Heterojunction bandgap engineered photodetector based on type-II InAs/GaSb superlattice for single color and bicolor infrared detection

We report a heterostructure bandgap engineered strained layer superlattice photodetector design for performance improvement for longwave infrared (LWIR) detection. At 77 K, the dark current density of the reported device was at least two orders of magnitude lower than that of the conventional PIN superlattice photodiode. We have obtained a shot-noise limited detectivity of 8.7 × 1010 cm Hz1/2 W−1 (λc = 10.8 μm), responsivity of 1.8 A/W, 23% QE at 250 mV of applied reverse bias. A three contact heterojunction bandgap engineered dual color detector was demonstrated with simultaneous detection of midwave and longwave infrared radiation. The design showed midwave responsivity of 0.93 A/W and detectivity of 1.0 × 1011 cm Hz1/2 W−1 (at 4 μm) at 77 K for Vb = −70 mV. Longwave responsivity and detectivity of 1.5 A/W and 2.42 × 1010 cm Hz1/2 W−1 (at 10 μm) were observed at −100 mV of applied bias at 77 K.

Research highlights
► We report on type-II InAs/GaSb strained layer superlattice (SLS) infrared photodiode.
► Bi-color detector for simultaneous detection of MWIR and LWIR signals.
► Dark current reduction is significant by incorporating unipolar barriers in photodiode design.