Self-assembled InAs-GaAs quantum-dot intersubband detectors

The use of self-assembled InAs-GaAs quantum dots in photoconductive intersubband detectors in the far-infrared is presented. Far-infrared absorption is observed in self-assembled quantum dots in the 6-18-/spl mu/m range for subband-subband and subband-continuum transitions. Photoconductive quantum-dot intersubband detectors were fabricated and demonstrate tunable operating wavelengths between 6-18 /spl mu/m using subband-subband or subband-continuum transitions. The use of AlAs barriers allows further tuning to shorter wavelengths of 3-7 /spl mu/m. Subband-continuum quantum dot intersubband detectors show encouraging normal incidence performance characteristics at T=40 K, with responsivities of 10-100 mA/W, detectivities of 1-10 /spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W and large photoconductive gain up to g=12 for a ten-layer quantum-dot heterostructure. With improvements in device structure, self-assembled quantum dots can be expected to provide intrinsic normal incidence broad-band detectors with advantages over quantum wells.