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G4 2

Mg-doped p-type GaN is a core component of solid state white lighting or blue lasers optoelectronic devices. Despite the technological maturity of GaN, there is an inherent doping limit since above a certain concentration of substitutional Mg introduced during growth, it becomes interstitial. Using the b-emission channeling radioactive technique, we obtained direct evidence for the amphoteric nature of Mg [U.Wahl et al. PRL 118 (2017) 095501]. Recent detailed studies showed that above 400°C interstitial 27Mg progressively converts to substitutional Ga sites in all GaN doping types with migration activation energy estimated between 1.3 and 2.1 eV. These studies performed at the CTN EC-SLI unique setup mounted at the ISOLDE beam line provide a breakthrough understanding of the Mg behaviour in GaN suggesting that ion implantation and annealing can achieve higher p-type doping levels, as required for high power electronics.  Arrhenius curves plotted as a function of temperature, for interstitial 27Mg becoming substitutional at Ga sites in GaN for differently doped samples: top-left n-GaN:Si, top-right GaN (undoped), bottom-left GaN:Mg (as grown), bottom-right p-GaN:Mg.