High resistance photoconductor structure for multi-element infrared detector arrays

• US 4,731,640 A
• Filed: 05/20/1986
• Issued: 03/15/1988
• Est. Priority Date: 05/20/1986
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Bluzer, Nathan
• Primary Examiner(s): Edlow, Martin H.
• Assistant Examiner(s): Mintel, William A.
• Application Number:
  US06/864,940
• Time in Patent Office: 665 Days
• Field of Search: 357/30 B, 357/30 I, 357/30 Q (U.S. only), 357/30 R (U.S. only), 357/30 D, 357/30 H, 357/58, 357/16
• US Class Current: 257/291
• CPC Class Codes: H01L 27/14669 Infrared imagers
• CPC Class Codes: H01L 27/14881 of the hybrid type
• CPC Class Codes: H01L 31/02966 including ternary compounds, e.g. HgCdTe
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: H01L 31/112 characterised by field-effect operation, e.g. junction field-effect phototransistor

Abstract

A high resistance, low noise, multi-layer, thin film photoconductive, infrared detector operable to be easily coupled to charge couple devices; having an enhanced photoconductive gain due to the use of a bias voltage across a depletion layer of n-doped HgCdTe resulting in the flow of electron charge in the bulk of depletion region and the flow of electron holes along the surface of the depletion region. In one embodiment of this invention an additional layer is incorporated into the structure having specific thickness, of 1/4 of the wavelength of the energy received. This additional layer of material behaves as resonant cavity enhancing the quantium efficiency. In a further embodiment, a configuration for a high resistance photoconductor detector structure is disclosed utilizing a cylindrical topography to circumvent lateral edge problems in the high resistance photoconductive structure. Finally, arrays composed of a multiplicity of the described detectors are taught using the cylindrical topography embodiment.

Claims

1. A high resistance, thin film, photoconductive device, operable for use in high density multi-element photodetector arrays, comprising:

a photoconductive layer of n-doped semiconductor material having a predetermined band gap, a first and second lateral face, and two opposing ends, said photoconductive layer further comprising a first and second N+ dopant region so positioned at the extreme of said two opposing ends of said photoconductive layer, said first and said second N+ dopant regions operable to serve as contact regions for said photoconductive layer, said photoconductive layer further operable to facilitate the migration of electrons and holes within said photoconductive layer;

a first insulating layer positioned upon said first lateral face of said photoconductive layer, said first insulating layer operable to serve as a barrier for said electrons and said holes migrating within said photoconductive layer and said first insulating layer having a predetermined band gap;

a second insulating layer positioned upon said second lateral face of said photoconductive layer, said second insulating layer operable to contain said electrons and said holes within said photoconductive layer, and said second insulating layer having a predetermined band gap;

a ground means affixed to said first N+ dopant region operable to provide an electrical path to ground for said photoconductive device;

a positive bias means affixed to said second N+ dopant region operable to provide positive electrical potential to said second N+ dopant region, whereby said second N+ dopant region is the most electrically positive region of said photoconductive layer; and

,

a metallic gate means layered upon said first and said second insulating layers, said electrical metallic gate means operable to place a negative electrical potential across said first insulating layer, said photoconductive layer and said second insulating layer whereby said electrons will migrate towards said positively biased second N+ dopant region, said electrons migrating within the bulk of said photoconductive layer and said holes migrating towards said ground means affixed to said first N+ dopant region along said first and said second lateral faces of said photoconductive layer, increasing said resistance of said photoconductive layer during photoconductive detector operation.

2. The photoconductive device as in claim 1 wherein the width of said photoconductive layer and said second insulating layer is one-quarter wavelength of the infrared radiation said device is operable to receive.

3. The photoconductive device as in claim 1, wherein said first insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe) having a band gap wider than said photoconductive layer.

4. The photoconductive device as in claim 1 wherein said second insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe) having a band gap wider than said photoconductive layer.

