The influence of the interfacial adhesion and reflectance of a p-GaN/NiAgNiAu p-electrode on the optical properties of vertical GaN-based light emitting diodes (LEDs) was investigated. The thickness of the sputter-deposited Ni ohmic contact was varied from 2 to 100 nm. The p-electrode with a 2 nm thick Ni layer showed the highest adhesion strength of 160 MPa to the p-GaN and the highest reflectance of 80.79% after annealing because all the Ni atoms participated in the indiffusion into p-GaN and formed a transparent NiO. The NiAgNiAu p-electrodes with a higher reflectance led to the improved output power of the vertical LEDs regardless of the interfacial adhesion strength of p-GaN/Ni. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3238468] All rights reserved.