Semiconductor photodetection device

1. A semiconductor photodetection device, comprising:

a semiconductor structure including an optical absorption layer having a photo-incidence surface on a first side thereof;

a dielectric reflecting layer formed on a second side of the semiconductor structure opposite to the first side;

a contact electrode surrounding the dielectric reflecting layer and contacting with the semiconductor structure; and

a metal reflecting layer formed within a region inside the contact electrode;

wherein a reactivity of the metal reflecting layer with the semiconductor material of the semiconductor structure is lower than a reactivity of the contact electrode with the semiconductor material; wherein the dielectric reflecting layer, surrounded by said contact electrode, surrounds the metal reflecting layer.

2. A semiconductor photodetection device as claimed in claim 1 , wherein said metal reflecting layer includes a transition metal belonging to any group of groups 3B through 8B.

3. A semiconductor photodetection device as claimed in claim 2 , wherein said metal reflecting layer includes one or more materials selected from the group consisting of Pt, Ni, TiW and TiN.

4. A semiconductor photodetection device as claimed in claim 1 , wherein said metal reflecting layer comprises a first metal reflecting layer having a thickness thinner than the absorption length at a signal light wavelength, and a second metal reflecting layer formed on the first metal reflecting layer.

5. A semiconductor photodetection device as claimed in claim 4 , wherein said first metal reflecting layer includes a transition metal belonging to any group of groups 3B through 8B and said second metal reflecting layer includes transition metal belonging to group 1B or 2B.

6. A semiconductor photodetection device as claimed in claim 5 , wherein said first metal reflecting layer includes one or more materials selected from the group consisting of Pt, Ni, TiW and TiN, and said second metal reflecting layer includes one or more atoms selected from the group consisting of Au, Ag and Cu.

7. A semiconductor photodetection device as claimed in claim 1 , wherein said contact electrode is of a ring shape.

8. A semiconductor photodetection device as claimed in claim 1 , wherein said semiconductor structure is mounted on a semiconductor substrate and the photo-incidence surface is placed on the substrate side of the semiconductor structure.

9. A semiconductor photodetection device as claimed in claim 1 , wherein said semiconductor structure is mounted on a semiconductor substrate and the photo-incidence surface is placed on a side opposite to the substrate of the semiconductor structure.

10. A semiconductor photodetection device as claimed in claim 1 , wherein said semiconductor structure further includes a carrier-multiplier layer, and said semiconductor photodetection device is an avalanche photodiode.

11. A semiconductor photodetection device, comprising:

a semiconductor structure including an optical absorption layer having a photo-incidence surface on a first side thereof;

a dielectric reflecting layer formed on a second side of the semiconductor structure opposite to the first side;

a contact electrode contacting with the semiconductor structure; and

a metal reflecting layer formed within a region inside the contact electrode;

wherein a reactivity of the metal reflecting layer with the semiconductor material of the semiconductor structure is lower than a reactivity of the contact electrode with the semiconductor material; wherein said contact electrode is formed partially surrounding the dielectric reflecting layer, wherein the dielectric reflecting layer, partially surrounded by said contact electrode, surrounds the metal reflecting layer.