5. A high resistance, thin film, multi-layer photoconductive device, operable for use in high density, multi-element photodetector arrays, comprising:

a photoconductive layer of n-doped semiconductor material having a predetermined band gap, a first and a second lateral face, and two opposing ends, said photoconductive layer further comprising a first and a second N+ dopant region so positioned at the extreme of said two opposing ends of said photoconductive layer, said first and said second N+ dopant regions operable to serve as contact regions for said photoconductive layer, said photoconductive layer further operable to facilitate the migration of electrons and holes within said photoconductive layer;

a first insulating layer positioned upon said first lateral face of said photoconductive layer, said first insulating layer operable to serve as a barrier for said electrons and said holes migrating within said photoconductive layer, and said first insulating layer having a predetermined band gap;

a second insulating layer positioned upon said second lateral face of said photoconductive layer operable to contain said electrons and said holes within said photoconductive layer and said second insulating layer having a predetermined band gap;

a substrate layer of semiconductor material transparent to photons of infrared radiation, having a predetermined band gap, said substrate layer positioned upon said first insulating layer and operable to provide a mechanical support structure for said photoconductive layer, said substrate layer further operable to be negatively biased during said photoconductive device operation;

a ground means affixed to said first N+ dopant region operable to provide an electrical path to ground for said photoconductive device;

a positive bias means affixed to said second N+ dopant region operable to provide positive electrical potential to said second N+ dopant region, whereby said second N+ dopant region is the most electrically positive region of said photoconductive layer; and

a metallic gate means layered upon said second insulating means, said metallic gate means operable when negatively biased in conjunction with said substrate layer to place a negative electrical potential across said first insulating layer, said photoconductive layer and said second insulating layer whereby said electrons will migrate towards said positively biased second N+ dopant region, said electrons migrating within the bulk of said photoconductive layer and said holes migrating towards said ground means affixed to said first N+ dopant region along said first and said second lateral faces of said photoconductive layer;

thereby increasing said resistance of said photoconductive layer during photoconductive device operation.

6. A photoconductive device as in claim 5, wherein said first insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

7. A photoconductive device as in claim 5, wherein said second insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

8. A photoconductive device as in claim 5, wherein said substrate layer is p-doped indium antimonide (InSb).

9. A photoconductive device as in claim 5, wherein said substrate layer is p-doped cadmium manganese telluride (CdMnTe).

10. A photoconductive device as in claim 5, wherein said substrate layer is p-doped cadmium telluride (CdTe).

11. A photoconductive device as in claim 5, wherein said substrate layer is p-doped zinc telluride (ZnTe).

12. A photoconductive device as in claim 5, wherein said predetermined band gap of said photoconductive layer is narrower than said predetermined band gaps of said first, said second insulating layers and said substrate layer.

13. A photoconductive device as in claim 5, wherein said photoconductive layer comprises n-doped mercury cadmium telluride (HgCdTe).

14. A photoconductive device as in claim 5 wherein said photoconductive layer comprises n-doped mercury zinc telluride (HgZnTe).

15. A photoconductive device as in claim 5, wherein the combined thickness of said photoconductive layer and said second insulating layer is equal to one-quarter of the wavelength of the infrared radiation being detected.

16. A high resistance, thin film, multi-layer dual gate, photoconductive device, operable for use in high density, multi-element photodetector arrays, comprising:

a photoconductor layer of n-doped semiconductor material having a predetermined band gap, a first and a second lateral face, and two opposing ends, said photoconductive layer further comprising a first and a second N+ dopant region so positioned at the extreme of said two opposing ends of said photoconductive layer, said first and said second N+ dopant regions operable to serve as contact regions for said photoconductive layer, said photoconductive layer further operable to facilitate the migration of electrons and holes within said photoconductive layer;

a first insulating layer positioned upon said first lateral face of said photoconductive layer, said first insulating layer operable to serve as a barrier for said electrons and said holes migrating within said photoconductive layer and said first insulating layer having a predetermined band gap;

a second insulating layer positioned upon said second lateral face of said photoconductive layer operable to contain said electrons and said holes within said photoconductive layer, and said second insulating layer having a predetermined band gap;

a first metallic gate means layered upon said second insulating layer, said first electrical gate means operable to be negatively charged during detector operation;

a second metallic gate means layered upon said second electrical gate means operable to be negatively charged during detector operation;

a substrate layer of semiconductor material transparent to photons of infrared radiation, having a predetermined band gap, said substrate layer positioned upon said second electrical gate means and said substrate layer operable to provide a mechanical support structure for said photoconductive layer, said substrate layer having a predetermined band gap;

a ground means affixed to said first N+ dopant region operable to provide an electrical path to ground for said photoconductive device;

a positive bias means affixed to said second N+ dopant region operable to provide positive electrical potential to said second N+ dopant region, whereby said second N+ dopant region is the most electrically positive region of said photoconductive layer; and

