Semiconductor device

A semiconductor device comprising:

• a substrate made of semi-insulating InP;
• a first lower semiconductor layer made of p-type InP on the substrate;
• a first optical active element on a first region of the substrate;
• a second optical active element on a second region of the substrate;
• and
• an optical waveguide disposed between the first optical active element and the second optical active element, configured to function as an electrical isolation portion between the first optical active element and the second optical active element, and configured to optically connect the first optical active element and the second optical active element with each other, wherein
• the first lower semiconductor layer includes a groove in a region where the optical waveguide is disposed,
• the first optical active element includes the first lower semiconductor layer on the first region of the substrate, a first active layer on the first lower semiconductor layer and having a ridge waveguide structure, an upper semiconductor layer made of n-type InP on the first active layer, a first n-electrode on the upper semiconductor layer, and a first p-electrode on the first lower semiconductor layer in a region where the first active layer is not present,
• the second optical active element includes the first lower semiconductor layer on the second region of the substrate, a second active layer on the first lower semiconductor layer and having a ridge waveguide structure, the upper semiconductor layer on the second active layer, a second n-electrode on the upper semiconductor layer, and a second p-electrode on the first lower semiconductor layer in a region where the second active layer is not present,
• the optical waveguide includes a second lower semiconductor layer made of semi-insulating or undoped InP in the groove of the first lower semiconductor layer, a third active layer on the second lower semiconductor layer and having a ridge waveguide structure, and the upper semiconductor layer on the third active layer,
• the first optical active element further includes an embedding layer on the first lower semiconductor layer and embedding the first active layer,
• the first p-electrode is at a position where the embedding layer is not present, and
• the first lower semiconductor layer where the first p-electrode has a thickness from 400 nm to 1000 nm.

A method for manufacturing a semiconductor device comprising:

• crystal-growing an etching stop layer on a substrate made of semi-insulating InP;
• crystal-growing a p-type InP layer having a thickness of 1000 nm on the etching stop layer;
• crystal-growing a first active layer on the p-type InP layer;
• removing the first active layer in a region to be a second optical active element;
• crystal-growing a second active layer at the removed portion to butt-join the first active layer and the second active layer in a waveguide direction;
• removing predetermined regions of the first active layer, the second active layer, and the p-type InP layer by etching processing using selective wet etching with the etching stop layer to form a first optical active element and a second optical active element with a region between them for an optical waveguide;
• crystal-growing a second lower semiconductor layer made of semi-insulating or undoped InP and a third active layer in the region for the optical waveguide;
• etching the first optical active element to thin p-type InP layers on both sides of a ridge waveguide structure of the first active layer, wherein the p-type InP layer is thinned with a thickness from 400 nm to 1000 nm as a limit;
• crystal-regrowing InP on the thinned p-type InP layers to embed the ridge waveguide structure with an embedding layer;
• crystal-growing an upper semiconductor layer made of n-type InP and a contact layer;
• and
• forming electrodes including a first p-electrode on the thinned p-type InP layer where the embedding layer is removed.

A semiconductor device comprising:

• a substrate made of semi-insulating InP;
• a first optical active element and a second optical active element on the substrate;
• an optical waveguide between the first optical active element and the second optical active element, the optical waveguide providing electrical isolation between the first optical active element and the second optical active element while optically connecting the first optical active element and the second optical active element;
• a first lower semiconductor layer made of p-type InP, wherein a portion of the first lower semiconductor layer under the first optical active element has a thickness from 400 nm to 1000 nm to enable single-phase driving of the first optical active element;
• and
• a second lower semiconductor layer made of semi-insulating or undoped InP under the optical waveguide, wherein the second lower semiconductor layer electrically isolates the first optical active element from the second optical active element to enable differential driving of the second optical active element.