Nanoscale GaN whiskers fabricated by photoelectrochemical etching

GaN whiskers with nanoscale dimensions have been fabricated by photoelectrochemical (PEC) etching in dilute H3PO4 electrolyte. Etching in lower concentration H3PO4 electrolyte for 1 h or for a short time of 5 min at a higher concentration results in individual whiskers with a density of similar to2x10(9)cm(-2) and diameters to 15nm. It is observed that similar to10% of them have formed nearly perfect hexagonal plates on the top of the whiskers, which appear to evolve into flowerlike features upon extended etching to 12 min. Such hexagonal plates have not been reported previously in the PEC etching of GaN. The presence of a dislocation along the central axis of the needles is clearly demonstrated, and the etch pattern is suggested to be related to the growth mechanism for GaN on sapphire. When etched for times >30 min, these whiskers are typically arranged in clusters with a density of 2-5x10(7)cm(-2) and have ten or more whiskers contributing to the central top of the cluster. (C) 2004 American Institute of Physics.