Bidirectional growth of indium phosphide nanowires.

We present a bidirectional growth mode of InP nanowires grown by selective-area metalorganic vapor-phase epitaxy (SA-MOVPE). We studied the effect of the supply ratio of DEZn ([DEZn]) on InP grown structure morphology and crystal structures during the SA-MOVPE. Two growth regimes were observed in the investigated range of the [DEZn] on an InP(111)B substrate. At low [DEZn], grown structures formed tripod structures featuring three nanowires branched toward the [111]A directions. At high [DEZn], we obtained hexagonal pillar-type structures vertically grown on the (111)B substrate. These results show that the growth direction changes from [111]A to [111]B as [DEZn] is increased. We propose a growth mechanism based on the correlation between the incident facet of rotational twins and the shapes of the grown structures. Our results bring us one step closer to controlling the direction of nanowires on a Si substrate that has a nonpolar nature. They can also be applied to the development of InP nanowire devices.