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Title: Strain-Mediated Sn Incorporation and Segregation in Compositionally Graded Ge1–xSnx Epilayers Grown by MBE at Different Temperatures

Journal Article · · Crystal Growth and Design
ORCiD logo [1];  [1]; ORCiD logo [1];  [2];  [1];  [1]; ORCiD logo [1];  [1];  [1]
  1. University of Arkansas, Fayetteville, AR (United States)
  2. University of Alabama, Tuscaloosa, AL (United States)
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We investigated the process of Sn incorporation and surface segregation for compositionally graded Ge1–xSnx epilayers grown on high-quality Ge (001) substrates. Here, the growth resulted in pseudomorphic GeSn layers with a ~6% maximal Sn fraction at a constant substrate temperature. The maximal fraction of Sn was increased to 9.0% when the growth temperature was continuously lowered while increasing the Sn flux. The analysis of surface droplets and SIMS profiles of elemental composition give evidence of Sn rejection during the growth, potentially associated with a critical energy of elastic strain. The intentional reduction of the coherent strain by decreasing the Sn flux near the sample surface has been shown to trap a higher fraction of Sn in the Ge1–xSnx layer and lower surface segregation. Our results demonstrate that strain relief by misfit dislocations in the compositionally graded layer is inhibited, which leads to Sn segregation. Specifically, the compressive strain in the graded Ge1–xSnx epilayer is effectively “zero” near the interface with the Ge substrate and increases up to about –1.5 × 10–2 near the surface. Thus, although the nucleation of a dislocation may reduce the compressive strain for the top region of the epilayer, it is not beneficial for the bottom region.

Research Organization:
Univ. of Arkansas, Fayetteville, AR (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); US Air Force Office of Scientific Research (AFOSR)
Grant/Contract Number:
SC0023412; FA9550-19-1-0341
OSTI ID:
2203514
Journal Information:
Crystal Growth and Design, Vol. 23, Issue 11; ISSN 1528-7483
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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42 ENGINEERING
Diffraction
Epitaxy
Fluxes
Layers
Molecular structure