UV-Raman scattering study of lattice recovery by thermal annealing of Eu+-implanted GaN layers

摘要

Lattice recovery of Eu-implanted GaN has been studied by means of Raman scattering under UV excitation. GaN epilayers implanted at 300 keV with doses ranging from 2 x 10(14) to 4 x 10(15) cm(-2) and subsequently annealed at 1000 degrees C for 20 min show an increasing degree of disorder as the implantation dose increases. Higher temperature annealings up to 1300 degrees C were also investigated in samples having an AlN capping layer. Disorder related modes, observed in samples annealed at 1000 degrees C, disappear at higher annealing temperatures, indicating an incomplete lattice recovery at 1000 degrees C. The Raman scattering spectra show resonant A(1)(LO) multiphonon scattering up to sixth order, whose relative intensities depend on the implantation dose. The intensity ratios between multiphonon peaks observed for the highest implantation doses suggest a spread of the resonance, which could be related to a heterogeneous strain distribution, also indicative of incomplete lattice recovery. (c) 2006 Elsevier Ltd. All rights reserved.