1. A strained silicon semiconductor device structure, comprising a relaxed buffer layer (RBL) formed on a substrate, and a strained silicon layer on said RBL, wherein said RBL comprises a silicon-germanium alloy, and said strained silicon layer comprises a silicon-carbon alloy, and wherein the RBL has a threading dislocation density, measured at a top surface thereof adjacent the strained silicon layer, which does not exceed 105 defectscm2.
2. The device structure of claim 1, wherein said silicon-carbon alloy contains from about 0.2 to about 1.5 atomic % of carbon, based on the total silicon and carbon in said alloy.
3. The device structure of claim 1, wherein said silicon-carbon alloy contains from about 0.4 to about 1.2 atomic % of carbon, based on the total silicon and carbon in said alloy.
4. The device structure of claim 1, wherein said silicon-carbon alloy contains from about 0.5 to about 1.0 atomic % of carbon, based on the total silicon and carbon in said alloy.
5. The device structure of claim 1, wherein the amount of carbon in said silicon-carbon alloy is such that substantially all of the carbon atoms are substitutionally incorporated in said silicon-carbon alloy.
6. The device structure of claim 1, wherein the amount of carbon in said silicon-carbon alloy is below the carbon concentration threshold for alloy scattering.
7. The device structure of claim 1, wherein the strained silicon layer has a thickness of from about 5 to about 50 nanometers.
8. The device structure of claim 1, wherein the strained silicon layer has a thickness of from about 8 to about 40 nanometers.
9. The device structure of claim 1, wherein the strained silicon layer has a thickness of from about 10 to about 20 nanometers.
10. The device structure of claim 1, wherein said silicon-germanium alloy has a formula SixGe1-x wherein x is from about 0.6 to about 0.95.
11. The device structure of claim 1, wherein said silicon-germanium alloy has a formula SixGe1-x wherein x is from about 0.65 to about 0.90.
12. The device structure of claim 1, wherein said silicon-germanium alloy has a formula SixGe1-x wherein x is from about 0.7 to about 0.85.
13. The device structure of claim 1, incorporated in a semiconductor device.
14. The device structure of claim 13, wherein the semiconductor device comprises a heterojunction CMOS device.
15. The device structure of claim 13, wherein the semiconductor device comprises a transistor device.
16. The device structure of claim 15, wherein said transistor device comprises an HFET.
17. The device structure of claim 15, wherein said transistor device comprises an MOSFET.
18. The device structure of claim 16, wherein said transistor device comprises an MODFET.
19. The device structure of claim 1, on a silicon wafer substrate.
20. A heterojunction field effect transistor including a relaxed buffer layer (RBL) comprising a silicon-germanium alloy, and a channel layer on the RBL comprising a silicon-carbon alloy including from about 0.5 to about 1.0 atomic % based on the total of silicon and carbon in said channel layer, wherein the silicon-germanium alloy includes about 10 to about 30 atomic % germanium, the channel layer is from about 10 to about 20 nanometers in thickness, and the RBL has a threading dislocation density, measured at a surface thereof adjacent the channel layer, which does not exceed 105 defectscm2.
21. A method of fabricating a semiconductor device structure including an SiGe relaxed buffer layer (RBL) formed on a substrate and a strained silicon channel layer on the RBL, said method comprising forming said silicon channel layer of a material comprising a silicon-carbon alloy, and wherein the RBL has a threading dislocation density, measured at a top surface thereof adjacent the strained silicon channel layer, which does not exceed 105 defectscm2.
22. The method of claim 21, wherein said silicon-carbon alloy contains from about 0.2 to about 1.5 atomic % of carbon, based on the total silicon and carbon in said alloy.
23. The method of claim 21, wherein said silicon-carbon alloy contains from about 0.4 to about 1.2 atomic % of carbon, based on the total silicon and carbon in said alloy.
24. The method of claim 21, wherein said silicon-carbon alloy contains from about 0.5 to about 1.0 atomic % of carbon, based on the total silicon and carbon in said alloy.
25. The method of claim 21, wherein the amount of carbon in said silicon-carbon alloy is such that substantially all of the carbon atoms are substitutionally incorporated in said silicon-carbon alloy.
26. The method of claim 21, wherein the amount of carbon in said silicon-carbon alloy is below the carbon concentration threshold for alloy scattering.
27. The method of claim 21, wherein the silicon channel layer has a thickness of from about 5 to about 50 nanometers.
28. The method of claim 21, wherein the silicon channel layer has a thickness of from about 8 to about 40 nanometers.
29. The method of claim 21, wherein the silicon channel layer has a thickness of from about 10 to about 20 nanometers.
30. The method of claim 21, wherein said RBL comprises a silicon-germanium alloy having a formula SixGe1-x wherein x is from about 0.6 to about 0.95.
