We report the influence of surface treatment, annealing temperature and metal bilayer thickness on the specific contact resistance (μc) of Au/Ni ohmic contacts to p-GaN and p-A1GaN. Ohnuc contact on p-GaN with a hole concentration of 6.5 x 1017 cm-3, shows the lowest μC of ~9.2x 10-6 Ω cm2, when GaN was treated in HCI:H20 (3:1) solution before metal deposition and annealed at 500°C for 10 minutes in 90% N2 and 10% o2 atmosphere. Similar procedure applied on p-AlGa,N (x = 5-7%), with a hole concentration of 2.3 x l017 cm3, yields aμc of 1.8 x l0-4 Ω cm2. An increase is observed in μ when Mg doping exceeds 4 x 1019 cm3 in both p-GaN and p-A1GaN. This is attributed to Mg self compensation. This increase is more pronounced in A1GaN which we attribute to the presence of residual native aluminum oxides.