, making them easy to integrate into existing designs. This is partly why 2020 marked a market high of GaN acceptance with more power supplies, audio amplifiers, data centers, and automotive systems implementing GaN than ever before.
The market opportunities for GaN power transistors have skyrocketed in 2020. Image used courtesy of GaN Systems
All About Circuits had the privilege of speaking with Jim Witham, the CEO of GaN Systems, (who we also interviewed back in 2018) to hear his predictions on the future of GaN and why 2021 might push this technology even further into ubiquity.
Medium Voltages: GaN’s Sweet Spot
To begin, it seems that GaN has hit its stride in a number of key industries, from fast chargers to data centers. While GaN isn’t the solution to every power application, its “sweet spot,” according to Witham falls in the 60 V to 1200 V range.
“Silicon works for low voltages (60 V and below) and low power, GaN is ideal for medium voltages (60–1200 V) and medium power, and SiC and IGBTs suit high voltages (1200 V and above) and high power,” he observes.
Chargers and Adapters
One market that saw widespread GaN adoption in 2020 was the charger and adapter market for applications like phones, tablets, and handheld gaming devices.
An immediate reason for this demand was the widespread push for fast charging, particularly from Asia-based manufacturers. Faster charging requires higher power levels, which often means bulkier equipment. GaN fills this market need with smaller chargers and higher power levels.
Block diagram of one of ON Semiconductor’s GaN-enabled power supplies. Image used courtesy of ON Semiconductor
“In particular, Huawei, Oppo, and Xiaomi are all really pushing fast charge,” says Witham. GaN Systems predicts that 2021 will see other big-name brands start to bring their own GaN chargers to market, too, as GaN becomes an industry standard.
During our conversation, Witham recounted his experience in a “sound off” between a silicon amplifier and a GaN amplifier. At first, he was concerned the difference wouldn’t be notable. “Man, it is so easy [to hear the difference],” he remarked. “You close your eyes and you think you’re hearing a live concert.”
Growing demand for small, high-quality audio devices at low power has made the Class D audio amplifier a fan favorite for designers. Relying on a MOSFET output stage, the Class D amplifier relies on the fast switching speed of these transistors to accurately recreate the audio waveforms.
A complete audio amplifier platform. Image used courtesy of GaN Systems
This is another place where GaN outpaces silicon thanks to its extremely high switching speeds, sometimes up to 1,000 times faster than silicon-based FETs. A whitepaper from GaN Systems quantifies this superior audio quality, showing that a GaN-based Class D amplifier can produce a total harmonic distortion (THD) as low as 0.004% compared to 0.015% for a silicon product.
Witham comments, “I have audio guys tell me, ‘You’re as close to the perfect transistor as I think we’ll ever get.’” Because of decreased size and superior audio quality, GaN Systems predicts that a significant number of the world’s noteworthy audio brands will be producing GaN-based amplifiers in the coming year.
From GaN Systems’ perspective, GaN is a must-have fortifying pillar for increasingly overburdened data centers, which are managing unprecedented power consumption and data density as more people work from home. The company says GaN transistors can make marked improvements in three key areas:
- AC-DC power supply, where high voltage enters server racks and must be stepped down to distribute power to all of the servers
- DC-DC converters on the server board itself, taking the voltage from a DC voltage—whether it’s 12, V, 24 V, or 48 V—down to a low chip-level voltage
- Backup power in the event of a main power blackout
GaN Systems recently announced an insulated metal substrate (IMS3) platform to be used with the company’s GaN E-HEMTs in data centers. Image used courtesy of GaN Systems
Achieving smaller and more efficient power supplies will allow data centers to put more servers into their racks, increasing performance per square meter.
The final sector in which GaN Systems sees great promise is in the automotive industry. Last year, in fact, an “all-GaN” vehicle was announced at the Toyota Motor Show. With international governments and the public increasingly demanding electric vehicles, designers are tasked with integrating smaller and more power-dense systems in addition to advanced battery technology.
Compared to silicon MOSFETs, GaN-based technology allows laser signals in LiDAR to be fired at significantly higher speeds. Image used courtesy of EPC
We recently discussed the challenges of establishing a universal reliability standard for GaN HEMTs, and GaN Systems seems attuned to this need to verify GaN safety on the road. This year, the company released its AutoQual+ program, which extends the testing sequences of AEC-Q.
In Witham’s eyes, 2021 is “all about seeing the GaN transistor on the road.”
On GaN’s Cost, Design, and “Green” Values
According to GaN Systems and many other semiconductor manufacturers, the early concerns surrounding GaN are no longer looming.
“GaN saves money above a kilowatt. As volumes go up, costs go down,” Witham says. Beyond price, though, suppliers provide robust technical documentation—white papers, application notes, reference designs, and more—to support designers who are still adjusting to such a fast MOSFET.
Speaking of the design learning curve, Witham observes in good humor, “GaN is kind of like a Ferrari; you’ve got to learn how to drive it.”
Conventional high-voltage half-bridge compared to a GaN FET half-bridge. Image used courtesy of Nexperia
One of the most exciting promises of GaN for Witham is the long-standing environmental impacts it will have. Witham concluded the conversation, saying, “We’re in the midst of a power revolution. We’re seeing these small, lightweight, very efficient power electronics coming out . . . [and] they’ll make the planet a better place.”
GaN Systems sees gallium nitride as the basic building block to accomplish the task.
Catch Up on How Other Suppliers Are Gunning for GaN
While GaN Systems is a pioneer in GaN transistor technology, other semiconductor manufacturers want a piece of the pie, too. Read up on how other big-name suppliers around the industry are making steep investments in GaN.