The influence of annealing on manganese implanted GaAs films

Besides low-temperature molecular beam epitaxy, ion implantation provides an alternative route to incorporate Mn into GaAs above the equilibrium solubility limit. However, post-implantation annealing can lead to the formation of secondary phases. In the published papers concerning Mn implanted GaAs, diluted magnetic GaAs is only obtained by pulsed laser annealing. In order to compare the post-annealing effect, we investigate GaMnAs by implanting up to 6 at% Mn followed by rapid thermal and flashlamp annealing. The structural properties were probed by high resolution X-ray diffraction. The magnetic properties were determined by SQUID measurements. Auger electron spectroscopy has been used to profile the depth distribution of Mn in GaAs after implantation and annealing. We elucidate after implantation a loss of As and that during rapid thermal annealing most of the Mn diffuses towards the surface. Flash lamp annealing prevents out-diffusion, but the recrystalisation effciency is low. Only the flash lamp annealed samples reveal weak ferromagnetism.