Abstract: An epitaxial growth method for a compound semiconductor thin film, capable of forming a p-n junction with an atomic-scale ultra-micro structure is disclosed. The method involves loading the compound semiconductor substrate in a reaction chamber, injecting Group V and III metal organic source gases not processed by a thermal pre-decomposition process into the reaction chamber, and growing a p- or n-type compound semiconductor on the compound semiconductor substrate while adjusting the growth temperature of the p- or n-type compound semiconductor.