Extended x-ray absorption fine structure and photoluminescence study of Er-implanted GaN films

Extended x-ray absorption fine structure and photoluminescence studies were performed on epitaxial GaN films implanted with 1 x 10(16) cm(-2) Er ions at 80 and 160 keV and, for a part of the samples, co-implanted with oxygen ions at 23 keV, followed by an anneal for 60 min at 900 degreesC. It was shown for the samples both with, as well as without, oxygen co-implantation that Er is incorporated in a six-fold coordination with respect to oxygen, as in the cubic bixbyite structure Er2O3. The oxygen contamination of the non-oxygen-implanted samples is assumed to be due to nitrogen-vacancy-assisted oxygen diffusion from the sapphire substrate during annealing. The Stark level splitting of the I-4(15/2) ground state of Er3+ observed in the 1.54 mum photoluminescence at low temperature in both types of samples is consistent with the low symmetry of the Er sites expected in cubic bixbyite Er2O3.