GaN Systems’ Next-Gen Platform Brings Major Improvements

As compared to its cousin silicon, gallium nitride (GaN) is an extremely young technology. On the one hand, that means there is still much work that needs to be done. On the other hand, the technology is improving drastically year over year.

 

GaNpx packaging with Island Technology. Image used courtesy of GaN Systems

 

Recently, GaN Systems announced its fourth-generation GaN solutions, bringing a significant improvement in some of the most important specifications for GaN devices. EEPower spoke with GaN System’s CEO Jim Witham to hear about the company’s new technology firsthand.

 

GaN Systems’ Fourth Gen Offerings

GaN Systems’ fourth-generation GaN power platform is the company’s latest introduction to the market and brings with it some significant performance benefits.

The first, and most noteworthy, improvement worth discussing is Figure of Merit (FoM). This specification, which is a comprehensive look at the device’s power performance, is said to have been improved by 20 percent as compared to the previous generation devices. With that comes significant improvements in achievable power density for designers. 

“Using our Gen-3, people who were able to design power supplies that got 100 watts per cubic inch, which is double or triple what’s achievable with silicon,” Witham told EE Power, “But now with Gen-4, they're able to get 120 watts per cubic inch and continue this keeping to make the power electronics smaller and smaller and more efficient and more efficient.”

Other improvements include more granular offerings, meaning that there are more available SKUs of varying resistance all having the same type of package. The result is that designers can more easily iterate on their system to find the right solution without having to redesign their board every single time.

While the improvements in performance are impressive, they beg the obvious question: what innovations led to these improvements? According to Witham, the answer is a twofold combination of improved processing technology and physical design. 

“We’ve implemented a new design by which we're able to better control the electric fields in the device and achieve reduced voltage spikes across the drain and the source,” Witham explained.  “On the processing side, we made some changes there with TSMC [Taiwan Semiconductor Manufacturing Company]. Combining those two things landed us with our hugely-improved fourth generation.”

 

What Is Figure of Merit?

One of the most notable specification improvements from GaN Systems’ fourth-generation solution is Figure of Merit. But what is this specification, and why is it so important for GaN?

In the context of GaN devices, the FoM serves as a quantitative metric to evaluate the performance and efficiency of the material in electronic applications. As Witham explained, FoM takes two forms: input and output. 

Input Figure of Merit for GaN is often defined as the inverse of the product of the channel resistance and gate charge. This is expressed mathematically as:

$$FoM~=~ \frac{1}{R_{on}~\times~Q_{g}}$$

 

Output FoM, on the other hand, is defined as the inverse of the product of the channel resistance and drain-source charge. It is expressed as:

$$FoM~=~ \frac{1}{R_{on}~\times~Q_{oss}}$$

 

Baliga’s FoM chart indicates the theoretical performance possible with GaN is much higher than other materials. Image used courtesy of Vecchia et al.

 

While both specifications are similar and are both effectively equivalent to the product of conduction losses and switching losses, Witham stated that designers of high-frequency systems are generally more concerned with input FoM, and designers of hard switching applications, like motors, are more concerned with output FoM.

In either case, the FoM provides a single value that comprehensively defines the power efficiency of a GaN device. A higher FoM indicates a more efficient device, capable of faster switching speeds and lower power losses. Hence, GaN Systems’ claims of a 20 percent increase in both input and output FoM indicates a truly improved product on their part.

 

Looking Toward the Future of GaN

Looking to the future, Witham is clearly optimistic. Concluding our conversation, he remarked,

“If you look back at silicon MOSFET history, it was kind of a 25-30 year journey, where the technology kept getting better and better with subsequent generations. With GaN, we're doing the same thing. It is our fourth generation and you should expect to see continued improvement because there's still a lot of performance to wring out of the technology.”