Diffusion and Aggregation of Mg Implanted in GaN on Si

We have studied the influence of thermal treatments on the redistribution of Mg implanted in GaN on Si. SIMS results highlights the strong effect of Mg concentration on its diffusion behaviour. In the range of 1018 at/cm3 or below, the Mg distribution is not modified after annealing up to 1100°C. In the order of 1019 at/cm3 or higher, such thermal treatment lead to fast diffusion of the implanted Mg in the [0001] direction and a trapping of the Mg at the GaN/capping layer interface. AFM analysis of the GaN surface after capping etching suggest that emerging dislocations are favourable diffusion path for Mg toward the GaN surface. APT analysis reveals that this diffusion behavior go-on with the formation of Mg rich clusters containing about typically a hundred atoms in our process conditions. This diffusion and aggregation behaviors are specific to the Mg specie and have to be taken into account to expect successful integration of p type doping process via Mg implantation in GaN on Si.