Typical n-type ohmic contact formation for GaN material systems requires high-temperature thermal processes. The high-temperature process often leads to a rough surface after the annealing step. Low-annealing-ohmic contact is advantageous to prevent undesired surface roughening on the metal stack during this thermal process.  We report an approach to achieve low contact resistance on n-type GaN layers using a nitrogen plasma and a conventional Ti/Al-based metal stacks.  We observed an as-deposit ohmic contact behavior on the n-type contact with a specific contact resistance (r_c,sp) in the mid-E-6 Ω∙cm² range.  The r_c,sp was further reduced to  6.8E-7 Ω∙cm² after an annealing step at 600 ^oC.