there is provide a method of manufacturing a compound semiconductor that can make the substrate surface of the semiconductor highly clean and plane so that no impurity may be left between the substrate surface and the grown crystal layer . in the step of cleaning a substrate with mbe , the substrate surface is irradiated with v molecular beams that cannot be significantly deposited out of molecular beams to be used for the crystal growth step , said v molecular beams being irradiated under a condition of p 1 ≦, where p 1 is the pressure of v molecular beams and p 2 is the pressure of molecular beams in the crystal growth step and the temperature of the substrate surface is raised by heating until stabilized group iii surfaces appear on the substrate surface . a very cleanand smooth substrate surface can be obtained with such an arrangement . harmful impurities can be completely eliminated from the interface of the substrate and the crystal . the formation of a buffer layer can be effectively prevented in the initial stages of crystal growth . in short , high - quality compound semiconductors can be produced on a reliable basis .