Materials, Systems and Methods for Optoelectronic Devices

• US 20090152664A1
• Filed: 04/18/2008
• Published: 06/18/2009
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Original Assignee: InVisage Technologies, Inc. (Apple Inc.)
• Inventors: Konstantatos, Gerasimos, Klem, Ethan Jacob Dukenfield, Brading, Michael Charles, Tang, Jiang, Sargent, Edward Hartley, Tian, Hui, MacNeil, Dean Delehanty
• Granted Patent: US 7,923,801 B2
• Time in Patent Office: Days
• 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. A photodetector comprising:

an integrated circuit; and

at least two optically sensitive layers, a first optically sensitive layer and a second optically sensitive layer, the first optically sensitive layer over at least a portion of the integrated circuit and the second optically sensitive layer over the first optically sensitive layer;

wherein each optically sensitive layer is interposed between two electrodes, the electrodes including a respective first electrode and a respective second electrode;

wherein the integrated circuit selectively applies a bias to the electrodes and reads signals from the optically sensitive layers, wherein the signal is related to the number of photons received by the respective optically sensitive layer.

2. The photodetector of claim 1, wherein at least one of the optically sensitive layers comprises nanocrystals of a material having a bulk bandgap, and wherein the nanocrystals are quantum confined to have an effective bandgap more than twice the bulk bandgap.

3. The photodetector of claim 1, wherein at least one of the optically sensitive layers includes nanocrystals comprising nanoparticles, wherein a nanoparticle diameter of the nanoparticles is less than a Bohr exciton radius of bound electron-hole pairs within the nanoparticle.

4. The photodetector of claim 1, wherein at least one optically sensitive layer comprises a continuous film of interconnected nanocrystal particles in contact with the respective first electrode and the respective second electrode.

5. The photodetector of claim 4, wherein the nanocrystal particles comprise a plurality of nanocrystal cores and a shell over the plurality of nanocrystal cores.

6. The photodetector of claim 5, wherein the plurality of nanocrystal cores are fused.

7. The photodetector of claim 5, wherein a physical proximity of the nanocrystal cores of adjacent nanocrystal particles provides electrical communication between the adjacent nanocrystal particles.

8. The photodetector of claim 5, wherein the plurality of nanocrystal cores are electrically interconnected with linker molecules.

9. The photodetector of claim 4, wherein at least one of the optically sensitive layers 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.

10. The photodetector of claim 4 nanocrystal particles, wherein the nanocrystal particles include closely-packed semiconductor nanoparticle cores.

11. The photodetector of claim 10, wherein each core is partially covered with an incomplete shell, where the shell produces trap states having substantially a single time constant.

12. The photodetector of claim 10, wherein the nanoparticle cores are passivated and crosslinked using at least one crosslinking molecule of at least one length.

13. The photodetector of claim 1, wherein the first optically sensitive layer comprises a first material having a first thickness, and a combination of the first material and the first thickness provides a first responsivity to light of a first wavelength, wherein the second optically sensitive layer comprises a second material having a second thickness, and a combination of the second material and the second thickness provides a second responsivity to light of a second wavelength, wherein the first responsivity and the second responsivity are approximately equal.

14. The photodetector of claim 1, wherein the first optically sensitive layer comprises a first material having a first thickness, and a combination of the first material and the first thickness provides a first photoconductive gain to light of a first wavelength, wherein the second optically sensitive layer comprises a second material having a second thickness, and a combination of the second material and the second thickness provides a second photoconductive gain to light of a second wavelength, wherein the first photoconductive gain and the second photoconductive gain are approximately equal.

15. The photodetector of claim 1, wherein the first optically sensitive layer comprises a first material having a first thickness, and a combination of the first material and the first thickness provides a first absorbance to light of a first wavelength, wherein the second optically sensitive layer comprises a second material having a second thickness, and a combination of the second material and the second thickness provides a second absorbance to light of a second wavelength, wherein the first absorbance and the second absorbance are approximately equal.

16. The photodetector of claim 1, wherein at least one of the optically sensitive layers comprises monodisperse nanocrystal particles.

