SEMICONDUCTOR OPTICAL COUPLING CIRCUIT AND ITS MANUFACTURE

PROBLEM TO BE SOLVED: To function as an etching stop layer in a wet etching by incorporating a specific mixed crystal in one of a plurality of optical waveguides having different refractive index distributions of a laminating direction. SOLUTION: An n-type InP clad layer 52 containing InGaAlAs 53, an InGaAsP active layer 54 and a p-type InP clad layer 55 are epitaxially grown on an InP substrate 51 by an MOVPE method. Then, after an SiO2 film 56 is vapor-deposited on the layer 55, with the film 56 used as an etching mask, the layers 55, 54 and 52 are removed by etching. An n-type InP layer 57 of a guide, an InGaAsP guide layer 58 as a core layer and an i-type InP layer 59 are grown on the removed parts. And, the one waveguide having the layer 58 contains Inx Gay Alz As1-y-z (0