Ni/Si-Based Ohmic Contacts to p- and n-Type GaN

Ni/Si-based ohmic contact scheme for GaN, based on the solid-phase regrowth (SPR) mechanism have been developed. Using Mg and Si as dopant species, ohmic contacts with a resistivity of ∼1*10-3Ωcm2 to p-GaN (p≈3*1017 cm-3) and n-GaN (n≈2*1017cm-3), respectively, have been obtained. SIMS, XRD, and RBS analysis show in as-deposited contacts, an initial reaction at GaN/Ni interface, leading to the formation of an Ni-Ga-N layer. The ohmic behavior of contacts, observed after annealing at 400°C, is accompanied by structural transformations in the contact region: i) the decomposition of Ni-Ga-N layer and ii) the growth of NiSi compound.