2900-248-R Report of Project MICHIGAN PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM D. F. EDWARDS* - C. ISiBUJTTER** L. D. MCGLAUCHLIN** March 1961 E"MeUte j ScUeze asi,7ec4n^ THE UNIVERSITY OF MICHIGAN Ann Arbor, Michigan *Present address, Massachusetts Institute of Technology, Lincoln Laboratory, Lexington, Mass. **Minneapolis-Honeywell Regulator Co., Research Center, Hopkins, Minn.

NOTICES Sponsorship. The work reported herein was conducted by the Institute of Science and Technology for the U. S. Army Signal Corps under Project MICHIGAN, Contract DA-36-039 SC-78801. Contracts and grants to The University of Michigan for the support of sponsored research by the Institute of Science and Technology are administered through the Office of the Vice-President for Research. Distribution. Initial distribution is indicated at the end of this document. Distribution control of Project MICHIGAN documents has been delegated by the U. S. Army Signal Corps to the office named below. Please address correspondence concerning distribution of reports to: U. S. Army Liaison Group Project MICHIGAN The University of Michigan P. 0. Box 618 Ann Arbor, Michigan ASTIA Availability. Qualified requesters may obtain copies of this document from: Armed Services Technical Information Agency Arlington Hall Station Arlington 12, Virginia Final Disposition. After this document has served its purpose, it may be destroyed. Please do not return it to the Institute of Science and Technology. ii

Institute of Science and Technology The University of Michigan PREFACE Documents issued in this series of Technical Memorandums are published by the Institute of Science and Technology in order to disseminate scientific and engineering information as speedily and as widely as possible. The work reported may be incomplete, but it is considered to be useful, interesting, or suggestive enough to warrant this early publication. Any conclusions are tentative, of course. Also included in this series will be reports of work in progress which will later be combined with other materials to form a more comprehensive contribution in the field. A primary reason for publishing any paper in this series is to invite technical and professional comments and suggestions. All correspondence should be addressed to the Technical Director of Project MICHIGAN. Project MICHIGAN, which engages in research and development for the U. S. Army Combat Surveillance Agency of the U. S. Army Signal Corps, is carried on by the Institute of Science and Technology as part of The University of Michigan's service to various government agencies and to industrial organizations. Robert L. Hess Technical Director Project MICHIGAN iii

Institute of Science and Technology The University of Michigan FIGURES 1. Glass Dewar with Sapphire Window.................. 4 2. Mounted Tellurium Element Cleaved from Melt-Grown Crystal....... 4 3. Noise Voltage Spectra for Two Types of Tellurium Cells......... 4 4. Spectral Detectivity for Tellurium, Indium Antimonide, and Lead Sulfide Photoconductive Cells..................... 4 TABLE I. Characteristics of Tellurium Single-Crystal Photoconductive Cells at 770K............................ 6 v

PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM ABSTRACT Measurements are reported of the photoconductive properties of tellurium crystals grown from the vapor phase as well as from the melt. The results are compared with measurements of other types of photoconductive cells and with theoretical estimates of the cell detectivity. For the "best" tellurium cell the measured detectivity at the spectral peak was D*(3. 4 A, 900) = 2. 3 x 10 cm-cps1/2/watt compared with the estimated value of DX(3. 4 g) = 2. 2 x 10cm-cps//watt. This is evidence that the tellurium photoconductive cell may be constructed to be background-radiation limited. Tellurium single crystals grown from either the vapor phase or the melt produce photoconductive effects comparable to lead sulfide photoconductive cells. In the present paper, measurements are reported for several tellurium photoconductive cells and the results compared with other types of photoconductive cells and with theoretical estimates of the cell characteristics. The use of tellurium as a photoconductive element was first investigated by Moss (see References 1 and 2), who used evaporated thin films. For a cell cooled to liquid nitrogen temperature, he reported a detectivityl value of D*(1 l, 80) = 1. 7 x 10 cm-cps /watt, and a response time of about 550 Asec for the cell having the greatest detectivity. This same tellurium film had only a moderate detectivity [Da(1 l, 80) = 105 to 106 cm-cps/2/watt] at room temperature. Loferski (see Reference 3) later made photoconductivity measurements The conditions of measurement of the detectivity are specified in the expression D*(1 p., 80 cps) where the * indicates that the cell area and amplifier bandwidth have been normalized to 1 cm2 and 1 cps, respectively; the subscript X indicates that the monochromatic detectivity is for the wavelength specified by the first number in parenthesis. The second number in the parenthesis is the chopping frequency of the radiation. For the case in which a 5000K blackbody is used as the radiation source, the X subscript is omitted and the I M is replaced by 5000K, e. g., D*(500~K, 80 cps). 1

