Thin film phototransistor and photosensor array using the same

Claim 2

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, a gate electrode, a gate insulating film, and a semiconductor layer, wherein there is a gap between one projection of said gate electrode and another projection of at least one of said source electrode and said drain electrode, said one projection and said another projection being obtained by projecting said gate electrode and said at least one of said source electrode and said drain electrode perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 3

A thin film phototransistor according to claim 1, wherein said gap has a length of at least 1 μm.

Claim 4

The thin film phototransistor according to claim 11 wherein the semiconductor layer is made of hydrogenated amorphous silicon.

Claim 5

The thin film phototransistor according to claim 1 wherein, wherein voltages of the source electrode, drain electrode, and gate electrode are Vs, Vd, and Vg respectively, a photoelectric conversion operation is performed in the region of Vs Vd and Vs Vg.

Claim 6

The thin film phototransistor according to claim 1, wherein said gate insulating film and said semiconductor layer intervene between said gate electrode and the source and drain electrodes, and wherein incident light is irradiated from a gate electrode side of said field effect transistor.

Claim 7

The thin film phototransistor according to claim 5, wherein said incident light is irradiated to a part of said semiconductor layer corresponding to a region where said gap exists between the projection of said gate electrode and the projection of said source electrode and is irradiated to another part of said semiconductor layer overlapped with the projection of said source electrode.

Claim 8

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least two gate electrodes, a gate insulating film, and a semiconductor layer, wherein there is a gap between projections of said gate electrodes obtained by projecting said gate electrodes perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 9

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least two gate electrodes, a gate insulating film, and a semiconductor layer, wherein there is a gap between projections of said gate electrodes obtained by projecting said gate electrodes perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 10

A thin film phototransistor according to claim 7, wherein said gap has a length of at least 1 μm.

Claim 11

The thin film phototransistor according to claim 7, wherein said gate insulating film and said semiconductor layer intervene between said at least two gate electrodes and the source and drain electrodes, and wherein incident light is irradiated from a gate electrode side of said field effect transistor.

Claim 12

The thin film phototransistor according to claim 7 wherein said at least two gate electrodes are connected together in common.

Claim 13

The thin film phototransistor according to claim 7 wherein said phototransistor includes means to apply the same voltage or different voltages to the at least two gate electrodes.

Claim 14

The thin film phototransistor according to claim 7 wherein the semiconductor layer is made of hydrogenated amorphous silicon.

Claim 15

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gage electrode but no light is applied.

Claim 16

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gage electrode but no light is applied.

Claim 17

A thin film phototransistor according to claim 13, wherein said group has a length of at least 1 μm.

Claim 18

The thin film phototransistor according to claim 13 wherein at least one of the source electrode, the drain electrode and the gate electrode is transparent.

Claim 19

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, a gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of said gate electrode and another projection of at least one of said source electrode and said drain electrode, said one projection and said another projection being obtained by projecting said gate electrode and at least one of said source electrode and said drain electrode perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied, and wherein at least one of said source electrode, said drain electrode and said gate electrode is transparent.

Claim 20

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, a gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of said gate electrode and another projection of at least one of said source electrode and said drain electrode, said one projection and said another projection being obtained by projecting said gate electrode and at least one of said source electrode and said drain electrode perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied, and wherein at least one of said source electrode, said drain electrode and said gate electrode is transparent.

Claim 21

A thin film phototransistor according to claim 16, wherein said gap has a length of at least 1 μm.

Claim 22

The thin film phototransistor according to claim 16 wherein the source electrode, the drain electrode, and the gate electrode are formed substantially on the same plane.

Claim 23

The thin film phototransistor according to claim 16 wherein the transparent electrode is made of indium-tin oxide.

Claim 24

The thin film phototransistor according to claim 16 wherein the semiconductor layer is made of hydrogenated amorphous silicon.

Claim 25

The thin film phototransistor according to claim 20 wherein the transparent electrode is an interface reaction layer of metal and hydrogenated amorphous silicon.

Claim 26

The thin film phototransistor according to claim 21 wherein the metal contains at least one selected from the group consisting of Cr, Mo, W, Ti, Ta, V, Zr, Nb, Hf, Ni, and Cu.

Claim 27

A one-dimensional photosensor array including an arrangement to reduce dark current and characterized in that a one-dimensional photosensor comprising picture elements is arranged on a substrate, wherein each picture element includes a thin film phototransistor comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gage electrode but no light is applied.

