Boosting Hole Mobility in Coherently Strained [110]-Oriented Ge-Si Core-Shell Nanowires.

Conesa-Boj, S; Li, A; Koelling, S; Brauns, M; Ridderbos, J; Nguyen, T T; Verheijen, M A; Koenraad, P M et al. · Nano Lett · 2017

basic_science · Level V

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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 cm<sup>2</sup>/(Vs) at 4 K and 1600 cm<sup>2</sup>/(Vs) at room temperature for high hole densities of 10<sup>19</sup> cm<sup>-3</sup>. 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.