| 摘要 |
PURPOSE:To enable a diffraction grating to be produced with good reproducibility and with ease, by a method wherein a thin film which is different from a substrate in composition is previously grown, and the diffraction grating which extends from the thin film to an underlying layer is then formed, and thereafter the upper layer is removed by selective etching. CONSTITUTION:A thin InGaAsP layer 2 with a thickness of 200Angstrom or so is grown on an InP substrate 1. In this connection, this thin layer 2 is uniformly grown by metal organic vapor phase growth method. Next, after a photoresist 3 is coated on the layer 2, interference exposure is performed. Next, etching is performed to form a diffraction grating by using Br-type etchant which is available to etch both the InP substrate 1 and the InGaAsP layer 2. Thereafter, only the InGaAsP layer 2 corresponding to the upper section of the diffraction grating is selectively etched to produce a trapezoid-shaped diffraction grating by heat nitric acid at 80 deg.C. On the resultant trapezoid-shaped diffraction grating, and an InGaAsP guide layer 7, an InGaAsP active layer 4, an InP clad layer 6, and an InGaAsP cap layer 6 are in this order grown by liquid phase growth method. As a result, the trapezoid-shaped diffraction grating is preserved without being dissipated. |