Claim 28

A one-dimensional photosensor array including an arrangement to reduce dark current and characterized in that a one-dimensional photosensor comprising picture elements is arranged on a substrate, wherein each picture element includes a thin film phototransistor comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gage electrode but no light is applied.

Claim 29

A one-dimensional photosensor array according to claim 23, wherein said gap has a length of at least 1 μm.

Claim 30

The one-dimensional photosensor array according to claim 23, wherein the gate and drain electrodes of the phototransistors constituting the picture elements are grouped and are wired together for each group, and wherein the picture elements are addressed one by one by matrix drive.

Claim 31

The one-dimensional photosensor array according to claim 23 wherein the semiconductor layer of the thin film phototransistor is made of amorphous silicon.

Claim 32

The one-dimensional photosensor array according to claim 23 wherein a hole region, through which light from the light source is irradiated, is provided on the substrate and the reflected light from a manuscript is directly received by the thin film phototransistor.

Claim 33

Facsimile terminal equipment using a one-dimensional contact photosensor as a sensor characterized in that the photosensor includes an arrangement to reduce dark current and comprises picture elements, comprised of thin film phototransistors, arranged on a substrate, wherein each thin film phototransistor comprises a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 34

Facsimile terminal equipment using a one-dimensional contact photosensor as a sensor characterized in that the photosensor includes an arrangement to reduce dark current and comprises picture elements, comprised of thin film phototransistors, arranged on a substrate, wherein each thin film phototransistor comprises a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 35

Facsimile terminal equipment according to claim 28, wherein said gap has a length of at least 1 μm.

Claim 36

An image scanner using a one-dimensional contact photosensor as a sensor characterized in that the photosensor includes an arrangement to reduce dark current and comprises picture elements, comprised of thin film phototransistors, arranged on a substrate, wherein each thin film phototransistor comprises a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 37

An image scanner using a one-dimensional contact photosensor as a sensor characterized in that the photosensor includes an arrangement to reduce dark current and comprises picture elements, comprised of thin film phototransistors, arranged on a substrate, wherein each thin film phototransistor comprises a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projection being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 38

An image scanner according to claim 30, wherein said gap has a length of at least 1 μm.

Claim 39

A two-dimensional photosensor array including an arrangement to reduce dark current and comprising photosensors arranged on a substrate characterized in that each picture element of the photosensors comprises at least one thin film phototransistor, a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projecting being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 40

A two-dimensional photosensor array including an arrangement to reduce dark current and comprising photosensors arranged on a substrate characterized in that each picture element of the photosensors comprises at least one thin film phototransistor, a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection and said another projecting being obtained by projecting said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 41

A two-dimensional photosensor array according to claim 25, wherein said gap has a length of at least 1 μm.

Claim 42

A two-dimensional photosensor array according to claim 32 wherein a hole region, through which light from the light source is irradiated, is provided on the substrate and the reflected light from a manuscript is directly received by the phototransistor.

Claim 43

A two-dimensional photosensor array according to claim 32, wherein said each picture element is provided with an additional thin film transistor for switching said thin film phototransistor.

Claim 44

A two-dimensional photosensor array according to claim 35, wherein said semiconductor layer of said thin film phototransistor is comprised of amorphous silicon, and wherein said thin film transistor for switching is a field effect transistor employing amorphous silicon.

Claim 45

An image data input unit using a two-dimensional photosensor array as an input unit characterized in that the two-dimensional photosensor array includes an arrangement to reduce dark current and comprises photosensors arranged on a substrate, wherein each picture element of the photosensors comprises at least one thin film phototransistor, a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 46

An image data input unit using a two-dimensional photosensor array as an input unit characterized in that the two-dimensional photosensor array includes an arrangement to reduce dark current and comprises photosensors arranged on a substrate, wherein each picture element of the photosensors comprises at least one thin film phototransistor, a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein there is a gap between one projection of at least one end of said at least one gate electrode and another projection of an electrode neighboring said at least one end, said one projection said at least one end and said electrode neighboring said at least one end perpendicularly onto a plane which is parallel with said semiconductor layer to reduce dark current to thereby increase a ratio between photocurrent that flows when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 47

An image data input unit according to claim 37, wherein said gap has a length of at least 1 μm.

Claim 48

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein said at least one gate electrode is separated from at least one of said source and drain electrodes in both a vertical direction which is substantially perpendicular to said semiconductor layer and in a horizontal direction which is substantially parallel to said semiconductor layer to reduce dark current to thereby increases a ratio between photocurrent that flow when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 49

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein said at least one gate electrode is separated from at least one of said source and drain electrodes in both a vertical direction which is substantially perpendicular to said semiconductor layer and in a horizontal direction which is substantially parallel to said semiconductor layer to reduce dark current to thereby increases a ratio between photocurrent that flow when light is applied and a predetermined voltage is applied to the gate electrode and dark current that flows when the same predetermined voltage is applied to the gate electrode but no light is applied.

