A semiconductor device (100, 200, 300) operable to demodulate incident modulated electromagnetic radiation, the semiconductor device (100, 200, 300) comprising: a pinned photodiode structure (101, 201, 301) including a substrate (103, 203, 303) of a first type; an implant layer (105, 205, 305) of a second type disposed within the substrate (103, 203, 303); a first auxiliary implant layer (206, 306) of the second type disposed within the substrate (103, 203, 303) and disposed adjacent to the implant layer (105, 205, 305) of the second type; a second auxiliary implant layer (208, 308) of the second type disposed within the substrate (103, 203, 303) and disposed adjacent to the implant layer of the second type; an implant layer (107, 207, 307) of the first type disposed within the implant layer of the second type and extending into the first auxiliary implant layer of the second type and the second auxiliary implant layer of the second type; an insulator (113, 213, 313) disposed on a surface of the substrate (103, 203, 303); a photo-detection region (119, 219, 319); a first transfer gate (115, 215, 315) and a second transfer gate (117, 217, 317) disposed on a surface of the insulator, the first transfer gate (115, 215, 315) and the second transfer gate (117, 217, 317) being operable to generate a field within the substrate of the first type; and a first floating diffusion implant layer (109, 209, 309) of the second type and a second floating diffusion implant layer (111, 211, 311) of the second type disposed within the substrate of the first type, wherein the first and second auxiliary implant layers (206, 306, 208, 308) of the second type each has a concentration gradient of dopants that varies linearly with thickness. a pinned photodiode structure (101, 201, 301) including a substrate (103, 203, 303) of a first type; an implant layer (105, 205, 305) of a second type disposed within the substrate (103, 203, 303); a first auxiliary implant layer (206, 306) of the second type disposed within the substrate (103, 203, 303) and disposed adjacent to the implant layer (105, 205, 305) of the second type; a second auxiliary implant layer (208, 308) of the second type disposed within the substrate (103, 203, 303) and disposed adjacent to the implant layer of the second type; an implant layer (107, 207, 307) of the first type disposed within the implant layer of the second type and extending into the first auxiliary implant layer of the second type and the second auxiliary implant layer of the second type; an insulator (113, 213, 313) disposed on a surface of the substrate (103, 203, 303); a photo-detection region (119, 219, 319); a first transfer gate (115, 215, 315) and a second transfer gate (117, 217, 317) disposed on a surface of the insulator, the first transfer gate (115, 215, 315) and the second transfer gate (117, 217, 317) being operable to generate a field within the substrate of the first type; and a first floating diffusion implant layer (109, 209, 309) of the second type and a second floating diffusion implant layer (111, 211, 311) of the second type disposed within the substrate of the first type, wherein the first and second auxiliary implant layers (206, 306, 208, 308) of the second type each has a concentration gradient of dopants that varies linearly with thickness.