Performance improvements of a split-off band infra-red detector using a graded barrier.

Uncooled split-off band infrared detectors have been demonstrated with an operational device response in the 3-5 µm range. We have shown that it is possible to enhance this device response through reducing the recapture rate by replacing one of the commonly used flat barriers in the device with a graded barrier, which was grown using a "digital alloying" approach. Responsivity of approximately 80 µA/W (D*=1.4x108 Jones) were observed at 78K under a 1V applied bias, with a peak response at 2.8 µm. This is an improvement by a factor of ~25 times compared to an equivalent device with a flat barrier. This enhancement is due to improved carrier transport resulting from the superlattice structure, and a low recapture rate enabled by a reduced distance to the image force potential peak in the graded barrier. The device performance can be further improved by growing a structure with repeats of the single emitter layer reported here. [ABSTRACT FROM AUTHOR]