Microjunction InAs/InAs1-xSbx type-II superlattice-based long-wavelength infrared photodetectors with reduced dark current density were demonstrated. A double electron barrier design was employed to reduce both bulk and surface dark currents. The photodetectors exhibited low surface leakage after passivation with SiO2, allowing the use of very small size features without degradation of the dark current. Fabricating microjunction photodetectors (25 × 25 μm2 diodes with 10 × 10 μm2 microjunctions) in combination with the double electron barrier design results in a dark current density of 6.3 × 10-6 A/cm2 at 77 K. The device has an 8 μm cut-off wavelength at 77 K and exhibits a quantum efficiency of 31% for a 2 μm-thick absorption region, which results in a specific detectivity value of 1.2 × 1012 cm·Hz1/2/W.
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