A GaAsxP1-x layer (4), in which the arsenic content (x) varies within a limit (a) with increasing thickness (d), is formed between a GaP layer (3) and a uniform GaAsaP1-a layer (5). The arsenic content (x) is increased in the state shown by the inclined lines C11-C13 and then decreased as shown by the inclined lines S11-S13 within such a range that the decreasing amount does offset the increasing amount. Since the arsenic content (x) of the layer (4) is increased to the limit (a) by repeating the combination of increase and decrease two or more times in the layer (4) in such a way, stresses caused by lattice unmatching can be removed effectively and a thin epitaxial wafer of compound semiconductor can be obtained with high productivity. In addition, the luminance of the wafer can be improved when a reflection layer is incorporated in the wafer.
