Double electron barrier structure for suppression of dark current in microjunction-based type-II InAs/InAsSb superlattice long-wavelength infrared photodetectors

Abstract

Reduction of dark current density in microjunction-based InAs/InAs1-xSbx type-II superlattice long-wavelength infrared photodetectors was demonstrated. A double electron barrier design was used to suppress both generation-recombination and surface dark currents. The photodetectors exhibited high surface resistivity after passivation with SiO2, which permits the use of small size features without having strong surface leakage current degrading the electrical performance. Fabricating a microjunction structure (25×25 μm2 mesas with 10×10 μm2 microjunctions) with this photodetector double 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 at 77 K.