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

We report on wide spectral tunability of narrow-band (Delta lambda/lambda similar to 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 8 to 11.6 mu m by annealing the devices at 800 degrees C for up to 4 min. 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 1.1x10(10) cm Hz(1/2) W-1 at 8 mu m to 3x10(9) cm Hz(1/2) W-1 at 11 mu m (T=77 K). Our results demonstrate that spectral tunability from 8 to 12 mu m can be achieved while maintaining good detector performance. (c) 2007 American Institute of Physics.