Abstract
Cathodoluminescence (CL) and Photoluminescence (PL) of Eu-implanted zincblende-GaN (ZB-GaN:Eu) and wurtzite-GaN (W-GaN:Eu) are compared in order to investigate the optical activation of GaN by Eu. The EU3+ emission spectrum depends critically on the crystal structure of the GaN host; implantation and post-annealing at 800 degrees C partially converts implantation-damaged ZB-GaN:Eu to W-GaN:Eu. Selective excitation of PL at wavelengths below the ZB-GaN band edge reveals a new sharp emission line at 627 nm, together with a number of satellites, which we ascribe to ZB-GaN: Eu.