Boosting Hole Mobility in Coherently Strained [110]-Oriented Ge-Si Core-Shell Nanowires
S. Conesa-Boj (Eindhoven University of Technology, TU Delft - QN/Conesa-Boj Lab)
A. Li (TU Delft - QRD/Kouwenhoven Lab, Eindhoven University of Technology)
Sebastian Koelling (Eindhoven University of Technology)
M. Brauns (University of Twente)
J. Ridderbos (University of Twente)
T. T. Nguyen (University of Twente)
M.A. Verheijen (Student TU Delft)
P. M. Koenraad (Eindhoven University of Technology)
F. A. Zwanenburg (University of Twente)
E. P.A.M. Bakkers (TU Delft - QN/Bakkers Lab, Eindhoven University of Technology)
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Abstract
The ability of core-shell nanowires to overcome existing limitations of heterostructures is one of the key ingredients for the design of next generation devices. This requires a detailed understanding of the mechanism for strain relaxation in these systems in order to eliminate strain-induced defect formation and thus to boost important electronic properties such as carrier mobility. Here we demonstrate how the hole mobility of [110]-oriented Ge-Si core-shell nanowires can be substantially enhanced thanks to the realization of large band offset and coherent strain in the system, reaching values as high as 4200 cm2/(Vs) at 4 K and 1600 cm2/(Vs) at room temperature for high hole densities of 1019 cm-3. We present a direct correlation of (i) mobility, (ii) crystal direction, (iii) diameter, and (iv) coherent strain, all of which are extracted in our work for individual nanowires. Our results imply [110]-oriented Ge-Si core-shell nanowires as a promising candidate for future electronic and quantum transport devices.