It was shown that epitaxial ZnO/(00•1) 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 . By continuing the ZnO growth hydrothermally, the nanorods grew laterally over the O-polar layer. threading dislocations 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 threading dislocation densities reduced to 1 x 109/cm2 from 7 x 1010/cm2 in the underlayer. It was noted that the same growth mode could be achieved in GaN/(00•1) sapphire films.

Defect Reduction by Epitaxial Lateral Overgrowth of Nanorods in ZnO/(0001) Sapphire Films. Cherns, D., Sun, Y.: Applied Physics Letters, 2008, 92[5], 051909