31. The method of claim 21, wherein said RBL comprises a silicon-germanium alloy having a formula SixGe1-x wherein x is from about 0.65 to about 0.90.
32. The method of claim 21, wherein said RBL comprises a silicon-germanium alloy having a formula SixGe1-x wherein x is from about 0.7 to about 0.85.
33. The method of claim 21, wherein the semiconductor device structure comprises a heterojunction CMOS device.
34. The method of claim 21, wherein the semiconductor device structure comprises a transistor device.
35. The method of claim 21, wherein the semiconductor device structure comprises an HFET.
36. The method of claim 21, wherein the semiconductor device structure comprises an MOSFET.
37. The method of claim 21, wherein the semiconductor device structure comprises an MOSFET.
38. A method of fabricating a strained semiconductor device structure including a relaxed buffer layer (RBL) formed on a substrate and a strained silicon layer on said RBL, said method comprising the steps of forming said RBL of a material comprising a silicon-germanium alloy and forming said strained silicon layer of a material comprising a silicon-carbon alloy, wherein the RBL is grown under conditions producing a threading dislocation density, measured at a top surface thereof adjacent the silicon channel layer, which does not exceed 105 defectscm2.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for determining the location of a physical disturbance, comprising:
at least one signal source;
two interferometers, each said interferometer comprising an input end coupled to one said signal source, an output end, and two waveguides, each end of said two waveguides coupled to at least one of said input end, said output end, and a means of waveguide coupling, said interferometer defining two different signal paths of substantially equal lengths, wherein signals can propagate from said input end to said output end,
wherein at least part of at least one of said waveguides from one of said two interferometers overlaps at least part of at least one of said waveguides from the other of said two interferometers,
wherein said two interferometers are substantially different in at least one of type and orientation with respect to said overlapping parts,
wherein said overlapping parts of said waveguides define a detection zone, wherein for each of said two interferometers the distance from any point in said detection zone to the output end is substantially the same along each waveguide traversing said detection zone,
wherein a disturbance instills a variation over time in a phase relationship of the signals traveling along the signal paths at the point where the disturbance occurs, for each of said interferometers;
at least one signal receiver coupled to the output ends of the interferometers, configured to sense said variations over time in the phase relationships of the signals traveling along the said signal paths for each of said interferometers;
a processor coupled to the said at least one signal receiver configured to derive at least two composite signals from the said variations over time in the phase relationships, wherein a relationship between said composite signals varies with the location of the point of the disturbance, said processor further configured to derive a value of said relationship between said composite signals, said value identifying said point in the detection zone at which the disturbance occurred.
2. The apparatus of claim 1, wherein the said at least one signal receiver is a phase responsive receiver, and comprises for each of said two interferometers:
at least one signal combiner configured to combine signals traveling along the signal paths for the said interferometer;
at least one detection device coupled to said signal combiner, wherein the detection device derives at least two mutually independent detector signals, wherein the detector signals developed by the detection device are processed to obtain said variation over time in the phase relationship between the signals traveling along the said signal paths of the said interferometer;
3. The apparatus of claim 1, wherein said input end of at least one of said two interferometers comprises a signal splitter configured to split signals in at least one of space and time.
4. The apparatus of claim 1, wherein the input end and the output end of at least one of said two interferometers are a same end.
5. The apparatus of claim 1, wherein at least one of an input end and an output end of one of said two interferometers and at least one of an input end and an output end of the other of said two interferometers are a same end.
6. The apparatus of claim 1, wherein said means of waveguide coupling comprises at least a mirror coupled to an end of a waveguide.
7. The apparatus of claim 1, wherein said means of waveguide coupling comprises at least a link coupling ends of two different waveguides.
8. The apparatus of claim 1, wherein signals from different interferometers traveling in said overlapping parts of said waveguides share same physical paths and are at least one of counter-propagating, wavelength division multiplexed, and time division multiplexed.
9. The apparatus in claim 1, wherein said two waveguides of at least one of said two interferometers overlap at least in part.
10. The apparatus in claim 9, wherein signals traveling in said overlapping parts of said two waveguides share a same physical path and are separated by time.
11. The apparatus of claim 1, wherein said two waveguides are two optical fibers, at least a part of said two optical fibers being one of a single-mode fiber and a multi-mode fiber.
12. The apparatus in claim 1, wherein said at least one signal source comprises at least one coherent light source.
13. The apparatus in claim 1, wherein said at least one signal source comprises at least one broadband light source.
14. The apparatus in claim 1, wherein said at least one signal source comprises two light sources producing substantially different wavelengths of light.
15. The apparatus in claim 1, wherein said at least one signal source comprises at least one modulated light source.
16. The apparatus of claim 1, wherein said composite signals are linear combinations of time-shifted phase relationships.
17. The apparatus of claim 1, wherein the relationship between the composite signals comprises a correlation of at least a component of each of said composite signals at a time lag that varies corresponding to variation in the point at which the disturbance occurred.
