To provide a semiconductor wafer manufactured by a simplified device manufacturing process, a method of manufacturing a semiconductor wafer, and a method of manufacturing a semiconductor optical amplifier.

Light of different light intensities P is irradiated to a predetermined region at the same time from a time Ta before supplying a raw material gas (TMIn, TEG, AsH3) for growing a strain bulk active layer (In1-xGaxAsyP1-y) to a time Tb after stopping the supply of the material gas to produce a local composition modulation, thereby forming a wafer having a desired amount of strain positively and widely.