Semiconductor photodetector device

Claim 2

A semiconductor photodetector device comprising an insulating gate field effect transistor having a channel region of a first conductivity type, a gate electrode of a second conductivity type, opposite to said first conductivity type, and a gate extension portion of said first conductivity type, said gate electrode and said gate extension portion forming a PN junction outside the channel region of said transistor and an area including the PN junction being able to receive light.

Claim 3

A photodetector device as claimed in claim 1, wherein the gate electrode is formed of doped silicon, the gate extension portion is formed of doped silicon, and at least adjoining portions of the gate electrode and the gate extension portion are single crystalline silicon.

Claim 4

A photodetector device according to claim 1, or 2, comprising an isolation oxide layer surrounding the channel region, source region and drain region of said transistor, said PN junction being located on said isolation oxide layer.

Claim 5

A photodetector device according to claim 1, 2, or 3, wherein said gate electrode and gate extension portion are made of single crystalline silicon.

Claim 6

A photodetector device according to any preceding claim, wherein said transistor has a gate oxide layer between said gate electrode and a single crystalline silicon substrate.

Claim 7

A photodetector device according to any preceding claim, wherein said transistor has a source electrode connecting with a source region and a drain electrode connecting with a drain region.

Claim 8

A photodetector device according to any preceding wherein claim,/said transistor further has a second gate electrode so as to form a dual gate type field effect transistor.

Claim 9

A photodetector device according to claim 2, or any of claims 3 to 7 as appended to claim 2, wherein said gate electrode and said gate extension portion except said single crystalline silicon portions are polycrystalline silicon.

Claim 10

A semiconductor photodetector device comprising an insulated gate field effect transistor having a channel region of a first conductivity type, a gate electrode of doped silicon having a second conductivity type, opposite to said first conductivity type, and a gate extension portion of another doped silicon having said first conductivity type, at least joining portions of said gate electrode and said gate extension portion being single crystalline so as to form a PN junction outside the channel region of said transistor, and an area including the PN junction being able to receive light.

Claim 11

A semiconductor photodetector device comprising an insulated gate field effect transistor having a channel region of a first conductivity type, a gate electrode of doped silicon having a second conductivity type, opposite to said first conductivity type, and a gate extension portion of another doped silicon having said first conductivity type, at least joining portions of said gate electrode and said gate extension portion being single crystalline so as to form a PN junction outside the channel region of said transistor, and an area including the PN junction being able to receive light.

Claim 12

A photodetector circuit, comprising a semiconductor photodetector device as claimed in any preceding claim, wherein the drain of the insulating gate field effect transistor (IGFET) is connectable to voltage supply means, and the source of the IGFET is connected to an output terminal, such that when light is incident upon the area including the PN junction, an output voltage is obtained at the output terminal the magnitude of which is related to the intensity of the incident light.

Claim 13

A photodetector circuit as claimed in claim 10, wherein the drain of the IGFET is connected to one electrode of a switching transistor, another electrode of which is connected to the voltage supply means and a control electrode of which is operable to receive a read signal; and the gate extension portion is operable to receive a control signal; such that the control signal is operable, in a SET operation, to bias the PN junction such as to cause charges to accumulate on the gate electrode when light is incident upon the area including the PN junction, hence turning ON the IGFET; the read signal is operable subsequently, in a READ operation,to turn ON the switching transistor, the thereby connecting/drain of the IGFET to the voltage supply means, a voltage from the voltage supply means hence being amplified by the IGFET in dependence upon the amount of charges on the gate electrode to provide the output voltage at the output terminal; and the control signal is further operable, in a RESET operation, to bias the PN junction such as to cause charges to conduct out of the gate electrode into the gate extension portion, hence turning OFF the IGFET.