An image sensor pixel includes a photodiode disposed in a semiconductor material, and doped regions surrounding the photodiode, at least in part. The doped regions include a doped portion of the semiconductor material. Deep trench isolation structures are disposed in the doped regions, and surround the photodiode at least in part. The deep trench isolation structures include a SiGe layer disposed on side walls of the deep trench isolation structures, a high-k dielectric disposed on the SiGe layer, and a filler material.