Materials, systems and methods for optoelectronic devices

• US 7,923,801 B2
• Filed: 04/18/2008
• Issued: 04/12/2011
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Original Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Inventors: Sargent, Edward Hartley, Tian, Hui
• Primary Examiner(s): HO, TU TU V
• Application Number:
  US12/106,256
• Publication Number:
  US 20090152664A1
• Time in Patent Office: 1,089 Days
• Field of Search: 257/440, 257/445, 257/463, 257/59, 257/72, 257/E31.111, 257/E27.132, 257/E27.139, 438/73
• US Class Current: 257/440
• CPC Class Codes: G06V 40/1318 using electro-optical elements or layers, e.g. electroluminescent sensing
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14641 Electronic components shared by two or more pixel-elements, e.g. one amplifier shared by two pixel elements
• CPC Class Codes: H01L 27/14647 Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H01L 27/14652 Multispectral infrared imagers, having a stacked pixel-element structure, e.g. npn, npnpn or MQW structures
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 27/14692 Thin film technologies, e.g. amorphous, poly, micro- or nanocrystalline silicon
• CPC Class Codes: H01L 31/036 characterised by their crystalline structure or particular orientation of the crystalline planes
• CPC Class Codes: H01L 31/1013 devices sensitive to two or more wavelengths, e.g. multi-spectrum radiation detection devices

Abstract

A photodetector is described along with corresponding materials, systems, and methods. The photodetector comprises an integrated circuit and at least two optically sensitive layers. A first optically sensitive layer is over at least a portion of the integrated circuit, and a second optically sensitive layer is over the first optically sensitive layer. Each optically sensitive layer is interposed between two electrodes. The two electrodes include a respective first electrode and a respective second electrode. The integrated circuit selectively applies a bias to the electrodes and reads signals from the optically sensitive layers. The signal is related to the number of photons received by the respective optically sensitive layer.

Claims

1. A photodetector comprising:

a semiconductor substrate;

a plurality of pixel regions, each pixel region comprising an optically sensitive layer over the substrate, wherein the optically sensitive layer employs an n-type semiconductor and is contacted using a deep-work-function metal having a work function deeper than 4.5 eV below vacuum;

a pixel circuit for each pixel region, each pixel circuit comprising a charge store and a read out circuit; and

circuitry to select the charge store of a plurality of adjacent pixel regions for simultaneous reading to a shared read out circuit.

2. The photodetector of claim 1, wherein the plurality of adjacent pixel regions includes two adjacent pixel regions.

3. The photodetector of claim 1, wherein the plurality of adjacent pixel regions includes four adjacent pixel regions.

4. The photodetector of claim 1, wherein the plurality of adjacent pixel regions includes 16 adjacent pixel regions.

5. The photodetector of claim 1, wherein the plurality of adjacent pixel regions is a number of pixel regions, wherein the number is a multiple of two.

6. The photodetector of claim 1, wherein the plurality of adjacent pixel regions is a number of pixel regions, wherein the number is a multiple of four.

7. The photodetector of claim 1, wherein the plurality of adjacent pixel regions is a number of pixel regions, wherein the number is a multiple of eight.

8. The photodetector of claim 1, wherein the plurality of adjacent pixel regions is a number of pixel regions, wherein the number is a multiple of sixteen.

9. The photodetector of claim 1, wherein each pixel region has a top surface area of less than 6, 5 or 4 micrometers squared.

10. The photodetector of claim 1, wherein each pixel region has at least two respective electrodes, and wherein the distance between the at least two respective electrodes for each pixel region is less than 3, 2 or 1.5 micrometers.

33. The photodetector of claim 1, wherein the optically sensitive layer has a composition of photoconductive material that controls a ratio of electron mobility to hole mobility.

34. The photodetector of claim 1, wherein the optically sensitive layer employs a p-type semiconductor;

and is contacted using a low-work-function metal having a work function shallower than 4.5 eV below vacuum.

35. The photodetector of claim 1, wherein the optically sensitive layer passes dark current that flows in response to electrons;

and passes light current that flows in response to excess holes and is related to a change in conductivity of the photoconductive material.

