Claims
- 1. A solid state, quantum mechanical, electron/hole wave switching device comprising:
- a layer of semiconductor material which supports substantially ballistic electron/hole transport; and
- a diffraction grating structure formed in said layer of semiconductor material comprising a modulation in electron/hole potential energy and/or effective mass for diffracting at least one input electron/hole beam into at least two separate output electron/hole beams.
- 2. The switching device of claim 1 wherein said grating structure is adapted to diffract an input electron/hole beam substantially completely into two output electron/hole beams to function as a switch.
- 3. The switching device of claim 1 wherein said grating structure is adapted to operate in the Bragg regime.
- 4. The switching device as claimed in claim 1 wherein said grating structure is adapted for diffracting an input electron/hole beam into three or more output electron/hole beams to form a multiplexor.
- 5. The switching device of claim 1 wherein said grating structure is adapted to operate in the Raman-Nath regime.
- 6. The switching device of claim 1 further comprising means for applying and varying said modulation.
- 7. The switching device of claim 1 further comprising input collimating means for collimating the input beam and output collimating means for collimating said output beams.
- 8. The switching device of claim 1 further comprising an emitter means for generating the input beam and collector means for collecting said output beams.
- 9. The switching device of claim 8 wherein said collector means comprises two collector elements.
- 10. The switching device of claim 8 wherein said collector means comprises at least three collector elements.
- 11. The switching device of claim 1 wherein said grating structure is adapted to divide the input beam into roughly equal output beams.
- 12. The switching device of claim 1 further comprising a means for applying said grating modulation.
- 13. The switching device of claim 12 wherein said means for applying the grating modulation comprises a periodic set of metallic electrodes positioned adjacent a surface portion of said semiconductor layer and a fixed bias voltage applied to said electrodes.
- 14. The switching device of claim 12 wherein said means for applying the grating modulation comprises a set of superlattice layers.
- 15. The switching device of claim 12 wherein said means for applying the grating modulation comprises an array of quantum wires.
- 16. The switching device of claim 12 wherein said means for applying the grating modulation comprises an array of electrode gate structures.
- 17. The switching device of claim 12 further comprising external field means for varying the grating modulation.
- 18. The switching device of claim 17 wherein said external field means comprises an electric field applied to a gate electrode structure.
- 19. The switching device of claim 18 wherein said gate electrode structure is periodic.
- 20. The switching device of claim 1 wherein
- the input electron/hole beam is incident upon the grating at an energy E,
- the grating is characterized by an angle of incidence, grating period, grating slant angle, grating average electron/hole effective mass, grating average electron/hole potential energy, grating modulated electron/hole effective mass profile, and grating modulated electron/hole potential energy profile,
- the switching device is constructed in accordance with the following in order to divide substantially all of the input beam of electrons/holes into two output beams, designated as the i=0 and i=i.sub.a electron/hole beams where i.sub.a is a positive or negative integer corresponding to a forward or a backward diffracted order:
- the grating period and grating slant angle are determined for said grating device which will make the i.sub.a backward- or forward-diffracted orders propagating, by having the progagating orders satisfy the grating equation for real angles .theta.'.sub.i.sbsb.a or .theta.".sub.i.sbsb.a :
- [2m*.sub.I (E-V.sub.I)].sup.1/2 sin.theta.'-(2.pi.i.sub.a h/.LAMBDA.)sin.phi.=r.sub.n [2m*.sub.n (E-V.sub.n)].sup.1/2 sin.theta..sup.n.sub.i.sbsb.a
- where
- n=I,III
- r.sub.I =-1
- r.sub.III =1
- .theta..sup.I.sub.i.sbsb.a =.theta.'.sub.i.sbsb.a and .theta..sup.III.sub.i.sbsb.a =.theta.".sub.i.sbsb.a are the angles (measured positive counter-clockwise from the grating surface normal) of propagation of the i.sub.a th backward- or forward-diffracted orders respectively,
- m*.sub.I and m*.sub.III are the eletron/hole effective mass of the input and output regions respectively,
- V.sub.I and V.sub.III are the electron/hole potential energy of the input and output regions respectively,
- .LAMBDA. is the grating period,
- .phi. is the grating slant angle
- .pi. is the irrational number 3.14159 . . .
