High Mg activation in implanted GaN by high temperature and ultrahigh pressure annealing

We demonstrate high p-type conductivity and hole concentrations >10(18)cm(-3) in Mg-implanted GaN. The implantation was performed at room temperature and by post-implantation annealing at 1GPa of N-2 and in a temperature range of 1200-1400 degrees C. The high pressure thermodynamically stabilized the GaN surface without the need of a capping layer. We introduce a diffusion budget, related to the diffusion length, as a convenient engineering parameter for comparing samples annealed at different temperatures and for different times. Although damage recovery, as measured by XRD, was achieved at relatively low diffusion budgets, these samples did not show p-type conductivity. Further analyses showed heavy compensation by the implantation-induced defects. Higher diffusion budgets resulted in a low Mg ionization energy (similar to 115meV) and almost complete Mg activation. For even higher diffusion budgets, we observed significant loss of Mg to the surface and a commensurate reduction in the hole conductivity. High compensation at low diffusion budgets and loss of Mg at high diffusion budgets present a unique challenge for shallow implants. A direct control of the formation of compensating defects arising from the implantation damage may be necessary to achieve both hole conductivity and low Mg diffusion.

Automated summary

This study demonstrates high p-type conductivity and hole concentrations in Mg-implanted GaN under different diffusion budgets, with Mg activation and loss affecting hole conductivity. The challenge lies in controlling compensating defects to achieve desired hole conductivity and low Mg diffusion.