Spectroscopic investigation of implanted epilayers of Tm3+:GaN

Two sets of GaN epilayers grown by using the MOCVD technique were implanted with different doses of Tm3+ ions ranging from 1x1015 to 10x1015 at cm-2 at various temperatures from 100 to 500 deg. C. After annealing, photoluminescence (PL) and PL excitation (PLE) spectra were recorded at 12 K by exciting the samples below and above the bandgap. An analysis of PLE spectra recorded around 800 nm reveals the existence of three distinct incorporation sites of Tm3+ ions, namely isolated Tm3+ ions, Tm3+ ions coupled to carrier traps and Tm3+ clusters. For the above bandgap excitation, two different Tm3+ sites coupled to carrier traps appear to be involved