Claim 50

A thin film phototransistor according to claim 39, wherein the other of said source and drain electrode is separated from said at least one gate electrode in said vertical direction but overlaps said at least one gate electrode in said horizontal direction.

Claim 51

A thin film phototransistor according to claim 39, wherein both of said source and drain electrodes are separated from said at least one gate electrode in said vertical and horizontal directions.

Claim 52

A thin film phototransistor according to claim 39, wherein said gate insulating film and said semiconductor layer are located between said at least one gate electrode and said source and drain electrodes in said vertical direction, and wherein said phototransistor is arranged to operate based on incident light impinging on said phototransistor from a gate electrode side of said phototransistor.

Claim 53

A thin film phototransistor according to claim 42, wherein said at least one gate electrode and said at least one of said source and drain regions are separated from one another in said horizontal direction by a gap which is at least 1 μm.

Claim 54

A thin film phototransistor according to claim 43, wherein the other of said source and drain electrodes is separated from said at least one gate electrode in said vertical direction but overlaps said at least one gate electrode in said horizontal direction.

Claim 55

A thin film phototransistor according to claim 43, wherein both of said source and drain electrodes are separated from said at least one gate electrode in said vertical and horizontal directions.

Claim 56

A thin film phototransistor according to claim 39, wherein said at least one gate electrode and said at least one of said source and drain regions are separated from one another in said horizontal direction by a gap which is at least 1 μm.

Claim 57

A thin film phototransistor according to claim 46, wherein the other of said source and drain electrodes is separated from said at least one gate electrode in said vertical direction but overlaps said overlaps said at least one gate electrode in said horizontal direction.

Claim 58

A thin film phototransistor according to claim 46, wherein both of said source and drain electrodes are separated from said at least one gate electrode in said vertical and horizontal directions.

Claim 59

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein said field effect transistor includes a channel formed in said semiconductor layer between said source electrode and said drain electrode, wherein a first portion of said channel is formed in a first region of said semiconductor layer which is overlapped by said gate electrode, said first portion of said channel being formed when a voltage is applied to said gate electrode, and wherein a second portion of said channel is formed in a second region of said semiconductor layer which is not overlapped by said gate electrode but is arranged so that it can be exposed to light so that said second portion of said channel is formed when light strikes said second region of said semiconductor layer, and wherein said second region of said semiconductor layer has a predetermined high resistance when light does not strike said second region to reduce dark current to thereby increase a ratio between photocurrent and dark current, wherein the photocurrent flows when light is applied to the second region of the semiconductor layer and a predetermined voltage is applied to the gate electrode, and wherein the dark current flows when the same predetermined voltage is applied to the gate electrode but no light is applied to the second region of the semiconductor layer.

Claim 60

A thin film phototransistor including an arrangement to reduce dark current and comprising a field effect transistor including a source electrode, a drain electrode, at least one gate electrode, a gate insulating film and a semiconductor layer, wherein said field effect transistor includes a channel formed in said semiconductor layer between said source electrode and said drain electrode, wherein a first portion of said channel is formed in a first region of said semiconductor layer which is overlapped by said gate electrode, said first portion of said channel being formed when a voltage is applied to said gate electrode, and wherein a second portion of said channel is formed in a second region of said semiconductor layer which is not overlapped by said gate electrode but is arranged so that it can be exposed to light so that said second portion of said channel is formed when light strikes said second region of said semiconductor layer, and wherein said second region of said semiconductor layer has a predetermined high resistance when light does not strike said second region to reduce dark current to thereby increase a ratio between photocurrent and dark current, wherein the photocurrent flows when light is applied to the second region of the semiconductor layer and a predetermined voltage is applied to the gate electrode, and wherein the dark current flows when the same predetermined voltage is applied to the gate electrode but no light is applied to the second region of the semiconductor layer.

Claim 61

A thin film phototransistor according to claim 49, wherein said second region of said semiconductor layer has a length of at least 1 μm.

Claim 62

A thin film phototransistor according to claim 49, wherein said second region of said semiconductor layer is directly in contact with said first region of said semiconductor layer.

Claim 63

A thin film phototransistor according to claim 51, wherein said second region of said semiconductor layer has a length of at least 1 μm.