TY - JOUR
T1 - Compositional dependence of optical interband transition energies in GeSn and GeSiSn alloys
AU - Xu, Chi
AU - Senaratne, Charutha L.
AU - Kouvetakis, John
AU - Menendez, Jose
N1 - Funding Information:
This work was supported by the Air Force Office of Scientific Research under contracts DOD AFOSR FA9550-12-1-0208 and DOD AFOSR FA9550-13-1-0022.
Publisher Copyright:
© 2015 Elsevier Ltd. All rights reserved.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - The dielectric functions of GeSn and GeSiSn alloys were measured in the 1-6 eV energy range using spectroscopic ellipsometry. The contributions from the E1, E1 + Δ1, E0′, E2, and E1′ critical points in the joint density of electronic states were enhanced by computing numerical second derivatives of the measured dielectric function, and the resulting lineshapes were fitted with model expressions from which the critical point energies, amplitudes, broadenings, and phases were determined. A detailed analysis of the compositional dependence of the different transition energies is presented. By describing this dependence in terms of quadratic polynomials, the bowing parameter (quadratic coefficient) for each transition is determined. It is shown that the bowing parameters in the ternary alloy follow a distinct chemical trend, in which the ternary is well described in terms of bowing parameters for the underlying binary alloys, and these bowing parameters increase as a function of the size and electronegativity mismatch of the alloy constituents.
AB - The dielectric functions of GeSn and GeSiSn alloys were measured in the 1-6 eV energy range using spectroscopic ellipsometry. The contributions from the E1, E1 + Δ1, E0′, E2, and E1′ critical points in the joint density of electronic states were enhanced by computing numerical second derivatives of the measured dielectric function, and the resulting lineshapes were fitted with model expressions from which the critical point energies, amplitudes, broadenings, and phases were determined. A detailed analysis of the compositional dependence of the different transition energies is presented. By describing this dependence in terms of quadratic polynomials, the bowing parameter (quadratic coefficient) for each transition is determined. It is shown that the bowing parameters in the ternary alloy follow a distinct chemical trend, in which the ternary is well described in terms of bowing parameters for the underlying binary alloys, and these bowing parameters increase as a function of the size and electronegativity mismatch of the alloy constituents.
KW - Band structure
KW - Ellipsometry
KW - IR semiconductors
KW - SiGeSn alloys
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U2 - 10.1016/j.sse.2015.01.015
DO - 10.1016/j.sse.2015.01.015
M3 - Article
AN - SCOPUS:84940007760
SN - 0038-1101
VL - 110
SP - 76
EP - 82
JO - Solid-State Electronics
JF - Solid-State Electronics
ER -