Annealing Behavior of Vacancy-Type Defects in Mg- and H-Implanted GaN Studied Using Monoenergetic Positron Beams

Vacancy-type defects in Mg-implanted GaN with and without hydrogen (H) implantation are probed by using monoenergetic positron beams. Mg⁺ and H⁺ ions are implanted into GaN(000 (Formula presented.)) to obtain 0.1 and 0.7-µm-deep box profiles with Mg and H concentrations of 1 × 10¹⁹ and 2 × 10²⁰ cm⁻³, respectively. For the as-implanted samples, the major defect species is determined to be Ga-vacancy (V_Ga) related defects such as V_Ga, divacancy (V_GaV_N), and their complexes with impurities. For Mg-implanted samples, an agglomeration of vacancies starts at 800 °C annealing, leading to the formation of vacancy clusters such as (V_GaV_N)₃. For the samples annealed above 1000 °C, the trapping rate of positrons by vacancies is increased by illumination of a He–Cd laser. This is attributed to the capture of photon-excited electrons by the defects and their charge transition. For Mg- and H-implanted samples, the hydrogenation of vacancy-type defects starts after 800 °C annealing. Comparing with the annealing behavior of defects for the samples without H-implantation, the clustering of vacancy-type defects is suppressed, which can be attributed to the interaction between Mg, H, and vacancies.