Defect reduction by epitaxial lateral overgrowth of nanorods in ZnO/(0001) sapphire films

It is shown that epitaxial ZnO/(0001) sapphire films grown by pulsed laser deposition have defect-free Zn-polar nanorods protruding from a continuous O-polar underlayer containing high densities of threading dislocations (TDs). By continuing the ZnO growth hydrothermally, the nanorods grew laterally over the O-polar layer. TDs in the underlayer were thereby blocked and only formed in the overlayer when nanorods coalesced. This epitaxial lateral overgrowth produced continuous Zn-polar films with TD densities reduced to 1x10(9)/cm(2) from 7x10(10)/cm(2) in the underlayer. It is noted that the same growth mode can be achieved in GaN/(0001) sapphire films. (c) 2008 American Institute of Physics.