Self-assembled InAs-GaAs quantum-dot intersubband detectors

The use of self-assembled InAs-GaAs quantum dots in photoconductive intersu bband detectors in the far-infrared is presented. Far-infrared absorption i s observed in self-assembled quantum dots: in the 6-18-mu m range for subba nd-subband and subband-continuum transitions. Photoconductive quantum-dot i ntersubband detectors were fabricated and demonstrate tunable operating wav elengths between 6-18 mu m using subband-subband or subband-continuum trans itions. The use of AlAs barriers allows further tuning to shorter wavelengt hs of 3-7 mu m. Subband-continuum quantum-dot intersubband detectors show e ncouraging normal incidence performance characteristics at T = 40 K, with r esponsivities of 10-100 mA/W, detectivities of 1-10 x 10(9) cm.Hz(1/2)/W, a nd large photoconductive gain up to g = 12 for a ten-layer quantum-dot hete rostructure, With improvements in device structure, self-assembled quantum dots can be expected to provide intrinsic normal incidence broad-band detec tors with advantages over quantum wells.