PURPOSE: To make it possible to form a group II-VI semiconductor superlattice into a mixed crystal by a method wherein an active layer consists of a superlattice structure and a semiconductor crystal on the periphery of a current injected region contains gallium and is formed into a mixed crystal.

CONSTITUTION: An N-type chlorine-doped S0.07Se0.93 layer 2, an N+ chlorine- doped ZnSe layer 3 and a superlattice structure 4 consisting of a non-doped Zn0.8Cd0.2Se well layer and a non-doped ZnSe barrier layer are formed on an N-type GaAs substrate 1. After that, a P-type nitrogen-doped ZnSe layer 5 and a P-type nitrogen-doped ZnS0.07Se0.93 layer 6 are grown. A crystal growth is performed to form a silicon oxide film on the whole surface of the layer 6 as an ion-implantation mask and one part of the silicon oxide film is etched into a striped form to form a window. The direction of this striped form is vertical to the axial direction of a resonator which is formed in future. Subsequently, gallium is implanted and a flash annealing is performed. By the introduction of this gallium, the formation of the superlattice structure into a mixed crystal can be contrived.