SLS technology: the FPA perspective

Abstract

ABSTRACT We present the performance of longwave infrared focal plane arrays (FPAs) made from Type-II InAs/GaSb strained layer superlattice (SLS) photodiodes. In 320x256 FPAs operating at 77K, we measure cutoff wavelength ~ 8.5 P m, dark current density ~ 10 -5 A/cm 2 , quantum efficiency > 5% (with 2 P m –thick absorber photodi ode), and pixel operability ~ 96%. Device physics and FPA performance are graphed. Current challenges are discussed. Keywords: SLS, Strained Layer Superlattices, InAs/GaSb, Longwave Infrared, LWIR, FPA 1. INTRODUCTION Type-II InAs/InGaSb strained layer superlattice (SLS) is a novel infrared sensor technology 1,2 with the theoretical promise of better performance than mercury cadmium telluride (MCT) 3 and indium antimonide (InSb) combined with the manufacturing ease and low cost of InSb and quantum well infrared photodetector (QWIP) 4 .Recent progress in longwave infrared SLS photodiodes has been rapid 5-10 , but much work remains to be done before SLS can achieve its potential in a high-performance focal plane array (FPA) – high quantum efficiency (QE), high pixel operability and uniformity, higher operating temperature (than MCT with the same cutoff wavelength), good image stability, reproducibility, etc. If successful, the payoff would be significant. Two fundamental areas requiring improvement are material quality and surface passivation of small pixels in large-format detector arrays. Our efforts are focused on these areas.