Growth and properties of m-plane GaN on m-plane sapphire by metalorganic chemical vapor deposition

A characterization study of heteroepitaxial grown m-plane GaN on m-plane sapphire substrates by MOCVD was undertaken. Using X-ray diffraction and photoluminescence, the growth characteristics and epi-layer properties of m-GaN layers were investigated with special emphasis on the role of AlN buffer layers in preventing unintentional nitridation prior to GaN deposition. Substrate nitridation was found to lead to undesirable crystallographic orientations. In-plane lattice parameters of m-GaN obtained from X-ray reciprocal space mapping indicate anisotropic residual strain is present in these layers even under optimized growth conditions. Compressive and tensile strains were observed along either [0001] or [112̄0] directions, depending on AlN buffer layer conditions and the presence of extended structural defects. In addition, extended structural defects commonly observed in GaN showed a significant effect on stacking fault related luminescence in m-GaN.

► m-GaN was grown on m-plane sapphire by MOCVD using a low temperature AlN buffer.
► m-GaN properties were studied by X-ray diffraction and photoluminescence.
► Lattice mismatch parameters were measured by XRD reciprocal space maps.
► Dislocations and stacking faults were estimated from XRD rocking curve broadening.
► Extended structural defects in m-GaN showed a significant effect on luminescence.