Fingerprint sensor and display device including the same
A fingerprint sensor comprises a read-out line disposed on a substrate and extending in a first direction, a first sensor transistor controlling a sensing current based on a voltage of a sensor node, a second sensor transistor supplying a reset voltage to the sensor node based on a reset signal, a third sensor transistor electrically connected a first electrode of the first sensor transistor and the read-out line based on a gate signal, and a fourth sensor transistor comprising a gate electrode connected to a bias voltage line, a first electrode connected to the bias voltage line, and a second electrode connected to the sensor node.
1 . A fingerprint sensor comprising:
a read-out line disposed on a substrate and extending in a first direction;
a first sensor transistor controlling a sensing current based on a voltage of a sensor node;
a second sensor transistor supplying a reset voltage to the sensor node based on a reset signal;
a third sensor transistor electrically connected a first electrode of the first sensor transistor and the read-out line based on a gate signal;
a fourth sensor transistor comprising a gate electrode connected to a bias voltage line, a first electrode connected to the bias voltage line, and a second electrode connected to the sensor node, and wherein a leakage current which flows through the fourth sensor transistor in proportion to the amount of light is applied to the sensor node to increase the voltage of the sensor node;
a first active layer disposed on the substrate and comprising a semiconductor region of each of the first sensor transistor, the third sensor transistor, and the fourth sensor transistor;
a first gate layer disposed on the first active layer;
a second gate layer disposed on the first gate layer;
a second active layer disposed on the second gate layer and comprising a semiconductor region of the second sensor transistor;
a third gate layer disposed on the second active layer;
a first source metal layer disposed on the third gate layer; and
a second source metal layer disposed on the first source metal layer.
2 . The fingerprint sensor of claim 1 ,
wherein the second sensor transistor supplies the reset voltage to the sensor node during a first period,
wherein the fourth sensor transistor supplies the leakage current to the sensor node during a second period after the first period, and
wherein the third sensor transistor is turned on during a third period after the second period.
3 . The fingerprint sensor of claim 1 ,
further comprising a shielding electrode disposed on the second source metal layer to overlap the second sensor transistor without overlapping the fourth sensor transistor.
4 . The fingerprint sensor of claim 3 , further comprising:
a hole transporting layer disposed on the shielding electrode to overlap the first to fourth sensor transistors;
an electron transporting layer disposed on the hole transporting layer to overlap the first to fourth sensor transistors; and
a common electrode disposed on the electron transporting layer to overlap the first to fourth sensor transistors.
5 . The fingerprint sensor of claim 1 ,
wherein a gate electrode of the fourth sensor transistor comprises a hole exposing a portion of a semiconductor region from a reflected light.
6 . A fingerprint sensor comprising:
a read-out line disposed on a substrate and extending in a first direction;
a first sensor transistor controlling a sensing current based on a voltage of a sensor node;
a second sensor transistor supplying a reset voltage to the sensor node based on a reset signal;
a third sensor transistor electrically connecting a first electrode of the first sensor transistor and the read-out line based on a gate signal;
a fourth sensor transistor comprising a gate electrode connected to a leakage voltage line to receive a leakage voltage, a first electrode connected to a bias voltage line to receive a bias voltage smaller than the leakage voltage, and a second electrode connected to the sensor node, and
wherein a leakage current which flows through the fourth sensor transistor in proportion to the amount of light is applied to the sensor node to increase the voltage of the sensor node;
a first active layer disposed on the substrate and comprising a semiconductor region of each of the first sensor transistor, the third sensor transistor, and the fourth sensor transistor;
a first gate layer disposed on the first active layer;
a second gate layer disposed on the first gate layer;
a second active layer disposed on the second gate layer and comprising a semiconductor region of the second sensor transistor;
a third gate layer disposed on the second active layer;
a first source metal layer disposed on the third gate layer; and
a second source metal layer disposed on the first source metal layer.
7 . The fingerprint sensor of claim 6 ,
wherein the second sensor transistor supplies the reset voltage to the sensor node during a first period,
wherein the fourth sensor transistor supplies the leakage current to the sensor node during a second period after the first period, and
wherein the third sensor transistor is turned on during a third period after the second period.
