Coplanar integration of a direct-bandgap chip into a silicon photonic device

1. A method for fabricating a composite device comprising:

providing a platform, the platform comprising:

a base layer;

a device layer; and

an insulating layer between the base layer and the device layer, wherein the insulating layer comprises a different material than the base layer;

etching the platform to form a plurality of walls in the device layer and the insulating layer, wherein the device layer and the insulating layer comprise the plurality of walls forming an opening in the device layer and the insulating layer such that:

a portion of the base layer of the platform is exposed through the device layer and the insulating layer through the opening; and

the opening is laterally surrounded by the plurality of walls;

providing a chip, the chip comprising:

a substrate comprising a III-V material; and

an active region comprising a III-V material;

aligning the active region with the device layer using pedestals formed in the platform;

bonding the chip to the portion of the base layer of the platform, so that the active region is optically aligned with the device layer of the platform;

removing at least a portion of the substrate from the chip after bonding the chip to the portion of the base layer of the platform; and

applying a material between the chip and a wall of the plurality of walls to form an optical bridge between the chip and the wall, wherein the material between the chip and the wall has an index of refraction matched to a refractive index of the device layer or the active region of the chip.

2. The method for fabricating the composite device as recited in claim 1 , wherein:

the chip extends through the opening of the device layer and the insulating layer, after bonding the chip to the portion of the base layer of the platform; and

the substrate of the chip extends above a top surface of the platform.

3. The method for fabricating the composite device as recited in claim 1 , wherein the platform comprises silicon.

4. The method for fabricating the composite device as recited in claim 1 , wherein the device layer of the platform comprises crystalline silicon.

5. A method for fabricating a composite device, the method comprising:

providing a platform having a base layer, a device layer, and an insulating layer, wherein:

the insulating layer is between the base layer and the device layer;

the insulating layer comprises a different material than the base layer;

the platform comprises a recess that forms an opening in the device layer and the insulating layer to expose a portion of the base layer;

the opening in the device layer and the insulating layer is defined by a plurality of walls such that the opening is laterally surrounded by the plurality of walls; and

the device layer comprises a first material;

providing a chip, wherein:

the chip comprises an active region and a portion of a substrate;

the active region comprises a second material; and

the portion of the substrate comprises the second material;

bonding the chip in the recess to the portion of the base layer of the platform, wherein the bonding the chip in the recess optically aligns the active region of the chip with the device layer of the platform;

removing the portion of the substrate from the chip after the chip is bonded to the platform; and

applying a material between the chip and a wall of the plurality of walls to form an optical bridge between the chip and the wall, wherein the material between the chip and the wall has an index of refraction matched to a refractive index of the device layer or the active region of the chip.

6. The method for fabricating the composite device as recited in claim 5 , wherein the portion of the substrate extends above the platform and after removing the portion of the substrate the chip does not extend above the platform.

7. The method for fabricating the composite device as recited in claim 5 , wherein removing the portion of the substrate is performed by etching.

8. The method for fabricating the composite device as recited in claim 5 , further comprising fabricating the chip by growing an etch stop above the substrate and then growing the active region above the etch stop.

9. The method for fabricating the composite device as recited in claim 5 , wherein:

the chip further comprises an etch stop; and

removing the portion of the substrate includes etching the chip to the etch stop.

10. The method for fabricating the composite device as recited in claim 5 wherein the insulating layer comprises an oxide.

11. The method for fabricating the composite device as recited in claim 5 , wherein the second material is a III-V material.

12. The method for fabricating the composite device as recited in claim 5 , wherein the device layer comprises silicon.