A photodiode assembly includes a semiconductor substrate, a photodiode cell, a ground diffusion region, and a guard band. The photodiode cell includes a first volume of the substrate doped with a first type of dopant. The diffusion region includes a second volume of the substrate that is doped with a second, opposite type of dopant. The guard band is disposed in the substrate and at least partially extends around an outer periphery of the photodiode cell. The guard band includes a third volume of the substrate that is doped with the first type of dopant. At least one of the ground diffusion region or the guard band is conductively coupled with a ground reference to conduct one or more of electrons or holes that drift from the photodiode cell through the substrate. The guard band is disposed closer to the photodiode cell than the ground diffusion region.