Low dark count rate semiconductor structures

A light sensitive semiconductor structure comprises a p-n junction 4 in a silicon substrate 12, the p-n junction comprising a central part 6 and an edge part 8 being in contact with a surface 9 of the substrate. A plasma shielding structure 18 covers at least a depletion width 16 of the p-n junction over at least a part of the edge part 8 where the edge part contacts the surface of the silicon substrate. The plasma shielding structure may comprise at least one of polysilicon or salicided polysilicon 20, silicide 25, and metal 22. The metal may be a part of a first metal layer in a backend stack. The silicon substrate may comprise a trench 24 filled with shallow trench isolation (STI) material. The plasma shielding structure protects the depletion region 14 close to the surface from damage due to plasma processes during manufacturing, leading to a low dark count rate (DCR). A single photon avalanche diode (SPAD) comprising the semiconductor structure and a light sensor comprising an array of SPADs are also provided.