Light information device and method for producing the same

• US 5,536,933 A
• Filed: 12/19/1994
• Issued: 07/16/1996
• Est. Priority Date: 12/20/1993
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Izumi, Yoshihiro, Yamamoto, Yoshitaka, Fujiwara, Sayuri, Hatano, Akitsugu
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): Steady, Jacqueline M.
• Application Number:
  US08/359,279
• Time in Patent Office: 575 Days
• Field of Search: 250/208.2, 359/72
• US Class Current: 250/208.2
• CPC Class Codes: G02F 1/1354 having a particular photoconducting structure or material
• CPC Class Codes: H01L 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells

Abstract

The light information device of the invention includes a semiconductor having a photoconductive effect or a photovoltaic effect. In the light information device, a photoconductivity and a dark conductivity of the semiconductor are varied by an aging process using an external stimulus, and the photoconductivity and the dark conductivity after the aging process have values which are equal to or lower than 20% of respective initial values thereof before the aging process.

Claims

1. A light information device produced in accordance with the following process steps:

producing a semiconductor element having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark conductivity;

combining one or more additional elements with the semiconductor element which, in cooperation with the semiconductor element, allow the light information device to be used for a predefined function; and

substantially upon completion of the combining step performing a deliberate aging process including the step of;

applying a controlled external stimulus to the semiconductor element substantially for the purpose of varying the photoconductivity and the dark conductivity of the semiconductor element so as to have reduced values which are equal to or lower than 20% of the initial photoconductivity and the initial dark conductivity,

whereby variation over time of the reduced photoconductivity and the reduced dark conductivity during the use of the light information device for the predefined function is reduced.

2. A light information device according to claim 1, wherein the semiconductor is an amorphous semiconductor including a Group-IV semiconductor as a main component.

3. A light information device according to claim 1, wherein a ratio of the photoconductivity to the dark conductivity of the semiconductor after the aging process is twice or more as high as an initial ratio of the photoconductivity to the dark conductivity before the aging process.

4. A method for producing a light information device, comprising the steps of:

selecting a semiconductor having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark photoconductivity;

applying a controlled external stimulus to said semiconductor;

inducing aging of said semiconductor in accordance with said step of applying said controlled external stimulus; and

selectively varying said initial conductivity and said initial dark conductivity, in accordance with said step of inducing aging, to produce a stabilized semiconductor having a reduced photoconductivity and a reduced dark conductivity which are 20% or less of said initial photoconductivity and said initial dark conductivity, wherein variation over time of said reduced photoconductivity and said reduced dark conductivity of said stabilized semiconductor is reduced.

5. A method for producing a light information device according to claim 4, wherein the aging step comprises the steps of:

irradiating the semiconductor with light; and

varying the photoconductivity and the dark conductivity of the semiconductor by continuously performing the light irradiation for a predetermined time period, and reducing the photoconductivity and the dark conductivity to be 20% or less of the respective initial values thereof before the light irradiation.

6. A method for producing a light information device according to claim 5, wherein the aging step further comprises the step of:

applying an electric field to the semiconductor for a predetermined time period.

7. A method for producing a light information device according to claim 4, wherein, in the step of light irradiation, the semiconductor is irradiated with light of an intensity of 100 mW/cm² or more.

8. A method for producing a light information device according to claim 7, wherein, in the step of light irradiation, the semiconductor is irradiated with light in a wavelength band including a wavelength corresponding to a bandgap of the semiconductor.

9. A method for producing a light information device according to claim 4, wherein the aging step comprises the steps of:

applying an electric field to the semiconductor; and

varying the photoconductivity and the dark conductivity of the semiconductor by continuously applying the electric field for a predetermined time period, and reducing the photoconductivity and the dark conductivity to be 20% or less of the respective initial values thereof before the application of the electric field.

10. A method for producing a light information device according to claim 9, wherein the aging step further comprises the step of:

irradiating the semiconductor with light for a predetermined time period.

11. A method for producing a light information device according to claim 9, wherein, in the step of applying the electric field, electric charge of 50-200 mA/cm² is injected into the semiconductor.

12. A light information apparatus comprising optical addressing means for selectively turning ON at least one of a plurality of switching devices in accordance with a light signal,

wherein each of the plurality of switching devices includes an input terminal for receiving an electric signal, an output terminal for outputting the received electric signal, and a semiconductor for providing a conductive path from the input terminal to the output terminal in accordance with the received light signal due to a photoconductive effect, and

a photoconductivity and a dark conductivity of the semiconductor of each of the switching devices are varied by an aging process using an external stimulus, and the photoconductivity and the dark conductivity after the aging process are reduced to be 20% or less of respective initial values thereof before the aging process wherein the light information device is produced according to the following steps:

producing a semiconductor element having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark conductivity;

combining one or more additional elements with the semiconductor element which, in cooperation with the semiconductor element, allow the light information device to be used for a predefined function; and

substantially upon completion of the combining step performing a deliberate aging process including the step of;

applying a controlled external stimulus to the semiconductor element substantially for the purpose of varying the photoconductivity and the dark conductivity of the semiconductor element so as to have reduced values which are equal to or lower than 20% of the initial photoconductivity and the initial dark conductivity,

whereby variation over time of the reduced photoconductivity and the reduced dark conductivity during the use of the light information device for the predefined function is reduced.

