Nanoscale carrier transport in Ti/Al/Ni/Au Ohmic contacts on AlGaN epilayers grown on Si(111)

In this letter, a correlation between nanostructure and current flow in Ti/Al/Ni/Au Ohmic contacts on AlGaN films grown on Si (111) is reported. A cross correlation between conductive-atomic force microscopy and structural analyses (x-ray diffraction, transmission electron microscopy) demonstrates that the structure and the electrical properties of the different phases formed inside the reacted layer upon annealing are crucial for the nanoscale current transport. The experimental measurement of the resistivity of the main phases formed upon annealing (AlNi, AlAu4, and Al2Au) indicated that the low resistivity Al2Au phase provides preferential conductive paths for the current flow through the contact.