18. The apparatus of claim 1, wherein the relationship between the composite signals comprises a ratio of at least a component of each of said composite signals, wherein said ratio varies corresponding to variation in the point at which the disturbance occurred.
19. The apparatus of claim 1, wherein the two interferometers comprise a Mach-Zehnder interferometer with one of a Sagnac interferometer, a Michelson interferometer and a second Mach-Zehnder interferometer.
20. The apparatus of claim 1, wherein the two interferometers comprise a Sagnac interferometer with one of a Mach-Zehnder interferometer, a Michelson interferometer and second Sagnac interferometer.
21. The apparatus of claim 1, wherein the two interferometers comprise a Michelson interferometer with one of a Mach-Zehnder interferometer, a Sagnac interferometer and a second Michelson interferometer.
22. The apparatus of claim 1, wherein the composite signals derived from the variations over time in phase relationships have corresponding waveshapes over time.
23. The apparatus of claim 1, wherein the processor is arranged to repetitively process the variations over time change in the phase relationships to obtain a value that varies with the location of the disturbance, and comprises a memory configured for storing values previously obtained, and wherein the processor is operable to determine changes in the value over time, representing at least one of a new disturbance, a movement of a previous said disturbance, and a disturbance that is distributed over a length.
24. The apparatus of claim 1, further comprising at least one polarization controlling device coupled to at least one of said interferometers.
25. The apparatus of claim 24, wherein said polarization controlling device is at least one of a polarization controller, a Faraday mirror, and a depolarizer.
26. The apparatus of claim 24, wherein said polarization controlling device is part of said interferometer.
27. A plurality of apparatuses of claim 1, sharing at least one of said signals source, said signals receiver, and said processor.
28. A method for determining a location of a physical disturbance, comprising:
coupling at least one signal source to two interferometers, each said interferometer defining two signal paths of substantially equal lengths;
arranging the signal paths such that at least part of at least one of said signal paths from one of said two interferometers overlaps at least part of at least one of said signal paths from the other of said two interferometers,
causing the signals traveling along the signal paths that overlap to traverse a detection zone, at least once,
wherein the disturbance instills a variation over time in a phase relationship of the signals traveling along the signal paths at a point where the disturbance occurs, for both of said interferometers;
coupling at least one signal receiver to the output ends of the interferometers and configuring the signal receiver to sense said variations over time in the phase relationships of the signals traveling along the signal paths for each of said two interferometers;
processing the outputs of the signal receiver to derive two composite signals from the said variations over time in the phase relationships, wherein a relationship between said composite signals varies with a location of the point of the disturbance, such that a value of the relationship corresponds to said point in the detection zone at which the disturbance occurred; and
determining from the value of the relationship, the point in the detection zone at which the disturbance occurred.
29. The method of claim 28, wherein deriving said two composite signals comprises obtaining two different linear combinations of time-shifted phase relationships.
30. The method of claim 28, wherein determining the value of the relationship comprises determining a time lag at which aspects of the composite signals correlate, and determining the point of the disturbance from the time lag.
31. The method of claim 28, wherein determining the value of the relationship comprises solving a composite signal ratio and determining the point of the disturbance from the ratio.
32. The method of claim 28, comprising combining two interferometer configurations of a same type, placed at least partly coextensively to provide said two interferometers, wherein the two interferometers are superimposed such that corresponding signals in respective ones of the two interferometers traverse the detection zone in opposite directions.
33. The method of claim 32, wherein the interferometer configurations of the same type are chosen from a group consisting of Mach-Zehnder, Sagnac, and Michelson interferometer configurations.
34. The method of claim 28, comprising combining two interferometer configurations of different type placed at least partly coextensively to provide said two interferometers, wherein the two interferometer configurations of different type are chosen from a group consisting of Mach-Zehnder, Sagnac, and Michelson interferometer configurations.
35. The method of claim 28, comprising combining two interferometer configurations placed at least partly coextensively to provide said two interferometers, wherein one of said two interferometer configurations comprises one of a Mach-Zehnder, Sagnac, and Michelson interferometer configuration.
36. The method of claim 28, wherein combining said at least two interferometers comprises at least one of counter-propagation, time division multiplexing, and wavelength division multiplexing of signals from different ones of said interferometers.
37. The method of claim 28, comprising coupling a Mach-Zehnder interferometer with a Sagnac interferometer, wherein the input ends of the interferometers define one end of a structure and wherein the output end of the Mach-Zehnder interferometer and a center point of a Sagnac interferometer loop define an other end of the structure;
further comprising deriving composite signals in the form:
\u03a6\u20321(t)=\u03a61(t)
\u03a6\u20322(t)=\u03a61(t\u2212t0)+\u03a62(t)
where \u03a61(t) and \u03a62(t) are said variations over time in phase relationships for the Mach-Zehnder interferometer and the Sagnac interferometer, respectively, and t0 is a one-way signal propagation time of the structure;
wherein the composite signals have substantially identical waveshapes at a time lag of t2\u2212t1, where t1 and t2 are signal propagation times from the point of disturbance to respective said ends of the structure;
and further comprising determining the location of the disturbance from said time lag.