8 . The fingerprint sensor of claim 6 ,
further comprising a shielding electrode disposed on the second source metal layer to overlap the second sensor transistor without overlapping the fourth sensor transistor.
9 . The fingerprint sensor of claim 8 , further comprising:
a hole transporting layer disposed on the shielding electrode to overlap the first to fourth sensor transistors;
an electron transporting layer disposed on the hole transporting layer to overlap the first to fourth sensor transistors; and
a common electrode disposed on the electron transporting layer to overlap the first to fourth sensor transistors.
10 . The fingerprint sensor of claim 6 ,
wherein a gate electrode of the fourth sensor transistor comprises a hole exposing a portion of a semiconductor region to a reflected light.
11 . A display device comprising:
a pixel disposed in an emission area and comprising a light emitting element; and
a fingerprint sensor disposed in a sensor area,
wherein the fingerprint sensor comprises:
a read-out line disposed on a substrate and extending in a first direction;
a first sensor transistor controlling a sensing current based on a voltage of a sensor node;
a second sensor transistor supplying a reset voltage to the sensor node based on a reset signal;
a third sensor transistor electrically connecting a first electrode of the first sensor transistor and the read-out line based on a first gate signal;
a fourth sensor transistor comprising a gate electrode connected to a leakage voltage line to receive a leakage voltage, a first electrode connected to a bias voltage line to receive a bias voltage smaller than the leakage voltage, and a second electrode connected to the sensor node, and
wherein a leakage current which flows through the fourth sensor transistor in proportion to the amount of light is applied to the sensor node to increase the voltage of the sensor node;
a first active layer disposed on the substrate and comprising a semiconductor region of each of the first sensor transistor, the third sensor transistor, and the fourth sensor transistor;
a first gate layer disposed on the first active layer;
a second gate layer disposed on the first gate layer;
a second active layer disposed on the second gate layer and comprising a semiconductor region of the second sensor transistor;
a third gate layer disposed on the second active layer;
a first source metal layer disposed on the third gate layer; and
a second source metal layer disposed on the first source metal layer.
12 . The display device of claim 11 ,
wherein the pixel comprises:
a first transistor controlling a driving current flowing through the light emitting element;
a second transistor supplying a data voltage to a first electrode of the first transistor based on the first gate signal;
a third transistor electrically connecting a second electrode and a gate electrode of the first transistor based on a second gate signal; and
a fourth transistor discharging the gate electrode of the first transistor to a first initialization voltage based on a third gate signal.
13 . The display device of claim 12 ,
wherein the semiconductor region of each of the first transistor and the second transistor contains a silicon-based material, and the semiconductor region of each of the third transistor and the fourth transistor contains an oxide-based material.
14 . The display device of claim 12 ,
wherein the pixel further comprises:
a fifth transistor supplying a driving voltage to the first electrode of the first transistor based on an emission signal;
a sixth transistor electrically connecting the second electrode of the first transistor and the light emitting element based on the emission signal; and
a seventh transistor discharging a first electrode of the light emitting element to a second initialization voltage based on a fourth gate signal.
15 . The display device of claim 11 ,
wherein the light emitting element comprises:
a pixel electrode disposed on the second source metal layer;
a hole transporting layer disposed on the pixel electrode and implemented as a common layer of the emission area and the sensor area;
a light emitting layer disposed on the hole transporting layer;
an electron transporting layer disposed on the light emitting layer and implemented as a common layer of the emission area and the sensor area; and
a common electrode disposed on the electron transporting layer.
16 . The fingerprint sensor of claim 15 ,
wherein the fingerprint sensor comprises a shielding electrode disposed on the same layer as the pixel electrode to overlap the second sensor transistor without overlapping the fourth sensor transistor.
17 . The fingerprint sensor of claim 11 ,
wherein a gate electrode of the fourth transistor comprises a hole exposing a portion of a semiconductor region to a reflected light.