,

an electrical bias voltage applied to said first and said second electrical gate means, such that a negative electrical potential is applied across said first and said second insulating means and said photoconductive layer whereby said electrons wil migrate towards said positively biased second N+ dopant region, and said electrons migrating within the bulk of said photoconductive layer and said holes migrating towards said ground means affixed to said first N+ dopant region along said first and said second lateral faces of said photoconductive layer;

thereby increasing said resistance of said photoconductive layer during photoconductive device operation.

17. A photoconductive device as in claim 16, wherein said substrate layer is mercury cadmium telluride (HgCdTe).

18. A photoconductive device as in claim 16, wherein said first insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

19. A photoconductive device as in claim 16, wherein said second insulating layer is n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

20. A photoconductive device as in claim 16, wherein said photoconductive layer is n-doped mercury cadmium telluride (HgCdTe).

21. A photoconductive device as in claim 16, wherein said photoconductive layer is n-doped mercury zinc telluride (HgZnTe).

22. A photoconductive device as in claim 16, wherein the combined width of said first, said second insulating layers and said photoconductive layer are equal to one-quarter wavelength of the infrared radiation being detected.

23. A photoconductive device as in claim 16, wherein said band gap of said photoconductive layer is narrower than said predetermined band gaps of said first and said second insulating layer and said substrate layer.

24. A high resistance, thin film, multi-layer photocondutive device with resonator structure, operable for use in high density, multi-element photodetector arrays, comprising:

a photoconductive layer of n-doped semiconductor material having a predetermined band gap, a first and a second lateral face and two opposing ends, said photoconductive layer further comprising a first and a second N+ dopant region so positioned at the extreme of said two opposing ends of said photoconductive layer, said first and said second N+ dopant regions operable to serve as contact regions for said photoconductive layer, said photoconductive layer further operable to facilitate the migration of electrons and holes within said photoconductive layer;

a first insulating layer positioned upon said first lateral face of said photoconductive layer, said first insulating layer operable to serve as a barrier for said electrons and said holes migrating within said photoconductive layer, and said first insulating layer having a predetermined band gap;

a second insulating layer positioned upon said second lateral face of said photoconductive layer operable to contain said electrons and said holes within said photoconductive layer and said second insulating layer having a predetermined band gap;

a substrate layer of semiconductor material transparent to photons of infrared radiation, having a predetermined band gap, said substrate layer positioned upon said first insulating layer and operable to provide a mechanical support structure for said photoconductive layer, said substrate layer further operable to be negatively biased during said photoconductive device operation and said substrate layer having a predetermined band gap;

a resonating layer of semiconductor material positioned upon said second insulating layer, said resonating layer having a combined thickness with said second insulating layer and said photoconductive layer to be equal to one-quarter wavelength of the energy being received;

a ground means affixed to said first N+ dopant region operable to provide an electrical path to ground for said photoconductive device;

a positive bias means affixed to said second N+ dopant region operable to provide positive electrical potential to said second N+ dopant region, whereby said second N+ dopant region is the most electrically positive region of said photoconductive layer; and

a metallic gate means layered upon said resonating layer, said electrical gate means operable when negatively biased in conjunction with said substrate layer to place a negative electrical potential across said first insulating layer, said photoconductive layer and said insulating layer whereby said electrons will migrate towards said positively biased second N+ dopant region, said electrons migrating within the bulk of said photoconductive layer and said holes migrating towards said ground means affixed to said first N+ dopant region along said first and said second lateral faces of said photoconductive layer thereby increasing said resistance of said photo-conductive layer during photoconductive device operation.

