Characterization of as-grown and ion-implanted GaN by photoluminescence and photoluminescence excitation spectroscopy

Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy have been used to characterize as-grown and ion-implanted epitaxial films of GaN grown on sapphire and SiC substrates by MOCVD, and on sapphire substrates by HVPE. Our studies have included a variety of near-band edge PL bands and deeper PL bands such as the ubiquitous yellow band which is present at varying strength in most as-grown films of GaN, and several types of deep emission bands introduced by the implantation of Er, Cr, and isovalent impurities such as As and P. PLE spectroscopy of the deep PL bands such as the yellow band, the broad implantation-induced defect bands, and the intra-f-shell emissions of Er/sup 3+/ been used to detect extrinsic (below gap) absorption bands due to defects and impurities over an extremely broad spectral range. Comparison of the PLE spectra of these deep PL bands and the temperature dependences of the PL and PLE spectra provide new insights concerning the competing excitation and recombination mechanisms for the deep centers in as-grown and ion-implanted GaN.