Vacancy‐Type Defects in N‐Implanted GaN and Their Impact on Mg Diffusion Studied by a Monoenergetic Positron Beam

Annealing behavior of vacancies in N‐ and Mg‐implanted GaN was studied using a monoenergetic positron beam. For N‐implanted GaN after ultrahigh‐pressure annealing at 1100 °C, the major defect species were identified as vacancy‐type defects coupled with hydrogen atoms (such as H‐V Ga V N , V Ga : Ga‐vacancy, V N : N‐vacancy). The positron trapping rate of vacancies was increased by illumination at photon energies above 1.5 eV, which was attributed to electron capture by vacancy complexes, resulting in a charge transfer of the defects from positive to neutral (or neutral to negative). The illumination‐active defects consisted of more V N than detectable vacancy complexes in darkness. For Mg‐implanted GaN with sequential N‐implantation, the diffusion property of Mg depended on the N implantation doses. The sequential N implantation caused recombination of vacancy complexes with excess N, which resulted in the reduction of the size of vacancies. This modification of vacancy species was attributed to the origin of suppressed Mg migration in the vacancy‐rich region.