Thermal diode for energy conversion

• US 6,396,191 B1
• Filed: 11/22/2000
• Issued: 05/28/2002
• Est. Priority Date: 03/11/1999
• Status: Expired due to Term

• Current Assignee: MicroPower Global Ltd.
• Original Assignee: ENECO, Inc.
• Inventors: Hagelstein, Peter L., Kucherov, Yan R.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US09/721,051
• Time in Patent Office: 552 Days
• Field of Search: 310/304,306
• US Class Current: 310/306
• CPC Class Codes: H01J 45/00 Discharge tubes functioning as thermionic generators structural combination of fuel element with thermoelectric element G21C3/40; nuclear power plants using thermionic converters G21D7/04; structural combination of a radioactive source with a thermionic converter, e.g. radioisotope batteries G21H1/10; generators in which thermal or kinetic energy is converted into electrical energy by ionisation of a fluid and removal of the charge therefrom H02N3/00
• CPC Class Codes: H01L 29/86 controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
• CPC Class Codes: H02N 3/00 Generators in which thermal or kinetic energy is converted into electrical energy by ionisation of a fluid and removal of the charge therefrom discharge tubes functioning as thermionic generators H01J45/00
• CPC Class Codes: H10N 10/00 Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects integrated devices or assemblies of multiple devices H10N19/00
• CPC Class Codes: H10N 10/13 characterised by the heat-exchanging means at the junction

Abstract

Solid state thermionic energy converter semiconductor diode implementation and method for conversion of thermal energy to electric energy, and electric energy to refrigeration. In embodiments of this invention a highly doped n* region can serve as an emitter region, from which carriers can be injected into a gap region. The gap region can be p-type, intrinsic, or moderately doped n-type. A hot ohmic contact is connected to the n*-type region. A cold ohmic contact serves as a collector and is connected to the other side of the gap region. The cold ohmic contact has a recombination region formed between the cold ohmic contact and the gap region and a blocking compensation layer that reduces the thermoelectric back flow component. The heated emitter relative to the collector generates an EMF which drives current through a series load. The inventive principle works for hole conductivity, as well as for electrons.

Claims

1. A solid state thermionic converter, comprising:

an emitter having at least a region comprising a first donor having a concentration N_d*;

a collector; and

a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and about 7.

2. A converter as recited in claim 1, further comprising a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region.

3. A converter as recited in claim 1, wherein said natural logarithm of the ratio N_d*/N_d is in a range between about 3 and about 7.

4. A converter as recited in claim 1, wherein the temperature of said emitter is higher than the temperature of said collector when an electric current flows from said emitter to said collector.

5. A converter as recited in claim 1, wherein said emitter comprises a metal.

6. A converter as recited in claim 1, wherein said gap region comprises an n-type semiconductor.

7. A converter as recited in claim 1, further comprising a recombination region either disposed in electric communication between said gap region and said collector or comprising a portion of said collector in electric communication with said gap region.

8. A converter as recited in claim 1, wherein said emitter comprises InSb.

9. A converter as recited in claim 1, wherein said emitter comprises InSb doped with Te.

10. A converter as recited in claim 1, wherein said gap region comprises InSb doped with Te at a concentration in the range from about 10¹⁶ cm⁻

3 to about 3·

10¹⁹ cm<sup>−

3</sup>.

11. A converter as recited in claim 1, wherein said emitter comprises InSb doped with Te at a concentration in the range from about 10¹⁸ cm⁻

3 to about 3·

10¹⁹ cm<sup>−

3</sup>.

12. A converter as recited in claim 1, wherein said gap region comprises InSb doped with Te at a concentration of about 10¹⁸ cm⁻

3.

13. A converter as recited in claim 1, wherein the thickness of said emitter is at least about 400 Å

.

14. A converter as recited in claim 1, wherein said gap region comprises a semiconductor whose dimensionless normalized conductivity χ

is within the range from about 1 to about 0.001.

15. A converter as recited in claim 1, wherein said gap region comprises HgSe.

16. A converter as recited in claim 1, wherein said gap region comprises HgTe.

17. A converter as recited in claim 1, wherein said gap region comprises Bi₁₋

ySb_y, wherein y is within the range from about 0.05 to about 0.2.

18. A converter as recited in claim 1, wherein said gap region comprises Se_zTe₁₋

z, wherein z satisfies 0≦

z ≦

1.

19. A converter as recited in claim 1, wherein said gap region comprises Hg₁₋

xCd_xTe, wherein x is within the range from about 0.08 to about 0.2.

