Control of nucleation site density of GaN nanowires

The control of nucleation site size and density for Au catalyst-driven growth of GaN nanowires is reported. By using initial Au film thicknesses of 15-50 Å we have shown that annealing between 300 and 900 °C creates Au cluster size in the range 30-100 nm diameter with a cluster density from 300 to 3500 μm⁻².Conventional optical lithography to create parallel Au stripes shoes that a minimum separation of ∼15 μm is needed to avoid overlap of wires onto neighboring lines with our growth conditions that yield wires of this same length. The GaN nanowires exhibit strong band-edge photoluminescence and total resistances of 1.2 × 10⁸-5.5 × 10⁶ Ω in the temperature range from 240 to 400 K, as determined for the temperature-dependent current-voltage characteristics.