The dependence of the radiation damage formation on the substrate implant temperature in GaN during Mg ion implantation

In pursuit of p-type doping, we have implanted GaN with Mg ions at 200 and 500 keV with the substrate temperature maintained at -150 (cold) or +300 degrees C (hot) during ion irradiation. The samples have been annealed at 1000 degrees C postion implantation. The radiation damage peak position (and its profile), the dopant distribution, and the damage stability during annealing were all shown to be dependent upon the GaN substrate temperature during implantation. The damage peak position in the solid was reduced for cold implantation. The dopant distribution in the solid depends upon the implant temperature and in agreement with the damage measurements, the Mg range is shallower in GaN for cold implants when compared to hot implants. The trends observed suggest that the dynamic defect annealing fate during irradiation is reduced for cold implantation, and the subsequent increase in the damage level (scattering centers) formed during the damage buildup reduces the ion range in the solid. In turn, the reduced ion range subsequently limits the final damage range. The rate of damage removal during thermal annealing in the samples implanted at cold temperature was increased: this is explained by the greater complexity of defects caused during high-temperature implantation, due to the raised level of dynamic defect annealing.