Method for forming semiconductor thin films where an argon laser is used to suppress crystal growth

A method for forming a thin film of a semiconductor having the steps of placing a substrate within a vacuum chamber, launching elements gallium and indium constituting a compound semiconductor onto said substrate as a molecular beam of an indium organometal compound and a gallium organometal compound, launching another element constituting said compound semiconductor onto said substrate as a molecular beam of the element, and decomposing said organometal compounds on said substrate to thus form a thin film of a ternary or quarternary compound semiconductor on said substrate, said method comprising the steps of:

• heating said substrate;
• launching argon laser rays to a predetermined position on said substrate while heating said substrate, said laser rays having a wavelength whose energy is less than photon energy required for directly decomposing said organometal incident upon said substrate;
• and
• establishing the temperature of said substrate at a temperature ranging from 500.degree. C. to 560.degree. C. so that a difference is growth rate of said thin film arises depending on the presence or absence of said incident laser beam and so that the growth of the film on the portion of said substrate irradiated with said laser rays is suppressed.