13. A light information apparatus according to claim 12 wherein the optical addressing means includes means for supplying the electric signal to each of the plurality of switching devices, and means for supplying the light signal to each of the plurality of switching devices.

14. A light information apparatus according to claim 13, wherein the means for supplying the light signal includes light emitting means for generating the light signal, and means for selectively transmitting the light signal from the light emitting means to the plurality of switching device.

15. A light information apparatus according to claim 13, further comprising:

pixel electrodes each provided for a corresponding one of the plurality of switching devices, and each connected to the output terminal of the corresponding one of the switching devices, each of the pixel electrodes receiving the electric signal via the corresponding one of the switching devices; and

a display medium driven by the pixel electrodes.

16. A light information apparatus according to claim 14, wherein the light emitting means is a semiconductor laser.

17. A method for producing a light information apparatus comprising optical addressing means for selectively turning ON at least one of a plurality of switching devices in accordance with a light signal,

each of the plurality of switching devices including an input terminal for receiving an electric signal, an output terminal for outputting the received electric signal, and a semiconductor for providing a conductive path from the input terminal to the output terminal in accordance with the received light signal due to a photoconductive effect,

wherein the method includes an aging step of varying a photoconductivity and a dark conductivity of the semiconductor by applying an external stimulus, and reducing the photoconductivity and the dark conductivity after the aging process to be 20% or less of respective initial values thereof before applying the external stimulus and wherein the light information device is produced in accordance with the following process steps:

producing a semiconductor element having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark conductivity;

combining one or more additional elements with the semiconductor element which, in cooperation with the semiconductor element, allow the light information device to be used for a predefined function; and

substantially upon completion of the combining step performing a deliberate aging process including the step of;

applying a controlled external stimulus to the semiconductor element substantially for the purpose of varying the photoconductivity and the dark conductivity of the semiconductor element so as to have reduced values which are equal to or lower than 20% of the initial photoconductivity and the initial dark conductivity,

whereby variation over time of the reduced photoconductivity and the reduced dark conductivity during the use of the light information device for the predefined function is reduced.

18. A method for producing a light information apparatus according to claim 17, wherein the optical addressing means includes light emitting means for generating the light signal, and

the aging step includes the steps of:

irradiating the semiconductor with light emitted from the light emitting means; and

varying the photoconductivity and the dark conductivity of the semiconductor by continuously performing the light irradiation for a predetermined time period, and reducing the photoconductivity and the dark conductivity after the light irradiation to be 20% or less of respective initial values thereof before the light irradiation.

19. A method for producing a light information apparatus according to claim 18, wherein the optical addressing means includes light guiding means for transmitting the light signal from the light emitting means to each of the plurality of switching devices, and the light irradiation is performed via the light guiding means.

20. A method for producing a light information apparatus according to claim 18, wherein the light emitting means is a semiconductor laser, and laser light is used for the light irradiation.

21. A method for producing a light information apparatus according to claim 18, wherein, in the step of light irradiation, the semiconductor is irradiated with light of an intensity of 100 mW/cm² or more.

22. A method for producing a light information apparatus according to claim 18, wherein, in the step of light irradiation, the semiconductor is irradiated with light in a wavelength band including a wavelength corresponding to a bandgap of the semiconductor.

23. A method for producing a light information apparatus according to claim 18, wherein the optical addressing means includes means for supplying the electric signal to each of the plurality of switching devices, and

the aging step further includes a step of applying an electric field to the semiconductor for a predetermined time period by applying the electric signal to the respective switching devices by the supplying means.

24. A method for producing a light information apparatus according to claim 17, wherein the optical addressing means includes means for supplying the electric signal to each of the plurality of switching devices, and

the aging step includes the steps of:

applying an electric field to the semiconductor by supplying the electric signal to the respective switching devices by the supplying means; and

varying the photoconductivity and the dark conductivity of the semiconductor by applying the electric field for a predetermined time period, and reducing the photoconductivity and the dark conductivity to be 20% or less of the respective initial values thereof before the application of the electric field.

25. A method for producing a light information apparatus according to claim 24, wherein, in the step of applying the electric field, electric charge of 50-200 mA/cm² is injected into the semiconductor.

26. A method for producing a light information apparatus according to claim 24, wherein the light address means includes light emitting means for generating the light signal, and the aging step includes a step of irradiating the semiconductor with light emitted from the light emitting means for a predetermined time period.

