Abrupt GaP/GaAs Interfaces in Self-Catalyzed Nanowires.

We achieve the self-catalyzed growth of pure GaP nanowires and GaAs1-xPx/GaAs1-yPy nanowire heterostructures by solid-source molecular beam epitaxy. Consecutive segments of nearly pure GaAs and GaP are fabricated by commuting the group V fluxes. We test different flux switching procedures and measure the corresponding interfacial composition profiles with atomic resolution using high-angle annular dark field scanning transmission electron microscopy. Interface abruptness is drastically improved by switching off all the molecular beam fluxes for a short time at the group V commutation. Finally, we demonstrate that the morphology of the growth front can be either flat or truncated, depending on the growth conditions. The method presented here allows for the facile synthesis of high quality GaP/GaAs axial heterostructures directly on Si (111) wafers.