A multi-faceted study on the reduction of ohmic contact resistance to AlN/GaN-based heterostructures is presented. Minimum contact resistance of 0.5 Omega mm has been achieved by partially etching the AlN barrier layer using a chlorine-based plasma dry-etch prior to ohmic contact metallization. For thin GaN-capped AlN/GaN heterostructures, we find it is necessary to remove the GaN cap in the vicinity of the contact metal in order to obtain a linear current-voltage relationship. We compare our results of the pre-metallization etched contacts to those without an etch as well as to results reported in the literature. Published by Elsevier Ltd.