In this paper, we report the dependence of Ni/Ag/diffusion barrier (D.B)/Au p-ohmic contact on Pt-D.B and Ti-D.B for GaN based flip-chip light emitting diodes (FC LEDs). It is shown that D. B metals have strongly influenced on the reflectance and contact resistivity of contacts. We present these results are caused by the variation of the morphology and atomic distribution due to D.Bs. The roles of Pt-D.B and Ti-D.B on Ni/Ag/D.B/Au p-GaN ohmic contacts are analyzed using the confocal laser scanning microscopy (CLSM) measurement and the secondary ion mass spectroscopy (SIMS) profiles in details. (C) 2011 Elsevier B.V. All rights reserved.