Patent ID: 7415185

Claim:
A buried-waveguide light detecting element comprising: a semiconductor substrate; an n-type cladding layer located on the semiconductor substrate and having a refractive index; a waveguide layer located on a portion of the n-type cladding layer, the waveguide layer including an n-type light guide layer having an impurity concentration, a first semiconductor layer having a refractive index equal to or higher than that of the n-type cladding layer and undoped or having an impurity concentration of 1×10 17 cm −3 or less, lower than the impurity concentration of the n-type light guide layer, a light absorption layer having a refractive index higher than that of the first semiconductor layer, a p-type light guide layer, and a p-type cladding layer successively layered in a ridge with respect to the semiconductor substrate; and a Fe-doped insulating material layer located on the semiconductor substrate and embedding side walls of the waveguide layer.