Multi-wafer based light absorption apparatus and applications thereof
Structures and techniques introduced here enable the design and fabrication of photodetectors (PDs) and/or other electronic circuits using typical semiconductor device manufacturing technologies meanwhile reducing the adverse impacts on PDs' performance. Examples of the various structures and techniques introduced here include, but not limited to, a pre-PD homogeneous wafer bonding technique, a pre-PD heterogeneous wafer bonding technique, a post-PD wafer bonding technique, their combinations, and a number of mirror equipped PD structures. With the introduced structures and techniques, it is possible to implement PDs using typical direct growth material epitaxy technology while reducing the adverse impact of the defect layer at the material interface caused by lattice mismatch.
1. A semiconductor structure comprising:
a first silicon wafer having a front side;
a photosensitive material layer deposited on the front side of the first silicon wafer, the photosensitive material layer including a number of Si x Ge (1-x) layers, wherein 0≤x<1;
a passivation layer on top of the photosensitive material layer; and
a second silicon wafer having a front side,
wherein the first silicon wafer and the second silicon wafer are bonded together with the passivation layer facing the front side of the second silicon wafer.
2. The structure of claim 1 , wherein, in the number of Si x Ge (1-x) layers, an x value of one Si x Ge (1-x) layer is different than another Si x Ge (1-x) layer.
3. The structure of claim 1 , wherein the passivation layer comprises a material also contained on top of the second silicon wafer.
4. The structure of claim 3 , wherein the material also contained on top of the second silicon wafer comprises silicon.
5. The structure of claim 1 , wherein the passivation layer comprises a semiconductor material that is not silicon-germanium based but exhibits a passivation effect to the photosensitive material layer.
6. The structure of claim 1 , wherein the passivation layer comprises a semiconductor material that is lattice-matched to germanium.
7. The structure of claim 1 , wherein the passivation layer is gallium arsenide.
8. The structure of claim 1 , wherein the photosensitive material layer is doped to a predetermined doping profile suitable for a photodetector.
9. The structure of claim 1 , wherein the passivation layer is doped by impurities.
10. The structure of claim 1 , wherein the passivation layer and the second silicon wafer are doped by a same kind of dopant.
11. The structure of claim 10 , wherein the dopant is N-type.
12. The structure of claim 1 , wherein the front side of the first silicon wafer has been polished.
13. The structure of claim 1 , wherein the first silicon wafer has been annealed.
14. The structure of claim 1 , wherein the second silicon wafer has been patterned.
15. The structure of claim 1 , further comprising:
an additional passivation layer on the front side of the second silicon wafer.
16. The structure of claim 1 , wherein the first and second silicon wafers are bonded together by one or more of: a dry wafer bonding, a wet wafer bonding, a chemical wafer bonding, or a plasma assisted wafer bonding.
17. The structure of claim 1 , further comprising other portions of a photodetector fabricated on the second silicon wafer.
18. The structure of claim 1 , further comprising a separation layer on the first silicon wafer.