A study of the vacancy-defect distribution in a GaAs/AlxGa1-xAs multi-layer structure grown at low temperature

S. Fleischer, C. Surya, Y. F. Hu, C. D. Beling, S. Fung, T. L. Smith, K. M. Moulding, M. Missous

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3 Citations (Scopus)


We have grown a multilayer structure of GaAs and AlxGa1-xAs (x = 0.25) by molecular beam epitaxy at low substrate temperature (250°C) in order to investigate the effects of annealing on arsenic precipitation and vacancy-defect formation. The as-grown heterostructure contained ∼5 × 1017 cm-3 gallium vacancies, but information about the individual layers was lost because the layer width ( ∼ 45 nm) was smaller than the average positron diffusion length ( ∼ 70 nm). Annealing at 500 and 600°C showed increases in the S-parameter (above the bulk value) of ∼2.5% and ∼1.5%, respectively, smaller than for a single LT-GaAs layer (∼3-4%). We explain this phenomenon by suggesting that the excess arsenic which migrates from the material with the higher precipitate/matrix energy (LT-AlxGa1-xAs) reduces the gallium vacancy concentration in the LT-GaAs and hence the S-parameter. This hypothesis is supported by SIMS data which shows a build-up of As in the LT-GaAs layers, and TEM images which indicate that arsenic precipitation occurs to a greater extent in the LT-GaAs than in the LT-AlxGa1-xAs.

Original languageEnglish
Pages (from-to)53-61
Number of pages9
JournalJournal of Crystal Growth
Issue number1
Publication statusPublished - Jan 1 1999
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

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