US2847329A - Sensitization of photoconductive cells by the use of indium vapor - Google Patents
Sensitization of photoconductive cells by the use of indium vapor Download PDFInfo
- Publication number
- US2847329A US2847329A US640563A US64056357A US2847329A US 2847329 A US2847329 A US 2847329A US 640563 A US640563 A US 640563A US 64056357 A US64056357 A US 64056357A US 2847329 A US2847329 A US 2847329A
- Authority
- US
- United States
- Prior art keywords
- photoconductive
- indium
- cadmium telluride
- tube
- sensitization
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229910052738 indium Inorganic materials 0.000 title description 16
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 title description 16
- 206010070834 Sensitisation Diseases 0.000 title description 3
- 230000008313 sensitization Effects 0.000 title description 3
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 17
- 238000000034 method Methods 0.000 description 14
- 230000035945 sensitivity Effects 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 239000011521 glass Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- 235000011089 carbon dioxide Nutrition 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000008016 vaporization Effects 0.000 description 3
- 229910052787 antimony Inorganic materials 0.000 description 2
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- 229910004613 CdTe Inorganic materials 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
Description
1958 L. E. SCHILBERG ETAL SENSITIZATION OF PHOTOCONDUCTIVE CELLS BY THE USE OF INDIUM VAPOR Filed Feb. 15, 1957 w ll! INVENTORS GEORGE G. KRETSCHMAR LLOYD E. SCHILBERG United StatesPatent O SENSITIZATIO'N OF PHOTOCONDUCTIV E CELLS BY THE USE OF INDIUM VAPOR Lloyd E. Schilberg, China Lake, and George G. Kretschmar, Arlington, Calif., assignors to the United States gt America as represented by the Secretary of the avy Application February 15, 1957, Serial No. 640,563
' 1 Claim. (Cl. 117-211 (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
This invention relates to a process for making photoconductive cells of the bimetallic type, more particularly, it relates to a process for making photoconductive cells of increased sensitivity by vaporization techniques.
The photoconductive bimetallic element of photoconductive tubes is ordinarily deposited between the terminals of the cell by vaporizing the metal in an evacuated glass Dewar type cell and condensing it on the area between the terminals by cooling the area. In order to increase the photoconductance, or change the spectral range of maximum sensitivity of the photoconductive element, it has been the practice to add very small quantities of other elements to the original melt, a process known as doping. The resulting doped materials may show a large increase of impurity carriers and smaller activation energies than the original bimetal. While these methods increase the photoconductive sensitivity of bimetallic elements to some extent they do not increase it sufiiciently for all purposes. This is particularly true in the case of cadmium telluride elements.
It is therefore an object of this invention to provide a process for making cadmium telluride photoconductive elements having greater sensitivity than those made by prior processes;
It is another object of this invention to provide a process as stated which is simple in application and provides reproducible results.
It has been found that the above objects are accomplished by the deposition of cadmium telluride in the presence of indium vapor.
The invention is best understood by reference to the following description taken in connection with the ac- 50 companying drawing hereby made a part of this specification, and in which:
Fig. 1 is a vertical crow-section of the photoconductive tube made by the process of the invention;
Fig. 2 is a vertical cross-section of the tube taken on a plane at 90 to the plane on which Fig. 1 is taken; and
Fig. 3 is a vertical cross-section taken on the line 3, 3 of Fig. l.
Referring to Figs. 1 and 2, there is shown a conventional double-walled glass tube of the Dewar type used for photoconductive cells. A strip of Aquadag coating 10 or other suitable conductive coating is coated on the outer surface of the inner tube as shown, leaving a gap 11 between the terminals formed by the ends of the coating. Aquadag is essentially a water suspension of carbon. Another suitable coating is silver paint. The ends of the coating are referred to herein as the terminals of the conducting coating. The gap 11 is coated with cadmium telluride to form the photosensitive element 12. At 13 is shown a small amount of the material, cadmium telluride, which is vaporized and the vapor condensed to form the photoconductive element 12 across the gap 11 between the terminals made by the broken strip 10. A small amount of indium has been added to the cadmium telluride in the bottom of the tube to produce indium vapor. A glass tube 14 is used for introducing cool air into the Dewar tube to cool the surface of the gap during the deposition of the element 12. Terminals 15 are provided for passing current through the cell. The Dewar tube is provided with a window 16 directly opposite the photoconductive element 12. Fig, 3 shows the arrangement of the photoconductive element as seen from the interior of the tube.
In application of the process of the invention, pure cadmium telluride was made by combining purified cadmium and tellurium in stoichiometric proportions in a separate evacuated tube. A small amount of the formed cadmium telluride and a small amount of metallic indium were then placed in the bottom of the Dewar tube at 13. The tube was heated to vaporize the cadmium telluride and indium and the cadmium telluride element 12 was deposited by condensation in the presence of indium vapor. It was necessary to raise the temperature to between about 580 C. and 640 C. to give sufiicient indium vapor for the sensitization to take place. During the step of vaporization of the material 13, cadmium telluride and indium, the area in the gap 11 between the terminals 10 was cooled by cool air introduced through the glass tube 14. Following deposition of the photoconductive element, the tube was cooled and tested using a standard light source of about 2 foot candle power and a megohmmeter connected to measure resistance across the tube.
