Boosting hole mobility in coherently strained [110]-oriented Ge-Si core-shell nanowires

Abstract

\u3cp\u3eThe 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\u3csup\u3e2\u3c/sup\u3e/(Vs) at 4 K and 1600 cm\u3csup\u3e2\u3c/sup\u3e/(Vs) at room temperature for high hole densities of 10\u3csup\u3e19\u3c/sup\u3e cm\u3csup\u3e-3\u3c/sup\u3e. 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.\u3c/p\u3