Low-dislocation, high-crystal-quality Si-doped AlN on 6-inch sapphire via plasma-seeded pulsed epitaxy

Aluminum nitride (AlN), a wide-bandgap semiconductor, is widely used in advanced power electronics, deep-ultraviolet optoelectronics, and high-frequency acoustic devices. However, high-quality AlN epitaxy on large-area sapphire substrates remains challenging due to high dislocation density, residual stress, and doping-induced strain in conventional metal-organic chemical vapor deposition (MOCVD). In this work, we propose a Plasma-Seeded Pulsed Epitaxy (PSPE) strategy based on conventional low-temperature MOCVD equipment. By controlling nucleation behavior, growth mode, and defect evolution, we successfully fabricated 6-in., low-dislocation Si-doped AlN on sapphire. Compared with the control sample prepared without PSPE, the Si-doped AlN exhibited significantly improved crystal quality: surface roughness was reduced to 1.17 nm (30% reduction), average stress was reduced to −0.129 GPa (57% reduction), and the densities of screw and edge dislocations were reduced to 9.2 × 107 cm−2 (84.7% reduction) and 1.8 × 109 cm−2 (96.0% reduction), respectively. HRTEM further reveals that the PSPE strategy relieves interfacial lattice mismatch while promoting dislocation turning and annihilation. Based on this high-quality AlN, p-Si/AlN PN diodes with a high rectification ratio (106), low leakage current (10−12 A), high breakdown voltage (500–650 V), and good electrical stability were successfully fabricated, providing a practical approach for achieving high-quality AlN epitaxy and device fabrication on traditional MOCVD systems.