Photodiode and image sensor including the same
A photodiode according to an embodiment includes a semiconductor substrate, a Schottky junction structure layer disposed on the semiconductor substrate and including a first layer including a conductive material and a semiconductor layer, and a pinning layer disposed adjacent to the Schottky junction structure layer and fixing potentials of the semiconductor substrate and the first layer.
1 . A photodiode comprising:
a semiconductor substrate;
a Schottky junction structure layer arranged on the semiconductor substrate, the Schottky junction structure layer including a first layer including a conductive material and a semiconductor layer; and
a pinning layer disposed adjacent to the Schottky junction structure layer, the pinning layer fixing potentials of the semiconductor substrate and the first layer.
2 . The photodiode of claim 1 , wherein the semiconductor layer is n-type, and
a work function of the first layer satisfies the following condition:
φ M >χ s
where φ M is a work function of the first layer, and χ s is electron affinity of the semiconductor layer.
3 . The photodiode of claim 1 , wherein the semiconductor layer is p-type, and
a work function of the first layer satisfies the following condition:
φ M <χ s +E g
where φ M is a work function of the first layer, χ s is electron affinity of the semiconductor layer, and E g is bandgap energy of the semiconductor layer.
4 . The photodiode of claim 1 , wherein the first layer includes a metal or a transparent conductive oxide (TCO) material.
5 . The photodiode of claim 4 , wherein the metal of the first layer includes at least one or a combination of Au, Al, Ag, Cu, Pt, Ni, W, Ti, Mo, Ru, Ge, Ta, Hf, Nb, Zr, and V.
6 . The photodiode of claim 4 , wherein the TCO material of the first layer includes at least one oxide semiconductor material, such as ITO, IWO, IZO, GZO, GIZO, and AZO.
7 . The photodiode of claim 4 , wherein the first layer has a thickness greater than 0 nm and less than or equal to about 100 nm.
8 . The photodiode of claim 1 , wherein the Schottky junction structure layer further includes a second layer including silicide in contact with the semiconductor layer.
9 . The photodiode of claim 8 , wherein a work function of the second layer is set to have a Schottky barrier height of the Schottky junction structure layer lower than a Schottky barrier height of a structure in which a material of the first layer and a material of the semiconductor layer are combined.
10 . The photodiode of claim 8 , wherein the second layer includes at least one silicide material, such as TiSi, TiSi 2 , Ti 5 Si 3 , VSi 2 , FeSi 2 , CoSi 2 , PtSi, Pt 2 Si, NiSi, NiSi 2 , Ni 2 Si, Cu 3 Si, YSi, ZrSi, NbSi 2 , MoSi 2 , PdSi, Pd 2 Si, ErSi, YbSi, YbSi 2 , ZrSi 2 , HfSi, HfSi 2 , TaSi, TaSi 2 , NbSi, NbSi 2 , ZrSi, ZrSi 2 , VSi, VSi 2 , WSi, WSi 2 , GeSi, OsSi, IrSi, IrSis, AlSi, CuSi, RuSi, and Ru 2 Si 3 or a combination thereof.
11 . The photodiode of claim 8 , wherein the second layer includes a metallic material having a work function less than that of the first layer.
12 . The photodiode of claim 8 , wherein the Schottky junction structure layer further includes an intermediate layer including an oxide or a nitride and disposed between the first layer and the second layer.
13 . The photodiode of claim 12 , wherein the intermediate layer includes an oxide, such as at least one of SiO 2 , Al 2 O 3 , HfO 2 , and TiO 2 , or a nitride, such as at least one of TiN, AlN, and Si 3 N 4 .
14 . The photodiode of claim 1 , wherein a portion of one surface of the first layer facing the semiconductor layer is in contact with the semiconductor layer, and
another portion of the one surface of the first layer is in contact with the pinning layer.
15 . The photodiode of claim 1 , wherein the one surface of the first layer facing the semiconductor layer is entirely in contact with the pinning layer.
16 . The photodiode of claim 1 , wherein the Schottky junction structure layer further includes a distributed Bragg reflective layer (DBR layer) on the first layer.
17 . The photodiode of claim 1 , wherein the photodiode is configured to sense light in visible and infrared bands.
18 . An image sensor comprising:
a photodiode comprising a semiconductor substrate, a Schottky junction structure layer arranged on the semiconductor substrate, the Schottky junction structure layer including a first layer including a conductive material and a semiconductor layer, and a pinning layer disposed adjacent to the Schottky junction structure layer, the pinning layer fixing potentials of the semiconductor substrate and the first layer; and
at least one transistor for controlling an electrical signal generated by the photodiode.
19 . The image sensor of claim 18 , wherein a sense node apart from the Schottky junction structure layer is further formed on the semiconductor substrate,
wherein the at least one transistor includes:
a reset transistor for resetting a potential of the sense node;
a drive transistor for amplifying a change in an electrical potential of the sense node and transferring a result of amplification to a selection transistor; and
a selection transistor that selects unit pixels to be read in units of rows.
20 . The image sensor of claim 18 , wherein a floating diffusion node is located apart from the Schottky junction structure layer,
wherein the at least one transistor includes:
a transfer transistor connected between the photodiode and the floating diffusion node;
a reset transistor for resetting a potential of the floating diffusion node;
a drive transistor for amplifying a change in an electrical potential of the floating diffusion node and transferring a result of amplification to a selection transistor; and
a selection transistor for selecting unit pixels to be read in units of rows.