US-20260130001-A1 - IMAGE SENSOR

Abstract

An image sensor includes first and second electrode layers, a photocharge generating layer between the first and second electrode layers and configured to generate a photocharge based on absorbing incident light, the photocharge generating layer configured to have a first highest occupied molecular orbital (HOMO) level, a hole transport layer between the first electrode layer and the photocharge generating layer and having a second HOMO level different from the first HOMO level by a difference value that is greater than or equal to a first threshold value, and an electron transport layer between the photocharge generating layer and the second electrode layer. The image sensor causes a pixel current based on the photocharge to flow between the second electrode layer and the first electrode layer, based on a first pixel voltage equal to or greater than a second threshold value being applied to the second electrode layer.

Inventors

• Moon Gyu Han
• Kyung Bae Park
• Taehyung Kim
• Dae-Yong SON

Assignees

• SAMSUNG ELECTRONICS CO., LTD.

Dates

Publication Date

20260507

Application Date

20250815

Priority Date

20241107

Claims (20)

1. 1 . An image sensor, comprising: a first electrode layer; a second electrode layer; a photocharge generating layer between the first electrode layer and the second electrode layer, the photocharge generating layer configured to generate a photocharge based on absorbing incident light, the photocharge generating layer configured to have a first highest occupied molecular orbital (HOMO) level; a hole transport layer between the first electrode layer and the photocharge generating layer, the hole transport layer configured to have a second HOMO level, the second HOMO level different from the first HOMO level by a difference value, the difference value greater than or equal to a first threshold value; and an electron transport layer between the photocharge generating layer and the second electrode layer, wherein the image sensor is configured to cause a pixel current based on the photocharge to flow between the second electrode layer and the first electrode layer, based on a first pixel voltage applied to the second electrode layer, the first pixel voltage equal to or greater than a second threshold value.
2. 2 . The image sensor of claim 1 , wherein the photocharge generating layer includes a plurality of short-wavelength infrared quantum dots, and the plurality of short-wavelength infrared quantum dots include an indium arsenide (InAs) material.
3. 3 . The image sensor of claim 1 , wherein the first threshold value is equal to or greater than 0.2 eV.
4. 4 . The image sensor of claim 1 , wherein the second threshold value is equal to or greater than 0.5 V.
5. 5 . The image sensor of claim 1 , wherein the image sensor is configured to cause the difference value to decrease based on the first pixel voltage being applied to the second electrode layer.
6. 6 . The image sensor of claim 1 , wherein the photocharge generating layer is configured to absorb the incident light to generate a plurality of holes and a plurality of electrons based on the first pixel voltage applied to the second electrode layer, and the image sensor is configured to cause the plurality of holes to be transferred to the first electrode layer through the hole transport layer and the plurality of electrons to be transferred to the second electrode layer through the electron transport layer.
7. 7 . The image sensor of claim 1 , wherein the image sensor is configured to cause the difference value to increase based on a second pixel voltage being applied to the second electrode layer, the second pixel voltage smaller than the second threshold value.
8. 8 . An image sensor, comprising: a first electrode layer on a first surface of a semiconductor substrate; a photosensitive layer positioned below the first electrode layer, the photosensitive layer including a plurality of short-wavelength infrared quantum dots, the photosensitive layer configured to generate a photocharge based on absorbing incident light; a second electrode layer positioned at a lower portion of the photosensitive layer; an insulating layer at a lower portion of the semiconductor substrate, the insulating layer configured to include a floating diffusion region on a second surface of the semiconductor substrate; and a first metal layer extending from a lower portion of the second electrode layer to the second surface of the semiconductor substrate, the first metal layer configured to transfer the photocharge to the floating diffusion region.
9. 9 . The image sensor of claim 8 , wherein the plurality of short-wavelength infrared quantum dots include an indium arsenide (InAs) material.
10. 10 . The image sensor of claim 8 , wherein the image sensor is configured to cause the photocharge to be accumulated in the floating diffusion region and the first metal layer.
11. 11 . The image sensor of claim 10 , further comprising: a plurality of transistors on the second surface; a plurality of contacts configured to transfer a plurality of control signals to the plurality of transistors; and a second metal layer between the second surface and the second electrode layer, the second metal layer configured to block light incident on the first surface from passing through the semiconductor substrate to reach the second surface.
12. 12 . The image sensor of claim 11 , wherein the floating diffusion region is spaced apart from the plurality of transistors, and the image sensor is configured to cause a size of the floating diffusion region to increase in response to accumulation of the photocharge in the floating diffusion region.
13. 13 . The image sensor of claim 8 , wherein the photosensitive layer includes: a photocharge generating layer including the plurality of short-wavelength infrared quantum dots, the photocharge generating layer configured to have a first highest occupied molecular orbital (HOMO) level; a hole transport layer between the first electrode layer and the photocharge generating layer, the hole transport layer configured to have a second HOMO level, the second HOMO level different from the first HOMO level by a difference value, the difference value greater than or equal to a first threshold value; and an electron transport layer between the second electrode layer and the photocharge generating layer.
14. 14 . The image sensor of claim 13 , wherein the image sensor is configured to cause a plurality of holes generated from the photosensitive layer to be transferred to the hole transport layer and a plurality of electrons generated from the photosensitive layer to be transferred to the electron transport layer, based on a first pixel voltage applied to the second electrode layer, the first pixel voltage equal to or greater than a second threshold value.
15. 15 . The image sensor of claim 13 , wherein the first threshold value is equal to or greater than 0.2 eV.
16. 16 . The image sensor of claim 14 , wherein the second threshold value is equal to or greater than 0.5 V.
17. 17 . The image sensor of claim 13 , wherein the image sensor is configured to cause the difference value to increase based on a second pixel voltage being applied to the second electrode layer, the second pixel voltage smaller than a second threshold value.
