SOI-based inverse nanotaper optical detector
A photodetector integrated within a silicon-on-insulator (SOI) structure is formed directly upon an inverse nanotaper endface coupling region to reduce polarization sensitivity at the detector's input. The photodetector may be germanium-based PN (PIN) junction photodetector, a SiGe photodetector, a metal/silicon Schottky barrier photodetector, or any other suitable silicon-based photodetector. The inverse nanotaper photodetector may also be formed as an in-line monitoring device, converting only a portion of the in-coupled optical signal and allowing for the remainder to thereafter propagate along an associated optical waveguide.
1 . A photodetector arrangement based on a silicon-on-insulator (SOI) structure, the photodetector arrangement comprising:
a silicon substrate;
a buried oxide layer disposed to a predetermined thickness over the silicon substrate;
an inverse nanotaper coupling region comprising a pair of adiabatically tapering sidewalls extending from a narrowed tip first end in proximity of an endface of the SOI structure to a wider, second endface, the narrowed tip first end increasing coupling efficiency of an incoming lightwave signal; and
a photodetecting element integral with the inverse nanotaper coupling region to convert the incoming lightwave signal into an output electrical signal, wherein the location of the photodetecting element integral with said inverse nanotaper coupling region increases conversion efficiency between the incoming lightwave signal and the output electrical signal.
2 . A photodetector arrangement as defined in claim 1 wherein the SOI structure further comprises a relatively thin silicon surface layer (SOI layer) disposed over the buried oxide layer, with the inverse nanotaper coupling region formed in the SOI layer.
3 . A photodetector arrangement as defined in claim 1 wherein the photodetecting element comprises photodetecting material formed as the inverse nanotaper coupling region.
4 . A photodetector arrangement as defined in claim 1 wherein the inverse nanotaper coupling region terminates at the wider, second endface.
5 . A photodetector arrangement as defined in claim 1 wherein the arrangement further comprises an optical waveguiding region coupled to the wider, second endface of the inverse nanotaper coupling region.
6 . A photodetector arrangement as defined in claim 1 wherein the photodetecting element comprises a germanium-based element.
7 . A photodetector arrangement as defined in claim 6 wherein the germanium-based element comprises single crystal germanium.
8 . A photodetector arrangement as defined in claim 6 wherein the germanium-based element comprises polycrystalline germanium.
9 . A photodetector arrangement as defined in claim 6 wherein the germanium-based element includes a first p-doped region and a second n-doped region, with a first electrical contact coupled to the p-doped region and a second electrical contact coupled to the n-doped region.
10 . A photodetector arrangement as defined in claim 9 wherein the first and second doped germanium regions are contiguous and form a PN-junction germanium-based photodetector.
11 . A photodetector arrangement as defined in claim 9 wherein the first and second doped germanium regions are separated by an undoped region and form a PIN germanium-based photodetector.
12 . A photodetector arrangement as defined in claim 9 wherein the first and second regions are disposed to form a vertical junction perpendicular to the SOI structure.
13 . A photodetector arrangement as defined in claim 9 wherein the first and second regions are disposed to form a horizontal junction parallel to the SOI structure.
14 . A photodetector arrangement as defined in claim 6 wherein the arrangement further comprises a relatively thin dielectric layer disposed between the SOI layer and the germanium-based element.
15 . A photodetector arrangement as defined in claim 1 wherein the photodetecting element comprises a SiGe material.
16 . A photodetector arrangement as defined in claim 2 wherein the photodetecting element comprises a Schottky barrier photodetecting structure including a silicide layer disposed over the SOI layer inverse nanotaper coupling region.
17 . A photodetector arrangement as defined in claim 16 wherein the silicide is formed using a metal selected from the group consisting of: platinum, cobalt, titanium, tantalum, tungsten, nickel and molybdenum.
18 . A photodetector arrangement as defined in claim 16 wherein the silicide comprises a monocrystalline silicide.
19 . A photodetector arrangement as defined in claim 16 wherein the silicide comprises a polycrystalline silicide.