Abstract: On an n-GaP substrate transparent against a radiation light of an InAlGaP based semiconductor element, a lattice distortion relaxation layer, a clad layer 13, an active layer, and a clad layer are created with InAlGaP. On top of the layers, there is formed an InxGa1-xP current diffusion layer with In composition ratio x equal to (0<X<1). Through these steps, uneven depth on the crystal surface is decreased and crystal defect concentration is lowered. In addition, the energy gap of the current diffusion layer is made larger than the energy gap of the active layer, so that the GaP substrate and the uppermost InGaP current diffusion layer become transparent against a radiation light from the active layer, resulting in increased light emitting efficiency. Further, simple formation of layers from the lattice distortion relaxation layer to the current diffusion layer in sequence enables reduction of the production costs.