Strategies to control morphology in hybrid group III-V/group IV heterostructure nanowires.

By combining in situ and ex situ transmission electron microscopy measurements, we examine the factors that control the morphology of "hybrid" nanowires that include group III-V and group IV materials. We focus on one materials pair, GaP/Si, for which we use a wide range of growth parameters. We show through video imaging that nanowire morphology depends on growth conditions, but that a general pattern emerges where either single kinks or inclined defects form some distance after the heterointerface. We show that pure Si nanowires can be made to exhibit the same kinks and defects by changing their droplet volume. From this we derive a model where droplet geometry drives growth morphology and discuss optimization strategies. We finally discuss morphology control for material pairs where the second material kinks immediately at the heterointerface and show that an interlayer between segments can enable the growth of unkinked hybrid nanowires.