- h is Planck's constant divided by 2.pi., the grating average election/hole effective mass, the grating average electron/hole potential energy, and angle .theta.' are selected such that they satisfy the Bragg condition for the i.sub.a th diffracted order: ##EQU3## where m*.sub.II is the average grating electron/hole effective mass,
- V.sub.II is the average grating electron/hole potential energy
- .theta. is the angle .theta.' refracted into the grating
- .LAMBDA. is the grating period
- .phi. is the grating slant angle
- .pi. is the irrational number 3.14159 . . .
- h is Planck's constant divided by 2.pi., and the grating electron/hole modulated effective mass profile and electron/hole modulated potential energy profile are selected such that the first harmonic of an exponential Fourier series of the effective mass profile and the first harmonic of an exponential Fourier series of the potential energy profile satisfy the Bragg regime equation:
- .rho..sub.B =Q'/2.gamma.>1,
- where
- .rho..sub.B is the Bragg regime parameter,
- Q' is the grating thickness parameter, and
- .gamma. is the grating strength parameter.
- 21. The switching device of claim 20 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made larger than approximately five such that the grating has substantial diffracted current for the i.sub.a th order for only a small range of incident angles around .theta.' and a small range of energies around E.
- 22. The switching device of claim 20 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made smaller than approximately five such that the grating has substantial diffracted current for the i.sub.a th order for a broad range of incident angles around .theta.' and a broad range of energies around E.
- 23. The switching device of claim 1 wherein the input electrons/holes are incident upon the device at an angle .theta.' and an energy E,
- wherein the grating structure is characterized by a grating period, grating slant angle, grating average electron/hole effective mass, grating average electron/hole potential energy, grating modulated electron/hole effective mass profile, and grating modulated electron/hole potential energy profile,
- and wherein the grating structure is constructed in accordance with the following so as to produce numerous diffracted beams of electrons/holes of substantially the same current:
- the grating period and grating slant angle are determined which will give desired number and directions of backward- and forward-diffracted orders, by having the propagating orders satisfy the grating equation for real angles .theta.'.sub.i and .theta.".sub.i :
- [2m*.sub.I (E-V.sub.I)].sup.1/2 sin.theta.'-(2.pi.ih/.LAMBDA.)sin.phi.=r.sub.n [2m*.sub.n (E-V.sub.n)].sup.1/2 sin.theta..sup.n.sub.i
- where
- n=I,III
- r.sub.I =-1
- r.sub.III =1
- .theta..sup.I.sub.i =.theta.'.sub.i and .theta..sup.III.sub.i =.theta.".sub.i are the angles (measured positive counter-clockwise from the grating surface normal) of propagation of the ith backward- or forward-diffracted orders respectively,
- m*.sub.I and m*.sub.III are the electron/hole effective mass of the input and output regions respectively,
- V.sub.I and V.sub.III are the electron/hole potential energy of the input and output regions respectively,
- .LAMBDA. is the grating period,
- .phi. is the grating slant angle,
- .pi. is the irrational number 3.14159 . . . ,
- h is Planck's constant divided by 2.pi., and
- the grating thickness, electron/hole modulated effective mass profile, and electron/hole modulated potential energy profile are selected such that the grating thickness, the first harmonic of an exponential Fourier series of the effective mass profile, and the first harmonic of an exponential Fourier series of the potential energy profile satisfy the Raman-Nath regime equation:
- .rho..sub.RN =Q'.gamma.>1
- where
- .rho..sub.RN is the Raman-Nath regime parameter
- Q' is the grating thickness parameter, and
- .gamma. is the grating strength parameter.
- 24. The device of claim 23 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made larger than five such that the grating has substantial diffracted current for the ith order for only a small range of incident angles around .theta.' and a small range of energies around E.
- 25. The device of claim 23 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made smaller than five such that the grating has substantial diffracted current for the ith order for only a broad range of incident angles around .theta.' and a broad range of energies around E.
- 26. A solid state, quantum mechanical, electron/hole wave device comprising a layer of semiconductor material which supports substantially ballistic electron/hole transport at energies above the conduction band and a diffraction grating structure formed in said layer of semiconductor material, said diffraction grating structure comprising a modulation in electron/hole potential energy and/or effective mass for diffracting an input electron/hole beam substantially completely into first and second separate output electron/hole beams.
- 27. The device of claim 26 wherein said grating structure is adapted to divide an input beam of electrons/holes into one of said first and second output beams of electrons/holes with substantially all of the input beam current and the other of said first and second output beams of electrons/holes with substantially none of the input beam current.
- 28. The device of claim 26 wherein said grating structure is adapted to divide an input beam of electrons/holes substantially equally into said first and second output beams of electrons/holes.
