Molecular beam epitaxy and structural anisotropy of m-plane InN grown on free-standing GaN

This study reports on the growth of high-quality nonpolar m-plane [1 (1) over bar 00] InN films on free-standing m-plane GaN substrates by plasma-assisted molecular beam epitaxy. Optimized growth conditions (In/ N ratio similar to 1 and T= 390-430 degrees C) yielded very smooth InN films with undulated features elongated along the [11 (2) over bar 20] orientation. This directionality is associated with the underlying defect structure shown by the anisotropy of x- ray rocking curve widths parallel to the [11 (2) over bar0] (i. e., 0.24 degrees- 0.34 degrees) and [0001] (i. e., 1.2 degrees-2.7 degrees) orientations. Williamson-Hall analysis and transmission electron microscopy identified the mosaic tilt and lateral coherence length and their associations with different densities of dislocations and basal-plane stacking faults. Ultimately, very low band gap energies of similar to 0.67 eV were measured by optical absorption similar to the best c-plane InN. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3001806]