Microscopic evidence of point defect incorporation in laterally overgrown GaN

Electron microscopy techniques are applied to investigate structural and optical properties of GaN layers selectively grown by hydride vapor phase epitaxy on crystalline GaN seed layers deposited on (0001)Al2O3 substrates. Regions with different optical properties are observed in the cross- sections of the layers. They are defined by the crystallographic planes that serve as growth facets. We give a simple geometrical explanation of point defect incorporation occurring more easily for the {11 (2) over bar2} GaN than for the {0001} GaN growth facets. Microscopic evidences supporting the model are higher concentrations of point-like defects and local strain variations in laterally grown regions that are revealed by high-resolution electron microscopy. (C) 2002 American Institute of Physics.