Low-resistance ohmic contacts on p-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 Mgdopedp-type GaN samples were grown by metalorganic chemical vapor deposition with a carrier concentration of 4.1×10 17 cm −3 . The as-grown Mgdoped 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 annealingtemperatures ranging from 350 to 650 °C. Linear I–V ohmic characteristics were observed with specific resistance as low as 1.0×10 −4 Ω cm 2 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 8.1×10 19 cm −3 . Without further annealing process, the samples show good ohmic contact with a lowest specific resistance of 4.5×10 −6 Ω cm 2 .