Evaluation of threading dislocation densities in In- and N-face InN

The threading dislocation (TD) structure and density has been studied in In-and N-face InN films grown on GaN by plasma-assisted molecular beam epitaxy. The TD densities were determined by nondestructive x-ray diffraction rocking curve measurements in on-axis symmetric and off-axis skew symmetric geometries and calibrated by transmission electron microscopy measurements. TD densities were dominated by edge-type TDs with screw-component TDs accounting for less than 10% of the total TD density. A significant decrease in edge-type TD density was observed for In-face InN films grown at increasingly higher substrate temperatures. In-face InN films grown with excess In exhibited lower TD densities compared to films grown under N-rich conditions. The edge-type TD density of N-face InN films was independent of substrate temperature due to the higher allowable growth temperatures for N-face InN compared to In-face InN. TD densities in In-face InN also showed a strong dependence on film thickness. Films grown at a thickness of less than 1 mu m had higher TD densities compared with films grown thicker than 1 mu m. The lowest measured TD density for an In-face InN film was similar to 1.5 x 10(10)/cm(2) for 1 mu m thick films. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3319557]