Download Silicon Carbide Power Electronic Devices

MSE SEMINAR
February 26, 2010
113 McBryde Hall
3:30 – 4:30
Refreshments at 3:00
Dr. Brett A. Hull
Cree, Inc.
Durham, NC
“Silicon Carbide Power Electronic Devices: From
Fundamental Materials Research to Marketplace”
ABSTRACT
There has been a great deal of interest in employing silicon carbide in the fabrication of semiconductor
devices since the early days of the development of Si integrated electronic devices. It was recognized that
the fundamental characteristics of SiC, such as its wide bandgap and high critical breakdown electric field,
made it an excellent candidate for the burgeoning integrated circuit revolution. Unfortunately, it took
decades for the technology needed (both SiC bulk single crystal growth and SiC homoepitaxy) to produce
SiC of suitable quality for electronic device applications to reach the level at which device research could be
conducted. Today, SiC-based power electronic devices are poised to significantly improve the efficiency of
power switching systems, in everything from power supplies to photovoltaic and wind power inverters, to
hybrid and electric vehicle motor drives and power conversion systems.
The benefits of SiC for power semiconductor devices (devices designed to operate at high voltages in the
off-state while conducting large amounts of current in the on-state) have long been recognized. The high
critical breakdown electric field, at about 10x that of single crystal Si, allows for the fabrication of devices
that can block to a given voltage with a blocking layer that is roughly 10x thinner than can be achieved with
Si. This reduced thickness leads to a device with an on-resistance that can be significantly lower than its
Si-based counterpart. Furthermore, with a bandgap of 3.2 eV (for the 4H SiC polytype, the most typically
employed), SiC devices have the potential to be operated at much higher temperatures than can Si devices.
These fundamental 4H SiC properties allow for unipolar SiC devices (Schottky diodes and MOSFETs, as an
example) to have comparable blocking and on-state performance as bipolar Si devices (PiN diodes and
insulated gate bipolar transistors (IGBTs)), with much smaller chip sizes. Since bipolar devices are
susceptible to large electron and hole storage times during switching, by replacing the Si bipolar devices
with SiC unipolar devices, huge power switching system efficiency gains can be achieved. These gains can
be realized as significantly reduced power losses at a given frequency, but there are perhaps much greater
opportunities to improve system efficiency by operating at the higher frequencies that SiC power electronic
devices permit.
A broad overview of SiC power electronic devices will be provided. Included in this overview will be a brief
introduction to power semiconductor devices, the basis for using SiC as a Si replacement in these devices,
and some general comments on the single crystal growth of SiC and on SiC homoepitaxy. Device
overviews will also be given, including junction barrier Schottky (JBS) diodes, PiN diodes and MOSFETs
designed for blocking 1200 V to 10 kV.
BIOSKETCH
Brett A. Hull received the B.S. degree in materials science and engineering,
Summa Cum Laude, from The Virginia Polytechnic Institute and State University in
Blacksburg, VA, USA in 1998. He then was awarded the Ph.D. degree in
materials science and engineering from The Pennsylvania State University in
University Park, PA, USA in 2004.
He is currently a Device Scientist in the Power Semiconductor Device Research
and Development group at Cree, Inc., in Durham, NC, USA. He has authored or
co-authored over 15 publications in wide bandgap semiconductor processing and
device development. Current research activities at Cree, Inc., include design,
development, and fabrication of high power electronic devices based on 4H SiC,
including unipolar and bipolar rectifiers and MOSFETs designed for operation from
1200 V to 10 kV.