Twins and strain relaxation in zinc-blende GaAs nanowires grown on silicon

Abstract

tTo integrate materials with large lattice mismatch as GaAs on silicon (Si) substrate, one possible approach,to improve the GaAs crystalline quality, is to use nanowires (NWs) technology. In the present contribution,NWs are grown on 111 oriented Si substrates by molecular beam epitaxy (MBE) using vapor-liquid-solid (VLS) method. Transmission electron microscopy (TEM) analyses show that NWs are mainly grownalternating wurtzite and zinc blend (ZB) phases, and only few are purely ZB. On the latter, High ResolutionElectron Microscopy (HREM) evidences the presence of twins near the surface of the NW showing limitedconcordance with the calculations of Yuan (2013) [1], where {111} twin planes in a 111 oriented GaAsNW attain attractive interactions mediated by surface strain. In addition, such twins allow slight strainrelaxation and are probably induced by the local huge elastic strain observed by HREM in the latticebetween the twin and the surface. The latter is attributed to some slight bending of the NW as shown bythe inversion of the strain from one side to the other side of the NW.