Pixel isolation of low dark-current large-format InAs/GaSb superlattice complementary barrier infrared detector focal plane arrays with high fill factor

Low dark current and high fill factor are two crucial characteristics for the realization of the InAs/GaSb superlattice (SL) technology as third generation focal plane arrays (FPAs). Recent development proved high performance results for the complementary barrier infrared detector (CBIRD) design, and a high-quality etch technique is required to minimize surface leakage currents. We report on a n-CBIRD with 10.3 μm cutoff, exhibiting a responsivity of 1.7 A/W and dark current density of 1×10^-5 A/cm² at 77K under 0.2 V bias, without AR coating and without passivation. Results from four different mesa isolation techniques are compared on single element diodes: chemical wet etch using C₄H₆O₆:H₃PO₄:H₂O₂:H₂O, BCl₃/Ar inductively coupled plasma (ICP), CH4/H2/Ar ICP, and CH₄/H₂/BCl₃/Cl₂/Ar ICP. The CH₄/H₂/BCl₃/Cl₂/Ar etched structures yielded more than 2.5 times improvement in dark current density and nearvertical sidewalls. Using this etching technique, we then implement a 1k x 1k p-CBIRD array with 11.5 μm cutoff and peak responsivity of 3 A/W. Operating at T = 80K, the array yielded a 81% fill factor with 98% operability and performance results of 21% quantum efficiency, 53 mK NE▵T, and NEI of 6.9×10¹³ photons/sec-cm².