25. A photoconductive device as in claim 24, wherein said substrate layer comprises p-doped cadmium telluride (CdTe).

26. A photoconductive device as in claim 24, wherein said substrate layer comprises p-doped cadmium manganese telluride (CdMnTe).

27. A photoconductive device as in claim 24, wherein said substrate layer comprises p-doped indium antimonide (InSb).

28. A photoconductive device as in claim 24, wherein said substrate layer comprises p-doped zinc telluride (ZnTe).

29. A photoconductive device as in claim 24, wherein said first insulating layer comprises n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

30. A photoconductive device as in claim 24, wherein said second insulating layer comprises n-doped mercury cadmium telluride (HgCdTe) and p-type mercury cadmium telluride (HgCdTe).

31. A photoconductive device as in claim 24, wherein said resonating layer comprises p-doped cadmium telluride (CdTe).

32. A photoconductive device as in claim 24, wherein said predetermined band gap of said photoconductive layer is narrower than said predetermined band gaps of said first and said second insulating layers, said substrate layer and said resonating layer.

33. A cylindrical high resistance, thin film photoconductive device, operable for use in high resistance, high density multi-element detector arrays, comprising:

a disk-shaped, photoconductive layer of n-doped semiconductor material having a predetermined band gap, a first and second lateral face, a circular external periphery and a predetermined width;

said photoconductive layer further comprising a first N+ dopant region so positioned in the center of said disk-shaped photoconductive layer, and said second N+ dopant region so positioned about said circular external periphery of said photoconductive layer;

said disk-shaped photoconductive layer further comprising a first and a second P+ dopant region so positioned between said first N+ dopant region and said second N+ dopant region operable to provide electrical contacts for said photoconductive layer;

said semiconductor photoconductive layer operable to facilitate the migration of electrons and holes within said photoconductive layer;

a disk-shaped, first insulating layer positioned upon said first lateral face of said disk-shaped photoconductive layer, comprising n-doped semiconductor material, said first insulating layer having a predetermined band gap, operable to serve as a barrier for said electrons and said holes in said photoconductive layer;

a disk-shaped, second insulating layer positioned upon said second lateral face of said disk-shaped photoconductive layer, said second insulating layer, said second insulating layer having a predetermined band gap, said second insulating layer further comprising n-doped semiconductor material and operable during said photocnductive device operation to serve as a barrier for said electrons and said holes in said photoconductive layer;

a disk-shaped substrate layer of p-doped semiconductor material having a predetermined band gap and a diameter greater than said diameter of said first insulating layer, said disk-shaped substrate layer further operable to be transparent to photons of infrared radiation and further operable to provide a mechanical support structure for said photoconductive device, said substrate layer also operable to be negatively biased during said photoconductive device operation;

a disk-shaped resonating layer of p-doped semiconductor material positioned upon said second insulating layer, said resonating layer having a diameter less than said diameter of said second insulating layer, said resonating layer having a width where combined with the width of said photoconductive and said second insulating layer of one-quarter wavelength of the radiant energy of said photoconductive device is operable to receive;

a ground means affixed to said second N+ dopant region of said photoconductive layer operable to provide an electrical path to ground for said photoconductive device;

a positive bias means affixed to said first N+ dopant region operable to provide positive electrical potential to said first N+ dopant region, whereby said first N+ dopant region is the most electrically positive region of said photoconductive layers,

a disk-shaped metallic gate means layered upon said disk-shaped resonating layer, said disk-shaped metallic gate having a diameter less than said diameter of said resonating layer, said metallic gate means operable when negatively biased in conjunction with said disk-shaped substrate layer to place a negative electrical potential across said first insulating layer, said photoconductive layer, said second insulating layer and said resonating layer whereby said electrons will migrate towards said positively biased first N+ dopant region, said electrons migrating within the bulk of said photoconductive layer and said holes migrating towards said ground means affixed to said second N+ dopant region in said photoconductive layer, along said first and said second lateral faces of said photoconductive layer, thereby increasing said resistance of said photoconductive layer during said photoconductive device operation.

34. A photoconductive device as in claim 33 wherein said substrate layer is p-doped cadmium telluride (CdTe).

35. A photoconductive device as in claim 33 wherein said substrate layer is p-doped cadmium manganese telluride (CdMnTe).

