Abstract: A semiconductor device comprises a first semiconductor structure, a second semiconductor structure located on the first semiconductor structure, and an active layer located between the first semiconductor structure and the second semiconductor structure. The first semiconductor structure has a first conductivity type, and includes a plurality of first layers and a plurality of second layers alternately stacked. The second semiconductor structure has a second conductivity type opposite to the first conductivity type. The plurality of first layers and the plurality of second layers include indium and phosphorus, and the plurality of first layers and the plurality of second layers respectively have a first indium atomic percentage and a second indium atomic percentage. The second indium atomic percentage is different from the first indium atomic percentage.