We have fabricated GaN-based high-speed ultraviolet Schottky photodiodes using indium-tin-oxide (ITO) Schottky contacts. Before device fabrication, the optical transparency of thin ITO films in the visible-blind spectrum was characterized via transmission and reflection measurements. The devices were fabricated on n - /n+ GaN epitaxial layers using a microwave compatible fabrication process. Our ITO Schottky photodiode samples exhibited a maximum quantum efficiency of 47% around 325 nm. Time-based pulse-response measurements were done at 359 nm. The fabricated devices exhibited a rise time of 13 ps and a pulse width of 60 ps. © 2001 American Institute of Physics.