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

Abstract

The implementation of strained layer superlattices (SLS) for detection of infrared (IR) radiation has enabled compact, high performance IR detectors and two-dimensional focal plane arrays (FPAs). Since initially proposed three decades ago, SLS detectors exploiting type II band structures existing in the InAs/GaSb material system have become integral components in high resolution thermal detection and imaging systems. The extensive technological progress occurring in this area is attributed in part to the band structure flexibility offered by the nearly lattice-matched InAs/AlSb/Ga(In)Sb material system, enabling the operating IR wavelength range to be tailored through adjustment of the constituent strained layer compositions and/or thicknesses. This has led to the development of many advanced type II SLS device concepts and architectures for low-noise detectors and FPAs operating from the short-wavelength infrared (SWIR) to very long-wavelength infrared (VLWIR) bands. These include double heterostructures and unipolar-barrier structures such as graded-gap M-, W-, and N-structures, nBn, pMp, and pBn detectors, and complementary barrier infrared detector (CBIRD) and pBiBn designs. These diverse type II SLS detector architectures have provided researchers with expanded capabilities to optimize detector and FPA performance to further benefit a broad range of electrooptical/IR applications.

Design and analytical modeling of high-performance mid-wavelength infrared photodetectors: an nBn architecture

“…Dark current, often referred to as leakage current in the absence of incident light, is the cumulative result of several processes, including diffusion currents in bulk regions, generation-recombination (GR) currents within the depletion region, BTB tunneling, trap-assisted tunneling (TAT), and surface leakage current within the device. 29,33,34 The device architecture, utilizing GaSb as the substrate, is depicted in Fig. 1(b).…”

Temporal stability and correctability of a MWIR T2SL focal plane array

“…Type-II Superlattice (T2SL) is a recent infrared detection technology whose excellent electro-optical performances (expressed as quantum efficiency, dark current density, specific detectivity or NETD) have been widely reported from the shortwave to the very longwave infrared domains [1][2][3][4][5][6][7][8][9][10]. They thus position themselves in competition with well-established cooled infrared technologies (HgCdTe, InSb, XBn, QWIP, etc) for high-performance applications such as radiometric imaging.…”

Residual fixed pattern noise and random telegraph signal noise of a MWIR T2SL focal plane array

“…Type-II Superlattice (T2SL) detectors are a recent commercial infrared technology designed to meet high-performance imaging applications [1][2][3][4][5][6][7][8][9][10], such that electro-optical characterisation efforts are now focused on system-oriented merit functions, for example MTF (Modulation Transfer Function) or stability over time. MTF describes how well a detector can reproduce spatial frequencies [11], whereas stability over time dictates how often the calibration of operational electro-optical systems has to be done, and thus reflects the availability of the system during an operational mission.…”