Highly conductive ammonothermal GaN substrates with controlled concentration of gallium vacancies

Implantation of Ga ions into ammonothermal GaN crystals is proposed as a method of controlling the concentration of gallium vacancies. Ultra-high pressure annealing (UHPA) is expected to facilitate the diffusion of the implanted Ga ions into the entire volume of the crystal. Gallium vacancies are expected to be replaced by the Ga ions. Since Ga vacancies act as acceptors in GaN, reducing their content will result in a higher free electron concentration in the crystal. Gallium ion implantation and UHPA processes will be presented in detail. Values of the main parameters of UHPA allowing for the complete replacement of the Ga vacancies with Ga ions in GaN crystals will be determined. The morphology as well as structural, optical, and electrical properties will be compared for samples without any treatment and those implanted and annealed. The ultimate goal is to obtain highly conductive GaN crystals with the lowest possible Ga vacancy concentration.