Ohmic and Schottky contact formation on n-GaN using novel boride-based metallization schemes was studied. The minimum specific contact resistance achieved is 1.6x10-6 ohm cm2 for Ti/Al/TiB2/Ti/Au after annealing over a broad range of temperatures (700-900oC). Boride/Ti/Au metallurgies exhibited rectifying behavior up to 700oC anneal, the barrier height being ~0.55 eV for all borides. Comparison of Ti/Al/TiB2/Ti/Au and conventional Ti/Al/Pt/Au metallizations for AlGaN/GaN high electron mobility transistors subjected to long-term annealing at 350oC show that the improved thermal stability of the boride-based Ohmic contacts has a beneficial effect on the long-term stability of the device.