Amorphization processes in Au ion irradiated GaN at 150-300 K

Epitaxial single-crystal gallium nitride (GaN) films on sapphire were irradiated at temperatures between 150 and 300 K using 1.0 MeV An(2+) ions over a range of fluences. The accumulation of disorder on the Ga sublattice has been investigated based on 2.0 MeV He+ RBS along the <0 0 0 1>-axial channeling direction. In general, the degree of disorder in the irradiated GaN increases at low doses and saturates at intermediate doses; at higher doses, a rapid amorphization process occurs as a result of the ingrowth of surface defects. Results from this study indicate that there may be a dynamic recovery stage on the Ga sublattice in GaN between 250 and 300 K. High-resolution TEM studies show that the microstructure in the disorder saturation stage contains a dense network of planar defects (basal-plane dislocation loops and stacking faults), while the more highly disordered regime includes amorphous domains and small crystalline zones that are randomly oriented. (C) 2003 Elsevier B.V. All rights reserved.