Avalanche diode having reduced dark current and method for its manufacture
An avalanche diode includes an absorption region in a germanium body epitaxially grown on a silicon body including a multiplication region. Aspect-ratio trapping is used to suppress dislocation growth in the vicinity of the absorption region.
1. An avalanche photodiode device comprising:
a silicon body having a planar upper surface and containing a multiplication region;
a germanium body laterally offset from the silicon multiplication region, grown epitaxially on portions of the silicon upper surface, and containing an absorption region;
a waveguide optically coupled to the germanium body with respect to light of at least one operating wavelength; and
a dielectric spacer region interposed between the silicon body and a major portion of the germanium body;
wherein the dielectric spacer region is formed with one or more aspect-ratio-trapping trenches extending vertically through the dielectric spacer region from the silicon body to the major portion of the germanium body; and
the germanium body comprises said major portion and further comprises a dislocation-trapping portion consisting of epitaxial germanium filling each of said one or more aspect-ratio-trapping trenches.
2. The avalanche photodiode device of claim 1 , wherein the germanium body is composed substantially of a silicon-germanium alloy.
3. The avalanche photodiode device of claim 1 , wherein the waveguide is optically coupled to the germanium body by evanescent coupling.
4. The avalanche photodiode device of claim 1 , wherein the waveguide is laterally displaced from the germanium body.
5. The avalanche photodiode device of claim 1 , wherein the waveguide is situated below the germanium body.
6. The avalanche photodiode device of claim 1 , wherein the germanium body is electrically continuous with the silicon body solely through the one or more dislocation-trapping germanium portions.
7. The avalanche photodiode device of claim 1 , wherein the waveguide is composed substantially of silicon.
8. The avalanche photodiode device of claim 1 , wherein the waveguide is composed substantially of silicon nitride.