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

• DOI: 10.1021/acs.nanolett.6b04891
• Publication Date: 2017-02-23T18:48:31Z
• Authors: S. Conesa-Boj; A. Li; S. Koelling; M. Brauns; J. Ridderbos; T. T. Nguyen; M. A. Verheijen; P. M. Koenraad; F. A. Zwanenburg; E. P. A. M. Bakkers
• Keywords: Mobility; Silicon; Germanium; epitaxy; silicon; 02 engineering and technology; mobility; Defect-free; Nanowire; germanium; defect-free; 0210 nano-technology; Epitaxy

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.