A semiconductor wafer includes a substrate (1), a buffer layer (2) deposited on the substrate (1), and an epitaxial layer (4) above the buffer layer (2). The buffer layer (2) includes a plurality of semiconductor material layers (22) and a plurality of oxygen-doped material layers (21). The semiconductor material layers (22) and the oxygen-doped material layers (21) are deposited in an alternating arrangement on top of each other. Oxygen concentrations of the oxygen-doped material layers (21) gradually decrease along a direction from the substrate (1) to the epitaxial layer (4).