Patent ID: 7701993

Claim:
A semiconductor optical device comprising a mesa-stripe stacked body including at least a p-type cladding layer, an active layer and an n-type cladding layer formed on a p-type InP substrate doped with Zn, a current-blocking layer buried in both sides of said stacked body, and an n-type over-cladding layer and an n-type contact layer disposed on said current-blocking layer and said stacked body, wherein said current-blocking layer is a single layer and a high-resistive layer made of an InP crystal doped with Ru, the upper surface of said current-blocking layer having a substantially level region disposed below the topmost height of the upper surface and above the height of the topmost layer of said stacked body, and a layer thickness of said current-blocking layer is between 3 and 5 μm; wherein said n-type over-cladding layer is made of an InP crystal doped with Se having a property for flattening a concavo-convex shape of upper surfaces of said current-blocking layer and said stacked body; and wherein doping concentration of Se is greater than or equal to 2×10 19 cm −3 such that said n-type over-cladding layer is hardly grown in the substantially level region.