Very-low-specific-resistance Pd/Ag/Au/Ti/Au alloyed ohmic contact to p GaN for high-current devices

We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to p GaN. An 800 °C anneal for 1 min in flowing nitrogen ambient produces an excellent ohmic contact with a specific contact resistivity close to ${\text{1×10}}^{\text{−6}}\mathrm{ \Omega }{\mathrm{cm}}^{\mathrm{2}}$ and with good stability under high current operation conditions. This high-temperature anneal forms an alloy between Ag, Au, and p GaN resulting in a highly p-doped region at the interface. Using x-ray photoelectron spectroscopy and x-ray diffraction analysis, we confirm that the contact formation mechanism is the metal intermixing and alloying with the semiconductor.