4.5 Article

Long Wavelength InAs/InAsSb Infrared Superlattice Challenges: A Theoretical Investigation

Journal

JOURNAL OF ELECTRONIC MATERIALS
Volume 49, Issue 11, Pages 6936-6945

Publisher

SPRINGER
DOI: 10.1007/s11664-020-08349-7

Keywords

Infrared detector; unipolar barrier; type-II superlattice; InAs; InAsSbsuperlattice

Funding

  1. National Aeronautics and Space Administration [80NM0018D004]

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InAs/InAsSb type-II superlattice focal plane arrays that demonstrate high operability and uniformity with cutoffs ranging from 5 mu m to 13 mu m have already been demonstrated. Compared to InAs/GaSb, the InAs/InAsSb superlattice is easier to grow and has longer minority carrier lifetimes, but requires a longer superlattice period to achieve long or very long wavelength cutoffs. A longer type-II superlattice period leads to smaller absorption coefficients and larger growth-direction hole conductivity effective masses. We explore by theoretical modeling some of the ideas aimed at addressing these challenges for the long and very long wavelength InAs/InAsSb superlattice. Increasing the Sb fraction in the InAsSb alloy can reduce the InAs/InAsSb superlattice period significantly, but this benefit can be negated by Sb segregation. Thin AlAsSb barrier layers can be inserted in InAs/InAsSb to form polytype W, M, and N superlattices in order to increase electron-hole wavefunction overlap for stronger optical absorption. However, this strategy can be unfavorable since the AlAsSb barriers increase the band gap, and thereby increase the superlattice period required to reach a given cutoff wavelength. Metamorphic growth on virtual substrates with larger lattice constants than GaSb can decrease the superlattice period needed to reach a specified cutoff wavelength, but this benefit should be weighed against the need for metamorphic buffer growth and the resulting higher defect density.

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