Effects of Supersaturation on the Crystal Structure of Gold Seeded III-V Nanowires

We present results that provide fundamental insights on how to experimentally tailor the planar defect density and even the crystal structure in III-V metal particle seeded nanowires, where zinc blende is the stable bulk crystal structure. We have grown GaP nanowires with metal-organic vapor phase epitaxy under different conditions: pulsing of the Ga source, and continuous growth with and without In background. The dominant crystal structure of the nanowires is zinc blende, which when grown under continuous conditions has a high density of twin planes perpendicular to the growth direction. Using pulsed growth, we observed that the twin plane separations were much longer than those observed for continuous growth with an In background. On the other hand, during continuous growth, under In-free conditions, a considerable amount of the wurtzite phase forms. We explain the importance of the In background during growth. With classical nucleation modeling we qualitatively relate the density of planar defects in a nanowire to the growth conditions. For low supersaturations, we predict a low twin plane density, consistent with our experimental observations of pulsed nanowire growth. In addition, we suggest that under certain conditions, it might be possible to grow wires with almost perfect wurtzite structure.