Damage accumulation and structural modification in c-plane and a-plane GaN implanted with 400 keV Kr and Gd ions

GaN is the most actively studied wide-bandgap material, applicable e.g. in short-wavelength optoelectronic devices, high-electron-mobility transistors, and semiconductor lasers. The crystallographic orientation of an implanted crystal can significantly influence the optical properties of the implanted layer, reflecting the rearrangement of the crystal matrix after annealing. The annealing procedure, influencing dynamic recovery, point defect diffusion and large defect stabilisation, depending on the GaN crystal orientation and the used ion implantation parameters, is still an important issue to be studied. We have studied the structural and compositional changes of the GaN-epitaxial-layers of c-plane and a-plane orientations grown by MOVPE and implanted with Gd and Kr ions using the ion energy of 400 keV and ion fluences of 5 × 1014 cm-2, 1 × 1015 cm-2 and 5 × 1015 cm-2 with subsequent annealing at 800 °C in ammonia. Dopant depth profiling was accomplished by Rutherford backscattering spectrometry (RBS). Induced structure disorder and its recovery during subsequent annealing were characterised by RBS channelling and Raman spectroscopy. Ion-implanted c-plane and a-plane GaN exhibit significant differences in damage accumulation simultaneously with post-implantation annealing, inducing a different structural reorganization of the GaN structure in the buried layer depending on the introduced disorder level, i.e. depending on the ion-implantation fluence and ion mass.