Low-resistance ohmic contacts on <i>p</i>-type GaN using Ni/Pd/Au metallization

Abstract

In this letter, a low-resistance ohmic contact on p-type GaN using an alloy of Ni/Pd/Au is reported. The Mg doped p-type GaN samples were grown by metalorganic chemical vapor deposition with a carrier concentration of 4.1×1017 cm−3. The as-grown Mg doped samples were deposited with Ni (20 nm)/Pd (20 nm)/Au (100 nm) and then annealed in air, nitrogen, and oxygen ambient conditions at different annealing temperatures ranging from 350 to 650 °C. Linear I–V ohmic characteristics were observed with specific resistance as low as 1.0×10−4 Ω cm2 for the samples annealed in oxygen atmosphere. Similar contact metal composition was also deposited on Be-implanted p-type GaN samples with a carrier density of 8.1×1019 cm−3. Without further annealing process, the samples show good ohmic contact with a lowest specific resistance of 4.5×10−6 Ω cm2.