Ohmic Contact With a Contact Resistivity of 12 Ω ⋅ mm on p-GaN/AlGaN/GaN

A robust ohmic contact process with ultralow contact resistivity on p-GaN/AlGaN/GaN is demonstrated. An in-situ removal of GaO _X interfacial layer after contact metal deposition is developed. Using the novel Mg/Pt/Au stack as the contact metal, a stable ohmic contact is obtained after 450°C/300 s annealing with ohmic contact resistivity of $12 \Omega \cdot {\mathrm {mm}}$ ( $1.8\times 10^{-5}\, \Omega \cdot {\mathrm {cm}}^{2}$ ). A new ohmic contact formation mechanism on p-GaN/AlGaN/GaN is also proposed.