X-ray absorption fine structure study of In implanted GaN: Effect of annealing

GaN implanted with 700 keV In ions with fluence 5 × 1015 cm−2 is studied using X-ray absorption fine structure (XAFS) spectroscopies at the N and Ga K edges. Rutherford backscattering (RBS) reveals that implantation renders the top 200 nm of the GaN film amorphous while the underlying 250 nm of the film are highly defective. The increase of the static disorder due to the implantation induced lattice damage is evident both in the N K edge NEXAFS and the Ga K edge EXAFS spectra. Indium implantation also induces the formation of N2 evinced by the evolution of a sharp resonance line (RL) that corresponds to 1s → π* transitions of molecular nitrogen. The N2 molecules dissociate after annealing at temperatures higher than 800 °C. The bonding environment of Ga is also affected by the implantation and annealing: a marginal increase of the Ga–Ga distance is observed due to the incorporation of In atoms and/or formation of defects. The coordination number of the second nearest neighboring (NN) shell is reduced by more than 50% after the implantation but recovers after annealing at 800 °C. Further increase of the annealing temperature causes nitrogen loss as it is deduced by the reduction of the coordination number in the first NN shell by about 20%.