Exagan targets GaN charger markets

As the dust settles on this year's PCIM Europe, myriad power electronics companies are taking home a vast array of GaN-based devices.

For example, GaN Systems showcased 100V and 650V GaN E-HEMTs, Transphorm unveiled 650V GaN FETs while EPC demonstrated its low voltage enhanced-mode GaN FETs, targeting automotive, power supply and data centre applications, and more.

At the same time, France-based Exagan, also a key power electronics player, launched its 650V G-FET power transistor alongside an integrated driver and transistor switching system, G-DRIVE, aimed at fast charger markets.

Described as being easy to design into electronic systems, the products are compliant with the USB power delivery 3.0 type C standard. And as Exagan president and chief executive, Frédéric Dupont, puts it: "The market potential here is enormous, including portable electronic devices as well as homes, restaurants, hotels, airports, automobiles and more."

"In the near future, users will be able to quickly charge their devices by plugging a standard USB cable into a small, generic mobile charger," he adds.

Since spinning out of CEA-Leti and Soitec in 2014, Exagan has firmly focused on developing 650V GaN-on-silicon products for photovoltaic, automotive and PC markets and more. So why focus on the charging market right now?

According to Dupont, silicon power devices simply cannot fulfill fast charging applications, opening the door to GaN-based systems. But moreover, the chief executive reckons his company can deliver more intelligent and cost-effective GaN device solutions for this application.

"This is a place where GaN can really have a play, but the challenge is the cost and providing a complete solution- this is why you won't see many GaN players addressing this segment," he says. "However, Exagan can bring a lot of value here in the short-term."

Indeed, thanks to a rich heritage of heteroepitaxy development from France-based CNRS-CRHEA, CEA-Leti, and Soitec, Exagan has been ahead of the pack on production, and consequent costs, from word go.

During processing, a stack of buffer, insulating and strain management layers is deposited between the silicon substrate and GaN epi-layers to relieve crystal stresses and prevent cracking.

As a result, Exagan has been able to take GaN-on-silicon FET fabrication to larger wafer sizes, focusing on 200mm production at X-Fab's CMOS foundry in Germany, as many other GaN players grapple with smaller, 150 mm wafer sizes.

"Most companies are at six inches today but we have been working at eight inch, which is a good size for GaN," points out Dupont. "This is important for costs, as most of the silicon power electronics market is currently being manufactured at eight inch... and we are using the same 200 mm CMOS infrastructure and equipment."

"In the future we will see some silicon power devices moving to twelve inches but we think GaN will stick with eight inches," he adds. "I don't want to say forever but certainly for a long time as the cost structure is already very competitive."

Exagan chief executive, Frédéric Dupont, believes the fast charger market holds massive potential for GaN FETs and systems.

Costs aside, Dupont is also certain that GaN-based systems are ideal for fast charging applications. As he points out, heteroepitaxial devices, such as GaN-on-silicon FETs, are fabricated as lateral devices.

"Compared to vertical SiC devices, these transistors are suited to integration and co-packaging," he says. "So while SiC devices are very suitable for high current and high power applications, GaN is a good choice for fast charging applications and, indeed, any application that can benefit from system in package integration."

"We have always believed that GaN should be approached as a system solution, rather than a transistor solution, this is why we are offering our intelligent GaN Power solutions to the market" he adds.

And for the future, Dupont says Exagan will be focusing on co-packaging silicon driver ICs with GaN transistors to achieve the best combination of cost, performance and functionality, rather than integrating the driver electronics onto the GaN transistor chip to produce a monolithic IC.

"Customers want to have a whole solution, not just a transistor," says Dupont. "And they also want to know how to drive it, how to control it, how to design a transformer and so on."

"We have to make sure our products have what a designer needs for a particular application... and many customers want to use an external silicon driver, this is why we developed G-FET," he adds. "Meanwhile, some customers and applications need a more integrated solution, and this is offered with G-DRIVE."

Right now, Exagan is sampling and finalizing application development of G-FET and G-DRIVE products with its customers and will ramp production with foundry partner X-Fab according to demand. The company is also working with TÜV NORD's aerospace and electronics arm, HIREX Engineering, on device testing and qualification in a range of applications.

"The power electronics industry has been very conservative about new technologies but wide bandgap materials - both SiC and GaN - are revolutionizing this space," says Dupont. "I do hope in a few years you will have a small GaN-based charger in your wallet, that can charge your phone, laptop, and anything you want to charge."