Implantation of N ions on sapphire substrate for improvement of GaN epilayer

In an effort to improve the initial nucleation and crystal quality of the GaN epilayer, N-ion implantation on the sapphire (0001) substrate has been attempted. As a result of implantation with 55 keV nitrogen ions (N⁺), to a dose ranging from 1 × 10¹⁵ to 1 × 10¹⁷ cm^-2, prior to GaN epilayer growth, the formation of a thin and disordered AlN phase was observed. The presence of the N-ion-implanted surface decreased internal free energies in the growth of the GaN epilayer, and the misfit strain was relieved to allow the formation of the AlN phase on the N-ion-implanted sapphire substrate. Through the estimation of the lattice strain value for GaN epilayers, it was confirmed that the reduction of strain was achieved with the N-ion-implanted surface with the ion dose of 1 × 10¹⁶ cm^-2. The present results show that N-ion implantation of the sapphire (0001) surface can improve the properties of GaN epilayers grown by metalorganic chemical vapor deposition (MOCVD).