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Photodetector and method of driving the same

Imported: 23 Feb '17 | Published: 22 Oct '02

Yasushi Ogimoto, Kenji Nakanishi, Kunio Kojima

USPTO - Utility Patents

Abstract

A photodetector includes a photoelectric conversion layer for performing an insulator-metal transition by receiving light, and a pair of electrodes provided opposite to each other in contact with the photoelectric conversion layer, between which a voltage is applied. In the photodetector, the pair of electrodes are arranged on the photoelectric conversion layer such that a region of the photoelectric conversion layer which performs the insulator-metal transition and a region to which the voltage is applied through the pair of electrodes are substantially coincident with each other.

Description

This object as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.

1(

a) is a schematic sectional view showing a conventional element structure;

FIG.

1(

b) is an enlarged sectional view showing an A′ portion of the conventional element structure;

FIG.

2(

a) is a schematic sectional view according to a first embodiment of the present invention;

FIG.

2(

b) is an enlarged sectional view showing an A″ portion according to the first embodiment of the present invention;

FIG.

3(

a) is a schematic sectional view according to a second embodiment of the present invention;

FIG.

3(

b) is an enlarged sectional view showing an A′″ portion according to the second embodiment of the present invention;

FIG.

4(

a) is a schematic sectional view according to a third embodiment of the present invention;

FIG.

4(

b) is an enlarged sectional view showing an A portion according to the third embodiment of the present invention;

FIG. 5 is a diagram showing the schematic structure of a circuit for driving a photodetector at a constant voltage according to the present invention;

FIG. 6 is a chart showing the relationship between an amount of incident light and an output signal in the photodetector when voltages of Va and Vb are applied;

FIG.

7(

a) is a chart showing the voltages Va and Vb to be applied to the photodetector according to the present invention;

FIG.

7(

b) is a chart showing a time variation in an output signal for an incident light signal of the photodetector which is obtained when the voltages Va and Vb are applied according to the present invention;

FIG. 8 is a diagram showing the schematic structure of a circuit for driving the photodetector according to the present invention;

FIG. 9 is a chart showing a voltage Vp to be applied to the photodetector according to the present invention;

FIG. 10 is a chart showing the relationship between an amount of incident light and an output signal in the photodetector which is obtained when the voltage Vp is applied;

FIG.

11(

a) is a chart showing a time variation in an output signal in the conventional element structure;

FIG.

11(

b) is a chart showing a time variation in an output signal in the element structure according to the present invention;

FIG.

12(

a) is a chart showing a time variation in an output signal for a continuous optical pulse by a constant voltage driving operation;

FIG.

12(

b) is a chart showing a time variation in an output signal for optical pulses having different cycles which is obtained by a DC pulse voltage driving operation synchronous with the minimum cycle of the optical pulse;

FIG.

12(

c) is a chart showing a time variation in an output signal for optical pulses having different cycles by a DC pulse voltage driving operation shifted from the minimum cycle of the optical pulse by T/4;

FIG.

13(

a) is a chart showing a time variation in an output signal for an optical pulse which is obtained by a DC pulse voltage driving operation having a T/10 cycle for the minimum cycle of the optical pulse;

FIG.

13(

b) is a chart showing a time variation in an output signal for optical pulses having different cycles which is obtained by a DC pulse voltage driving operation having the T/10 cycle for the minimum cycle of the optical pulse;

FIG.

14(

a) is a chart showing the relationship between an amount of incident light and an output signal in the photodetector which is obtained when voltages V

PH and V

PL are applied;

FIG.

14(

b) is a chart showing a time variation in an output signal for optical pulses having different cycles which is obtained by a DC pulse voltage driving operation having pulse heights defined by the voltages V

PH and V

PL and synchronous with the minimum cycle of the optical pulse having a pulse height defined by the voltage V

PH and V

PL;

FIG.

14(

c) is a chart showing a time variation in an output signal in an optical pulse shifted by a T/4 cycle from the minimum cycle of the optical pulse by a DC pulse voltage driving operation having pulse heights defined by the voltages V

PH and V

PL and synchronous with the minimum cycle of the optical pulse; and

FIG. 15 is a diagram showing the schematic structure of an optical pickup using the photodetector according to the present invention.

Claims

1. A photodetector comprising:

2. A photodetector according to claim 1, wherein said electrodes are placed in a pair of concave portions provided on said photoelectric conversion layer.

3. A photdetector according to claim 1, wherein said electrodes permit passage of light.

4. A photodetector according to claim 1, wherein said photoelectric conversion layer is interposed between said electrodes and one of said electrodes has transparency.

5. A method of driving a photodetector comprising applying a constant DC voltage between said pair of electrodes of said photodetector as set forth in claim 1, thereby causing said photodetector to be operated in such a state that said photoelectric conversion layer of said photodetector performs said transition from an insulator to a metal in an analog manner according to the amount of received light.

6. A method of driving a photodetector according to claim 5, wherein a threshold for a minimum amount of light which can be detected is controlled by a value of said DC voltage to be applied between said electrodes.

7. A method of driving a photodetector comprising applying a DC pulse voltage between said pair of electrodes of said photodetector as set forth in claim 1, thereby causing said photodetector to be operated in such a state that said photoelectric conversion layer of said photodetector performs said transition from an insulator to a metal in a digital manner according to the amount of received light.

8. A method of driving a photodetector according to claim 7, wherein a pulse width of said DC voltage to be applied between said electrodes is 1/10 or less of a minimum pulse width of said received light.

9. A method of driving a photodetector according to claim 7, wherein a minimum value of said DC pulse voltage to be applied between said electrodes is set greater than a voltage value with which said photoelectric conversion layer starts said insulator-metal transition and is set smaller than a minimum voltage value capable of maintaining a resistance value obtained when said photoelectric conversion layer completes said insulator-metal transition.

10. An optical pickup incorporating a photodetector as set forth in claim 1 for reading a light signal from an optical memory by driving said photodector by a driving method as set forth in claim 5 or 7.