27. A light information device comprising:

a first substrate and a second substrate;

a semiconductor layer disposed on one face of the first substrate facing the second substrate; and

an electro-optic medium provided on one face of the second substrate facing the first substrate, the light information device writing spatial light information input from the outside to the semiconductor layer through the first substrate into the electro-optic medium using a photoconductive effect of the semiconductor layer, and the light information device reading the spatial light information written in the electro-optic medium by modulating light input through the second substrate by the electro-optic medium,

wherein the semiconductor layer has a photoconductivity and a dark conductivity varied by an aging process using an external stimulus, and values of the varied photoconductivity and the dark conductivity are 20% or less of respective initial values thereof before the aging process and wherein the light information device is produced by the following process steps;

producing a semiconductor element having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark conductivity;

combining one or more additional elements with the semiconductor element which, in cooperation with the semiconductor element, allow the light information device to be used for a predefined function; and

substantially upon completion of the combining step performing a deliberate aging process including the step of;

applying a controlled external stimulus to the semiconductor element substantially for the purpose of varying the photoconductivity and the dark conductivity of the semiconductor element so as to have reduced values which are equal to or lower than 20% of the initial photoconductivity and the initial dark conductivity,

whereby variation over time of the reduced photoconductivity and the reduced dark conductivity during the use of the light information device for the predefined function is reduced.

28. A method for producing a light information device comprising:

a first substrate and a second substrate;

a semiconductor layer disposed on one face of the first substrate facing the second substrate; and

an electro-optic medium provided on one face of the second substrate facing the first substrate, the light information device writing spatial light information input from the outside to the semiconductor layer through the first substrate into the electro-optic medium using a photo conductive effect of the semiconductor layer, and the light information device reading the spatial light information written in the electro-optic medium by modulating light input through the second substrate by the electro-optic medium, the method comprising

an aging process including the steps of

applying a controlled external stimulus to said semiconductor;

inducing aging of said semiconductor in accordance with said step of applying said controlled external stimulus; and

selectively varying said initial conductivity and said initial dark conductivity, in accordance with said step of inducing aging, to produce a stabilized semiconductor having a reduced photoconductivity and a reduced dark conductivity which are 20% or less of said initial photoconductivity and said initial dark conductivity, wherein variation over time of said reduced photoconductivity and said reduced dark conductivity of said stabilized semiconductor is reduced.

29. A method for producing a light information device according to claim 28, wherein the aging process includes the steps of:

irradiating the semiconductor layer with light; and

varying the photoconductivity and the dark conductivity of the semiconductor layer by continuously performing the light irradiation for a predetermined time period, and reducing the photoconductivity and the dark conductivity to be 20% or less of respective initial values thereof before the light irradiation.

30. A method for producing a light information device according to claim 29, wherein, in the step of light irradiation, the semiconductor layer is irradiated with light with an intensity of 100 mW/cm².

31. A method for producing a light information device according to claim 29, wherein, in the step of light irradiation, the semiconductor layer is irradiated with light in a wavelength band including a wavelength corresponding to a bandgap of the semiconductor layer.

32. A method for producing a light information device according to claim 29, wherein the light irradiation is performed by using a lamp selected from a group of a halogen lamp, a metal halide lamp, and a xenon lamp.

33. A method for producing a light information device according to claim 29, wherein the aging process further includes the step of applying an electric field to the semiconductor layer for a predetermined time period.

34. A method for producing a light information device according to claim 28, wherein the aging process includes the steps of:

applying an electric field to the semiconductor layer; and

varying the photoconductivity and the dark conductivity of the semiconductor layer by continuously performing the application of the electric field for a predetermined time period, and reducing the photoconductivity and the dark conductivity to be 20% or less of respective initial values thereof before the application of the electric field.

35. A method for producing a light information device according to claim 34, wherein, in the step of applying the electric field, electric charge of 50-200 mA/cm² is injected into the semiconductor layer.

36. A method for producing a light information device according to claim 34, wherein the aging process further includes the step of irradiating the semiconductor layer with light for a predetermined time period.

37. A light information device produced in accordance with the following process steps:

producing a semiconductor element having a photoconductive effect or a photovoltaic effect and having an initial photoconductivity and an initial dark conductivity;

combining one or more additional elements with the semiconductor element which, in cooperation with the semiconductor element, allow the light information device to be used for a predefined function; and

substantially upon completion of the combining step performing a deliberate aging process including the step of;

applying for a predetermined time period at least one of light irradiation and an electric field to the semiconductor element substantially for the purpose of varying the photoconductivity and the dark conductivity of the semiconductor element so as to have reduced values which are equal to or lower than 20% of the initial photoconductivity and the initial dark conductivity,

whereby variation over time of the reduced photoconductivity and the reduced dark conductivity during the use of the light information device for the predefined function is reduced.