Type-II InAs/GaSb superlattices lead to new IR camera

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).