Automotive Engineering - March 2024 - 19

COVER STORY
Silicon-carbide semiconductor produced by Bosch at its fabrication site near
Dresden, Germany.
semiconductors with gallium nitride once it can solve at least one
challenge: the current moves vertically in SiC devices but laterally
along the plane in GaN devices.
" There are no gallium-nitride vertical devices available, " Ozpineci
said. " The challenge with them is they're usually low-voltage, lowcurrent
right now. In a low-power onboard charger, or if you're looking
at other DC/DC converters - again, low-voltage, low-power -
you can use GaN, which will beat SiC at the power level. The vertical
GaN devices, which actually will have better properties than SiC, are
not ready yet - and they might not be ready for another ten years. "
Bosch's Medisetty agreed, saying that for now, gallium-nitride
doesn't have the performance needed by the transportation sector.
" [GaN devices] are quite a bit lower-voltage, not readily suitable for
automotive electromobility applications, but there are other gallium
nitride approaches which are more similar to silicon-carbide devices, "
he said. " These have higher voltages, are more robust and more suited
for electromobility applications.
" Bosch is working extensively on gallium nitride that is more suitable
for electromobility applications, " he added. " We see a potential for it,
but it's still further out and there is lot more ground to be covered on
silicon-carbide optimization. There're generations before we get there. "
AUTOMOTIVE ENGINEERING
Burak Ozpineci, section head of the Vehicle and Mobility Systems
Research Section at Oak Ridge National Laboratory.
Sandia National Laboratories, for example, started a
development project in 2019 for better next-generation
vertical GaN devices for high-power-density electric
drivetrains. Testing both GaN JBS diodes and GaN
MOSFET devices, the teams have so far discovered
that the main problem is the low maturity of the two
devices. Engineers have reached current limitations for
both the MOSFET devices (where the problem lies
with the current output) and the JBS diodes (where
the limitation is in the reverse leakage due to the etchand-regrowth
process).
Sandia said in a summer 2023 presentation that it will
conduct further tests once either a multi-amp device can
be made (for MOSFET) or the leakage problem is solved
(JBS). These new, vertical GaN devices, like so much of
the research that the DOE supports, are being developed
to hit three key targets. The DOE's power-density target
for 2025 is 100 kW-per-liter for a 300,000-mile lifetime
powertrain that costs, at most, $2.7 per kW. Ozpineci said
that regardless of the technology the VTO is helping
with, money is always top of mind.
March 2024 19
FROM LEFT: BOSCH; ORNL

Automotive Engineering - March 2024

Table of Contents for the Digital Edition of Automotive Engineering - March 2024

Automotive Engineering - March 2024 - INTRO
Automotive Engineering - March 2024 - SPONSOR
Automotive Engineering - March 2024 - CVRA
Automotive Engineering - March 2024 - CVRB
Automotive Engineering - March 2024 - CVR1
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