Abstract: An ultraviolet radiation monitor is disclosed. The monitor includes an aluminum gallium nitride-based detector, such as a Schottky junction fabricated with aluminum gallium nitride and a Schottky layer containing palladium, and a processor. The composition of the detector is tailored so that the detector is responsive substantially only to radiation of certain wavelengths, such as UV-B. The processor is adapted to receive user input of the user's skin type and ultraviolet-blocking power of any sunscreen the user is wearing. The processor is also adapted to read the signal generated by the detector and calculate the intensity of the ultraviolet radiation received by the detector. The processor is further adapted to calculate the maximum length ultraviolet exposure time for the user, based on the radiation intensity, skin type and sunscreen information.