A multicolor, broadband (5-20 μm), quaternary-capped InAs/GaAs quantum dot infrared photodetector

An InAs/GaAs quantum dot infrared photodetector with strong, multicolor, broadband (5-20 mu m) photoresponse is reported. Using a combined quaternary In0.21Al0.21Ga0.58As and GaAs capping that relieves strain and maintains strong carrier confinement, we demonstrate a four color infrared response with peaks in the midwave-(5.7 mu m), longwave-(9.0 and 14.5 mu m), and far-(17 mu m) infrared regions. Narrow spectral widths (7% to 9%) are noted at each of these wavelengths including responsivity value similar to 95.3mA/W at 14.5 mu m. Using strain field and multi-band k.p theory, we map specific bound-to-bound and bound-to-quasibound transitions to the longwave and midwave responses, respectively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773373]