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

Abstract

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/cm 2 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 C 4 H 6 O 6 :H 3 PO 4 :H 2 O 2 :H 2 O, BCl 3 /Ar inductively coupled plasma (ICP), CH4/H2/Ar ICP, and CH 4 /H 2 /BCl 3 /Cl 2 /Ar ICP. The CH 4 /H 2 /BCl 3 /Cl 2 /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 NEuT, and NEI of 6.9×10 13 photons/sec-cm 2 .