Improved surface morphology of a Ti/Al/Ni/Au ohmic contact for AlGaN/GaN heterostructure by Al2O3 particles

An effective method to improve the surface morphology of a Ti/Al/Ni/Au ohmic contact on an AlGaN/GaN heterostructure was proposed. The ohmic contact with the Al2O3 particles prepared before metal deposition had a much smoother surface than the conventional ohmic contact with surface roughness of 116 nm and 195 nm, respectively, when the metal was annealed at 850 °C for 60 s. Also, the enlargement of the alloy lump was negligible at longer annealing times and higher temperatures. The ohmic contact has a contact resistivity of 3.9 × 10− 6 Ω-cm2, which is slightly higher than the resistivity of the contact without Al2O3.