Method for manufacturing optical semiconductor waveguide window structure
Provided is a semiconductor light source element or an optical device including a semiconductor optical waveguide of a high-mesa semi-insulated embedded structure having a window structure made of the same material as an overclad layer at a light emission end, and a method for manufacturing thereof, in which an active layer at a portion of the window structure is removed, and then the same layer as the overclad layer is formed.
1. A method for manufacturing a semiconductor light source element, the method comprising:
forming an active layer on an InP substrate, wherein the active layer is a crystal grown layer and wherein a crystal orientation of a surface thereof was a (1 0 0) plane and an orientation flat thereof was a (0 −1 −1) plane;
forming a first etching mask on the active layer, and removing a part of the active layer, wherein a remaining part of the active layer is perpendicular to the orientation flat;
forming an EA (Electro-Absorption) layer, wherein the EA layer is a crystal grown layer and wherein the EA layer forms a core layer of an EA modulator, without removing the first etching mask;
removing the first etching mask and forming a second etching mask on the active layer;
partially removing the EA layer, such that a region serving as a window structure remains, wherein the region remaining is wider than a mesa stripe;
removing the second etching mask and then forming the window structure by forming an overclad layer on an entire surface; and
forming a third etching mask on the overclad layer, and then forming the mesa stripe by removing each of the overclad layer, the active layer, the EA layer, and a part of the InP substrate, wherein the mesa strip has a height of at least 3 μm.
2. The method for manufacturing the semiconductor light source element according to claim 1 ,
wherein the method further comprises:
forming a diffraction grating on a part of the active layer after removing the second etching mask.
3. The method for manufacturing the semiconductor light source element according to claim 2 , wherein the forming the EA layer comprises regrowing through butt joint growth.
4. The method for manufacturing the semiconductor light source element according to claim 3 , wherein the method further comprises, in the forming of the first etching mask on the active layer and the removing of the part the active layer, removing the active layer partially so that the remaining part of the active layer is divided into a first active layer to form the diffraction grating located on an input side and a second active layer to be a semiconductor optical layer (SOA layer) located on an output side, wherein the window structure is formed in an output side of the SOA layer.