36. The photodetector of claim 1, wherein the optically sensitive layer consists of a photoconductive material comprising two carrier types comprising a hole type carrier and an electron type carrier, wherein one of the types is a flowing carrier and the other type is a trapped carrier;

and the optically sensitive layer is contacted using an injecting contact proximate the photoconductive material, wherein under biasing conditions, the injecting contact injects the flowing carrier into the active layer with much greater relative efficiency than it withdraws the trapped carrier from the active layer into the contact; and

in which a withdrawing contact proximate the photoconductive material, wherein under biasing conditions, the withdrawing contact withdraws the flowing carrier from the active layer into the contact with much greater efficiency than it injects the trapped carrier into the active layer.

11. A photodetector comprising:

a semiconductor substrate;

a plurality of pixel regions over the semiconductor substrate, each pixel region comprising a first electrode, a second electrode and an optically sensitive layer between the first electrode and the second electrode, wherein the optically sensitive layer employs an n-type semiconductor and is contacted using a deep-work-function metal having a work function deeper than 4.5 eV below vacuum;

a pixel circuit for each pixel region, each pixel circuit comprising a charge store and a read out circuit;

circuitry to electrically connect the first electrode for a set of pixel regions to a shared charge store during an integration period of time, the plurality of pixel regions including the set of pixel regions, wherein the shared charge store is the charge store corresponding to one pixel circuit of one pixel region; and

circuitry to read out a signal from the shared charge store, the signal based on intensity of light absorbed by each pixel region of the set of pixel regions during the integration period of time.

12. The photodetector of claim 11, wherein the set of pixel regions includes two pixel regions.

13. The photodetector of claim 11, wherein the set of pixel regions includes four pixel regions.

14. The photodetector of claim 11, wherein the set of pixel regions includes 16 pixel regions.

15. The photodetector of claim 11, wherein the set of pixel regions includes a number of pixel regions, wherein the number is a multiple of two.

16. The photodetector of claim 11, wherein the set of pixel regions includes a number of pixel regions, wherein the number is a multiple of four.

17. The photodetector of claim 11, wherein the set of pixel regions includes a number of pixel regions, wherein the number is a multiple of eight.

18. The photodetector of claim 11, wherein the set of pixel regions includes a number of pixel regions, wherein the number is a multiple of sixteen.

37. The photodetector of claim 11, wherein the optically sensitive layer has a composition of photoconductive material that controls a ratio of electron mobility to hole mobility.

38. The photodetector of claim 11, wherein the optically sensitive layer employs a p-type semiconductor;

and is contacted using a low-work-function metal having a work function shallower than 4.5 eV below vacuum.

39. The photodetector of claim 11, wherein the optically sensitive layer passes dark current that flows in response to electrons;

and passes light current that flows in response to excess holes and is related to a change in conductivity of the photoconductive material.

40. The photodetector of claim 11, wherein the optically sensitive layer consists of a photoconductive material comprising two carrier types comprising a hole type carrier and an electron type carrier, wherein one of the types is a flowing carrier and the other type is a trapped carrier;

and the optically sensitive layer is contacted using an injecting contact proximate the photoconductive material, wherein under biasing conditions, the injecting contact injects the flowing carrier into the active layer with much greater relative efficiency than it withdraws the trapped carrier from the active layer into the contact; and

in which a withdrawing contact proximate the photoconductive material, wherein under biasing conditions, the withdrawing contact withdraws the flowing carrier from the active layer into the contact with much greater efficiency than it injects the trapped carrier into the active layer.

19. A photodetector comprising:

a semiconductor substrate;

a plurality of pixel regions over the semiconductor substrate, each pixel region comprising a first electrode, a second electrode and an optically sensitive layer between the first electrode and the second electrode, wherein the optically sensitive layer employs an n-type semiconductor and is contacted using a deep-work-function metal having a work function deeper than 4.5 eV below vacuum; and

pixel circuitry configured in a first mode to read out a signal for each pixel region based on the intensity of light absorbed by the optically sensitive layer of the respective pixel region, and configured in a second mode to read out a signal for a plurality of sets of pixel regions based on the intensity of light absorbed by the optically sensitive layers of each set of pixel regions.

20. The photodetector of claim 19, wherein the pixel circuitry electrically connects the first electrode of each set of pixel regions to a common charge store for the respective set of pixel regions for an integration period of time.

