Damage accumulation and structural modification in a‐ and c‐plane GaN implanted with 400‐keV and 5‐MeV Au⁺ ions

Abstract

c‐plane (0001) and a‐plane (11‐20) gallium nitride (GaN) epitaxial layers were grown by Metal organic Vapour Phase epitaxy (MOVPE) on sapphire and subsequently implanted with 400‐keV and 5‐MeV Au+ ions using fluences 5 × 1014 to 5 × 1015 cm−2. The shallow Au depth profiling was accomplished by Rutherford backscattering spectrometry. The structural changes during implantation and subsequent annealing were characterised by Rutherford backscattering spectrometry channelling and Raman spectroscopy. The interplay between nuclear and electronic stopping, influencing defect accumulation, was monitored and discussed depending on GaN orientation. Post‐implantation annealing induced a structural reorganisation of the GaN structure depending on the ion‐implantation fluence, ion energy, and on the crystallographic orientation.

High energy Au+ ion implantation of polar and nonpolar ZnO—Structure modification and optical properties

“…Raman spectroscopy follows the longitudinal and transverse vibrations of Zn and O‐sublattices, which could be influenced by heavy dopant incorporation and oxygen rearrangement. Concerning the right‐hand shoulder at the E 2 low phonon (see Figure 2), similar results were obtained in Li et al 21 where the authors observed a low‐frequency shoulder at the E 2 low phonon caused by the substitutional disorder, whose intensity increased with increasing Ag concentration in the ZnO lattice; this effect could also be presumed for Au ions, however it was shown that Au is not entering subsitutional positions in wurtzite structure to the higher extent 22. Thus this phenomenon is more likely connected to selection rules relaxation.…”

“…Thermally more stable and persistent damage was also observed in the past in a ‐plane GaN after annealing in N 2. 20,22 Oxygen rearrangement after annealing has been confirmed with Raman spectroscopy in all ZnO orientations; it could be connected to DLE reduction and a shift to higher wavelengths.…”

“…The rise of E 1 (LO) and A 1 (LO) phonons is attributable to oxygen rearrangement in the ZnO structure, 20 which appeared mainly in nonpolar ( a ‐plane and m ‐plane) ZnO orientations after Au implantation. The broadening of the band around the A 1 (LO) phonon mode can be attributed to scattering contributions of the A 1 (LO) phonon branch outside the Brillouin zone centre 22,23 …”

“…The broadening of the band around the A 1 (LO) phonon mode can be attributed to scattering contributions of the A 1 (LO) phonon branch outside the Brillouin zone centre. 22,23 The influence of annealing on ZnO structural recovery is presented for the higher ion fluence only in c-plane, a-plane and m-plane…”

Measuring strain caused by ion implantation in GaN

“…For higher fluences the formation of extended defects such as stacking faults and dislocation loops sets in [25]. Furthermore, for the highest fluence the RDL is considerably higher in c-GaN than in a-GaN, a fact that has been previously seen for Ar implantation at low temperature [25] as well as for rare earth implantation at room temperature [33,34]. Figure 1 -Relative defect level profiles derived from the RBS/C spectra using a two-beam model for both planar orientations.…”