- 29. The device of claim 26 wherein said first output beam has an arbitrary selected portion of the input beam current and said second output beam has substantially the remainder of the input beam current.
- 30. The device of claim 26 further comprising a means for applying said grating modulation.
- 31. The device of claim 30 wherein said means for applying the grating modulation comprises a periodic set of metallic electrodes positioned adjacent a surface portion of said semiconductor layer and a fixed bias voltage applied to said electrodes.
- 32. The device of claim 30 wherein said means for applying the grating modulation comprises a set of superlattice layers.
- 33. The device of claim 30 wherein said means for applying the grating modulation comprises an array of quantum wires.
- 34. The device of claim 30 wherein said means for applying the grating modulation comprises an array of electrode gate structures.
- 35. The device of claim 30 further comprising external field means for varying the grating modulation.
- 36. The device of claim 35 wherein said external field means comprises an electric field applied to a gate electrode structure.
- 37. The device of claim 36 wherein said gate electrode structure is periodic.
- 38. The device of claim 26 further comprising input collimating means for collimating the input beam and first and second output collimating means for collimating said first and second output beams.
- 39. The device of claim 26 further comprising an emitter means for generating the input beam and first and second collector means for collecting said first and second output beams.
- 40. The device of claim 39 wherein said emitter means comprises means for generating a plurality of input beams which are incident upon said grating structure.
- 41. The device of claim 26 wherein
- the input electron/hole beam is incident upon the grating at an energy E,
- the grating is characterized by an angle of incidence, grating period, grating slant angle, grating average electron/hole effective mass, grating average electron/hole potential energy, grating modulated electron/hole effective mass profile, and grating modulated electron/hole potential energy profile,
- the device being constructed in accordance with the following in order to divide substantially all of the input beam of electrons/holes into two output beams, designated as the i=0 and i=i.sub.a electron/hole beams where i.sub.a is a positive or negative integer corresponding to a forward or a backward diffracted order:
- the grating period and grating slant angle are determined for said grating device which will make the i.sub.a backward- or forward-diffracted orders propagating, by having the progagating orders satisfy the grating equation for real angles .theta.'.sub.i.sbsb.a or .theta.".sub.i.sbsb.a :
- [2m*.sub.1 (E-V.sub.I)].sup.1/2 sin .theta.'-(2.pi.i.sub.a h/.LAMBDA.) sin .phi.=r.sub.n [2m*.sub.n (E-V.sub.n)].sup.1/2 sin .theta..sup.n.sub.i.sbsb.a
- where
- n=I,III
- r.sub.I =-1
- r.sub.III =1
- .theta..sup.I.sub.i.sbsb.a =.theta.'.sub.i.sbsb.a and .theta..sup.III.sub.i.sbsb.a =.theta.".sub.i.sbsb.a are the angles (measured positive counter-clockwise from the grating surface normal) of propagation of the i.sub.a th backward- or forward-diffracted orders respectively,
- m*.sub.I and m*.sub.III are the electron/hole effective mass of the input and output regions respectively,
- V.sub.I and V.sub.III are the electron/hole potential energy of the input and output regions respectively,
- .LAMBDA. is the grating period,
- .phi. is the grating slant angle,
- .pi. is the irrational number 3.14159 . . . ,
- h is Planck's constant divided by 2.pi.,
- the grating average electron/hole effective mass, the grating average electron/hole potential energy, and angle .theta.' are selected such that they satisfy the Bragg condition for the i.sub.a th diffracted order: ##EQU4## where m*.sub.II is the average grating electron/hole effective mass,
- V.sub.II is the average grating electron/hole potential energy,
- .theta. is the angle .theta.' refracted into the grating,
- .LAMBDA. is the grating period,
- .phi. is the grating slant angle,
- .pi. is the irrational number 3.14159 . . . ,
- h is Planck's constant divided by 2.pi., and the grating electron/hole modulated effective mass profile and electron/hole modulated potential energy profile are selected such that the first harmonic of an exponential Fourier series of the effective mass profile and the first harmonic of an exponential Fourier series of the potential energy profile satisfy the Bragg regime equation:
- .rho..sub.B =Q'/2.gamma.>1,
- where
- .rho..sub.B is the Bragg regime parameter,
- Q' is the grating thickness parameter, and
- .gamma. is the grating strength parameter.
- 42. The device of claim 41 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made larger than five (5.0) such that the grating has substantial diffracted current for the i.sub.a th order for only a small range of incident angles around .theta.' and a small range of energies around E.