21. The photodetector of claim 19, wherein the pixel circuitry is configured in the first mode to electrically connect the first electrode of each pixel region to a separate charge store for an integration period of time and is configured in the second mode to electrically connect the first electrodes for each set of pixel regions to a shared charge store for the integration period of time.

22. The photodetector of claim 19, wherein each set of pixel regions includes two pixel regions.

23. The photodetector of claim 19, wherein each set of pixel regions includes four pixel regions.

24. The photodetector of claim 19, wherein each set of pixel regions includes 16 pixel regions.

25. The photodetector of claim 19, wherein each set of pixel regions includes a number of pixel regions, wherein the number is a multiple of two.

26. The photodetector of claim 19, wherein each set of pixel regions includes a number of pixel regions, wherein the number is a multiple of four.

27. The photodetector of claim 19, wherein each set of pixel regions includes a number of pixel regions, wherein the number is a multiple of eight.

28. The photodetector of claim 19, wherein each set of pixel regions includes a number of pixel regions, wherein the number is a multiple of sixteen.

41. The photodetector of claim 19, wherein the optically sensitive layer has a composition of photoconductive material that controls a ratio of electron mobility to hole mobility.

42. The photodetector of claim 19, wherein the optically sensitive layer employs a p-type semiconductor;

and is contacted using a low-work-function metal having a work function shallower than 4.5 eV below vacuum.

43. The photodetector of claim 19, wherein the optically sensitive layer passes dark current that flows in response to electrons;

and passes light current that flows in response to excess holes and is related to a change in conductivity of the photoconductive material.

44. The photodetector of claim 19, wherein the optically sensitive layer consists of a photoconductive material comprising two carrier types comprising a hole type carrier and an electron type carrier, wherein one of the types is a flowing carrier and the other type is a trapped carrier;

and the optically sensitive layer is contacted using an injecting contact proximate the photoconductive material, wherein under biasing conditions, the injecting contact injects the flowing carrier into the active layer with much greater relative efficiency than it withdraws the trapped carrier from the active layer into the contact; and

in which a withdrawing contact proximate the photoconductive material, wherein under biasing conditions, the withdrawing contact withdraws the flowing carrier from the active layer into the contact with much greater efficiency than it injects the trapped carrier into the active layer.

29. An image sensor comprising:

a semiconductor substrate;

a photosensor array having a plurality of pixel regions, the pixel regions arranged into a plurality of rows and a plurality of columns;

each pixel region comprising at least one optically sensitive material over a portion of the semiconductor substrate, wherein the optically sensitive layer employs an n-type semiconductor and is contacted using a deep-work-function metal having a work function deeper than 4.5 eV below vacuum; and

circuitry formed on the semiconductor substrate that is configured to apply a voltage difference across a plurality of respective pixel regions of the optically sensitive material and to read out a signal based on a flow of current through the plurality of respective pixel regions over a period of time.

30. The image sensor of claim 29 wherein at least a portion of the circuitry is formed under the optically sensitive material for the plurality of respective pixel regions.

31. The image sensor of claim 29, wherein the signal is integrated to a common charge store for the plurality of pixel regions.

32. The image sensor of claim 31, wherein the common charge store is a single capacitance.

45. The image sensor of claim 29, wherein the optically sensitive layer has a composition of photoconductive material that controls a ratio of electron mobility to hole mobility.

46. The image sensor of claim 29, wherein the optically sensitive layer employs a p-type semiconductor;

and is contacted using a low-work-function metal having a work function shallower than 4.5 eV below vacuum.

47. The image sensor of claim 29, wherein the optically sensitive layer passes dark current that flows in response to electrons;

and passes light current that flows in response to excess holes and is related to a change in conductivity of the photoconductive material.

48. The image sensor of claim 29, wherein the optically sensitive layer consists of a photoconductive material comprising two carrier types comprising a hole type carrier and an electron type carrier, wherein one of the types is a flowing carrier and the other type is a trapped carrier;

and the optically sensitive layer is contacted using an injecting contact proximate the photoconductive material, wherein under biasing conditions, the injecting contact injects the flowing carrier into the active layer with much greater relative efficiency than it withdraws the trapped carrier from the active layer into the contact; and

in which a withdrawing contact proximate the photoconductive material, wherein under biasing conditions, the withdrawing contact withdraws the flowing carrier from the active layer into the contact with much greater efficiency than it injects the trapped carrier into the active layer.