Temperature-Dependent Photoluminescence Studies of Ge$_{1-y}$Sn$_y$ ($y$ = 4.3%$-$9.0%) Grown on Ge-Buffered Si: Evidence for a Direct Bandgap Cross-Over Point
J. Korean Phys. Soc. 2019; 75: 577~585
Published online October 31, 2019 © 2019 The Korean Physical Society.


1Department of Physics, Kangwon National University, Chuncheon 24341, Korea
2Department of Engineering Physics, Air Force Institute of Technology, Ohio 45433, U.S.A.
3Department of Physics, Yeungnam University, Gyeongsan 38541, Korea
4School of Molecular Science, Arizona State University, Arizona 85287, U.S.A.
Correspondence to: Mee-Yi Ryu
Abstract
The temperature-dependent photoluminescence (PL) from Ge$_{1−y}$Sn$_y$ ($y$ = 4.3%–9.0%) alloys grown on Ge-buffered Si substrates was studied as a function of the Sn content. The PL from Ge1−ySny alloys with high Sn contents (≥7.0%) exhibited the typical characteristics of direct bandgap semiconductors. For the Ge$_{1−y}$Sn$_y$ alloys with low Sn contents (≤6.2%), the PL emission peaks corresponding to both the direct bandgap (ED) and the indirect bandgap (EID) PL appeared at most temperatures. The cross-over point for unstrained Ge$_{1−y}$Sn$_y$ was found to be about 6.4%–6.7% Sn by using linear fits to the data in the range of Sn contents from 0% to 9.0%.
PACS numbers: 78.55.-m, 68.55.ag, 81.15.Gh, 61.66.Dk
Keywords: Germanium tin, Alloys, Photoluminescence, Ultra-high vacuum chemical vapor deposition, Photoreflectance


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