PHOTODIODE AND OTHER SENSOR STRUCTURES IN FLAT-PANEL X-RAY IMAGERS AND METHOD FOR IMPROVING TOPOLOGICAL UNIFORMITY OF THE PHOTODIODE AND OTHER SENSOR STRUCTURES IN FLAT-PANEL X-RAY IMAGERS BASED ON THIN-FILM ELECTRONICS

• US 20100320391A1
• Filed: 06/17/2010
• Published: 12/23/2010
• Est. Priority Date: 06/17/2009
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: ANTONUK, Larry E.
• Granted Patent: US 8,492,728 B2
• Time in Patent Office: Days
• US Class Current: 250/366
• CPC Class Codes: G01T 1/20184 Detector read-out circuitry, e.g. for clearing of traps, compensating for traps or compensating for direct hits
• CPC Class Codes: G01T 1/208 Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section
• CPC Class Codes: G01T 1/241 Electrode arrangements, e.g. continuous or parallel strips or the like constructional or manufacturing details H01L31/00
• CPC Class Codes: H01L 27/14612 involving a transistor
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14658 X-ray, gamma-ray or corpuscular radiation imagers measuring X-, gamma- or corpuscular radiation G01T1/00
• CPC Class Codes: H01L 27/14663 Indirect radiation imagers, e.g. using luminescent members
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: H01L 31/105 the potential barrier being of the PIN type

Abstract

A radiation sensor including a scintillation layer configured to emit photons upon interaction with ionizing radiation and a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer. The photosensitive layer is configured to generate electron-hole pairs upon interaction with a part of the photons. The radiation sensor includes pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of the electron-hole pairs generated in the photosensitive layer and a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry. A surface of at least one of the first electrode and the second electrode at least partially overlaps the pixel circuitry and has a surface inflection above features of the pixel circuitry. The surface inflection has a radius of curvature greater than one half micron.

Claims

1. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and having a surface inflection above features of the pixel circuitry; and

said surface inflection having a radius of curvature greater than one half micron.

2. The sensor of claim 1, wherein said surface inflection has a radius of curvature greater than one micron.

3. The sensor of claim 1, wherein said surface inflection has a radius of curvature greater than five microns.

4. The sensor of claim 1, wherein said surface inflection has a radius of curvature greater than ten microns.

5. The sensor of claim 1, wherein said surface inflection has a radius of curvature greater than one hundred microns.

6. The sensor of claim 1, wherein said planarization layer at least partially planarizes over said features of the pixel circuitry.

7. The sensor of claim 1, wherein said planarization layer at least partially planarizes over array features, over electrical via interconnects connecting to the source or drain of TFTs, over one-stage in-pixel amplifier elements, or over two-stage in-pixel amplifier elements.

8. The sensor of claim 1, wherein said planarization layer comprises at least one of a passivation layer, a dielectric layer, or an insulation layer.

9. The sensor of claim 1, further comprising:

address and data lines disposed underneath the photodetector; and

said planarization layer is disposed on the address and data lines and on vias of the address and data lines.

10. The sensor of claim 1, further comprising:

an electrical via interconnect extending through the planarization layer and connecting the first electrode to said pixel circuitry, wherein a surface inflection of the electrical via interconnect in contact with the photosensitive layer has a radius of curvature greater than one half micron.

11. The sensor of claim 10, wherein said surface of the electrical via interconnect has a radius of curvature greater than one micron.

12. The sensor of claim 10, wherein said surface of the electrical via interconnect has a radius of curvature greater than five microns.

13. The sensor of claim 10, wherein said surface of the electrical via interconnect has a radius of curvature greater than ten microns.

14. The sensor of claim 10, wherein said surface of the electrical via interconnect has a radius of curvature greater than one hundred microns.

15. The sensor of claim 1, wherein the photosensitive layer comprises one of a p-i-n semiconductor stack, a n-i-p semiconductor stack, or a metal insulator semiconductor stack.

16. The sensor of claim 1, wherein said pixel circuitry comprises one of thin film transistors, diodes, capacitors, resistors, traces, vias, control lines, address lines, and ground planes.

17. The sensor of claim 1, wherein said pixel circuitry comprises one of an amorphous semiconductor transistor or a polycrystalline semiconductor transistor or a microcrystalline semiconductor transistor.

