Growth and Optical Properties of Direct Band Gap Ge/Ge0.87Sn0.13 Core/Shell Nanowire Arrays
S. Assali (Eindhoven University of Technology)
A. Dijkstra (Eindhoven University of Technology)
A. Li (Eindhoven University of Technology, Beijing University of Technology, TU Delft - QRD/Kouwenhoven Lab)
Sebastian Koelling (Eindhoven University of Technology)
M. A. Verheijen (Philips Innovation Labs, Eindhoven University of Technology)
L Gagliano (Eindhoven University of Technology)
N. Von Den Driesch (Forschungszentrum Jülich)
D. Buca (Forschungszentrum Jülich)
P. M. Koenraad (Eindhoven University of Technology)
J. E.M. Haverkort (Eindhoven University of Technology)
E. P.A.M. Bakkers (Eindhoven University of Technology, TU Delft - QN/Bakkers Lab)
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Abstract
Group IV semiconductor optoelectronic devices are now possible by using strain-free direct band gap GeSn alloys grown on a Ge/Si virtual substrate with Sn contents above 9%. Here, we demonstrate the growth of Ge/GeSn core/shell nanowire arrays with Sn incorporation up to 13% and without the formation of Sn clusters. The nanowire geometry promotes strain relaxation in the Ge0.87Sn0.13 shell and limits the formation of structural defects. This results in room-temperature photoluminescence centered at 0.465 eV and enhanced absorption above 98%. Therefore, direct band gap GeSn grown in a nanowire geometry holds promise as a low-cost and high-efficiency material for photodetectors operating in the short-wave infrared and thermal imaging devices.