Developing high-performance III-V superlattice IRFPAs for defense: challenges and solutions

Abstract

The antimonide superlattice infrared detector technology program was established to explore new infrared detector materials and technology. The ultimate goal is to enhance the infrared sensor system capability and meet challenging requirements for many applications. Certain applications require large-format focal plane arrays (FPAs) for a wide field of view. These FPAs must be able to detect infrared signatures at long wavelengths, at low infrared background radiation, and with minimal spatial cross talk. Other applications require medium-format pixel, co-registered, dual-band capability with minimal spectral cross talk. Under the technology program, three leading research groups have focused on device architecture design, high-quality material growth and characterization, detector and detector array processing, hybridization, testing, and modeling. Tremendous progress has been made in the past few years. This is reflected in orders-of-magnitude reduction in detector dark-current density and substantial increase in quantum efficiency, as well as the demonstration of good-quality long-wavelength infrared FPAs.Many technical challenges must be overcome to realize the theoretical promise of superlattice infrared materials. These include further reduction in dark current density, growth of optically thick materials for high quantum efficiency, and elimination of FPA processing-related performance degradation. In addition, challenges in long-term research and development cost, superlattice material availability, FPA chip assembly availability, and industry sustainability are also to be met. A new program was established in 2009 with a scope that is different from the existing technology program. Called Fabrication of Superlattice Infrared FPA (FastFPA), this 4-year program sets its goal to establish U.S. industry capability of producing high-quality superlattice wafers and fabricating advanced FPAs. It uses horizontal integration strategy by leveraging existing III-V industry resources and taking advantage of years of valuable experiences amassed by the HgCdTe FPA industry. By end of the program span, three sets of FPAs will be demonstrated-a small-format long-wave FPA, a large-format long-wave FPA, and a medium-format dual-band FPA at long-wave and mid-wave infrared.

New concepts in infrared photodetector designs

“…94 Figure 37 shows tremendous progress made in past few years in the performance of type-II superlattice single element detectors or mini-arrays from USA major institutions: Northwestern University (NWU), Naval Research Laboratory (NRL), Jet Propulsion Laboratory (JPL), and Teledyne Imaging Scientific (TIS). 95 This figure shows superlattice detector performance through measurements of the dark current density as a multiple of Rule 07 versus time. The best SL device is within three times the value of HgCdTe Rule 07.…”

Barrier infrared detectors

“…Measured at 230 K spectral response curves show about 3.6 μm cut−off wave− length (at 50% of the initial rise in the response). Figure 20 shows tremendous progress made in the past few years in the performance of type−II superlattice single ele− ment detectors or mini−arrays from USA major institutions: Northwestern University (NWU), Naval Research Labora− tory (NRL), Jet Propulsion Laboratory (JPL), and Teledyne Imaging Scientific (TIS) [56]. This figure shows super− lattice detector performance measured by dark current den− sity as a multiple of "Rule 07" vs. time in years.…”

Design and Development of Two-Dimensional Strained Layer Superlattice (SLS) Detector Arrays for IR Applications

“…Figure 5(a) and (b) compare the dark current performance of type II SLS detectors from various groups with a "Rule 07" model providing a theoretical prediction of MCT detector performance as a function of wavelength and over time, respectively [7,110,[40][41][42]. Likewise, Figure 6(a) and (b) chart the carrier lifetimes at 77 K for HgCdTe and type II SLS detectors operating at MWIR and LWIR wavelengths, respectively, as a function of doping concentration [11].…”

“…(a) Dark current densities plotted against cutoff wavelength for type II SLS non-barrier and barrier detectors at 78 K [7,11]. The solid line indicates the dark current density calculated using the empirical "rule 07" model, and the circle indicates results from DeCuir et al [39] (b) Detector dark current density as multiple of rule 07 [40][41][42]. The black line represents the trend line of dark current reduction over time for single element detectors, while the red line shows this trend for FPAs.…”