High sensitivity image sensors including a single electron field effect transistor and methods of operating the same
A high sensitivity image sensor including a pixel, the pixel including a single electron field effect transistor (SEFET), the SEFET including a first conductive type well in a second conductive type substrate, second conductive type source and drain regions in the well and a first conductive type gate region in the well between the source and the drain regions.
1. A high sensitivity image sensor, comprising:
a substrate;
a first well in the substrate,
the first well being configured to be a photoelectric transformation region to generate charges by incident light,
the first well including a first well region and a second well region,
a concentration of impurities in the first well region being greater than a concentration of impurities in the second well region;
source and drain regions in the first well;
a gate region in the first well between the source and drain regions, the gate region being configured to accumulate the generated charges; and
a channel region on the gate region in the substrate,
the channel region being configured to connect the source and drain regions.
2. The high sensitivity image sensor of claim 1 , wherein the gate
region is configured to be a photo detecting region.
3. The high sensitivity image sensor of claim 1 , wherein the first well, the gate region, the source region and the drain region are part of a single electron field effect transistor (SEFET) of a pixel, and
the pixel includes a source follower resistor connected in series to the SEFET.
4. The high sensitivity image sensor of claim 1 , wherein the gate region is configured to generate an input voltage in response to light incident onto the gate region, and
the high sensitivity image sensor is configured to detect an output voltage from the source region.
5. The high sensitivity image sensor of claim 1 , wherein
the source and drain regions are spaced apart from each other in a first direction,
the first direction is perpendicular to a second direction,
the channel region includes a first width extending in the first direction that is wider than a first width of the gate region extending in the first direction, and
the gate region includes a second width extending in the second direction that is wider than a second width of the channel region extending in the second direction.
6. The high sensitivity image senor of claim 1 , wherein
the first well, the gate region, the source region and the drain region are part of a single electron field effect transistor (SEFET), and
the SEFET is connected to one of a source follower transistor and a source follower resistor.
7. A pixel of a high sensitivity image sensor, comprising:
the SEFET of claim 6 , wherein
the SEFET is configured to detect light and output a voltage based on a quantity of the detected light,
the SEFET is connected to the source follower transistor, and
the pixel includes a selective transistor connected to the SEFET.
8. The high sensitivity image sensor of claim 1 ,
wherein the substrate is of a first conductive type,
the first well is of a second conductive type,
the source and drain regions are of the first conductive type,
the gate region is of the second conductive type, and
the channel region is of the first conductive type.
9. The high sensitivity image sensor of claim 8 , wherein the first well region and the second well region of the, first well are p-type.
10. The high sensitivity image sensor of claim 8 , wherein the first conductive type is p-type, and
the second conductive type is n-type.
11. The high sensitivity image sensor of claim 10 , further comprising:
a second well of the first conductive type under the first well.
12. The high sensitivity image sensor of claim 11 , wherein the second well includes a third well region and a fourth well region, and
an impurity concentration of the third well region is less than an impurity concentration of the fourth well region.
13. A high sensitivity image sensor comprising:
a substrate,
the substrate being of a first conductive type;
a first well in the substrate,
the first well being of a second conductive type;
source and drain regions in the first well
the source and drain regions being of the second conductive type;
a gate region in the first well between the source and drain regions,
the gate region being of the first conductive type; and
an impurity region in the gate region,
the impurity region being of the second conductive type.
14. The high sensitivity image sensor of claim 13 , wherein the first
well surrounds the gate region below a surface of the substrate, and
at least a part of the first well between the source and drain regions is a channel region.
15. The high sensitivity image sensor of claim 13 , wherein the first conductive type is n-type, and
the second conductive type is p-type.
16. The high sensitivity image sensor of claim 13 , wherein the gate region encircles the impurity region.
17. A high sensitivity image sensor, comprising:
a substrate;
a first well in the substrate;
source and drain regions in the first well; and
a gate region in the first well between the source and drain regions, wherein
the first well, the gate region, the source region and the drain region are part of a single electron field effect transistor (SEFET) of a pixel, and
the pixel includes a source follower transistor connected to the SEFET.
18. The high sensitivity image sensor of claim 17 , comprising:
the pixel of claim 17 ; and
a selective transistor connected to the SEFET.