Fast Si diodes and arrays with high quantum efficiency built on dielectrically isolated wafers
Fast silicon diodes and arrays with high quantum efficiency built on dielectrically isolated wafers. A waveguide is formed in the top surface of the silicon that utilizes total internal reflection from the Si—Si Oxide interface to form an internal mirror. This mirror reflects incoming light into the waveguide cavity, with the light being trapped there by surrounding reflective interfaces. A masking layer may be used to define an input window. Individual diodes or linear arrays may be formed as desired. Some alternate embodiments are described.
1. A photodiode comprising:
an active volume of silicon of a first conductivity type having a top surface, a bottom surface and side surfaces;
a first silicon layer on the bottom surface of the active volume of silicon, the first silicon layer being of the first conductivity type and more highly doped than the active volume;
a first silicon oxide layer over the first silicon layer and the bottom and sides of the active volume of silicon;
a second silicon layer of a second conductivity type on most of the top surface of the active volume of silicon and not touching the first silicon layer;
a first metal region in electrical contact with the first silicon layer; and,
a second metal region in electrical contact with the second silicon layer;
at least a first side surface of the active volume being inclined to provide substantially total reflection of light from the silicon-silicon oxide interfaces for light entering the active volume perpendicular through the first surface of the active volume over the inclined surface.
2. The photodiode of claim 1 wherein the first silicon layer extends up at least one side surface of the active volume for electrical contact with the first metal region.
3. The photodiode of claim 2 wherein the first silicon layer extends up all side surfaces of the active volume.
4. The photodiode of claim 1 wherein all side surfaces of the active volume are inclined, the light reflected from the first surface being substantially totally confined within the active volume by further reflections from silicon-silicon oxide interfaces and silicon-metal interfaces.
5. The photodiode of claim 4 further comprising an oxide layer separating the first and second metal regions.
6. The photodiode of claim 1 further comprising an opaque masking layer defining a window over the first inclined side surface for entry of light into the active volume.
7. A plurality of photodiodes, each in accordance with claim 6 , the photodiodes being disposed and supported in a body to form a linear photodiode array.
8. The plurality of photodiodes of claim 7 wherein the opaque masking layer is a metal layer.
9. The plurality of photodiodes of claim 8 wherein the opaque masking layer, the first metal regions and the second metal regions are formed by patterning a single metal layer.
10. The photodiode of claim 1 wherein the photodiode is supported in a body.
11. A plurality of photodiodes, each in accordance with claim 1 , the photodiodes being disposed and supported in the body to form a linear photodiode array.
12. The plurality of photodiodes of claim 1 further comprising an opaque masking layer defining a window over the first inclined side surface for entry of light into the active volume.
13. The plurality of photodiodes of claim 1 wherein the opaque masking layer is a metal layer.
14. The plurality of photodiodes of claim 13 wherein the opaque masking layer, the first metal region and the second metal region are formed by patterning a single metal layer.
15. A photodiode comprising:
an active volume of silicon of a first conductivity type having a top surface, a bottom surface and side surfaces;
a first silicon layer on the bottom surface and side surfaces of the active volume of silicon, the first silicon layer being of the first conductivity type and more highly doped than the active volume;
a first silicon oxide layer over the first silicon layer;
a second silicon layer of a second conductivity type on most of the top surface of the active volume of silicon and not touching the first silicon layer;
a first metal region in electrical contact with the first silicon layer; and,
a second metal region in electrical contact with the second silicon layer;
the side surfaces of the active volume being inclined to provide substantially total reflection of light from the silicon-silicon oxide interfaces for light entering the active volume perpendicular through the first surface of the active volume over the inclined surface.
16. The photodiode of claim 15 further comprising an oxide layer separating the first and second metal regions.
17. The photodiode of claim 16 further comprising an opaque masking layer defining a window over the first inclined side surface for entry of light into the active volume.
18. A plurality of photodiodes, each in accordance with claim 17 , the photodiodes being disposed and supported in a body to form a linear photodiode array.
19. The plurality of photodiodes of claim 18 wherein the opaque masking layer is a metal layer.
20. The plurality of photodiodes of claim 19 wherein the opaque masking layer, the first metal regions and the second metal regions are formed by patterning a single metal layer.
21. The photodiode of claim 15 wherein the photodiode is supported in a body.
22. A plurality of photodiodes, each in accordance with claim 15 , the photodiodes being disposed and supported in the body to form a linear photodiode array.
23. The plurality of photodiodes of claim 22 further comprising an opaque masking layer defining a window over the first inclined side surface for entry of light into the active volume.
24. The plurality of photodiodes of claim 23 wherein the opaque masking layer is a metal layer.
25. The plurality of photodiodes of claim 24 wherein the opaque masking layer, the first metal regions and the second metal regions are formed by patterning a single metal layer.