GaN Systems Details the Reliability of Gallium Nitride Transistors

It can be argued that GaN devices surpass MOSFETs when evaluated by JEDEC and AEC-Q101 testing standards. But the one major issue is the failure modes for the two technologies are different, so the comparison is something of an apples to oranges to oranges situation.

 

Image courtesy of GaN Systems

 

The Whitepaper, “Qualification and Reliability of GaN Power Semiconductors: A Collaborative Approach with Partners and Customers,” is the product of a joint effort between GaN Systems and its customers.

 

GaN Systems’ Journey with GaN

CEO of GaN Systems’ CEO, Jim Witham, pointed out that in 2007 he became intrigued by the promise of superior performance promised by nascent GaN technology. 

As described by Witham, it was clear to him that GaN beat both SiC and Silicon in the most critical needs of power devices: minimizing switching and conduction losses. With few if any commercial availability of GaN parts, he and his company decided to develop their own.

 

Key Elements of the Study 

Device Failure Modes 

• Testing to failure and analyzing failure mechanisms.

Understanding Transistor Design

• Better preventing failure and understanding target lifetime.

Test Design

• Testing with the JEDEC and AEC-Q101 standards in mind. And, testing under conditions that match “GaN-specific needs.”

Manufacturing Process

• Understanding the control for unique manufacturing requirements, including those from the automotive industry. 

 

And now, perhaps the most critical question: “Is GaN reliable?”

 

Apples to Oranges

Current qualification guidelines and standards for GaN power transistors are based on the decades-old foundations of evaluating silicon devices. However, GaN and other wideband gap transistors, such as SiC-based transistors, are different in both construction and material. Hence, qualification requires a closer look at not only on how and which testing guidelines apply, but also on what new methodologies will be required. 

Another issue is that power GaNs, as an example, can be clocked at frequencies far higher than silicon MOSFETS can sustain. This is an absolutely tremendous advantage. But, because of it, truly direct comparisons, in some cases, are not possible.

 

Taking the Lifetime and Reliability Challenge Head-On

GaN Systems and its partners from the industrial and automotive industries have taken an approach that draws considerations from JEDEC and AEC-Q and combined it with their own considerable experience in qualification testing. The approach outlined in GaN Systems’ Whitepaper: 

• Includes a frank discussion of the possible failure modes of GaN transistors. 

• The testing methodologies considered start from a baseline of accepted JEDEC and AEC-Q101 MOSFET testing.

• Additional test methods to account for differences between silicon and GaN

Lifetime models are defined by consideration of GaN failure mechanisms and by applying Failure Mode and Effects Analysis (FMEA), builds parts, and Test-to-Failure processes.

 

Working With JEDEC

SiC Systems is one of the founding members of JEDEC, and working with JEDEC is critical if any standards developed are to become universally recognized. But there are two critical issues to be overcome.

• Different companies' devices are targeted at different applications, so an important standard for us might not be all too relevant to others.

• We’re all competitors, and not everybody wants to share proprietary information that they feel afford them a competitive advantage, even for the attainment of the common goal of establishing industry standards.

The bottom line, according to Witham, is that “The assumption that GaN is unproven or unreliable is no longer in question. In the last few years, we’ve seen global companies continue to use and introduce innovative products and systems using GaN Systems power semiconductors as the basis for the design. It is clear that the work we have done with our customers to create an enhanced reliability test set ensures that GaN Systems’ devices demonstrate industry-leading performance and lifetime in the most challenging environments.”

 

Now and In the Future

Even without universally accepted standards, SiC devices, because of their low quiescent current and low switching and conduction losses, are well accepted in applications for chargers, data centers, renewable energy, and for consumer devices.

The next big step for GaN is industrial and automotive devices. The latter market is exceptionally conservative, because of safety issues and the exceptionally harsh nature of the automotive arena. As automotive manufacturers continue to see GaN’s growth and reliability this big step will seem more and more achievable.