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US-20260129989-A1 - COLLOIDAL QUANTUM DOT BASED IMAGE SENSOR

US20260129989A1US 20260129989 A1US20260129989 A1US 20260129989A1US-20260129989-A1

Abstract

A colloidal quantum dot (CQD) based image sensor. The CQD based image sensor includes a top contact layer, a light absorption layer, a readout integrated circuit (ROIC), and a pixel electrode. The quantum dot film includes colloidal quantum dots. The pixel electrode is positioned between the quantum dot film and the ROIC.

Inventors

  • Jet Meitzner

Assignees

  • Attollo Engineering, LLC

Dates

Publication Date
20260507
Application Date
20241104

Claims (19)

  1. 1 . A colloidal quantum dot (CQD) based image sensor, comprising: a top contact layer; a light absorption layer including a quantum dot film, the quantum dot film including colloidal quantum dots; a readout integrated circuit (ROIC); and a pixel electrode positioned between the quantum dot film and the ROIC, wherein the pixel electrode includes a base portion having a planar surface and a pillar extending from the planar surface toward the top contact layer.
  2. 2 . The CQD based image sensor of claim 1 , wherein the pillar of the pixel electrode extends into the light absorption layer to reduce a transit distance to collect charge carriers.
  3. 3 . The CQD based image sensor of claim 1 , wherein the light absorption layer includes lead sulfide (PbS) quantum dots.
  4. 4 . The CQD based image sensor of claim 1 , wherein the top contact layer includes one or more top contact pillars extending into the light absorption layer, wherein the one or more top contact pillars collects electrons or holes from the light absorption layer to reduce recombination probability.
  5. 5 . The CQD based image sensor of claim 1 , further comprising a first plurality of the pixel electrodes and a second plurality of the pixel electrodes, wherein the first plurality of the pixel electrodes have a first height and the second plurality of the pixel electrodes have a second height which is greater than the first height.
  6. 6 . The CQD based image sensor of claim 1 , wherein the pillar is positioned on a center point of the pixel electrode.
  7. 7 . The CQD based image sensor of claim 1 , wherein the pixel electrode includes a plurality of the pillars.
  8. 8 . A colloidal quantum dot (CQD) based image sensor system, comprising: a top contact layer; a light absorption layer including a quantum dot film; a readout integrated circuit (ROIC); a first plurality of pixel electrodes having a first height positioned between the quantum dot film and the ROIC; a second plurality of pixel electrodes having a second height positioned between the quantum dot film and the ROIC, wherein the second height is greater than the first height, wherein the first plurality of pixel electrodes and the second plurality of pixel electrodes collect minority carriers from the light absorption layer and are coupled to the ROIC.
  9. 9 . The CQD based image sensor system of claim 8 , wherein a first volume of the quantum dot film above the first plurality of pixel electrodes is greater than a second volume of the quantum dot film above the second plurality of pixel electrodes.
  10. 10 . The CQD based image sensor system of claim 8 , wherein the first plurality of pixel electrodes and the second plurality of pixel electrodes are positioned on a planar surface, wherein at least one of the second pixel electrodes is positioned between two or more of first pixel electrodes.
  11. 11 . The CQD based image sensor system of claim 8 , further comprising an image analysis unit in communication with the ROIC, wherein the image analysis unit is configured to measure a first image signal from the first plurality of pixel electrodes, and a second image signal from the second plurality of pixel electrodes and output an image based on the first image signal and the second image signal.
  12. 12 . The CQD based image sensor system of claim 11 , wherein the image analysis unit is configured to measure a saturation of the first plurality of pixel electrodes and the second plurality of pixel electrodes.
  13. 13 . The CQD based image sensor system of claim 12 , wherein if the saturation exceeds a threshold, the image analysis unit increases a weight associated with the second image signal.
  14. 14 . The CQD based image sensor system of claim 11 , wherein the image analysis unit provides a dynamic pixel saturation range by selectively weighting the first image signal and the second image signal based on a measured saturation.
  15. 15 . The CQD based image sensor system of claim 8 , wherein the first plurality of pixel electrodes and the second plurality of pixel electrodes each include a pillar extending into the light absorption layer, wherein the pillar reduces a transit distance to collect minority or majority carriers.
  16. 16 . A colloidal quantum dot (CQD) based image sensor, comprising: a top contact layer; a light absorption layer including a quantum dot film; a readout integrated circuit (ROIC); a pixel electrode positioned between the quantum dot film and the ROIC on a planar surface, wherein the pixel electrode includes a pyramidal structure.
  17. 17 . The CQD based image sensor of claim 16 , wherein the pyramidal structure includes a surface oriented at an angle of between 10° and 80° relative to the planar surface.
  18. 18 . The CQD based image sensor of claim 17 , wherein the surface of the pyramidal structure is configured to reflect an incident photon laterally within the quantum dot film.
  19. 19 . The CQD based image sensor of claim 16 , wherein the pyramidal structure includes an inverted pyramidal structure.

