Effect of Pt and Ti on Ni/Ag/(Pt or Ti)/Au p-ohmic contacts of GaN based flip-chip LEDs

► In this paper, we report the dependence of Ni/Ag/diffusion barrier (D.B)/Au p-ohmic contact on PtD.B and TiD.B for GaN based flip-chip light emitting diodes (FC LEDs). ► The reflectance and contact resistivity of p-ohmic contact were analyzed by confocal laser scanning microscopy (CLSM) and SIMS depth profile. ► PtD.B and TiD.B showed the clearly different effect on the atomic distribution, which influenced on reflectance and contact resistivity of p-ohmic contact. ► We especially focused on the interface between p-electrode and p-GaN contact layer, which was analyzed by CLSM and SIMS depth profile in details, and identified the origins of properties. ► We think that our experimental results and interpretation could be of much help in understanding the roles of two kinds of diffusion barrier, Pt and Ti, on the p-ohmic contact based on Ni/Ag.