18. The sensor of claim 1, wherein said pixel circuitry comprises at least one of an addressing transistor, an amplifier transistor, and a reset transistor.

19. The sensor of claim 1, wherein said pixel circuitry comprises at least one of amorphous silicon, low temperature amorphous silicon, and microcrystalline silicon.

20. The sensor of claim 1, wherein said pixel circuitry comprises at least one of a silicon semiconductor, a chalcogenide semiconductor, a cadmium selenide semiconductor, an organic semiconductor, an organic small molecule or polymer semiconductor, carbon nanotubes, or graphene.

21. The sensor of claim 1, wherein said photosensitive layer comprises at least one of 1) a continuous photosensitive layer extending across plural photodetector pixels or 2) discrete photosensitive layers associated with respective ones of the plural photodetector pixels.

22. The sensor of claim 1, wherein said scintillation layer comprises at least one of CsI:

TI, Gd₂O₂S;

Tb, CsI;

Na, NAI;

TI, CaWO₄, ZnWO₄, CdWO₄, Bi₄Ge₃O₁₂, Lu_1.8Yb_0.2SiO₅;

Ce, Gd₂SiO₅;

Ce, BaFCl;

Eu²⁺, BaSO₄;

Eu²⁺, BaFBr;

Eu²⁺, LaOBr;

Tb³⁺, LaOBr;

Tm³⁺, La₂O₂S;

Tb³⁺, Y₂O₂S;

Tb³⁺, YTaO₄, YTaO₄;

Nb, ZnS;

Ag, (Zn,Cd)S;

Ag, ZnSiO₄;

Mn²⁺, CsI, LiI;

Eu²⁺, PbWO₄, Bi₄Si₃O₁₂, Lu₂SiO₅;

Ce³⁺, YAlO₃;

Ce³⁺, CsF, CaF₂;

Eu²⁺, BaF₂, CeF₃, Y_1.34Gd_0.6O₃;

Eu³⁺, Pr, Gd₂O₂S;

Pr³⁺, Ce, SCGI, HFG;

Ce³⁺ (5%) and C₁₄H₁₀.

23. The sensor of claim 1, further comprising:

a base substrate supporting the pixel circuitry, the photodetector, and the scintillation layer; and

a plurality of photodetector pixels arranged in a regular pattern on the base substrate, wherein

said photon-transmissive second electrode forms a bias plane for said plurality of the photodetector pixels.

24. The sensor of claim 23, wherein a part of the pixel circuitry is disposed on the base substrate in a gap region between adjacent photodetector pixels.

25. The sensor of claim 24, wherein said part of the pixel circuitry disposed in the gap region comprises one of thin film transistors, diodes, capacitors, resistors, vias, traces, control lines, address lines, and ground planes.

26. The sensor of claim 23, wherein said first electrode has beveled ends terminating near the gap region.

27. The sensor of claim 1, wherein a dark current, normalized to unit photodetector area, between the first electrode and the photon-transmissive second electrode is less than 10 pA/mm².

28. The sensor of claim 1, wherein a dark current, normalized to unit photodetector area, between the first electrode and the photon-transmissive second electrode is less than 5 pA/mm².

29. The sensor of claim 1, wherein a dark current, normalized to unit photodetector area, between the first electrode and the photon-transmissive second electrode is less than 1 pA/mm².

30. The sensor of claim 1, wherein a dark current, normalized to unit photodetector area, between the first electrode and the photon-transmissive second electrode is less than 0.5 pA/mm².

31. The sensor of claim 1, wherein an electric field in regions in the photosensitive layer proximate said surface inflection is greater than 60 percent and less than 300 percent of an electric field in the photosensitive layer between a pair of parallel first and second electrodes.

32. The sensor of claim 1, further comprising a metal plate disposed on the scintillation layer or on an encapsulation on the scintillation layer.

33. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer; and

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry,

wherein

the planarization layer has a first surface inflection along a peripheral edge of features of the pixel circuitry elements,

the first electrode has a second surface inflection above the first surface inflection and on a surface of the planarization layer opposite the base substrate, and

said second surface inflection has a radius of curvature greater than one-half micron.

34. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photodetector having a dark current, normalized to unit photodetector area, between the first electrode and the photon-transmissive second electrode that is less than 10 pA/mm².

35. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photodetector having a level of charge trapping per photodetector pixel, quantified by the amount of said imaging signal lost to trapping during a single radiographic frame, and expressed as a percentage of the imaging signal obtained under conditions where charge trapping and charge release are in equilibrium, that is less than ˜

20%.

36. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photodetector having a charge release per photodetector pixel, quantified by the amount of said imaging signal released from trapping states during the first frame acquired in the absence of radiation following a series of frames acquired with radiation and under conditions where charge trapping and charge release are in equilibrium, and expressed as a percentage of the imaging signal obtained under conditions where charge trapping and release are in equilibrium, that is less than ˜

15%.

37. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photodetector having a lag per photodetector pixel, quantified by the amount of said imaging signal that originates from charge trapped in one or more previous frames and is released from trapping states during the first frame acquired in the absence of radiation following one, or a series of frames acquired with radiation, and expressed as a percentage of the imaging signal from the previous frame, that is less than ˜

15%.

38. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

said first electrode extending over a part of the pixel circuitry and having a lateral edge, a longitudinal edge, and a corner at the intersection of the lateral and longitudinal edges; and

at least one of said lateral edge and said longitudinal edge comprising a beveled edge.

39. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector pixel including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a passivation layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is disposed above a plane including the pixel circuitry;

the passivation layer having a first surface inflection above the pixel circuitry elements;

said second electrode having a second surface inflection above the first surface inflection; and

said second surface inflection having a radius of curvature greater than one-half a micron.

40. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer;

a passivation layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and exhibiting no surface features indicative of the underlying pixel circuitry.

41. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and having a surface inflection above features of the pixel circuitry; and

said surface inflection having a radius of curvature greater than one half micron.

42. The sensor of claim 41, wherein the photoconductive layer comprises at least one of VB-VIB, VB-VIIB, IIB-VIB, IIB-VB, IIIB-VB, IIIB-VIB, IB-VIB, and IVB-VIIB semiconductors.

43. The sensor of claim 41, wherein the photoconductive layer comprises at least one of a-Se, PbI₂, HgI₂, PbO, CdZnTe, CdTe, Bi₂S₃, Bi₂Se₃, BiI₃, BiBr₃, CdS, CdSe, HgS, Cd₂P₃, InAs, InP, In₂S₃, In₂Se₃, Ag₂S, PbI₄⁻

2 and Pb₂I₇<sup>−

3</sup>.

44. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry,

wherein

the planarization layer has a first surface inflection along a peripheral edge of features of the pixel circuitry elements,

the first electrode has a second surface inflection above the first surface inflection and on a surface of the planarization layer opposite the base substrate, and

said second surface inflection has a radius of curvature greater than one-half micron.

45. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photoconductor detector having a dark current, normalized to unit photoconductor detector area, between the first electrode and the second electrode that is less than 10 pA/mm².

46. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photoconductor detector having a level of charge trapping per photoconductor detector pixel, quantified by the amount of said imaging signal lost to trapping during a single radiographic frame, and expressed as a percentage of the imaging signal obtained under conditions where charge trapping and charge release are in equilibrium, that is less than ˜

20%.

47. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photoconductor detector having a charge release per photoconductor detector pixel, quantified by the amount of said imaging signal released from trapping states during the first frame acquired in the absence of radiation following a series of frames acquired with radiation and under conditions where charge trapping and charge release are in equilibrium, and expressed as a percentage of the imaging signal obtained under conditions where charge trapping and release are in equilibrium, that is less than ˜

15%.

48. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said photoconductor detector having a lag per photoconductor detector pixel, quantified by the amount of said imaging signal that originates from charge trapped in one or more previous frames and is released from trapping states during the first frame acquired in the absence of radiation following one, or a series of frames acquired with radiation, and expressed as a percentage of the imaging signal from the previous frame, that is less than ˜

15%.

49. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

said first electrode extending over the pixel circuitry and having a lateral edge, a longitudinal edge, and a corner at the intersection of the lateral and longitudinal edges; and

at least one of said lateral edge and said longitudinal edge comprising a beveled edge.

50. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a passivation layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

the passivation layer having a first surface inflection above the pixel circuitry elements;

said second electrode having a second surface inflection above the first surface inflection; and

said second surface inflection having a radius of curvature greater than one-half a micron.

51. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode;

said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer;

a passivation layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and exhibiting no surface features indicative of the underlying pixel circuitry.

52. A method for fabricating a radiation sensor, comprising:

forming pixel circuitry elements on a base substrate;

forming a planarization layer over the pixel circuitry elements;

forming a hole in the planarization layer to expose a connection to the pixel circuitry elements;

metallizing the patterned hole;

forming a first electrode in electrical contact to the metallized hole; and

forming on the first electrode a layer sensitive to light or ionizing radiation,

wherein forming a planarization layer provides, on a surface of the first electrode at least partially overlapping the pixel circuitry, a surface inflection, above features of the pixel circuitry, having a radius of curvature greater than one half micron.

53. A method for fabricating a radiation sensor, comprising:

forming pixel circuitry elements on a base substrate;

forming above the pixel circuitry a first electrode and a photosensitive layer;

planarizing the photosensitive layer;

forming on the planarized photosensitive layer a photon-transmissive second electrode; and

forming a scintillator layer on the photon-transmissive second electrode,

wherein at least one of the first electrode and the second electrode has a surface inflection, above features of the pixel circuitry, having a radius of curvature greater than one half micron.

54. A method for fabricating a radiation sensor, comprising:

forming pixel circuitry elements on a base substrate;

forming a planarization layer over the pixel circuitry elements;

forming a hole in the planarization layer to expose a connection to the pixel circuitry elements;

metallizing the patterned hole;

forming a first electrode in electrical contact to the metallized hole; and

forming on the first electrode a layer sensitive to light or ionizing radiation,

wherein forming a planarization layer provides a surface of said first electrode, at least partially overlapping the pixel circuitry, that exhibits no surface features indicative of the underlying pixel circuitry.

55. A method for fabricating a radiation sensor, comprising:

forming pixel circuitry elements on a base substrate;

forming above the pixel circuitry a first electrode and a photosensitive layer;

planarizing the photosensitive layer;

forming on the planarized photosensitive layer a photon-transmissive second electrode; and

forming a scintillator layer on the photon-transmissive second electrode,

wherein planarizing the photosensitive layer provides a surface of said second electrode, at least partially overlapping the pixel circuitry, that exhibits no surface features indicative of the underlying pixel circuitry.

56. A radiation sensor comprising:

a scintillation layer configured to emit photons upon interaction with ionizing radiation;

a photodetector including in order a first electrode, a photosensitive layer, and a photon-transmissive second electrode disposed in proximity to the scintillation layer;

said photosensitive layer configured to generate electron-hole pairs upon interaction with a part of said photons;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photosensitive layer, said pixel circuitry comprising oxide semiconductors;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry; and

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and having a surface inflection above features of the pixel circuitry.

57. A radiation sensor comprising:

a photoconductor detector including in order a first electrode, a photoconductive layer, and an ionizing radiation transmissive second electrode, and said photoconductive layer configured to generate electron-hole pairs upon interaction with ionizing radiation;

pixel circuitry electrically connected to the first electrode and configured to measure an imaging signal indicative of said electron-hole pairs generated in the photoconductive layer, said pixel circuitry comprising oxide semiconductors;

a planarization layer disposed on the pixel circuitry between the first electrode and the pixel circuitry such that the first electrode is above a plane including the pixel circuitry;

a surface of at least one of said first electrode and said second electrode at least partially overlapping the pixel circuitry and having a surface inflection above features of the pixel circuitry.

58. A method for fabricating a radiation sensor, comprising:

forming pixel circuitry elements on a base substrate, said pixel circuitry comprising oxide semiconductors;

forming a planarization layer over the pixel circuitry elements;

forming a hole in the planarization layer to expose a connection to the pixel circuitry elements;

metallizing the patterned hole;

forming a first electrode in electrical contact to the metallized hole; and

forming on the first electrode a layer sensitive to light or ionizing radiation,

wherein forming a planarization layer provides, on a surface of the first electrode at least partially overlapping the pixel circuitry, a surface inflection, above features of the pixel circuitry.