Critical Thickness of Atomically Ordered III-V Alloys

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The critical thickness model is modified with a general boundary energy that describes the change in bulk energy as a dislocation regularly alters the atomic structure of an ordered material. The model is evaluated for dislocations gliding through CuPt-ordered GaInP and GaInAs, where the boundary energy is negative and the boundary is stable. With ordering present, the critical thickness is significantly lowered and remains finite as the mismatch strain approaches zero. The reduction in critical thickness is most significant when the order parameter is greatest and the amount of misfit energy is low. The modified model is experimentally validated for low-misfit GaInP epilayers with varying order parameters using in situ wafer curvature and ex situ cathodoluminescence. With strong ordering, relaxation begins at a lower thickness and occurs at a greater rate, which is consistent with a lower critical thickness and increased glide force. Thus, atomic ordering is an important consideration for the stability of lattice-mismatched devices.

Original languageAmerican English
Article numberArticle No. 151903
Number of pages4
JournalApplied Physics Letters
Issue number15
StatePublished - 12 Oct 2015

Bibliographical note

Publisher Copyright:
© 2015 AIP Publishing LLC.

NREL Publication Number

  • NREL/JA-5J00-64874


  • atomic ordering
  • boundary energy
  • critical thickness
  • CuPt
  • dislocation
  • gallium indium arsenide (GaInAs)
  • gallium indium phosphide (GaInP)
  • glide force
  • relaxation


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