Low dark current quantum-dot infrared photodetectors with an AlGaAs current blocking layer

Low dark current InAs/GaAs quantum-dot infrared photodetectors (QDIPs) are demonstrated. The dark current is reduced by over three orders of magnitude by using a thin AlGaAs current blocking layer. This thin AlGaAs layer reduces the dark current much more than the response signal. The responsivity at 0.5 V is 0.08 A/W with a peak detection wavelength at 6.5μm. The corresponding detectivity is 2.5×109 cm Hz1/2/W1/2, which is the highest detectivity reported for a QDIP at 77 K.