Electron microscopy was used to investigate structural and optical properties of GaN layers selectively grown by hydride vapor phase epitaxy on crystalline GaN seed layers deposited on (00•1)Al2O3 substrates. Regions with different optical properties were observed in the cross- sections of the layers. They were defined by the crystallographic planes that serve as growth facets. A simple geometrical explanation was given for point defect incorporation occurring more easily for the {11•2} GaN than for the {00•1} GaN growth facets. Microscopic evidences supporting the model were higher concentrations of point-like defects and local strain variations in laterally grown regions that were revealed by high-resolution electron microscopy.

Microscopic Evidence of Point Defect Incorporation in Laterally Overgrown GaN. S.Gradečak, V.Wagner, M.Ilegems, T.Riemann, J.Christen, P.Stadelmann: Applied Physics Letters, 2002, 80[16], 2866-8