Materials, systems and methods for optoelectronic devices

• US 8,004,057 B2
• Filed: 03/19/2010
• Issued: 08/23/2011
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Original Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Inventors: Tian, Hui, Sargent, Edward
• Primary Examiner(s): HO, TU TU V
• Application Number:
  US12/728,181
• Publication Number:
  US 20100187404A1
• Time in Patent Office: 522 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
• CPC Class Codes: H04N 25/17 Colour separation based on photon absorption depth, e.g. full colour resolution obtained simultaneously at each pixel location

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. An image sensor comprising:

a semiconductor substrate;

a plurality of pixel regions, each pixel region comprising a first electrode, a second electrode, and an optically sensitive layer over the substrate, the optically sensitive layer positioned to receive light;

a pixel circuit for each pixel region, each pixel circuit comprising a charge store and a read out circuit, the charge store and the read out circuit in electrical communication with the optically sensitive layer of the respective pixel region; and

a plurality of conductive layers positioned between the charge store of the respective pixel region and the optically sensitive layer of the corresponding pixel region, the conductive layers providing an opaque shield such that the respective charge store is shielded from the light incident on the optically sensitive layer when the light is in a wavelength band, wherein a set of conductive layers of the plurality of conductive layers is in electrical communication with the optically sensitive layer, the second electrode being a common second electrode that is common to all pixel regions of the plurality of pixel regions, the common second electrode being connected through an interconnect metal layer, the plurality of conductive layers including the interconnect metal layer.

2. The image sensor of claim 1, wherein the plurality of conductive layers includes at least three metal layers, wherein the set of conductive layers includes two metal layers of the at least three metal layers.

3. The image sensor of claim 1, wherein the charge store comprises capacitance.

4. The image sensor of claim 1, wherein the charge store comprises parasitic capacitance.

5. The image sensor of claim 1, wherein the charge store is parasitic capacitance between metal in an interconnect layer.

6. The image sensor of claim 1, wherein the charge store comprises parasitic capacitance from a drain of a reset transistor and gate of a read out transistor.

7. The image sensor of claim 1, comprising a transistor coupled between the charge store of each pixel circuit and the optically sensitive layer of the corresponding pixel region.

8. The image sensor of claim 1, comprising a diode coupled between the charge store of each pixel circuit and the optically sensitive layer of the corresponding pixel region.

9. The image sensor of claim 1, comprising a parasitic diode coupled between the charge store of each pixel circuit and the optically sensitive layer of the corresponding pixel region.

10. The image sensor of claim 1, wherein each respective pixel circuit resets a voltage difference across the optically sensitive layer of the corresponding pixel region.

11. The image sensor of claim 1, wherein each respective pixel circuit independently resets a voltage of the charge store of the respective pixel circuit.

12. The image sensor of claim 1, wherein each respective pixel circuit comprises:

a first reset circuit in electrical communication with the charge store of the respective pixel circuit;

a switch between the respective charge store and a first electrode of the corresponding pixel region; and

a second reset circuit in electrical communication with the first electrode of the respective pixel region when the switch electrically isolates the respective first electrode from the charge store.

13. The image sensor of claim 12, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 3 micrometers.

14. The image sensor of claim 12, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 2 micrometers.

15. The image sensor of claim 12, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 1.5 micrometers.

16. The image sensor of claim 1, wherein the optically sensitive layer for each pixel region has a top surface area of less than approximately 6 square micrometers.

17. The image sensor of claim 1, wherein the optically sensitive layer for each pixel region has a top surface area of less than approximately 5 square micrometers.

18. The image sensor of claim 1, wherein the optically sensitive layer for each pixel region has a top surface area of less than approximately 4 square micrometers.

19. The image sensor of claim 1, wherein the pixel circuit applies a voltage difference across the optically sensitive layer.

20. The image sensor of claim 19, wherein the optically sensitive layer has a photoconductive gain when the voltage difference is applied and the optically sensitive layer is exposed to the light.

21. The image sensor of claim 1, wherein the optically sensitive layer comprises a nanocrystal material having photoconductive gain and a responsivity of at least approximately 0.4 amps/volt (A/V).

22. The image sensor of claim 21, wherein the responsivity is achieved when a bias is applied across the optically sensitive layer, wherein the bias is approximately in a range of 1 volt to 5 volts.

23. The image sensor of claim 1, wherein the optically sensitive layer comprises monodisperse nanocrystals.

24. The image sensor of claim 1, wherein the optically sensitive layer comprises a continuous film of interconnected nanocrystal particles in contact with the respective first electrode and the common electrode.

25. The image sensor of claim 24, wherein the nanocrystal particles comprise a plurality of nanocrystal cores and a shell over the plurality of nanocrystal cores.

26. The image sensor of claim 25, wherein the plurality of nanocrystal cores are fused.

27. The image sensor of claim 25, wherein a physical proximity of the nanocrystal cores of adjacent nanocrystal particles provides electrical communication between the adjacent nanocrystal particles.

28. The image sensor of claim 27, wherein the physical proximity includes a separation distance of less than approximately 0.5 nm.

29. The image sensor of claim 27, wherein the electrical communication includes a hole mobility of at least approximately 1E-5 square centimeter per volt-second across the nanocrystal particles.

30. The image sensor of claim 25, wherein the plurality of nanocrystal cores are electrically interconnected with linker molecules.

31. The image sensor of claim 1, wherein the optically sensitive layer comprises a unipolar photoconductive layer including a first carrier type and a second carrier type, wherein a first mobility of the first carrier type is higher than a second mobility of the second carrier type.

32. An image sensor comprising:

a semiconductor substrate;

a plurality of pixel regions, each pixel region comprising a first electrode, a second electrode, and an optically sensitive layer over the substrate, the optically sensitive layer positioned to receive light;

a pixel circuit for each pixel region, each pixel circuit comprising a charge store and a read out circuit, the charge store and the read out circuit in electrical communication with the optically sensitive layer of the respective pixel region, each respective pixel circuit comprising;

a first reset circuit in electrical communication with the charge store of the respective pixel circuit;

a switch between the respective charge store and a first electrode of the corresponding pixel region; and

a second reset circuit in electrical communication with the first electrode of the respective pixel region when the switch electrically isolates the respective first electrode from the charge store; and

a plurality of conductive layers positioned between the charge store of the respective pixel region and the optically sensitive layer of the corresponding pixel region, the conductive layers providing an opaque shield such that the respective charge store is shielded from the light incident on the optically sensitive layer when the light is in a wavelength band, wherein a set of conductive layers of the plurality of conductive layers is in electrical communication with the optically sensitive layer.

33. The image sensor of claim 32, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 3 micrometers.

34. The image sensor of claim 32, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 2 micrometers.

35. The image sensor of claim 32, wherein a distance between the first electrode and the second electrode of each pixel region is less than approximately 1.5 micrometers.

36. The image sensor of claim 32, wherein the second electrode is a common second electrode that is common to all pixel regions of the plurality of pixel regions, wherein the common second electrode is connected through an interconnect metal layer, wherein the plurality of conductive layers includes the interconnect metal layer.