Deep-UV LEDs fabricated on AlN/sapphire templates with low screw dislocation density

To fabricate deep-ultraviolet (DUV) LEDs with high efficiency, the crystallinity of AlGaN must be improved, which is strongly influenced by the quality of the underlying AlN template. Face-to-face annealed sputter-deposited AlN templates (FFA Sp-AlN) on sapphire substrates have achieved screw and edge threading dislocation densities (TDDs) as low as 10⁴cm⁻² and 10⁷cm⁻², respectively. The reduction of TDDs in FFA Sp-AlN and the resulting surface flattening of AlₓGa₁₋ₓN layers grown on it play critical roles in enhancing the external quantum efficiency (EQE). Following MOVPE homoepitaxial AlN growth, the FFA Sp-AlN exhibits an atomically smooth surface morphology. The EQE of UV-C LEDs fabricated on FFA Sp-AlN increased as the TDDs decreased. A maximum EQE of 8.0% and output power of 6.6mW at a 20mA injection current were achieved, with a peak emission wavelength of 263nm. Furthermore, we successfully fabricated LEDs with emission wavelengths of 230nm and 236nm on FFA Sp-AlN templates.