Barrier heights and Fermi level pinning in metal contacts on p-type GaN

In this work, we investigate the current-voltage (I-V) characteristics of various metal contacts such as Ni/Au, Ir/Au, Ru/Au, Mo/Au, and W/Au on p-GaN. For this, we fabricated different bilayer metal contacts on the same epitaxial heterostructure of GaN, which ensures the uniformity of the experimental data. I-V measurements were then carried out for circular and/or linear contact pads with different spacing values. In each case, the Schottky barrier height of the metal contacts is calculated using the reverse I-V method. A strong Fermi level pinning was found in all these structures on p-GaN, with a pinning factor of similar to 0.15. In addition, a very low Ohmic contact resistivity of 3.45 x 10(-6) Omega cm(2) was measured for the Ru/Au contacts on p-GaN. Published under license by AIP Publishing.