Toward high-conductivity N-polar p-GaN: coordinated control of growth pressure and annealing temperature

Low Mg acceptor activation efficiency, compensation by donor-like defects, and high resistivity remain major obstacles for N-polar p-GaN. Here, we investigate how MOCVD growth pressure and in situ annealing temperature affect the electrical, optical, structural, and morphological properties of N-polar p-GaN. Increasing the growth pressure from 150 to 300 mbar improves conductivity and suppresses blue-related luminescence associated with deep-level recombination. SIMS measurements reveal simultaneous decreases in Mg and C concentrations, indicating that the enhanced hole concentration is associated with reduced compensation and improved electrical effectiveness of incorporated Mg. At 375 mbar, further reduced Mg incorporation and deteriorated crystalline quality are associated with electrical degradation. For samples grown at 300 mbar, increasing the annealing temperature to 900 °C increases the hole concentration to 7.34 × 10 17 cm −3 and reduces the resistivity to 0.96 Ω · cm. The accompanying decrease in H concentration supports thermally promoted Mg–H dissociation and enhanced effective Mg acceptor activation. Further annealing at 960 °C causes pronounced surface roughening and electrical degradation. These results identify a practical process window for high-conductivity N-polar p-GaN.