PURPOSE: To disperse thermal stress even when GaAs substrates are deformed due to thermal stress, to reduce generation of curvature and cracks and to obtain a wafer having high quality by dividing a GaAs substrate into a plurality of substrate pieces and growing Ga1-xAlxAs layers thereon.

CONSTITUTION: In the manufacture of a wafer in which Ga1-xAlxAs layers are formed onto GaAs substrates by using a liquid-phase epitaxial growth method, GaAs substrates divided into two pieces or more are used as the substrates. When epitaxial growth is conducted by employing the substrates and the size of curvature is measured regarding the Ga1-xAlxAs epitaxial wafer completed, the size of curvature is reduced distinctly with the increase of the number of division. Accordingly, when the Ga1-xAlxAs epitaxial layer is grown on the GaAs substrate, the epitaxial layers can stably be formed even when the divided substrates are used.