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In
addition to its new silicon-based light emitting technology
(pictured), ST says it is also investigating integrated optical
data-transmission systems for use in advanced CMOS circuits where
clock signals are distributed through the chip at the speed of
light, as well as low-cost integrated devices for Dense Wavelength
Division Multiplexing (DWDM) fiber-optic communication.
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According to ST,
the new technology opens up many potential applications in which optical
and electrical functions are combined on a single silicon
chip. This, the company says, was not previously possible because although
silicon is ideal for building memories, microprocessors, and other complex
circuits, it could not be made to act as an efficient light emitter.
"The ability to combine optical and electronic processing on the
same chip presents enormous opportunities for ST to be the first to develop
many
new types of semiconductor products, especially as the technology is
compatible with existing volume production process flows and equipment.
ST has already
identified a number of promising applications, and key manufacturing
issues have already been solved so that the technology can be rapidly
moved into
production," explains GianGuido Rizzotto, director, Corporate Technology
R&D.
The new silicon-based light emitting technology reportedly sets
a world record for efficiency. It is based on a structure in which
ions of rare-earth
metals such as erbium or cerium are implanted in a layer of Silicon
Rich Oxide (SRO) (i.e., silicon dioxide enriched with silicon nanocrystals
of 1-2 nm diam).
The company says the quantum efficiencies achieved
are about 100-times better than has previously been possible with silicon
and are, for
the first time, comparable to those obtained from GaAs and other
compound semiconductors that are traditionally used to make light-emitting
diodes.
The frequency
of the emitted light depends on the choice of rare-earth dopant,
and ST says it has patented techniques for implanting the rare-earth
ions
into
the silicon.
One of the first applications of the new technology is
to build power control devices in which the control circuitry is electrically
isolated
from the
power switching transistors. Currently, electrical isolation, which
is mandatory in many applications for safety reasons, can only
be achieved by using external devices such as relays, transformers,
or discrete
optocouplers,
all of which involve additional cost, power consumption, or bulk,
according to the company.
ST has patented a structure in which two
circuits, built on the same chip but electrically separated from each
other by insulating
silicon
dioxide,
communicate via optical signals using integrated silicon light
emitters and detectors. These devices will have numerous applications,
including
motor control, power supplies, solid-state relays, and similar
applications where the power circuit needs to handle much higher
voltages than
the control circuit. Engineering samples are now available.
This
information is provided by STMicroelectronics, Lexington, MA, U.S. |
