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Home > Knowledge > 5.Silicon Carbide Technology > 5.6.1 SiC Optoelectronic Devices
5.6.1 SiC Optoelectronic Devices

5.6 SiC Electronic Devices and Circuits
5.6.1 SiC Optoelectronic Devices
The wide bandgap of SiC is useful for realizing short-wavelength blue and ultraviolet (UV) optoelectronics.
6H-SiC-based pn junction light-emitting diodes (LEDs) were the first semiconductor devices
to cover the blue portion of the visible color spectrum, and became the first SiC-based devices to reach
high-volume commercial sales . Because SiC’s bandgap is indirect (i.e., the conduction minimum
and valence band maximum do not coincide in crystal momentum space), luminescent recombination
is inherently inefficient . Therefore, LEDs based on SiC pn junctions were rendered quite obsolete
by the emergence of much brighter, much more efficient direct-bandgap Group III-nitride (III-N such
as GaN, and InGaN) blue LEDs . However, SiC wafers are still employed as one of the substrates
(along with sapphire) for growth of III-N layers used in high-volume manufacture of green and blue
nitride-based LEDs.
SiC has proven much more efficient at absorbing short-wavelength light, which has enabled the
realization of SiC UV-sensitive photodiodes that serve as excellent flame sensors in turbine-engine
combustion monitoring and control . The wide bandgap of 6H-SiC is useful for realizing
low photodiode dark currents as well as sensors that are blind to undesired near-infrared wavelengths
produced by heat and solar radiation. Commercial SiC-based UV flame sensors, again based on epitaxially
grown dry-etch mesa-isolated 6H-SiC pn junction diodes, have successfully reduced harmful pollution
emissions from gas-fired ground-based turbines used in electrical power generation systems . The
low dark-currents of SiC diodes are also useful for X-ray, heavy ion, and neutron detection in nuclear
reactor monitoring and enhanced scientific studies of high-energy particle collisions and cosmic
radiation .