Unit pixel of image sensor and photo detector using the same

1. A sensitivity adjustment photo detector, comprising:

a light-absorbing part configured to absorb light;

a source and a drain that are separated from the light-absorbing part by an oxide film;

a channel that is formed between the source and the drain and configured to generate a flow of electric current between the source and the drain; and

a sensitivity adjustment terminal configured to apply an external voltage to the light-absorbing part and a P-well or N-well of the sensitivity adjustment terminal is connected to a drain of a reset device,

wherein the light-absorbing part is doped with first type impurities, and the source and the drain are doped with second type impurities,

wherein the flow of electric current in the channel is adjusted based on a change in a quantity of electric charges in the light-absorbing part according to tunneling of electrons excited by light incident to the light-absorbing part to the source or the drain, and

wherein the channel is configured to have a threshold voltage adjusted by controlling the external voltage,

wherein when the external voltage is adjusted, a gap between a Fermi level and an intrinsic level of the channel is adjusted, and the threshold voltage is adjusted,

wherein, when an absolute value of the external voltage is adjusted to be higher than the absolute value of a set voltage, the light-absorbing part has a first potential state and no current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be equal to the absolute value of the set voltage, the light-absorbing part has a second potential state, and when the light is incident on the light-absorbing part, the current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be 0V to reduce dark electric current, the light-absorbing part has a third potential state and the current always flows through the channel, and

wherein a value of set voltage when light is suddenly incident to the light-absorbing part is higher than the value of the set voltage so as to prevent the image saturation in the sensitivity adjustment photo detector in advance, and

wherein the drain of the reset device is connected to a P-well or N-well body of the sensitivity adjustment photo detector, and a bias voltage for reset is applied to a source of the reset device, and

where all remaining electric charges in the floated N-well are eliminated before operating the sensitivity adjustment photo detector to suppress generation of dark electric current due to the remaining electric charges.

2. The sensitivity adjustment photo detector according to claim 1 , wherein the source and the drain are formed on a well doped with the first type impurities, and wherein the well is in a flattened state.

3. The sensitivity adjustment photo detector according to claim 1 , wherein the sensitivity adjustment terminal is configured to adjust a magnitude of the external voltage applied to the light-absorbing part so as to adjust a sensitivity of the light-absorbing part.

4. The sensitivity adjustment photo detector according to claim 1 , wherein the tunneling occurs in a region between any one of the source and the drain, and the light-absorbing part.

5. The sensitivity adjustment photo detector according to claim 1 , wherein the sensitivity adjustment terminal is configured to apply a voltage higher than or equal to a set voltage to the light-absorbing part so as to reset the light-absorbing part.

6. A unit pixel of an image sensor, comprising:

a photo detector configured to generate a flow of electric current using a change in a quantity of electric charges by incident light; and

a select device configured to output an electric current generated in the photo detector to a unit pixel output terminal,

wherein the photo detector includes a light-absorbing part configured to absorb light, a source and a drain which are separated from the light-absorbing part by an oxide film, a channel which is formed between the source and the drain to generate a flow of electric current between the source and the drain, and a sensitivity adjustment terminal configured to apply an external voltage to the light-absorbing part and a P-well or N-well of the sensitivity adjustment terminal is connected to a drain of a reset device,

wherein the photo detector is configured to adjust the flow of electric current in the channel based on the change in the quantity of electric charges in the light-absorbing part according to tunneling of an electron excited by light incident to the light-absorbing part to the source or the drain, and

wherein the photo detector is configured to adjust the external voltage,

wherein when the external voltage is adjusted, a gap between a Fermi level and an intrinsic level of the channel is adjusted, and the threshold voltage is adjusted,

wherein, when an absolute value of the external voltage is adjusted to be higher than the absolute value of a set voltage, the light-absorbing part has a first potential state and no current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be equal to the absolute value of the set voltage, light-absorbing part has a second potential state, so that and when the light is incident on the light-absorbing part, the current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be 0V to reduce dark electric current, the light-absorbing part has a third potential state and the current always flows through the channel, and

wherein the value of set voltage when light is suddenly incident to the light-absorbing part is higher than the value of the set voltage so as to prevent the image saturation in the photo detector in advance, and

wherein the drain of the reset device is connected to a P-well or N-well body of the photo detector, and a bias voltage for reset is applied to a source of the reset device, and

where all remaining electric charges in the floated N-well are eliminated before operating the photo detector to suppress generation of dark electric current due to the remaining electric charges.

7. The unit pixel of the image sensor according to claim 6 , wherein the select device includes a drain and a source which are connected to the photo detector and a unit pixel output terminal, respectively, and a gate to which a select signal is capable of being externally applied, and performs a switching operation based on the applied select signal.

8. The unit pixel of the image sensor according to claim 6 , wherein the source of the photo detector and the drain of the select device are formed on the same active area.

9. The unit pixel of the image sensor according to claim 6 , wherein the photo detector is configured to adjust the voltage applied to the sensitivity adjustment terminal based on an amount of the incident light so as to suppress image saturation due to a sudden increase in an amount of photoelectric current.

10. A unit pixel of an image sensor, comprising:

a photo detector configured to generate a flow of electric current using a change in a quantity of electric charges by incident light;

as select device configured to output the electric current generated in the photo detector to a unit pixel output terminal; and

a reset device configured to eliminate a remaining electric charge in the photo detector,

wherein the photo detector includes a light-absorbing part configured to absorb light, a source and a drain that are separated from the light-absorbing part by an oxide film, a channel that is formed between the source and the drain and configured to generate the flow of electric current between the source and the drain, and a sensitivity adjustment terminal configured to apply an external voltage to the light-absorbing part and a P-well or N-well of the sensitivity adjustment terminal is connected to a drain of a reset device,

wherein the photo detector is configured to control the flow of electric current based on the change in the quantity of electric charges in the light-absorbing part according to tunneling of an electron excited by the light incident to the light-absorbing part to the source or the drain, and

wherein the photo detector is configured to adjust the external voltage,

wherein when the external voltage is adjusted, a gap between a Fermi level and an intrinsic level of the channel is adjusted, and the threshold voltage is adjusted,

wherein, when an absolute value of the external voltage is adjusted to be higher than the absolute value of a set voltage, the light-absorbing part is has a first potential state and no current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be equal to the absolute value of the set voltage, light-absorbing part is has a second potential state, and when the light is incident on the light-absorbing part, the current flows through the channel,

wherein, when the absolute value of the external voltage is adjusted to be 0V to reduce dark electric current, the light-absorbing part has a third potential state and the current always flows through the channel, and

wherein the value of set voltage when light is suddenly incident to the light-absorbing part is higher than the value of the set voltage so as to prevent the image saturation in the photo detector in advance, and

wherein the drain of the reset device is connected to a P-well or N-well body of the photo detector, and a bias voltage for reset is applied to a source of the reset device, and

where all remaining electric charges in the floated N-well are eliminated before operating the photo detector to suppress generation of dark electric current due to the remaining electric charges.

11. The unit pixel of the image sensor according to claim 10 , wherein the reset device is configured to eliminate the remaining electric charge in a diffusion well on which the photo detector is formed.

12. The unit pixel of the image sensor according to claim 11 , wherein the diffusion well is maintained in a floating state during an operation of the photo detector.

13. The unit pixel of the image sensor according to claim 10 , wherein the photo detector is configured to apply a voltage higher than or equal to a set voltage through the sensitivity adjustment terminal to increase the threshold voltage of the channel, to thereby reset the unit pixel.