263 nm wavelength UV-C LED on face-to-face annealed sputter-deposited AlN with low screw- and mixed-type dislocation densities

Abstract Regarding deep-ultraviolet optical device applications, face-to-face annealed sputter-deposited AlN (FFA Sp-AlN) is a promising alternative to the conventional metalorganic vapor phase epitaxy (MOVPE)-prepared AlN templates on sapphire substrates. However, FFA Sp-AlN tends to exhibit AlGaN growth-related hillock generation and surface morphology deterioration. In this study, we optimized the sputter-deposition conditions for AlN and MOVPE growth conditions for AlGaN to respectively reduce hillock density and size. After confirming AlGaN surface-flattening, we fabricated 263 nm wavelength UV-C LEDs on the FFA Sp-AlN and achieved maximum external quantum efficiencies of approximately 4.9% and 8.0% without and with silicone encapsulation, respectively.