Thin films of GaN doped with manganese were grown on sapphire substrates by pulsed laser deposition. The deposition plasma was characterised using a Langmuir ion probe and the film growth process was monitored in situ using optical reflectometry. The films showed higher Mn concentrations than the target preparations, suggesting a loss of gallium during the growth process. Photoluminescence measurements carried out on pure and doped films showed a quenching of the blue-green luminescence with the inclusion of manganese. (C) 2002 Elsevier Science Ltd. All rights reserved.