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

Abstract

Epitaxial single-crystal gallium nitride (GaN) films on sapphire were irradiated at temperatures between 150 and 300 K using 1.0 MeV Au 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.