Silicon-based Schottky barrier infrared optical detector
View Patent ↗A silicon-based IR photodetector is formed within a silicon-on-insulator (SOI) structure by placing a metallic strip (preferably, a silicide) over a portion of an optical waveguide formed within a planar silicon surface layer (i.e., “planar SOI layer”) of the SOI structure, the planar SOI layer comprising a thickness of less than one micron. Room temperature operation of the photodetector is accomplished as a result of the relatively low dark current associated with the SOI-based structure and the ability to use a relatively small surface area silicide strip to collect the photocurrent. The planar SOI layer may be doped, and the geometry of the silicide strip may be modified, as desired, to achieve improved results over prior art silicon-based photodetectors.
1. A monolithic arrangement comprising a Schottky barrier, silicon-based infrared photodetector integrated on a silicon-on-insulator (SOI) platform with an optical waveguide, the monolithic arrangement including
an SOI structure with a planar SOI surface layer, the planar SOI surface layer being less than one micron in thickness and forming at least a portion of the optical waveguide for supporting transmission of an optical signal;
a metallic strip disposed over a portion of the planar SOI surface layer along the direction of propagation within the optical waveguide, the metallic strip forming a Schottky barrier with the optical waveguide;
a first ohmic contact disposed on the planar SOI surface layer at a first contact area; and
a second ohmic contact disposed on the metallic strip at a second contact area, wherein the application of a bias voltage between the first and second ohmic contacts generates a photocurrent output from the metallic strip as a function of the portion of the optical signal that impinges the metallic strip as said optical signal propagates along said optical waveguide, the first and second ohmic contacts disposed to minimize the absorption of said optical signal in the first and second contact areas.
2. A monolithic arrangement as defined in claim 1 wherein the planar SOI surface layer comprises a single crystal silicon.
3. A monolithic arrangement as defined in claim 1 wherein the planar SOI surface layer comprises strained lattice crystalline silicon.
4. A monolithic arrangement as defined in claim 1 wherein the planar SOI surface layer comprises Si—Ge.
5. A monolithic arrangement as defined in claim 1 wherein the first and second ohmic contacts are disposed at substantially the same distance above the top surface of the planar SOI surface layer.
6. A monolithic arrangement as defined in claim 1 wherein the metallic strip does not overlap any corners or edges of the planar SOI surface layer, the nonoverlapping arrangement for reducing the associated dark current and providing room temperature operation.
7. A monolithic arrangement as defined in claim 1 wherein the metallic strip is formed to exhibit rounded corner and edges so as to reduce the associated dark current and provide room temperature operation.
8. A monolithic arrangement as defined in claim 1 wherein the planar SOI surface layer is doped.
9. A monolithic arrangement as defined in claim 8 wherein the planar SOI surface layer is p-doped.
10. A monolithic arrangement as defined in claim 8 wherein the planar SOI surface layer is n-doped.
11. A monolithic arrangement as defined in claim 8 wherein the doping within the planar SOI surface layer is graded such that the resultant electric field improves the collection and transportation of carriers injected over the Schottky barrier into the planar SOI surface layer.
12. A monolithic arrangement as defined in claim 1 wherein the metallic strip comprises a silicide strip.
13. A monolithic arrangement as defined in claim 12 wherein the silicide comprises a monocrystalline silicide.
14. A monolithic arrangement as defined in claim 12 wherein the silicide comprises a polycrystalline silicide.
15. A monolithic arrangement as defined in claim 12 wherein the silicide strip is formed using a metal selected from the group consisting of:
platinum, cobalt, titanium, tantalum, tungsten, nickel, and molybdenum.
16. A monolithic arrangement as defined in claim 15 wherein the silicide strip comprises cobalt silicide.
17. A monolithic arrangement as defined in claim 1 wherein the first and second ohmic contacts each comprise a silicide material.
18. A monolithic arrangement as defined in claim 17 wherein the first and second silicide ohmic contacts and the metallic strip all comprise a same silicide material.
19. A monolithic arrangement as defined in claim 17 wherein the first and second silicide ohmic contacts comprise a first silicide and the metallic strip comprises a second silicide material.