Photosensor and display device

Patent metadata

Field	Value
Publication number	US-9450133-B2
Application number	US-62466609-A
Country	US
Kind code	B2
Filing date	Nov 24, 2009
Priority date	Nov 28, 2008
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

Thin film transistors including an oxide semiconductor containing indium, gallium, and zinc are easily arranged in a matrix over a large substrate and have small characteristic variations. With amplifier circuits and driver circuits of display elements which include the thin film transistors including an oxide semiconductor containing indium, gallium, and zinc with small characteristic variations, intensity distribution of light received by the photodiodes arranged in a matrix is converted into electrical signals with high reproducibility and output, and the display elements arranged in a matrix can be uniformly driven.

First claim

What is claimed is:

1. A photosensor comprising:
a photoelectric conversion element including a photoelectric conversion layer, the photoelectric conversion layer including silicon; and
an amplifier circuit including a thin film transistor, the thin film transistor comprising:
an oxide semiconductor layer;
buffer layers; and
a source electrode and a drain electrode electrically connected to the oxide semiconductor layer with the buffer layers therebetween,

wherein the oxide semiconductor layer and the buffer layers comprise indium, gallium, and zinc,
wherein a ratio of indium, gallium, and zinc in the oxide semiconductor layer is the same as that in the buffer layers,
wherein the oxide semiconductor layer is richer in oxygen than the buffer layers, and
wherein the buffer layers consist of non-single crystalline oxide semiconductor including nanocrystal structure.

2. The photosensor according to claim 1 ,
wherein the buffer layers have higher electrical conductivity than the oxide semiconductor layer.

3. The photosensor according to claim 1 ,
wherein the oxide semiconductor layer and the buffer layers are formed by a sputtering method using oxygen gas and rare gas, and
wherein a ratio of oxygen gas to rare gas for the oxide semiconductor layer is higher than a ratio of oxygen gas to rare gas for the buffer layers.

4. A photosensor comprising:
a photoelectric conversion element including a photoelectric conversion layer, the photoelectric conversion layer comprising:
a first semiconductor layer including an impurity element having one conductivity type;
a second semiconductor layer in contact with the first semiconductor layer; and
a third semiconductor layer in contact with the second semiconductor layer, wherein the third semiconductor layer includes an impurity element having a conductivity type opposite to the conductivity type of the first semiconductor layer; and

an amplifier circuit including at least a selection thin film transistor, an amplifying thin film transistor, and a reset thin film transistor, each thin film transistor comprising:
an oxide semiconductor layer;
buffer layers; and
a source electrode and a drain electrode electrically connected to the oxide semiconductor layer with the buffer layers therebetween,

wherein the oxide semiconductor layer and the buffer layers comprise indium, gallium, and zinc,
wherein a ratio of indium, gallium, and zinc in the oxide semiconductor layer is the same as that in the buffer layers,
wherein the oxide semiconductor layer is richer in oxygen than the buffer layers,
wherein a gate electrode of the reset thin film transistor is electrically connectable to a reset gate signal line,
wherein one of the source electrode and the drain electrode of the reset thin film transistor is electrically connectable to a sensor power supply line,
wherein the other one of the source electrode and the drain electrode of the reset thin film transistor is electrically connectable to a gate electrode of the amplifying thin film transistor and one of an anode and a cathode of the photoelectric conversion element,
wherein one of the source electrode and the drain electrode of the amplifying thin film transistor is electrically connectable to the sensor power supply line,
wherein one of the source electrode and the drain electrode of the selection thin film transistor is electrically connectable to a sensor output wiring,
wherein the other one of the source electrode and the drain electrode of the selection thin film transistor is electrically connectable to the other one of the source electrode and the drain electrode of the amplifying thin film transistor,
wherein a gate electrode of the selection thin film transistor is electrically connectable to a sensor gate signal line, and
wherein the buffer layers consist of non-single crystalline oxide semiconductor including nanocrystal structure.

5. The photosensor according to claim 4 ,
wherein the reset thin film transistor and the selection thin film transistor are turned on or off according to signals input to the reset gate signal line and the sensor gate signal line.

6. The photosensor according to claim 4 ,
wherein the buffer layers have higher electrical conductivity than the oxide semiconductor layer.

7. The photosensor according to claim 4 ,
wherein the oxide semiconductor layer and the buffer layers are formed by a sputtering method using oxygen gas and rare gas, and
wherein a ratio of oxygen gas to rare gas for the oxide semiconductor layer is higher than a ratio of oxygen gas to rare gas for the buffer layers.

8. An area sensor comprising:
a plurality of pixels, each of the plurality of pixels comprising:
a photoelectric conversion element including a photoelectric conversion layer, the photoelectric conversion layer comprising:
a first semiconductor layer including an impurity element having one conductivity type;
a second semiconductor layer in contact with the first semiconductor layer; and
a third semiconductor layer in contact with the second semiconductor layer, wherein the third semiconductor layer includes an impurity element having a conductivity type opposite to the conductivity type of the first semiconductor layer; and

an amplifier circuit including at least a selection thin film transistor, an amplifying thin film transistor, and a reset thin film transistor, each thin film transistor comprising:
an oxide semiconductor layer;
buffer layers; and
a source electrode and a drain electrode electrically connected to the oxide semiconductor layer with the buffer layers therebetween,

wherein the oxide semiconductor layer and the buffer layers comprise indium, gallium, and zinc,
wherein a ratio of indium, gallium, and zinc in the oxide semiconductor layer is the same as that in the buffer layers,
wherein the oxide semiconductor layer is richer in oxygen than the buffer layers,
wherein a gate electrode of the reset thin film transistor is electrically connectable to a reset gate signal line,
wherein one of the source electrode and the drain electrode of the reset thin film transistor is electrically connectable to a sensor power supply line,
wherein the other one of the source electrode and the drain electrode of the reset thin film transistor is electrically connectable to a gate electrode of the amplifying thin film transistor and one of an anode and a cathode of the photoelectric conversion element,
wherein one of the source electrode and the drain electrode of the amplifying thin film transistor is electrically connectable to the sensor power supply line,
wherein one of the source electrode and the drain electrode of the selection thin film transistor is electrically connectable to a sensor output wiring,
wherein the other one of the source electrode and the drain electrode of the selection thin film transistor is electrically connectable to the other one of the source electrode and the drain electrode of the amplifying thin film transistor,
wherein a gate electrode of the selection thin film transistor is electrically connectable to a sensor gate signal line, and
wherein the buffer layers consist of non-single crystalline oxide semiconductor including nanocrystal structure.

9. The area sensor according to claim 8 ,
wherein the reset thin film transistor and the selection thin film transistor are turned on or off according to signals input to the reset gate signal line and the sensor gate signal line.

10. The area sensor according to claim 8 ,
wherein the buffer layers have higher electrical conductivity than the oxide semiconductor layer.

11. The area sensor according to claim 8 ,
wherein the oxide semiconduct

Assignees

• Nakamura Yasuo
• Tanada Yoshifumi
• Semiconductor Energy Lab

Inventors

• Nakamura Yasuo
• Tanada Yoshifumi

Classifications

• H10D30/6755

  Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate · CPC title

• H10D86/60

  wherein the TFTs are in active matrices · CPC title

• H10F30/2235 Primary

  the devices comprising Group IV amorphous materials · CPC title

• H10D86/423

  comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO · CPC title

• H01L27/1225

  Electricity · mapped topic