Formation of Low-Resistant and Thermally Stable Nonalloyed Ohmic Contact to N-Face n-GaN

We report on the formation of Ohmic contacts with low resistance and high thermal stability to N-face n-GaN for vertical structure light emitters using a Ti(50nm)/Pt(50nm)/Au(50nm) metal scheme, where the Pt layer is introduced as a blocking layer to suppress the diffusion of Au onto the N-face n-GaN surface. It is shown that unlike the conventional Ti/Al/Ti/Au contacts, the Ti/Pt/Au contacts exhibit an Ohmic behavior with a relatively low specific contact resistivity of 1.1×10⁻⁴ Ω⋅cm² even after annealing at 350 °C. X-ray diffraction (XRD) measurements by synchrotron radiation and Auger electron spectroscopy (AES) examination are performed to understand the effects of heat treatment.