20. A converter as recited in claim 1, wherein said gap region comprises Hg₁₋

xCd_xTe, wherein x is about 0.08.

21. A converter as recited in claim 1, wherein said gap region comprises a doped semiconductor with a dopant concentration in the range from about 10¹⁵ cm⁻

3 to about 10²⁰ cm<sup>−

3</sup>.

22. A converter as recited in claim 1, wherein said gap region comprises a p-type semiconductor.

23. A converter as recited in claim 1, wherein said gap region comprises an intrinsic semiconductor.

24. A converter as recited in claim 1, wherein the energy barrier for electron injection from said emitter to said gap region is in the range from about 4 k_BT to about 5 k_BT, where k_B is the Boltzman constant and T is the absolute temperature at which the electron injection takes place.

25. A converter as recited in claim 1, wherein said emitter is thermally insulated.

26. A solid state thermionic converter of thermal energy, comprising:

an emitter having at least a region comprising a first donor having a concentration N_d*;

a first ohmic contact in electric and thermal communication with said emitter;

a metal-semiconductor-interface-barrier-reduction layer between said first ohmic contact and said emitter;

a collector;

a second ohmic contact in electric communication with said collector;

a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and about 7.

27. A converter as recited in claim 26, wherein said natural logarithm of the ratio N_d*/N_d is in a range from about 3 to about 7.

28. A converter as recited in claim 26, further comprising a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region.

29. A converter as recited in claim 26, wherein said collector is formed on said second ohmic contact.

30. A converter as recited in claim 26, further comprising a thermally conducting layer deposited on at least one of said first and second ohmic contacts.

31. A converter as recited in claim 26, further comprising a recombination region either disposed in electric and thermal communication between said gap region and said collector or comprising a portion of said collector in electric and thermal communication with said gap region.

32. A solid state thermionic converter of thermal energy, comprising:

a plurality of plates P_i, with 1≦

i≦

m, where m is the total number of said plates, each one of said plates P_i having

an emitter E_i having at least a region comprising a first donor having a concentration N_d*;

a collector C_i; and

a gap region G_i between said emitter E_i and said collector C_i in electric and thermal communication with said emitter E_i and said collector C_i, said gap region G_i comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and about 7, and such that 1≦

i≦

m;

wherein each plate P_j having an emitter E_j+1, a gap region G_j+1, and a collector C_j+1, so configured is connected in series with a group of an emitter E_j, a gap region G_j, and a collector C_j, for 1≦

j≦

(m−

1), the indexes i and j being integers, and such that collector C_j is in electric communication with emitter E_j+1 for each j satisfying 1≦

j≦

(m−

1).

33. A converter as recited in claim 32, wherein said natural logarithm of the ratio N_d*/N_d is in a range from about 3 to about 7.

34. A converter as recited in claim 32, further comprising a compensated region disposed between said gap region G_i and said collector C_i, said compensated region R_i being configured to suppress electric current from said collector to said gap region, wherein each plate P_j having an emitter E_j+1, a gap region G_j+1, a compensated region R_j+1, and a collector C_j+1, so configured is connected in series with a group of an emitter E_j, a gap region G_j, a compensated region R_j+1, and a collector C_j, for 1≦

j≦

(m−

1).

35. A converter as recited in claim 34, wherein emitters E_i and E_j comprise substantially the same materials, collectors C_i and C_j comprise substantially the same materials, and compensated regions R_i and R_j comprise substantially the same materials, for i≠

j, and 1≦

i≦

m, 1≦

j≦

m.

36. A converter as recited in claim 32, such that the temperature of each of said emitter E_i is higher than the temperature of each of said collector C_i when an electric current flows between said emitter E_i and said collector C_i.

37. A converter as recited in claim 32, wherein said first plate P₁ comprises InSb.

38. A converter as recited in claim 32, wherein said first plate P₁ comprises InSb doped with Te.

39. A converter as recited in claim 32, wherein said first plate P₁ comprises InSb doped with Te at a concentration of about 10¹⁸ cm⁻

3.

40. A converter as recited in claim 32, wherein at least said first plate emitter E₁ comprises InSb doped with Te.

41. A converter as recited in claim 32, wherein at least said first plate emitter E₁ comprises InSb doped with Te at a concentration of about 3·

10¹⁹ cm<sup>−

3</sup>.

