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 .