Abstract: A semiconductor material avalanche photodiode photodetector having ultraviolet response, solar radiation immunity and response speed in excess of that available from conventional ultraviolet photodetectors is described. The detector is an avalanche photodiode comprised of periodic table group III-Nitride semiconductor material, such as aluminum gallium nitride, serving as a photon to charge carrier transducer, and an avalanche charge carrier multiplication region comprised of different semiconductor materials such as silicon. The photodetector is capable of selective ultraviolet signal transducing while exposed to a mixture of ultraviolet and solar energy “noise” radiation. The included avalanche multiplication region is optically shielded from solar and other energy components to enable this selective capability. A multiplied ultraviolet photoresponsive electric signal is collected from output electrodes disposed adjacent the avalanche multiplication structure.