A detailed microphotoluminescence study was made of the long-range strain fields surrounding threading dislocations as well as their interaction and pattern formation in GaN bulk crystals. The stress patterns were detected by tiny energy shifts of the near-band-edge spectral lines and showed a dipole-like stress state around the dislocation core of edge- or mixed-type dislocations, with an angular orientation coinciding with high-symmetry crystal directions. Tens of μm-long linear line-ups of edge dislocations having marked effects upon the local strain states and photoluminescence peak positions were detected. With continuum elastic strain simulations, it was demonstrated that the observed patterns of threading dislocations were energetically favorable. Calculations were made of the binding energy per threading dislocation length of 50meV/µm against gliding of an edge dislocation within a line-up of edge dislocations of parallel Burgers vector orientation.

Pattern Formation and Directional and Spatial Ordering of Edge Dislocations in Bulk GaN - Microphotoluminescence Spectra and Continuum Elastic Calculations. N.Gmeinwieser, U.T.Schwarz: Physical Review B, 2007, 75[24], 245213 (7pp)