38. The method of claim 28, comprising coupling a Mach-Zehnder interferometer with a Michelson interferometer, wherein the input ends of the interferometers define one end of a structure and wherein the output end of the Mach-Zehnder interferometer and at least one reflection point of the Michelson interferometer define an other end of the structure;
further comprising deriving composite signals in the form:
\u03a6\u20321(t)=\u03a61(t)
\u03a6\u20322(t)=\u03a61(t\u2212t0)\u2212\u03a62(t)
where \u03a61(t) and \u03a62(t) are said variations over time in phase relationships for the Mach-Zehnder interferometer and the Michelson interferometer, respectively, and t0 is a one-way signal propagation time of the structure;
wherein the composite signals have substantially identical waveshapes at a time lag of t2\u2212t1, where t1 and t2 are signal propagation times from the point of disturbance to respective said ends of the structure;
and further comprising determining the location of the disturbance from said time lag.
39. The method of claim 28, comprising coupling a Sagnac interferometer with a Michelson interferometer by means of signal multiplexing, wherein the input ends of the interferometers define one end of a structure and wherein a center point of a Sagnac interferometer loop and at least one reflection point of the Michelson interferometer define an other end of the structure;
further comprising deriving composite signals in the form:
\u03a6\u20321(t)=\u03a62(t)\u2212\u03a61(t)2
\u03a6\u20322(t)=\u03a62(t)+\u03a61(t)2
where \u03a61(t) and \u03a62(t) are said variations over time in phase relationships for the Sagnac interferometer and the Michelson interferometer, respectively;
wherein the composite signals have substantially identical waveshapes at a time lag of 2t2, where t2 is a signal propagation time from the point of disturbance to an end of the structure opposite from the input ends of the interferometers;
and, further comprising determining the location of the disturbance from said time lag.
40. The method of claim 28, comprising coupling two Sagnac interferometers by means of signal multiplexing, wherein the input ends of the interferometers define opposite ends of a structure and wherein the input end of each one of said two Sagnac interferometers is at a same end of the structure as a center point of a Sagnac loop of an other one of said two Sagnac interferometers;
further comprising deriving composite signals in the form:
\u03a6\u20321(t)=\u03a61(t)+\u03a62(t\u2212t0)
\u03a6\u20322(t)=\u03a61(t\u2212t0)+\u03a62(t)
where \u03a61(t) and \u03a62(t) are said variations over time in phase relationships for the said Sagnac interferometers, and t0 is a one-way signal propagation time of the structure;
wherein the composite signals have substantially identical waveshapes at a time lag of t1\u2212t2, where t1 and t2 are signal propagation times from the point of disturbance to respective said ends of the structure;
and further comprising determining the location of the disturbance from said time lag.
41. The method of claim 28, comprising coupling two Michelson interferometers by means of signal multiplexing, wherein the input ends of the interferometers define opposite ends of a structure and wherein the input end of each one of said two Michelson interferometers is at a same end of the structure as at least one reflection point of an other one of said two Michelson interferometers;
further comprising deriving composite signals in the form:
\u03a6\u20321(t)=\u03a61(t)\u2212\u03a62(t\u2212t0)
\u03a6\u20322(t)=\u03a61(t\u2212t0)\u2212\u03a62(t)
where \u03a61(t) and \u03a62(t) are said variations over time in phase relationships for said Michelson interferometers, and t0 is a one-way signal propagation time of the structure;
wherein the composite signals have substantially identical waveshapes at a time lag of t1\u2212t2, where t1 and t2 are signal propagation times from the point of disturbance to respective said ends of the structure;
and, further comprising determining the location of the disturbance from said time lag.
42. The method of claim 28, further comprising repetitively determining said value of relationship between the composite signals, and detecting the disturbance from a change in said value over time from an arbitrary value to a value representing a point of a disturbance.
43. The method in claim 28, comprising coupling at least one mirror to at least one signal path in at least one of the two interferometers, causing said signal path to retrace a same physical path, further comprising configuring said at least one mirror to operate as a Faraday mirror.
44. The method in claim 28, further comprising configuring two signal paths of at least one of said two interferometers to be of identical length, further comprising coupling a broadband light source to the input end of said interferometer, and further comprising inserting a signal depolarizer into at least one of said two signal paths.
45. The method in claim 28, further comprising coupling at least one polarization controller to the input end of at least one of the said two interferometers, further comprising using said polarization controller to mitigate polarization fading effects.