Abstract: A high sensitivity radiation detecting photodiode formed in silicon carbide comprises a monocrystalline silicon carbide substrate; a first monocrystalline portion of silicon carbide upon the substrate and having a first conductivity type; a second monocrystalline portion of silicon carbide adjacent the first portion and having the opposite conductivity type from the first portion; and a p-n junction between the adjacent first and second portions. The photodiode provides a dark current density of no more than about 1.times.10.sup.-9 amps/cm.sup.2 at a reverse bias of -1.0 volts and at temperatures of 170.degree. C. or less.