Atomically sharp catalyst-free wurtzite GaAs∕AlGaAs nanoneedles grown on silicon

Abstract

We report a catalyst-free, self-assembled growth mode generating single-crystal wurtzite phase ultrasharp GaAs∕AlGaAs nanoneedles on both GaAs and Si substrates via low-temperature metal-organic chemical vapor deposition. The needles exhibit record-narrow tip diameters of 2–4nm wide and sharp 6°–9° taper angles. The length is dependent on growth time and up to 3–4μm nanoneedles are attained. The structures do not exhibit twinning defects, contrary to typical GaAs nanowires grown by vapor-liquid-solid catalyzed growth. AlGaAs layered nanoneedle structures are also demonstrated.