InAs/GaSb type II superlattices: A developing material system for third generation of IR imaging

Manijeh Razeghi*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter

6 Scopus citations


The idea of type II InAs/GaSb superlattice (T2SL) was first proposed by Sai-Halasz and Esaki in the 1970s. The superlattice is formed by alternating the InAs and GaSb layers over several periods. For practical realization of superlattices, the materials that are grown on top of each other need to be closely lattice-matched. Fortunately, InAs and GaSb, along with AlSb, belong to a family of III-V compounds that is called 6.1Å family since they all have lattice constants that are close to 6.1Å. Similar lattice constants, fairly similar growth conditions, and the availability of GaSb substrate have made possible the growth of superlattices using this material system with low density of defects and dislocations. The type II broken-gap alignment leads to the separation of electrons and holes into the InAs and GaSb layers, respectively. The charge transfer gives rise to a high local electric field and strong interlayer tunneling of carriers without the requirement of an external bias or additional doping. Large-period superlattices behave like semimetals, but if the superlattice period is shortened, the quantization effects are enhanced causing a transition from a semimetal to a narrow-gap semiconductor. The resulting energy gaps depend upon the layer thicknesses and interface compositions.

Original languageEnglish (US)
Title of host publicationMid-infrared Optoelectronics
Subtitle of host publicationMaterials, Devices, and Applications
Number of pages35
ISBN (Electronic)9780081027097
StatePublished - Jan 1 2019


  • Focal plane array
  • Infrared
  • Photodetector
  • Type-II superlattice

ASJC Scopus subject areas

  • General Engineering


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