By Philip Zuk, Vice President Technical Marketing, Transphorm
Knowledge is Power:
Practical Guidance for
GaN Power Conversion
Gallium Nitride technology hasn’t been dominating the market, but that’s changing as industries experience its power efficiency.
More than 10 percent of electricity is lost in power conversion, even as silicon (Si) semiconductors are
optimized to their utmost level of efficiency. This loss
equates to tens of billions of dollars in wasted energy,
along with systems that run hot and require additional
cooling mechanisms—meaning more money and physical
space spent generating power. This is why the industry is
shifting toward alternative materials, like wide bandgap
Gallium Nitride (GaN) is gaining traction as a more
efficient alternative to Si, particularly in high voltage
(HV) power applications. According to research firm
Yole Développement, the GaN power supply market
is expected to exhibit a compound annual growth rate
(CAGR) of 79 percent through 2022. This growth will be
driven by GaN’s use in markets such as automotive, data
center, and renewables.
The adoption pace is generally due to the tech’s
“newness.” Si has been the material of choice for many
decades. As such, all design and testing methods,
understanding of quality and reliability (Q+R), and just
general working knowledge in the power engineering
space is centered on a material that behaves very
differently than GaN.
Yet, markets stand to benefit greatly from GaN’s
advantages that average a 40 percent increase in
power density, 20 percent reduction in overall system
cost, and potential to achieve 99 percent efficiency.
Following are three topics that, while often presented
as deterrents to GaN adoption, are actually easy to
navigate and move beyond.
Fear of the Unknown: GaN Quality + Reliability
GaN is stressed more today than any Si or silicon carbide
(SiC) technology. Why? Si is mature, and SiC is considered
an extension of Si MOSFETs, given it is a vertical normally-off device with diodes that have been around for nearly 20
years. However, as the market’s newest solution and viable
replacement for both Si and SiC, GaN testing is rigorous,
extensive, and goes beyond the norm.
First, GaN platforms can be put through JEDEC and,
for the automotive market, AEC-Q101 qualification
testing. Though these test methods are designed for Si,
they serve as a starting point. Manufacturers then take
GaN through extended-JEDEC testing—not technically
required to qualify under current JEDEC Si standards—
to understand the GaN’s basic Q+R. (Note: the JEDEC
Association recently launched the JC-70 committee
to establish standards specifically for wide bandgap
Second, GaN should be subjected to additional testing
beyond fundamental quality and reliability to understand
its failure modes. This is typically referred to as lifetime
or robustness testing. Following are select robustness
tests to be considered. Also included are results that can
be used to establish a proven Q+R and lifetime baseline.
These results were compiled after conducting and
repeating these and other robustness tests on large sample
sets exceeding the required baseline to ensure the results
• The High Temperature Operating Life (HTOL)
test mimics hard switching conditions and assesses
possible interactions that will affect reliability.
The tested GaN shows no significant change in
performance after HTOL, indicating that its GaN is
robust after 3000 hours at a junction temperature of
175°C operating at 300 kHz.
• The High Voltage Off State (HVOS) testing evaluates
high field reliability, like High Temperature Reverse
Bias (HTRB), but taken to failure. This is where
step stress is used by stepping the devices from 600
V to 1800 V with a time between steps of between
one minute and one hour. While this takes place the
leakage current is monitored to detect device voltage
• The High Temperature DC Current (HTDC) test
determines failure from trapped charge in the gate
region and high on resistance with lower IDSS. Tested
GaN shows a median lifetime of >2x107 hours at the
peak rated junction temperature of 175°C.