Fabrication of Low-Dislocation-Density AlN Templates for Deep-Ultraviolet Light-Emitting Diodes Applications

Abstract

  Combination of sputter deposition and high-temperature annealing is a promising technique for preparing AlN templates with a low threading dislocation density (TDD) at a lower film thickness compared to those prepared by the conventional metalorganic vapor phase epitaxy. We controlled the residual stress of the sputter-deposited AlN films by modifying the sputtering conditions. By optimizing the sputtering and annealing conditions, TDDs of 2 × 10⁸ cm⁻² and 5 × 10⁷ cm⁻² were achieved for the AlN templates with thicknesses of 480 nm and 1200 nm, respectively. By utilizing the substrates with appropriate surface off-cut, dislocation-induced hillock structures on the Al_xGa_1-xN surfaces grown on the AlN templates were suppressed. The advantages of low-dislocation densities of the AlN templates for achieving high external quantum efficiencies were demonstrated.