Characteristics of a multicolor InGaAs-GaAs quantum-dot infrared photodetector

A three-color quantum-dot infrared photodetector has been fabricated and characterized. The active absorption region consists of undoped In/sub 0.4/Ga/sub 0.6/As quantum dots separated by GaAs barriers. Intersublevel transitions of electrons in the quantum dots results in absorption peaks at /spl sim/3.5, 7.5, and 22 μm. The devices were characterized at 80 K and 120 K. The dark current density is 10/sup -6/ A/cm 2 at 120 K for an applied bias of 1 V. The responsivity and specific detectivity D/sup */ are 0.07 A/W and 4.8×10/sup 10/ cm/spl middot/Hz 1 2//W for the 7.5-μm response at 80 K for an applied bias of 3 V.