Opto Diode’s UVG20C radiation-hard photodiode is a 20-mm² device with a circular active area that is ideal for electron detection. The component offers 100% internal quantum efficiency and unparalleled stability. The absence of a surface dead region results in 100% collection efficiency. The radiation-hard, junction-passivating, oxynitride protective entrance window makes the device extremely stable even after exposure to intense flux of UV photons (showing <2% responsivity degradation after megajoules/cm² of 254 nm and tens of kilojoules/cm² of 193 nm photon exposure). The radiation-hardness makes these diodes better suited than conventional silicon photodiodes for space missions and/or satellite applications.