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Evolution of optical phonons in epitaxial Ge 1− y Sn y structures
Author(s) -
Kim Young Chan,
Lee Taegeon,
Ryu MeeYi,
Kouvetakis John,
Rho Heesuk
Publication year - 2020
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5986
Subject(s) - phonon , raman spectroscopy , germanium , raman scattering , materials science , wavenumber , epitaxy , relaxation (psychology) , analytical chemistry (journal) , crystallography , condensed matter physics , molecular physics , chemistry , layer (electronics) , optics , nanotechnology , physics , optoelectronics , psychology , social psychology , chromatography , silicon
We report polarized Raman scattering results of Ge 1− y Sn y ( 0 ≤ y ≤ 0.09 ) epitaxial layers grown on Ge‐buffered Si substrates. Polarized Raman spectra from the sample surfaces revealed strong Ge–Ge longitudinal optical (LO) phonon responses. The Ge–Ge LO(z) phonon wavenumber decreased systematically as the Sn content increased. Linear fitting results of the Ge–Ge LO(z) phonon wavenumber shifts as a function of Sn content suggested that a partial strain relaxation occurred in the Ge 1− y Sn y layers. Spatially resolved Raman mapping measurements from the cross section of a Ge 0.938 Sn 0.062 samplev showed that the peak wavenumber of the Ge–Ge transverse optical phonon decreased gradually toward the top surface, providing direct evidence that the residual built‐in strain initially formed at the Ge 0.938 Sn 0.062 /Ge interface tended to relax gradually along the growth direction. Further, a hydrogen inductively coupled plasma treatment induced a greater homogeneous strain profile in the Ge 0.938 Sn 0.062 layer.