Description

TECHNICAL FIELD The subject matter disclosed herein relates to photodetectors and, in particular, to colloidal quantum dot (CQD) based image sensors. BACKGROUND Colloidal quantum dot (CQD) based image sensors (e.g., photodetectors) utilize a quantum dot film in the light absorption layer. The exciton absorption wavelength of the CQD layer is tunable due to the quantum confinement effect. To maintain the desired optical properties of the CQD, the quantum dots have a degree of physical and electronic isolation after deposition into the film layer of the photodetector device. However, the electronic isolation between quantum dots can result in low charge carrier mobilities, typically <0.1 cm2/V/s, which translates to lower drift velocity, higher probability of recombination, and lower quantum efficiency (QE). Light absorption, and therefore QE, can be enhanced by increasing CQD film thickness, however issues with film stress and adhesion limit this approach. Therefore, there exists a need to improve QE of CQD based image sensors. Further, CQD based image sensors can suffer from pixel saturation when incident light is too intense. Therefore, there exists a need for an improved dynamic range for quantum dot pixels within an array. SUMMARY According to one aspect, a colloidal quantum dot (CQD) based image sensor. The CQD based image sensor includes a top contact layer, a light absorption layer, a readout integrated circuit (ROIC), and a pixel electrode. The quantum dot film includes colloidal quantum dots. The pixel electrode is positioned between the quantum dot film and the ROIC. The pixel electrode includes a base portion having a planar surface and a pillar extending from the planar surface toward the top contact layer. According to another aspect, a colloidal quantum dot (CQD) based image sensor system. The CQD based image sensor system includes a top contact layer, a light absorption layer, a ROIC, a first plurality of pixel electrodes, and a second plurality of pixel electrodes. The light absorption layer includes a quantum dot film. The first plurality of pixel electrodes have a first height positioned between the top of the quantum dot film and the ROIC. The second plurality of pixel electrodes have a second height positioned between the top of the quantum dot film and the ROIC. The second height is greater than the first height. The first plurality of pixel electrodes and the second plurality of pixel electrodes collect charge carriers from the light absorption layer and are coupled to the ROIC. According to another aspect, a colloidal quantum dot (CQD) based image sensor. The CQD based image sensor includes a top contact layer, a light absorption layer, a ROIC, and a pixel electrode positioned between the top of the quantum dot film and the ROIC on a planar surface. The pixel electrode includes a pyramidal structure. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a cross sectional diagrammatic view of a colloidal quantum dot (CQD) based image sensor, according to some embodiments. FIG. 1B is a cross sectional diagrammatic view of a CQD based image sensor, according to some embodiments. FIG. 2A is a cross sectional diagrammatic view of a CQD based image sensor with a plurality of top contact pillars, according to some embodiments. FIG. 2B is a cross sectional diagrammatic view of a CQD based image sensor with a plurality of pixel electrode pillars, according to some embodiments. FIG. 2C is a top view of a pixel electrode with a single electrode pillar, according to some embodiments. FIG. 2D is a top view of a pixel electrode with a plurality of electrode pillars, according to some embodiments. FIG. 2E is a top view of a pixel electrode with a plurality of electrode pillars, according to some embodiments. FIG. 3A is a cross sectional diagrammatic view of a CQD based image sensor with a first plurality of pixel electrodes and a second plurality of pixel electrodes having a different height from the first plurality of pixel electrodes, according to some embodiments. FIG. 3B is a top diagrammatic view of a sample region of pixel electrodes of a CQD based image sensor including a first plurality of pixel electrodes and a second plurality of pixel electrodes, according to some embodiments. FIG. 4 is a flow chart of a method of improving dynamic range of pixels of a CQD based image sensor, according to some embodiments. FIG. 5A is a cross sectional diagrammatic view of a CQD based image sensor with a plurality of pyramidal pixel electrodes, according to some embodiments. FIG. 5B is a cross sectional diagrammatic view of a CQD based image sensor with a plurality of inverted pyramidal pixel electrodes, according to some embodiments. DETAILED DESCRIPTION The present disclosure describes devices, systems, and methods for improving quantum efficiency (QE) and/or dynamic pixel saturation range of colloidal quantum dot (CQD) based image sensors. The CQD based image sensor includes a top contact layer, a plurality of pi