Tuning the photoresponse of quantum dot infrared photodetectors across the 8–12μm atmospheric window via rapid thermal annealing

We report on wide spectral tunability of narrow-band (Δλ∕λ∼12%) InAs∕In0.15Ga0.85As∕GaAs quantum dot-in-a-well infrared photodetectors using postgrowth rapid thermal annealing. The well resolved absorption and photocurrent peaks shift from 8to11.6μm by annealing the devices at 800°C for up to 4min. Upon annealing, the dot confinement potential becomes shallower and the tunneling probability increases, resulting not only in an increased responsivity but also in an increased dark current. The combined effect is to reduce detector detectivity from 1.1×1010cmHz1∕2W−1 at 8μmto3×109cmHz1∕2W−1 at 11μm (T=77K). Our results demonstrate that spectral tunability from 8to12μm can be achieved while maintaining good detector performance.