Impact of rapid thermal annealing on Mg-implanted GaN with a SiO x/AlN cap-layer.

Local p-type doping in GaN is a key issue for device development but it remains a challenge to be achieved. In this work, we studied the activation of Mg implanted in the GaN. Multi-energy implantations were performed to achieve a 'box-like' profile. SIMS measurements showed unexpected deep Mg profile due to defect-assisted channeling in the GaN. In addition, a high-density defect region induced by the implantation was evidenced by TEM characterization. To protect the GaN surface prior to high temperature annealing, an AlN cap-layer was deposited by reactive sputtering followed by SiO _x deposition leading to a double cap-layer. Afterwards, the capped samples were RTA-annealed at high temperatures for several minutes under nitrogen. Two types of annealing processes were applied: a monocycle and a multicycle annealing. After annealing, the double cap-layer was etched using chemical solutions. AFM characterizations, after annealing and cap-layer etching, demonstrated that a GaN surface with similar roughness to as-grown samples and pit-free can be achieved after both monocycle and multicycle annealing steps. However, an AlGaN layer at the AlN/GaN interface is observed by ToF-SIMS and remained after the etching of the AlN layer. Finally, Schottky diodes were processed on the unimplanted and annealed samples, evidencing a double barrier, while P/N junction diodes are still being processed on the implanted and annealed samples. [ABSTRACT FROM AUTHOR]