PURPOSE: To improve output of light by mono-crystallizing a light emitting layer of a thin film EL device and interposing the light emitting layer between layers with a low fraction factor.

CONSTITUTION: A metallic electrode 5, an insulating layer 4, a high resistance ZnSe monocrystal layer with a light emitting center doped or a high resistance ZnSxSe1-x (x<1) mixed crystal monocrystal layer 3 with the light emitting center doped, a low resistance ZnS monocrystal buffer layer 2 and a ZsAs substrate 1 or an Si substrate 1 are laminated to structure a solid light source, wherein ac voltage is applied between the substrate 1 and the metallic electrode 5 to excite the light emitting center to emit light, and light is taken out from a substrate edge in parallel with the substrate. Thus the a light emitting layer with small loss of a ZnS mixed crystal monocrystal thin film or the ZnSxSe1-x (x<1) with the light emitting center doped is formed by MOCVD method to seal light so that a refraction factor of the light emitting layer is made maximum while refraction factors of the light emitting layer, the insulating layer, the buffer layer and the substrate are taken into consideration. Thus light with high output can be obtained.