17. The photodetector of claim 16, wherein the nanocrystal particles are colloidal quantum dots.

18. The photodetector of claim 17, wherein the quantum dots include a first carrier type and a second carrier type, wherein the first carrier type is a flowing carrier and the second carrier type is one of a substantially blocked carrier and a trapped carrier.

19. The photodetector of claim 1, wherein the first optically sensitive layer comprises a first composition including one of lead sulfide (PbS), lead selenide (PbSe), lead tellurium sulfide (PbTe), indium phosphide (InP), indium arsenide (InAs), and germanium (Ge), and the second optically sensitive layer comprises a second composition including one of indium sulfide (In₂S₃), indium selenide (In₂Se₃), indium tellurium (In₂Te₃), bismuth sulfide (Bi₂S₃), bismuth selenide (Bi₂Se₃), bismuth tellurium (Bi₂Te₃), indium phosphide (InP), silicon (Si), and germanium (Ge).

20. The photodetector of claim 1, wherein the bias comprises:

biasing the optically sensitive layers to operate as a current sink during a first period of time; and

biasing the optically sensitive material to operate as a current source during a second period of time.

21. A vertically stacked pixel, comprising:

a plurality of optically sensitive layers including a first optically sensitive layer and a second optically sensitive layer, the first optically sensitive layer overlying at least a portion of a first side of an integrated circuit and the second optically sensitive layer overlying at least a portion of a second side of the first optically sensitive layer;

a plurality of electrodes, wherein the plurality of optically sensitive layers is interposed between a respective first electrode and a respective second electrode of the plurality of electrodes; and

a coupling between the integrated circuit and the plurality of electrodes by which the integrated circuit selectively applies a bias and reads from the optically sensitive layers pixel information corresponding to light absorbed by the optically sensitive layers.

22. A photosensor array comprising:

an integrated circuit; and

a plurality of photodetectors over the integrated circuit, wherein each photodetector forms a vertically stacked pixel that comprises,

at least two optically sensitive layers, a first optically sensitive layer and a second optically sensitive layer, the first optically sensitive layer over at least a portion of the integrated circuit and the second optically sensitive layer over the first optically sensitive layer; and

wherein each optically sensitive layer is interposed between two electrodes, the electrodes including a respective first electrode and a respective second electrode, wherein the integrated circuit is coupled to the electrodes and selectively applies a bias to the electrodes and reads signals from the optically sensitive layers, wherein the signals are related to the number of photons received by the respective optically sensitive layer.

23. A sensor comprising:

at least one optically sensitive layer; and

a circuit comprising at least one node in electrical communication with the optically sensitive layer, wherein the circuit stores an electrical signal proportional to the intensity of light incident on the optically sensitive layer during an integration period, wherein a non-linear relationship exists between electrical characteristics of the optically sensitive layer and the intensity of light absorbed by the optically sensitive layer, wherein a continuous function represents the non-linear relationship.

24. A photodetector comprising:

a pixel region comprising an optically sensitive material;

pixel circuitry electrically coupled to the optically sensitive material, the pixel circuitry establishing a voltage over an integration period of time, wherein the voltage has a non-linear relationship with intensity of light absorbed by the optically sensitive material of the respective pixel region, wherein a signal is generated based on the voltage after the integration period of time, the signal having a noise level;

a converter configured to convert the signal into digital pixel data, wherein the converter has an input range; and

at least one of the pixel circuitry and the optically sensitive layer providing a dynamic range more than at least twice the ratio of the input range of the converter divided by the noise level.

25. A photodetector comprising:

a pixel region comprising an optically sensitive material;

pixel circuitry electrically coupled to the optically sensitive material, the pixel circuitry providing a current flow through the optically sensitive material, wherein a rate of the current flow through the optically sensitive material has a non-linear relationship with intensity of the light absorbed by the optically sensitive material;

charge collection circuitry that collects charge relating to the current flow over a period of time; and

read out circuitry that generates a signal from the charge collected over the period of time.