36. A photoconductive device as in claim 33 wherein said substrate layer is p-doped indium atinomide (IbSb).

37. A photoconductive device as in claim 33 wherein said first insulating layer is n-doped mercury cadmium telluride (HgCdTe).

38. A photoconductive device as in claim 33 wherein said photoconductive layer is n-doped mercury cadmium telluride (HgCdTe).

39. A photoconductive device as in claim 33 wherein said second insulating layer is mercury cadmium telluride (HgCdTe).

40. A photoconductive device as in claim 33 wherein said resonating layer is p-doped cadmium telluride (CdTe).

41. A photoconductive device as in claim 33 wherein said band gap of said photoconductive layer is a narrower band gap than the band gaps of said substrate, first insulating, second insulating and resonating layers.

42. A planar, high resistance, thin film photoconductive array, having a multiplicity of cylindrical photoconductive devices impregnated therein, said photoconductive array operable to detect predetermined wavelengths of external infrared radiation, comprising:

a shared common substrate layer of p-doped semi-conductor material, said common substrate layer having a predetermined band gap,

said common substrate layer further transparent to photons of infrared radiation and operable to receive said photons, and further operable to provide a mechanical support structure for said multiplicity of cylindrical photoconductive devices, said common substrate layer further operable to be negatively biased during said array operation;

a common first insulating layer, positioned upon said common substrate layer, said common first insulating layer operable to serve as a barrier for electrons and holes, said common first insulating layer having a predetermined band gap;

a photoconductive layer positioned upon said common first insulating layer having a predetermined band gap, said photoconductive layer comprising alternating regions of n-doped semiconductor material, N+ doped semiconductor material and P+ doped regions of semiconductor material, said alternating regions positioned within said photoconductive layer in a circular configuration;

said photoconductive layer operable to facilitate the migration of electrons and holes within said semiconductor layer;

a second common insulating layer of n-doped semiconductor material positioned over said photoconductive layer having a predetermined band gap, said second insulating layer operable to contain said electrons and said holes within said photoconductive layer, said second common insulating layer, selectively removed from said photoconductive layer to facilitate electrical contact with said arrays;

a common resonating layer of p-doped semiconductor material having a predetermined band gap, said common resonating layer having, when combined with said photoconductor layer, a depth of approximately one-quarter of the wavelength of said infrared radiation received, said common resonating layers electrically removed over said arrays to facilitate electrical contact with said arrays;

metal gate layer positioned upon said common resonating layer, said gate layer operable to be negatively biased during detector operation;

a ground means affixed to selected first N+ doped regions of said photoconductive layer, said ground means interconnecting said devices in said array, said ground means operable to provide an electrical path to ground for said devices in said photoconductive layer;

a positive bias means affixed to selected said second N+ dopant areas in said photoconductive layer, said positive bias means operable to provide positive electrical potential to said second N+ dopant region, whereby said selected second N+ dopant regions are the most electrically positive regions of said photoconductive layer such that during array operation said electrons in said photoconductive layer will migrate towards said positively biased second N+ dopant regions, and said electrons migrating in the bulk of said photoconductive layer, and said holes migrate towards said ground means affixed to said other selected first N+ doped regions in said photoconductive layer during photoconductive device array operation.

43. A photoconductive multi-device array as in claim 42, wherein said shared common substrate layer is p-doped cadmium telluride (CdTe).

44. A photoconductive multi-device array as in claim 42, wherein said common substrate layer is p-doped cadmium manganese telluride (CdMnTe).

45. A photoconductive multi-device array as in claim 42, wherein said common first insulating layer is n-doped mercury cadmium telluride (HgCdTe).

46. A photoconductive multi-device array as in claim 42, wherein said photoconductive layer is n-doped mercury cadmium telluride (HgCdTe).

47. A photoconductive multi-device array as in claim 42, wherein said resonating layer is p-doped cadmium telluride (CdTe).

48. A photoconductive multi-device array as in claim 42, wherein said band gap of said photoconductive layer is a narrower band gap than the band gaps of said common substrate, said first insulating said second insulating and said resonating layers.