Improved Light Output Power of Ultraviolet GaN-Based Light-Emitting Diode by Using AgPdCu Reflector

Abstract

We investigated the output performance of UV LEDs with Ag-Pd-Cu (APC) and Ag-only reflectors. After annealing at 600°C, the Ag-only layer surface was seriously roughened, while the APC sample revealed a smooth surface with hillocks. The 600 °C-annealed APC and Ag samples gave reflectance of 84.9% and 70.9%at 385 nm. The contact resistivities of the Ag and APC contacts annealed at 500 °C were measured to be 2.59×10– 4 and 1.85×10– 4 Ωcm2, respectively. For the annealed APC sample, the Ga 2p core level was shifted towards the lower binding-energies by 0.67 eV as compared to that of the as-deposited sample. The UV LEDs with the annealed APC reflector yielded 9.04% higher output at 100 mA than those with the Ag reflector. Based on the XRD pole figure and SEM results, the better thermal property of the APC sample is described in terms of thermal stress and surface energy.