Electro-absorption modulator

A method of fabricating an electro-absorption modulator (EAM), the method comprising:

• providing a silicon-on-insulator substrate, the substrate comprising:
• a silicon support layer;
• a buried oxide (BOX) layer on top of the silicon support layer;
• and a silicon device layer on top of the BOX layer;
• etching through a portion of the silicon device layer and the BOX layer to create a cavity in the substrate which exposes a portion of the silicon support layer;
• epitaxially growing a replacement layer of silicon on top of the exposed portion of the silicon support layer;
• epitaxially growing a crystalline oxide layer on top of the replacement layer of silicon, the replacement layer of silicon and the crystalline oxide layer replacing the portion of the BOX layer that had been etched away;
• epitaxially growing a layer of a first material on top of the crystalline oxide layer;
• and
• fabricating a waveguide structure within the layer of the first material, the waveguide structure including a P doped region, and an N doped region with an intrinsic region in-between, creating a PIN junction across which a bias can be applied to function as a modulation region.