42. A converter as recited in claim 32, wherein said first plate P₁ is coated with a material comprising In-Ga.

43. A converter as recited in claim 32, wherein at least said first plate P₁ is coated with a material having In₁₋

uGa_u, wherein u is in a range from about 0 to about 0.3.

44. A converter as recited in claim 32, wherein at least said first plate P₁ is coated with a material having In₁₋

uGa_u, wherein u is about 0.25.

45. A converter as recited in claim 32, wherein at least one of said plates comprises Hg₁₋

xCd_xTe, with x being in the range from about 0.08 to about 0.2.

46. A converter as recited in claim 32, wherein at least one of said plates comprises Hg₁₋

xCd_xTe, with x being in a range from about 0.08 to about 0.14.

47. A converter as recited in claim 32, wherein said first emitter E₁ is thermally insulated.

48. A solid state thermionic converter of thermal energy, comprising:

an emitter having at least a reaction product of Hg<sub>1−

x</sub>Cd_xTe, x being in the range from about 0.08 to about 0.25, with a substrate comprising In;

a collector; and

a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor selected from the group consisting of n-type, p-type and intrinsic semiconductors.

49. A converter as recited in claim 48, further comprising a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region.

50. A converter as recited in claim 48, wherein said substrate comprises In-Ga.

51. A converter as recited in claim 48, wherein x is within the range from about 0.08 to about 0.2.

52. A converter as recited in claim 48, wherein x is within the range from about 0.08 to about 0.15.

53. A converter as recited in claim 48, wherein said substrate comprises In₁₋

wGa_w, wherein w is within the range from about 0.1 to about 0.3.

54. A converter as recited in claim 48, wherein said emitter is provided with a diffusion barrier.

55. A converter as recited in claim 48, wherein said emitter is provided with a diffusion barrier comprising ytterbium.

56. A converter as recited in claim 48, wherein said emitter is thermally insulated.

57. A solid state thermionic converter of thermal energy, comprising:

an emitter having at least a region comprising a first donor having a concentration N_d*;

a gap region adjacent to and in electric and thermal communication with said emitter, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and about 7;

a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region; and

a cold ohmic contact in electric and thermal communication with said gap region, wherein said cold ohmic contact comprises a recombination collector region next to said gap region.

58. A converter as recited in claim 57, wherein said natural logarithm of the ratio N_d*/N_d is in a range from about 3 to about 7.

59. A converter as recited in claim 57, wherein said recombination collector region is formed on said cold ohmic contact.

60. A converter as recited in claim 57, wherein said collector comprises a metal.

61. A converter as recited in claim 57, wherein said gap region comprises an n-type semiconductor.

62. A converter as recited in claim 57, wherein said gap region is adjacent to said emitter.

63. A solid state thermionic converter of thermal energy, comprising:

an emitter having at least a region comprising a first donor having a concentration N_d*;

a compensated region;

a gap region between said emitter and said compensated region, such that said gap region is in electric and thermal contact with said emitter and said compensated region, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and 7; and

a collector in electric and thermal contact with said compensated region, said compensated region having p-type doping such that electric current from said collector to said gap region can be substantially suppressed while allowing thermionic current from said gap region to said collector.

64. A converter as recited in claim 63, wherein the temperature of said emitter is higher than the temperature of said collector when an electric current flows between said emitter and said collector.

65. A converter as recited in claim 63, wherein said natural logarithm of the ratio N_d*/N_{d i}s in a range from about 3 to about 7.

66. A solid state thermionic converter comprising a plurality of individual converters arranged in series, wherein each of said individual converters is configured as recited in claim 63.

67. A converter as recited in claim 63, wherein said compensated region is formed by ion implantation into said gap region.

68. A converter as recited in claim 63, wherein said compensated region comprises vacancies created by ion implantation.

69. A converter as recited in claim 63, wherein said emitter is thermally insulated.

70. A method for refrigeration by using a solid state thermionic converter, comprising:

establishing externally an electric potential difference across a thermionic converter having

a thermally insulated emitter having at least a region having a first donor concentration N_d*;

a collector;

a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration N_d, said concentration of said second donor being selected such that the natural logarithm of the ratio N_d*/N_d is between a numerical value greater than 0 and about 7; and

delivering a thermal load to said emitter such that said thermal load is cooled by heat flow as said externally established electric potential difference causes the flow of electric current between said emitter and said collector.

71. A method as recited in claim 70, wherein said natural logarithm of the ratio N_d*/N_d is in a range between about 3 and bout 7.

72. A method as recited in claim 70, with said thermionic converter further having a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region.