Optical semiconductor device and fabrication method therefor

• US 20060145276A1
• Filed: 04/22/2005
• Published: 07/06/2006
• Est. Priority Date: 01/05/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamamoto, Tsuyoshi, Tomabechi, Shuichi
• Granted Patent: US 7,598,106 B2
• Time in Patent Office: Days
• US Class Current: 257/431
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 5/2237 with a non-planar active layer
• CPC Class Codes: H01S 5/2272 grown by a mask induced selective growth
• CPC Class Codes: H01S 5/2275 mesa created by etching
• CPC Class Codes: H01S 5/3412 quantum box or quantum dash
• CPC Class Codes: H01S 5/5009 the arrangement being polarisation-insensitive

Abstract

An optical semiconductor device such as, for example, a quantum dot SOA and a fabrication method therefor are disclosed wherein an active layer and a current constriction structure can be formed leftwardly and rightwardly symmetrically to minimize the polarization dependency. The fabrication method for an optical semiconductor device includes the steps of forming a semiconductor layer on a semiconductor substrate, forming a groove by removing the semiconductor layer at an opening of a mask, forming a first clad layer in the form of a projection having two symmetrical inclined faces in the groove by selective growth by using the mask as a selective growth mask, forming an active layer on the two inclined faces of the first clad layer, and removing the mask and burying the active layer with a second clad layer.

Claims

1. A fabrication method for an optical semiconductor device, comprising the steps of:

forming a semiconductor layer on a semiconductor substrate;

forming a groove by removing the semiconductor layer at an opening of a mask;

forming a first clad layer in the form of a projection having two symmetrical inclined faces in the groove by selective growth by using the mask as a selective growth mask;

forming an active layer on the two inclined faces of the first clad layer; and

removing the mask and burying the active layer with a second clad layer.

2. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein, at the semiconductor layer forming step, a plurality of current block layers having different conduction types are formed as the semiconductor layer.

3. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein, at the groove forming step, a dielectric mask having a striped opening extending in the [110] direction is formed as the mask.

4. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein, at the groove forming step, a mask having an opening of a width corresponding to a desired active layer width is formed as the mask.

5. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein, at the active layer forming step, an active layer formed from one of quantum dots, quantum wires and quantum wells is formed as the active layer.

6. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein:

at the semiconductor layer forming step, the semiconductor layer is formed on a (001) semiconductor substrate;

at the first clad layer forming step, the first clad layer having two (111) B surfaces on the (001) semiconductor substrate; and

at the active layer forming step, the active layer is formed on the two (111) B surfaces of the first clad layer.

7. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein:

at the semiconductor layer forming step, a semi-insulating current block layer and an n-type current block layer are formed in order as the semiconductor layer on an n-type semiconductor substrate;

at the groove forming step, a dielectric mask is formed as the mask, and the semi-insulating current block layer and the n-type current block layer at the opening are etched to form the groove;

at the first clad layer forming step, an n-side clad layer is formed as the first clad layer in the groove;

at the active layer forming step, an active layer is formed on the two inclined faces of the n-side clad layer; and

at the active layer burying step, the dielectric mask is removed and the active layer is buried with a p-side clad layer as the second clad layer.

8. The fabrication method for an optical semiconductor device as claimed in claim 1, wherein, at the semiconductor layer forming step, an n-type current block layer and a p-type current block layer are formed in-order as the semiconductor layer on a p-type semiconductor substrate;

at the groove forming step, a dielectric mask is formed as the mask, and the n-type current block layer and the p-type current block layer at the opening are etched to form the groove;

at the first clad layer forming step, a p-side clad layer is formed as the first clad layer in the groove;

at the active layer forming step, an active layer is formed on the two inclined faces of the p-side clad layer; and

at the active layer burying step, the dielectric mask is removed and the active layer is buried with an n-side clad layer as the second clad layer.

9. The fabrication method for an optical semiconductor device as claimed in claim 1, further comprising, after all of the steps, the conditional step of forming electrodes at the top and the bottom.

10. An optical semiconductor device, comprising:

a semiconductor substrate;

a clad layer in the form of a projection formed on said semiconductor substrate and having two symmetrical inclined faces;

an active layer formed on the two inclined faces of said clad layer; and

a semiconductor layer formed in a contacting relationship with at least side faces of said clad layer and having an equal thickness at portions in the proximity of contacting portions thereof with said clad layer and any other portion thereof than the portions.

11. The optical semiconductor device as claimed in claim 10, wherein said active layer is formed from one of quantum dots, quantum wires and quantum wells is formed as the active layer.

12. The optical semiconductor device as claimed in claim 10, wherein said semiconductor layer includes a plurality of semiconductor layers having different conduction types in which a current constriction structure can be formed.

13. The optical semiconductor device as claimed in claim 10, wherein said clad layer is formed on a (001) semiconductor substrate and each of said inclined faces thereof is formed as a (111) B surface, and said active layer is formed on the two (111) B surfaces of said clad layer.

14. The optical semiconductor device as claimed in claim 10, wherein said clad layer and said active layer extend in a [110] direction.

15. The optical semiconductor device as claimed in claim 10, wherein said semiconductor substrate is an n-type semiconductor substrate while said clad layer is an n-side clad layer, and said semiconductor layer includes a semi-insulating current block layer and an n-type current block layer.

16. The optical semiconductor device as claimed in claim 10, wherein said semiconductor substrate is a p-type semiconductor substrate while said clad-layer is a p-side clad layer, and said semiconductor layer includes an n-type current block layer and a p-type current block layer.