Multicolor InGaAs quantum-dot infrared photodetectors

We report two-color InGaAs quantum-dot infrared photodetectors. The InGaAs self-assembled quantum dots were grown on InGaP matrix via metal-organic chemical vapor deposition and fabricated as intersubband photoconductive structure. Bias-controlled two-color photoconductive responses were obtained at two different infrared window, mid-infrared of /spl lambda/=5.5 μm and far-infrared of /spl lambda/=9.2 μm at 77 K. Our devices were operated with low dark currents and high optical gains, and resulted in peak detectivity D/sup */ of 4.7×10/sup 9/ cm Hz
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2//W at /spl lambda/=5.5 μm with bias of -2.0 V, and 7.2×10/sup 8/ cm Hz
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2//W at /spl lambda/=9.2 μm with bias of -0.8 V.