Structural characteristic of cubic GaN nucleation layers on GaAs(0 0 1) substrates by MOCVD

Abstract

The structural characteristic of cubic GaN (C-GaN) nucleation layers on GaAs(0 0 1) substrates by metalorganic chemical vapor deposition was in detail investigated first by X-ray diffraction (XRD) measurements, using a Huber five-circle diffractometer and an intense synchrotron X-ray source. The XRD results indicate that the C-GaN nucleation layers are highly crystallized. Φ scans and pole figures of the (1 1 1) reflections give a convincing proof that the GaN nucleation layers show exactly cubic symmetrical structure. The GaN(1 1 1) reflections at 54.74° in χ are a measurable component, however (0 0 2) components parallel to the substrate surface are not detected. Possible explanations are suggested. The pole figures of { 1 0 1 ̄ 0 } reflections from H-GaN inclusions show that the parasitic H-GaN originates from the C-GaN nucleation layers. The coherence lengths along the close-packed 〈1 1 1〉 directions estimated from the (1 1 1) peaks are nanometer order of magnitude.