DURHAM, N.C., June 30 /PRNewswire/ -- Cree Research, Inc. (NASDAQ:CREE),
the world's leading manufacturer and supplier of silicon carbide (SiC) wafers
and SiC-based semiconductor products, announced it has demonstrated a power
diode with the highest blocking voltage ever reported for a silicon carbide
device and with a switching efficiency an order of magnitude greater than
similarly-rated silicon diodes. The company also announced it has
demonstrated a microwave transistor, formed using gallium nitride on a silicon
carbide substrate, that achieved the highest power density ever reported for a
solid state field effect transistor operating at radio or microwave
frequencies. These results were presented last week at the prestigious Device
Research Conference sponsored by the IEEE Electronic Devices Society.
Silicon-based power diodes are currently used in a wide range of
applications including industrial motors, power conditioning systems and power
distribution networks. The diode fabricated by Cree exhibited a blocking
voltage of 5900 volts, and the switching efficiency made possible by Cree's
silicon carbide technology produced losses that were only 5% of the power lost
during operation of comparable silicon devices. This greatly enhanced
efficiency is due in part to the fact that the voltage-blocking epitaxial
layer in Cree's device was only 50 microns thick, whereas equivalent silicon
diodes require layers 500 microns thick. In addition to power savings, SiC
power diodes promise other advantages over silicon devices in many
applications. These advantages include reduced cooling requirements, higher
possible switching frequencies and greater reliability at high temperatures.
The quality of the SiC epitaxial material grown by Cree's materials group
also contributed to the results achieved by its power diode. Although thinner
than that used in similar silicon diodes, the epi material in Cree's device is
considered thick compared to layers previously grown on silicon carbide
substrates, and the growth of such thick layers required the development of
new processes. Olle Kordina, the Cree scientist who heads its "thick epi"
team, commented: "The results reported by our device scientists are
particularly gratifying since they show our team's thick epi is of exceptional
quality. The ability to produce high quality epi is essential to fabrication
of high power silicon carbide diodes, and Cree is at the forefront in this
arena."
The microwave device Cree demonstrated was equally impressive. Cree
scientists reported achieving a power density of 6.8 watts per millimeter in a
device operating at 10 gigahertz, with a power-added efficiency of 52% and
10.7 dB of associated gain. This power density is the highest ever reported
for a solid state field effect transistor operating at radio or microwave
frequencies and more than twice that reported by any other group developing
similar devices. The high efficiency and gain of the Cree device at this
frequency are also substantially greater than the results reported by other
groups developing high power gallium nitride-based transistors.
Power density refers to a measurement of the output power of the device
relative to device size. Although Cree's demonstration device produced only
one watt total power, the high power density attained with its gallium
nitride-on-silicon carbide design should enable the development of larger
devices with higher total output power at a given frequency. Transistors of
the type demonstrated by Cree have potential applications in high power
amplifiers for military radar and communications systems operating in the X
band range and at higher frequencies. The higher output power made possible
by Cree's design could permit the development of radar and communications
systems with substantially increased operating ranges.
No timetable has been established for the release of commercial products
based on the results announced by the company. |
