Type-II InAs/GaSb superlattices lead to new IR camera
EVANSTON, Ill. – A novel IR camera based on Type-II InAs/GaSb superlattices produces
images with much higher resolution than previous IR cameras could produce.
The camera’s long-wavelength IR (LWIR) focal plane array
can provide IR images in the dark and offers a sixteenfold increase in the number
of pixels in the image, according to the researchers at Northwestern University
who created it.
Existing LWIR cameras are based on mercury cadmium telluride materials;
the Type-II superlattice is mercury-free and can be deposited with better uniformity,
increasing yield, reducing camera cost and broadening the range of applications
for which LWIR imaging can be used.
The LWIR detection mechanism in a Type-II InAs/GaSb superlattice
relies on quantum-size effects in a completely artificial layer sequence to tune
the wavelength sensitivity and demonstrate high efficiency.
The group at Northwestern demonstrated the world’s first
Type-II-based 256 x 256 IR camera just a few years ago. The new camera operates
at 81 K, can collect 78 percent of the light, and can show temperature differences
as small as 0.02 °C.
The work was published in the journal Applied Physics Letters,
Vol. 97, Issue 19, p. 193505 (2010).
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