Interdigital metal-semiconductor-metal (MSM) and p-n UV photodetectors have been successfully grown and fabricated from GaN based materials. The MSM devices were produced using two types of GaN; high-resistive GaN and Mg doped GaN. For the high-resistive GaN detector, the lowest dark current is approximately 0.1 nA and the UV responsivity of the device was about 460 A/W at a DC bias of 30 V. The Mg doped GaN exhibited larger gains, 1150 A/W at 2.0 V, but at much higher dark currents, 400 nA. The high gain in this device is not well understood but has attributed to an 'avalanche' effect and is under further investigation. The feasibility of a photovoltage detector structure based on alloys of GaN has also been proven. A GaN/GaInN structure exhibited a cut- off at 2.9 eV with a responsivity of 0.28 A/W at zero bias for an active region of only 500 angstrom thick.