Type II superlattice detectors at SCD

P. C. Klipstein, Y. Benny, Y. Cohen, N. Fraenkel, R. Fraenkel, S. Gliksman, A. Glozman, I. Hirsh, O. Klin, L. Langof, I. Lukomsky, I. Marderfeld, B. Milgrom, H. Nahor, M. Nitzani, D. Rakhmilevich, L. Shkedy, N. Snapi, I. Strichman, E. WeissN. Yaron

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations


The InAs/InSb/GaSb/AlSb family of III-V alloys and superlattice materials offer unique possibilities for band structure engineering, because they can be grown on GaSb or InSb substrates with high quality and satisfactory control of strain, doping and composition. The band profiles and oscillator strengths are also quite predictable, enabling full simulation of detector performance from a basic knowledge of layer and stack thicknesses. In conventional III-V p-n devices, Shockley-Read-Hall (SRH) traps generate a significant flow of thermal carriers in the device depletion region. At SCD, we have overcome this problem by developing XBn and XBp barrier device architectures that suppress these depletion currents, leading to higher operating temperatures or lower dark currents. Our first barrier detector product was launched in 2013 and operates at 150K. It uses a mid-wave infrared (MWIR) XBn device with an InAsSb absorber well matched to the most transparent of the atmospheric windows, at wavelengths between 3 and 4.2µm. However to span the full MWIR and to sense the long-wave infrared (LWIR) spectrum, we have investigated InAs/GaSb type II superlattices (T2SLs), because they offer full tunability. In this work we show that minority carriers in n-type T2SLs are localized and diffuse by variable range hopping, even when the period is short and the valence mini-band has a width of 30-40 meV. Unfortunately, this leads to sub-micron diffusion lengths and a low quantum efficiency (QE) of ~20% in a full MWIR XBn device. On the other hand, p-type layers exhibit “metallic” minority carrier transport with much longer diffusion lengths, typically ~7 µm in our LWIR device layers. The successful development of p-type devices has led to our second barrier detector product, which uses an XBp LWIR T2SL and operates at 77K with a cut-off wavelength of 9.5 μm, a focal plane array (FPA) QE of ~50% and background limited performance up to ~90K at F/3. Moreover, the FPA operability is typically above 99.5%, based on stringent production-line criteria. Together with high spatial uniformity and good temporal stability, these barrier detectors are already a realistic alternative to MCT photodiode arrays, and further products operating at other wavelengths will be launched in due course.

Original languageEnglish
Title of host publicationInfrared Technology and Applications XLVII
EditorsBjorn F. Andresen, Gabor F. Fulop, Lucy Zheng, Masafumi Kimata, John Lester Miller
ISBN (Electronic)9781510643192
StatePublished - 2021
Externally publishedYes
EventInfrared Technology and Applications XLVII 2021 - Virtual, Online, United States
Duration: 12 Apr 202116 Apr 2021

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceInfrared Technology and Applications XLVII 2021
Country/TerritoryUnited States
CityVirtual, Online

Bibliographical note

Publisher Copyright:
© 2021 SPIE


  • Focal Plane Array
  • Infrared Detector
  • LWIR
  • MWIR
  • PBp
  • Type II superlattice
  • XBn
  • XBp


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