Electron microscopic techniques were used to investigate the structural and optical properties of layers which had been selectively grown, using hydride vapor-phase epitaxy, onto crystalline GaN seed layers deposited on (00•1) Al2O3 substrates. Regions having different optical properties were observed on cross-sections of the layers. They were defined by the crystallographic planes that served as growth facets. A simple geometrical explanation was given for why point-defect incorporation occurred more easily for {11•2} GaN than for {00•1} GaN growth facets. The microscopic evidence which supported the model included higher concentrations of point-like defects and local strain variations in laterally grown regions, as 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