- 43. The device of claim 41 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made smaller than approximately five such that the grating has substantial diffracted current for the i.sub.a th order for a broad range of incident angles around .theta.' and a broad range of energies around E.
- 44. A solid state, quantum mechanical, electron/hole wave device comprises:
- a layer of semiconductor material which supports substantially ballistic electron/hole transport at energies above the conduction band edge; and
- a grating structure formed in the layer of semiconductor material and comprised of a modulation in electron/hole potential engergy and/or effective mass for diffracting substantially all of an input electron/hole beam into three or more output electron/hole beams.
- 45. The device of claim 44 wherein said grating is adapted to divide substantially all of the input beam of electrons/holes substantially equally among multiple output beams.
- 46. The device of claim 44 further comprising means for applying the grating modulation.
- 47. The device of claim 46 wherein said means for applying the grating modulation comprises a set of metallic electrodes adjacent a surface portion of said semiconductor layer and a fixed bias voltage applied to said electrodes.
- 48. The device of claim 46 wherein said means for applying the grating modulation comprises a set of superlattice layers.
- 49. The device of claim 46 wherein said means for applying the grating modulation comprises an array of quantum wires.
- 50. The device of claim 46 wherein said means for applying the grating modulation comprises an array of electrode gate structures.
- 51. The device of claim 46 further comprising external field means for varying the grating modulation.
- 52. The device of claim 51 wherein said external field means comprises an electric field applied to a gate electrode structure.
- 53. The device of claim 52 wherein said gate electrode structure is periodic.
- 54. The device of claim 44 wherein the input electrons/holes are incident upon the device at an angle .theta.' and an energy E,
- wherein the grating structure is characterized by a grating period, grating slant angle, grating average electron/hole effective mass, grating average electron/hole potential energy, grating modulated electron/hole effective mass profile, and grating modulated electron/hole potential energy profile,
- and wherein the grating structure is constructed in accordance with the following so as to produce numerous diffracted beams of electrons/holes of substantially the same current:
- the grating period and grating slant angle are determined which will give desired number and directions of backward- and forward-diffracted orders, by having the propagating orders satisfy the grating equation for real angles .theta.'.sub.i and .theta.".sub.i :
- [2m*.sub.1 (E-V.sub.I)].sup.1/2 sin .theta.'-(2.pi.ih/.LAMBDA.) sin .phi.=r.sub.n [2m*.sub.n (E-V.sub.n)].sup.1/2 sin .theta..sup.n.sub.i
- where
- n=I,III
- r.sub.I =-1
- r.sub.III =1
- .theta.'.sub.i =.theta..sup.I.sub.i and .theta..sup.III.sub.i =.theta.".sub.i are the angles (measured positive counter-clockwise from the granting surface normal) of propagation of the ith backward- or forward-diffracted orders respectively,
- m*.sub.I and m*.sub.III are the electron/hole effective mass of the input and output regions respectively,
- V.sub.I and V.sub.III are the electron/hole potential energy of the input and output regions respectively,
- .LAMBDA. is the grating period,
- .phi. is the grating slant angle,
- .pi. is the irrational number 3.14159 . . . ,
- h is Planck's constant divided by 2.pi., and
- the grating thickness, electron/hole modulated effective mass profile, and electron/hole modulated potential energy profile are selected such that the grating thickness, the first harmonic of an exponential Fourier series of the effective mass profile, and the first harmonic of an exponential Fourier series of the potential energy profile satisfy the Raman-Nath regime equation:
- .rho..sub.RN =Q'.gamma.>1
- where
- .rho..sub.RN is the Raman-Nath regime parameter,
- Q' is the grating thickness parameter, and
- .gamma. is the grating strength parameter.
- 55. The device of claim 54 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made larger than approximately five such that the grating has substantially diffracted current for the ith order for a small range of incident angles around .theta.' and a small range of energies around E.
- 56. The device of claim 54 wherein the grating also is constructed according to the following: the effective grating thickness, d/.LAMBDA., is made smaller than approximately five such that the grating has substantial diffracted current for the ith order for a broad range of incident angles around .theta.' and a broad range of energies around E.
- 57. The device of claim 44 further comprising means for generating an input beam, means for collimating the input beam, and collector means for collecting output beams.
- 58. The device of claim 57 wherein said means for generating an input comprises means for generating a plurality of input beams.
Government Interests
This invention was made with government support under Contract No. DAAL03-90-C-004 awarded by the U.S. Army Research Office and by Grant No. ECS-8909971 granted by the National Science Foundation. The government has certain rights in this invention.
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