Optical properties of neodymium ions in nanoscale regions of gallium nitride

Wide bandgap semiconductors are increasingly important for bioimaging applications, as they can possess good biocompatibility and host a large range of fluorescent defects spanning the visible to infrared. Gallium nitride is one promising host for photostable fluorophores. In particular, neodymium (Nd)-doped gallium nitride (GaN) shows bright near-infrared fluorescence and narrow room temperature linewidth and is therefore a candidate material for fluorescent probes for bioimaging. To explore the conditions necessary to generate biomarkers based on Nd:GaN, this paper reports the room temperature photoluminescence (FL) properties of small ensembles of Nd ions implanted into the nanoscale regions of GaN epilayers. The minimum volume of Nd-implanted GaN that can be optically detected in this study is about 8x10(4) nm(3) and the minimum detected ensemble of Nd ions is about 4x10(3), although not all of implanted Nd ions activate as luminescence centers. We show from the PL excitation spectra that the strongest resonant excitation appears at 619 nm, attributed to the I-4(9/2) -> (4)G(5/2) ((4)G(7/)(2)) transition in the 4f-shell. We measure the luminescence lifetime to be several tens of microseconds. We also identify the presence of a different excitation mechanism from the resonant excitation when excited below 510 nm (above 2.43 eV). (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement