Channeling study of lattice disorder and gold implants in gallium nitride

Abstract

Irradiation experiments have been performed 60° off normal for a gallium nitride (GaN) single-crystal film at 300 K using 3 MeV Au 3+ ions over fluences ranging from 0.88 to 86.2 ions/nm 2. The accumulation of disorder on both the Ga and N sublattices has been simultaneously investigated using 3.8 MeV He + non-Rutherford backscattering spectrometry (non-RBS) along the 〈0 0 0 1〉 and 〈1 0 1 ̄ 1〉 axial channeling directions. The accumulated disorder at the damage peak increases with dose below 10 dpa and saturates at a relative level of ∼0.7 between 10 and 60 dpa. Complete amorphization starts at the surface and grows into the damage peak regime. A higher rate of disordering on the N sublattice is observed at low damage levels, which suggests a lower threshold displacement energy on the N sublattice in GaN. Isochronal annealing (20 min) at temperatures up to 1000 K has been used to follow the thermal response of the Ga disorder and Au implants. Some defect recovery occurs at the intermediate damage levels. A fraction of Au occupancy on the Ga lattice site is observed in the as-implanted GaN, and the substitutional fraction of the implanted Au increases with increasing temperature.