Multi layer metallization scheme (Ni/Pd/Ag) ohmic contact on p-type GaN

In this work, we report on the characteristics of the first ever work using a multilayer Ni/Pd/Ag contacts on p-GaN with the carrier concentration of 8 10¹⁷ cm^-3. The electrical behavior and thermal stability at different annealing temperatures (400 C-800 C) with annealing time of 5 minutes and 10 minutes were investigated. Specific contact resistivity using transmission line method (TLM) and current voltage (I-V) measurements were investigated. The minimum specific contact resistivity of 2.8 10^-1 Ω-cm² was achieved after annealing at 400 C for 5 minutes. As-deposited samples exhibited near linear characteristics. Changes in the surface morphology of the contacts were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The agglomeration of the samples increased with the annealing temperatures.