Er-defect complexes and isolated Er center spectroscopy in Er-implanted GaN

Photoluminescence (PL), photoluminescence excitation (PLE) spectra and luminescence decay of the Er3+ I-4(13/2) --> I-4(15/2) transition are investigated at 7 K in Er-implanted GaN samples. Under below-gap excitation, PL and PLE spectra reveal the existence of two types of Er centers. One type of Er center which can only be excited by resonant intra 4f shell transition is predominant while other Er centers are clearly excited via local defects. Evolution of Er luminescence as a function of implantation dose and implantation geometry is presented for both types of Er centers. Luminescence dynamics study shows that the I-4(13/2) manifold has a shorter lifetime (tau similar to 1 ms) when Er ions are part of Er-defect complexes than when Er ions are isolated from any defect (tau = 3.8 ms). This result indicates the existence of non-radiative energy transfers in Er-defect complexes from Er ions towards defects or impurities. Er decay in Er-defect complexes is then successfully compared with classical energy transfer models. (C) 2003 Elsevier B.V. All rights reserved.