Semiconductor structure and method for preparing the same

A semiconductor structure, comprising:

• a substrate;
• and
• a plurality of functional film layers stacked on the substrate,
• wherein the plurality of functional film layers comprise a first semiconductor layer and a second semiconductor layer stacked with each other, the first semiconductor layer is arranged between the substrate and the second semiconductor layer, the first semiconductor layer comprises a plurality of defect pits recessed toward the substrate, the plurality of defect pits are filled by the second semiconductor layer, and one side of the second semiconductor layer away from the first semiconductor layer is a plane;
• and
• the first semiconductor layer comprises doping elements, the first semiconductor layer is a superlattice structure with a plurality of film layers stacked, and the superlattice structure comprises a plurality of repeating units;
• and a doping concentration of the doping elements in each of the repeating units increases first and then decreases in a direction from the substrate to the plurality of functional film layers.