We report on the design, fabrication and characterization of solar-blind Schottky photodiodes with high detectivity and low noise. The devices were fabricated on n/n+ AlGaN/GaN hetero-structures using a microwave compatible fabrication process. Using Al(0.38)Ga(0.62)N absorption layer, true solar-blind operation with a cutoff wavelength of similar to274 nm was achieved. The solar-blind detectors exhibited < 400 fA dark current in the 0-25 V reverse bias regime, and a maximum responsivity of 89 mA/W around 267 nm. The photovoltaic detectivity of the devices were in excess of 2.6x10(12) cmHz(1/2)/W, and the detector noise was 1/f limited with a noise power density less than 3x10(-29) A(2)/Hz at 10 KHz.