18. 18 . An image sensor, comprising: a photodetector including a photosensitive layer, the photosensitive layer including a plurality of short-wavelength infrared quantum dots, the plurality of short-wavelength infrared quantum dots including an indium arsenide material; a floating diffusion node connected to a first end of the photodetector, the floating diffusion node configured to accumulate a photocharge generated from the photodetector based on a pixel voltage applied to a pixel of the image sensor being equal to or greater than a first threshold value; a reset transistor connected to the first end of the photodetector and configured to transmit a power supply voltage as a reset signal to the floating diffusion node; a driving transistor including a driving transistor gate, the image sensor configured to cause a voltage of the floating diffusion node to be applied to the driving transistor gate; and a selection transistor connected to a first end of the driving transistor, the selection transistor and configured to transmit the voltage of the floating diffusion node as a pixel signal.
19. 19 . The image sensor of claim 18 , wherein the photodetector includes a first electrode layer, a second electrode layer, the image sensor configured to cause the pixel voltage to be applied to the second electrode layer, a photocharge generating layer between the first electrode layer and the second electrode layer, the photocharge generating layer configured to generate the photocharge based on absorbing incident light, the photocharge generating layer configured to have a first highest occupied molecular orbital (HOMO) level, a hole transport layer between the first electrode layer and the photocharge generating layer, the hole transport layer configured to have a second HOMO level, the second HOMO level different from the first HOMO level by a difference value, the difference value greater than or equal to a second threshold value, and an electron transport layer between the photocharge generating layer and the second electrode layer.
20. 20 . The image sensor of claim 19 , wherein the image sensor is configured to cause the difference value to increase based on the pixel voltage being smaller than the first threshold value.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0157328, filed in the Korean Intellectual Property Office on Nov. 7, 2024, the entire contents of which are incorporated herein by reference. BACKGROUND 1. Field The present inventive concepts relate to image sensors. 2. Description of the Related Art An image sensor is a device that captures a 2D or 3D image of an object. The image sensor creates an image of the object using a photoelectric conversion device that reacts according to intensity of light reflected from the object, for example based on photoelectrically converting incident light into an electrical signal, etc. Recently, with the advancement of complementary metal-oxide semiconductor (CMOS) technology, CMOS image sensors using CMOS are being widely used. In a CMOS image sensor, when using analog pixels that process output of pixels into analog signals, there is a limit to full well capacity, which is an amount of charge that can be processed within the pixel. SUMMARY Some example embodiments provide image sensors using Pb free quantum dots (QD). Some example embodiments provide driving methods for such image sensors. Some example embodiments provide image sensors capable of increasing a full well capacity. Some example embodiments provide driving methods for such image sensors. Some example embodiments provide image sensors capable of improving a shutter efficiency. Some example embodiments provide driving methods for such image sensors. In some example embodiments of the present inventive concepts, an image sensor may include a first electrode layer, a second electrode layer, a photocharge generating layer between the first electrode layer and the second electrode layer, the photocharge generating layer configured to generate a photocharge based on absorbing incident light, the photocharge generating layer configured to have a first highest occupied molecular orbital (HOMO) level, a hole transport layer between the first electrode layer and the photocharge generating layer, the hole transport layer configured to have a second HOMO level, the second HOMO level different from the first HOMO level by a difference value, the difference value greater than or equal to a first threshold value, and an electron transport layer between the photocharge generating layer and the second electrode layer. The image sensor may be configured to cause a pixel current based on the photocharge to flow between the second electrode layer and the first electrode layer, based on a first pixel voltage applied to the second electrode layer, the first pixel voltage equal to or greater than a second threshold value. In an image sensor according to some example embodiments, the photocharge generating layer may include a plurality of short-wavelength infrared quantum dots, and the plurality of short-wavelength infrared quantum dots may include an indium arsenide (InAs) material. In an image sensor according to some example embodiments, the first threshold value may be equal to or greater than 0.2 eV. In an image sensor according to some example embodiments, the second threshold value may be equal to or greater than 0.5 V. In an image sensor according to some example embodiments, the image sensor may be configured to cause the difference value to decrease based on the first pixel voltage being applied to the second electrode layer. In an image sensor according to some example embodiments, the photocharge generating layer may be configured to absorb the incident light to generate a plurality of holes and a plurality of electrons based on the first pixel voltage applied to the second electrode layer, and the image sensor may be configured to cause the plurality of holes to be transferred to the first electrode layer through the hole transport layer and the plurality of electrons to be transferred to the second electrode layer through the electron transport layer. In an image sensor according to some example embodiments, the image sensor may be configured to cause the difference value to increase based on a second pixel voltage being applied to the second electrode layer, the second pixel voltage smaller than the second threshold value. According to some example embodiments of the present inventive concepts, an image sensor may include a first electrode layer on a first surface of a semiconductor substrate, a photosensitive layer positioned below the first electrode layer, the photosensitive layer including a plurality of short-wavelength infrared quantum dots, the photosensitive layer configured to generate a photocharge based on absorbing incident light, a second electrode layer positioned at a lower portion of the photosensitive layer, an insulating layer at a lower portion of the semiconductor substrate, the insulating layer configured to include a floating diffusion region on a second surface of the semiconductor substrate, and a first metal l