Role of annealing conditions and surface treatment on ohmic contacts to p-GaN and p-Al0.1Ga0.9N/GaN superlattices

The effects of the initial Mg reactivation annealing temperature, surface cleaning treatments, and contact annealing conditions on the specific contact resistance of Ni/Au ohmic contacts on p-GaN are reported. The lowest contact resistances were obtained for 900 degreesC activation annealing and cleaning steps that reduced the native oxide thickness (i.e., KOH rinsing). Removal of this interfacial oxide reduced the barrier for hole transport, providing a contact resistance of 9x10(-4) Omega cm(2) for Ni/Au metallization annealed at 500 degreesC. The use of a ten period p-Al0.1Ga0.9N(Mg)/GaN(Mg) superlattice with individual layer thickness 50 Angstrom led to a specific contact resistance of 9x10(-5) Omega cm(2) under the same conditions. (C) 2001 American Institute of Physics.