As an alternative to the standard Au-based ohmic contacts, in this letter, Ti/TiN contacts were used to fabricate GaN high-electron mobility transistors (HEMTs) with two barrier designs (Al0.2Ga0.8N/AlN and Al0.35wGa0.65N). The ohmic contact resistance for this Au-free metallization scheme with a very smooth surface morphology is $0.13~\Omega $ mm and the specific contact resistance is $\sim 10^{\mathrm {\mathbf {-6}}}~\Omega $ $\mathrm{cm}^{\mathrm {\mathbf {2}}}$ . Our best 100-nm gate transistors show a maximum drain current density of 1.13 A/mm and a peak extrinsic transconductance of 388 mS/mm. The fastest transistors with a gate length of 80-nm achieve cutoff frequencies of 176 GHz, rivaling the fastest GaN HEMTs on silicon and silicon carbide substrate with comparable gate length and Au-based ohmic contacts.