Disclosed are embodiments of a wafer that incorporates fill structures with varying configurations to provide uniform reflectance. Uniform reflectance is achieved by distributing across the wafer fill structures having different semiconductor materials such that approximately the same ratio and density between the different semiconductor materials is achieved within each region and, optimally, each sub-region. Alternatively, it is achieved by distributing across the wafer fill structures, including one or more hybrid fill structure containing varying proportions of different semiconductor materials, such that approximately the same ratio between the different semiconductor materials is achieved within each region and, optimally, each sub-region. Alternatively, it is achieved by distributing across the wafer fill structures having semiconductor materials with different thicknesses such that approximately the same overall ratio between the semiconductor material with the different thicknesses is achieved within each region and, optimally, each sub-region.