Touch screen substrate, method of manufacturing the same, and display panel including the touch screen substrate

1. A touch screen substrate comprising:

a base substrate;

a first switching element disposed on the base substrate, the first switching element comprising:

a first switching gate electrode;

a first active pattern disposed on the first switching gate electrode;

a first switching source electrode disposed on the first active pattern; and

a first switching drain electrode disposed apart from the first switching source electrode; and

a first sensing element disposed on the base substrate and configured to sense infrared light reflected by an object on the base substrate, the first sensing element comprising:

a first sensing drain electrode connected to the first switching source electrode;

a first sensing source electrode disposed apart from the first sensing drain electrode;

a second active pattern disposed below the first sensing drain electrode and the first sensing source electrode and including a first amorphous layer, a second amorphous layer vertically spaced apart from the first amorphous layer, and a doped amorphous layer interposed between the first amorphous layer and the second amorphous layer; and

a first sensing gate electrode disposed on the first sensing drain electrode and the first sensing source electrode.

2. The touch screen substrate of claim 1 , wherein the first amorphous layer and the second amorphous layer include one of amorphous silicon germanium and amorphous germanium.

3. The touch screen substrate of claim 1 , wherein the doped amorphous layer includes one of amorphous silicon germanium doped with at least one selected from a group consisting of phosphorus, arsenic and antimony, and amorphous germanium doped with at least one selected from a group consisting of phosphorus, arsenic and antimony.

4. The touch screen substrate of claim 1 , wherein the first active pattern comprises:

a silicon layer including amorphous silicon; and

an ohmic contact layer disposed on the silicon layer and doped with n-type impurities.

5. The touch screen substrate of claim 1 , wherein a thickness of the doped amorphous layer is greater than zero angstroms and not greater than 100 angstroms.

6. The touch screen substrate of claim 1 , further comprising a light blocking pattern disposed below the first sensing element and connected to the first sensing gate electrode.

7. The touch screen substrate of claim 1 , further comprising:

a first sensing gate line connected to the first switching gate electrode;

a bias line connected to the first sensing source electrode;

a first read-out line connected to the first switching drain electrode and which transmits an infrared light sensing signal generated from the first sensing element; and

a second sensing gate line connected to the first sensing gate electrode.

8. The touch screen substrate of claim 7 , further comprising:

a second sensing element which senses visible light, the second sensing element comprising:

a second sensing source electrode connected to the bias line;

a second sensing drain electrode disposed apart from the second sensing source electrode;

a third active pattern overlapping the second sensing source electrode and the second sensing drain electrode; and

a second sensing gate electrode connected to the second sensing gate line; and

a second switching element comprising:

a second switching source electrode connected to the second sensing drain electrode;

a second switching drain electrode disposed apart from the second switching source electrode;

a fourth active pattern overlapping the second switching source electrode and the second switching drain electrode; and

a switching gate electrode overlapping the fourth active pattern.

9. The touch screen substrate of claim 8 , further comprising:

a third sensing gate line connected to the second switching gate electrode; and

a second read-out line connected to the second switching drain electrode and which transmits a visible light sensing signal generated from the second sensing element.

10. A display panel comprising:

an array substrate including a pixel electrode and a pixel switching element connected to the pixel electrode; and

a touch screen substrate disposed opposite the array substrate and including a switching element and a sensing element configured to sense infrared light reflected by an object on the touch screen substrate,

wherein the switching element comprises:

a switching gate electrode;

a first active pattern disposed on the switching gate electrode;

a switching source electrode disposed on the first active pattern; and

a switching drain electrode disposed apart from the switching source electrode, and

the sensing element comprises:

a sensing drain electrode connected to the switching source electrode;

a sensing source electrode disposed apart from the sensing drain electrode;

a second active pattern disposed below the sensing drain electrode and the sensing source electrode and including a first amorphous layer, a second amorphous layer spaced apart from the first amorphous layer, and a doped amorphous layer interposed between the first amorphous layer and the second amorphous layer; and

a sensing gate electrode disposed on the sensing drain electrode and the sensing source electrode.