IEEE Power Electronics Magazine - March 2017 - 50

Expert View

by Alex Lidow

gan-on-silicon Power Devices:
How to Dislodge silicon-Based
Power MosFEts

allium nitride (GaN) power
transistors designed for efficient power conversion have
been in production for seven years.
New markets, such as light detection
and ranging, envelope tracking, and
wireless charging, have emerged due
to the superior switching speed of
GaN. These markets have enabled
GaN products to achieve significant
volumes, low production costs, and
an enviable reliability reputation. All
of this provides adequate incentive for
the more conservative design engineers
in applications such as dc-dc converters, ac-dc converters, and automotive
to start their evaluation process. So
what are the remaining barriers to the
conversion of the US$12 billion silicon
power metal-oxide-semiconductor
field-effect transistor (MOSFET) market? In a word: confidence.
Design engineers, manufacturing
engineers, purchasing managers, and
senior management all need to be
confident that GaN will provide benefits that more than offset the risk of
adopting a new technology. Let's look
at three key risk factors: supply chain
risk, cost risk, and reliability risk.

Supply Chain Risk
The list of companies selling GaN
power devices is growing almost
monthly. As of this writing, the list
included the following companies:
Digital Object Identifier 10.1109/MPEL.2016.2642278
Date of publication: 7 March 2017

IEEE PowEr ElEctronIcs MagazInE

Efficient Power Conversion Corp.
■ GaN Systems
■ Dialog Semiconductor
■ Navitas Semiconductor
■ Panasonic
■ Transphorm
■ Texas Instruments
■ ON Semiconductor
■ Sanken
■ VIS Technologies
■ Cambridge Electronics, Inc.
It should be noted that GaN Systems, Dialog Semiconductor, and
Navitas Semiconductor all use a
Taiwan Semiconductor Manufacturing Company, Limited (TSMC)developed enhancement-mode process that is open to any fabless
company wanting to enter this market. With all of these participants,
and with the backing of major companies such as Texas Instruments,
Panasonic, ON Semiconductor, and
TSMC, the supply chain risk should
be minimal.
■

Cost Risk
Design engineers may delight in the
performance of a system using GaN
instead of a power MOSFET, but
unless that system costs significantly
less than its predecessor, there will
be resistance from purchasing
departments and upper management.
Often component suppliers will
make the argument that their costly
product will save overall system
costs. In my experience, this is a
hard, but not impossible, argument

z March 2017

to make. However, if the actual component cost is lower than the component being replaced, the argument
changes. Instead of a design engineer
having to convince upper management and purchasing of the benefits
of the new component, it becomes
upper management and purchasing
asking the design engineer why he/
she has not yet converted. In May
2015, the Efficient Power Conversion
Corporation's (EPC's) latest generation of product crossed over the
price curve with MOSFETs of similar
voltage and on-resistance. There
were three main reasons for this
change: 1) volumes had reached the
point where economies of scale
kicked in, 2) GaN transistor die
sizes are three to five times smaller
than MOSFETs, and 3) EPC's eGaN
transistors are in chip-scale format,
which eliminates all the costs associated with packaging-costs that
are 50% or more of the costs of a silicon MOSFET.
The area efficiency of current GaN
transistors is more than 500 times
lower than theoretically possible. It
should therefore be expected that die
sizes will continue to shrink, while
performance increases and costs go
down at each step.

Reliability Risk
There has been an enormous amount
of reliability testing performed on
GaN devices from several manufacturers, including EPC, GaN Systems,

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - March 2017