Abstract: When a highly resistive GaAs film doped with a metal impurity such as Fe, Ni or Cr is epitaxially grown from the vapor phase, a metallocene of this metal impurity such as Fe(C.sub.5 H.sub.5).sub.2, Cr(C.sub.5 H.sub.5).sub.2 or Ni(C.sub.5 H.sub.5).sub.2 or a derivative of this metallocene is employed as a starting material of this impurity. Even at room temperature or a temperature lower than room temperature a metallocene or a derivative thereof has such a high vapor pressure as to permit the epitaxial growth of a semi-insulating film so that heating of a line for feeding an impurity into a reaction tube may be eliminated and consequently an epitaxial system may be much simplified. Furthermore introduction of the impurity into the reaction tube may be instantaneously started or stopped by opening or closing a stop valve inserted into the feed line so that the impurity distribution may be sharply changed from one semi-insulating epitaxially grown film to another.

Abstract: A mesa region of a stripe geometry is formed by mesa-etching a surface of a GaAs crystal substrate, forming a crystal layer of higher resistivity than the abovementioned crystal substrate so as to fill the abovementioned mesa-etched recesses in a manner that the stripe shaped mesa region is buried in the higher resistivity regions making top faces of the mesa region and the higher resistivity regions flush with each other, then forming, on the abovementioned flush surface, several epitaxial growth regions of semiconductor crystal including a light emitting region, for instance, an active region for lasing, subsequently forming contact isolation region having an opening of the stripe geometry corresponding to and above said mesa region. The current flow in the active region is confined in a narrow stripe region.