US Patent 7514349 Semiconductor optical device and manufacturing method thereof

The object of the invention is to reduce the deterioration of crystallinity in the vicinity of an active layer when C, which is a p-type dopant, is doped and to suppress the diffusion of Zn, which is a p-type dopant, into an undoped active layer, thus to realize a sharp doping profile. When a Zn-doped InGaAlAs layer having favorable crystallinity is provided between a C-doped InGaAlAs upper-side guiding layer and an undoped active layer, the influence of the C-doped InGaAlAs layer whose crystallinity is lowered can be reduced in the vicinity of the active layer. Further, the Zn diffusion from a Zn-doped InP cladding layer can be suppressed by the C-doped InGaAlAs layer.