A large number of tubes were prepared by the above outlined process and tested for dark resistance and light resistance using a standard light source of about 2 foot candle power illumination. The table below ShOWs the results obtained on five tubes, two of which, tubes 129 and 131, had elements of pure cadmium telluride and three of which, tubes 128, 130 and 132, had elements of cadmium telluride applied in the presence of indium vapor. Measurements were taken at three temperatures, room temperature (298 K.), Dry Ice temperature (194 K.) and liquid nitrogen temperature (81 K.). The ratio of the dark resistance to the light resistance i shown for each tube. It will be noted that no dark resistance value is given for tubes 129 and 131 at liquid nitrogen Room Temp., 298 K. Dry Ice Temp., 194 K. Liquid Nsifgolgcen 'Iemp.,
Tube Material No. Megohms Megohms Megohms (dark) Ratio (dark) Ratio (dark) Ratio Megohms Megohms Megohms (2 f. e.) (2 f. c.) (2 f. c.)
OdTe In sensitized.-- 30/0. 5 40, 000/5 8, 000 5, 000/0. 26 20, 000 Od'le 170/53 3 700, 000/5, 000 140 -/15,000 OdTe In sensitized... 20/0. 7 30 20, 000/1. 2 17,000 20, 000/0. 26 800, 000 CdTe (Sb) 34/ 4 50, 000/500 /2, 20 OdTed (Sh) In Sensl- 4 9/0. 6 8 250/0. 9 280 250/0. 2 12, 000
tize
1 These two samples of CdIe contained a trace of antimony.
temperature of 81 K. The dark resistances of these tubes at this temperature was too high to permit measurement with the equipment available. When indium was used for doping the cadmium telluride element in accordance to the prior art procedure, no appreciable increase in sensitivity was noted.
Using the ratio of the dark resistance to the resistance under an illumination of two foot candles as a measure of the sensitivity, it will be seen that in each case the indium vapor sensitized tubes have a higher sensitivity. This is still more marked in tubes cooled with Dry Ice and which are at a temperature of 194 K. The tendency is still seen in the data taken at liquid nitrogen temperature even though the comparison cannot be made, as the dark resistances of the tubes processed without indium are too high to be measured accurately with available equipment. It will be noted from examples 131 and 132 that the invention is also effective to increase the sensitivity of antimony doped cadmium telluride elements.
From the above results it is readily seen that a process has been provided for increasing the sensitivity of cadmium telluride photoconductive elements by a factor up to 20 at room temperatures, and up to 120 at 194 K., with a still greater increase in sensitivity indicated at a temperature of 81 K.
Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed is:
A process for making photoconductive elements which consists in simultaneously evaporating cadmium telluride and indium at a temperature between about 580 C. to about 640 C. onto a surface in a vacuum.
References Cited in the file of this patent UNITED STATES PATENTS
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US640563A US2847329A (en) | 1957-02-15 | 1957-02-15 | Sensitization of photoconductive cells by the use of indium vapor |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US640563A US2847329A (en) | 1957-02-15 | 1957-02-15 | Sensitization of photoconductive cells by the use of indium vapor |
Publications (1)
Publication Number | Publication Date |
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US2847329A true US2847329A (en) | 1958-08-12 |
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Family Applications (1)
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US640563A Expired - Lifetime US2847329A (en) | 1957-02-15 | 1957-02-15 | Sensitization of photoconductive cells by the use of indium vapor |
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US (1) | US2847329A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3006786A (en) * | 1957-12-06 | 1961-10-31 | Emi Ltd | Photo-emissive surfaces |
US3135704A (en) * | 1959-10-21 | 1964-06-02 | Union Carbide Corp | Photosensitive compositions and process for the production thereof |
US3531335A (en) * | 1966-05-09 | 1970-09-29 | Kewanee Oil Co | Method of preparing films of controlled resistivity |
US4097775A (en) * | 1955-08-04 | 1978-06-27 | Rca Corporation | Infrared sensitive photoconductive pickup tube |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2636855A (en) * | 1948-03-25 | 1953-04-28 | Hilger & Watts Ltd | Method of producing photoconductive coatings |
US2759861A (en) * | 1954-09-22 | 1956-08-21 | Bell Telephone Labor Inc | Process of making photoconductive compounds |
-
1957
- 1957-02-15 US US640563A patent/US2847329A/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2636855A (en) * | 1948-03-25 | 1953-04-28 | Hilger & Watts Ltd | Method of producing photoconductive coatings |
US2759861A (en) * | 1954-09-22 | 1956-08-21 | Bell Telephone Labor Inc | Process of making photoconductive compounds |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4097775A (en) * | 1955-08-04 | 1978-06-27 | Rca Corporation | Infrared sensitive photoconductive pickup tube |
US3006786A (en) * | 1957-12-06 | 1961-10-31 | Emi Ltd | Photo-emissive surfaces |
US3135704A (en) * | 1959-10-21 | 1964-06-02 | Union Carbide Corp | Photosensitive compositions and process for the production thereof |
US3531335A (en) * | 1966-05-09 | 1970-09-29 | Kewanee Oil Co | Method of preparing films of controlled resistivity |
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