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

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 2-4 nm wide and sharp 6 degrees-9 degrees taper angles. The length is dependent on growth time and up to 3-4 mu m 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. (C) 2008 American Institute of Physics.