Crystal structure of branched epitaxial III-V nanotrees

In this review we discuss the morphology and crystal structure of branched epitaxial III-V semiconductor structures, so called nanotrees, based on our own work with GaP, InAs and GaP/InP. These structures are formed by epitaxial growth in a step-wise procedure where each level can be individually controlled in terms of diameter, length and composition. Poly-typism is commonly observed for III-Vs with zinc blende, wurtzite or combinations thereof as the resulting crystal structure. Here we review GaP as an example of zinc blende and InAs of wurtzite type of growth in terms of nanotrees with two to three levels of growth. Included are also previously unpublished results on the growth of GaP/InP nanotrees to demonstrate effects of heteroepitaxial growth with substantial mismatch. For these structures a topotaxial growth behavior was observed with InP wires crawling along or spiraling around the GaP nanowires acting as a free-standing substrates.