N/Ge co-implantation into GaN for N-type doping

We have investigated the doping characteristics and Structural defects of N/Ge co-implanted GaN. N-type regions are produced in undoped GaN films by Ge and N/Ge implantation and subsequent annealing with an SiO2 encapsulation layer at 1300degreesC, Improved Ge-doping characteristics are achieved for GaN by N/Ge co-implantation, attaining activation efficiencies above 95%, whereas in the case of conventional Ge implantation, the activation efficiency is low due to the lack of N atoms for maintaining the GaN stoichiometry. From transmission electron microscopic observations, the damage induced by the co-implantation is entirely restored by annealing at 1300degreesC. However, positron annihilation spectroscopic measurements reveal the creation of new vacancy-type defects with markedly different characteristics in the electrically activated re-ion,, by the annealing of both Ge- and N/Ge-implanted samples.