Institute of Science and Technology The University of Michigan on cooled single crystals of tellurium with about the same results as Moss had found for the cooled evaporated films. The single crystals used by Loferski were cleaved from large tellurium crystals and etched to the desired dimensions. Nickel was electroplated to the ends of the samples before soldering the copper leads. The impurity concentration of these crystals 15 -3 was estimated by Loferski to be about 10 cm 3 Suits (see Reference 4) in 1957 found that thin hexagonal crystal prisms of tellurium when cooled to liquid nitrogen temperature had detectivities and response times comparable to those of cooled PbS cells. These thin single-crystal prisms (about 10 mm x 1/2 mm x 1/2 mm) were grown from the vapor phase in a low-pressure hydrogen atmosphere starting with 99. 999+ 2 percent pure material, and always resulted in a needle-like cell element. The electrical contacts were made by welding a wire, in most cases platinum, to the tellurium. The crystal was then mounted in a glass dewar with a sapphire window similar to the dewar shown in Figure 1. Tellurium cells3 having large detectivities have also been made from samples cleaved from 2 melt-grown tellurium single crystals. Cells with sensitive elements as large as 16 mm have been made in this way. The single crystals grown by the Czochralski methods along the C-axis -2 (see Reference 6), were found to have low etch pit counts (as low as 1000 cm ) and long carrier lifetime (-70 /sec at 3000K), indicating a high degree of perfection (see Reference 7). Blakemore et al., report a change in room-temperature lifetime from 70 [sec to about 1 [Isec for 4 -2 6 -2 an increase in the defect density from 10 cm to 10 cm. Thus, the carrier lifetime is sensitively dependent on the defect density. The highest lifetime value previously reported 8 9 (see Reference 8) was 0. 01 /isec, probably indicating a large defect density (about 10 to 10 -2 cm ). Since tellurium can be plastically deformed under relatively small stresses, caution must be taken in preparing the tellurium samples to preserve the high degree of perfection. This is true for the vapor-phase-grown crystals (Te-N) as well as the melt-grown ones (Te-C). 2Obtained from American Smelting and Refining Company, South Plainfield, New Jersey. 3A preliminary report of tellurium cells utilizing large single crystals was presented in Reference 5. 4As a convenience in referring to these two types of tellurium cells, the cells made with vapor-phase-grown elements will be given the suffix N (e. g., Te-N or Te-59-N), meaning needle-like, and the suffix C (e. g., Te-C or Te-100-C) for cells with elements cleaved from large single crystals. 2

Institute of Science and Technology The University of Michigan For the elements used in the Te-C cells, the electrical contacts were made of evaporated gold to which the leads were soldered. This method was adopted for these elements of larger area to reduce the effects of current-density variation across the element. The gold contacts also helped to define the sensitive area. Figure 2 is an end-on view of a mounted tellurium element cleaved from a melt-grown crystal, with evaporated gold electrodes. The sensitive area is about 2 mm x 2 mm. The electrical noise, 5000K blackbody detectivity, and spectral detectivity were measured for a number of tellurium cells. For making these measurements the Te-N cells were connected directly across the primary of a G-5 Geoformer" whose impedance was approximately matched to the cell dark resistance. For the Te-C cells, a low-noise transistor preamplifier was used. At optimum bias, the noise of the Te-C cells was considerably greater than the preamplifier noise. Typical noise voltage values in a 5-cycle bandwidth vs. frequency curves for both types of cells are shown in Figure 3. For cell Te-59-N, the noise voltage is given for the optimum bias and zero bias. For this latter case, the noise voltage is approximately frequency independent and equal to the thermal noise of the cell (2 mpv for 200 Q at 770K and 5cycle bandwidth). For optimum bias, i. e., the applied bias that produces maximum signal-tonoise ratio, the noise voltage for Te-59-N and Te-100-C are both typical semiconductor noise, i. e., the noise power has a 1/f frequency dependence. The increased noise at 10 kcs for cell Te-59-N with and without bias is produced by the increased transformer losses at high frequencies. The spectral detectivity, D~, is shown in Figure 4 for a typical Te-N and Te-C cell. Also shown for comparison are curves for a few typical cells of different materials having DA curves competitive with those of the Te cells. Two curves are shown for the lead sulfide cells, PbS-I and PbS-II, to illustrate the two variations possible for this material. The PbS-I is the standard Eastman Type-N cell and PbS-II is the Eastman plumbide variation called Type-P. For PbS cells of the type represented by curve PbS-I, Dx at the spectral peak is greater at 1980K than at 770K, and has a long-wavelength cutoff of about 3.5 y/ at 770K. For cells of the type PbS-II, D* is greater at 77K than at 1980K, and has a long-wavelength cutoff of about 4.5 Mi at 770K, and in general D* at the spectral peak is greater for the PbS-I type cells than for the PbS-II cells. The temperature effect for the two types of PbS cells has also been observed by Spencer (see Reference 9) who attributes the effect to the rate of absorption of ambient photons at the two temperatures. Made by Triad Transformer Corporation, Venice, California. 3

Institute of Science and Technology The University of Michigan FIGURE 1. GLASS DEWAR WITH FIGURE 2. MOUNTED TELLURIUM SAPPHIRE WINDOW ELEMENT CLEAVED FROM MELTGROWN CRYSTAL 12 10 ~0PbS-I (198~K) D; (2. 5p, 90) Te-67-N D (3. 4L, 1000) 10- /-^"'~ \ \ Te-100-C -710 PbS-II (770K) D (3. 11, 900)' Te-59-N 19Optimum Bias b \\ \ \ Optimum t 1010 SZ - Zero Bias -f Bias y \ D< (5L, 900) 010 ^ _ >^\ \ \\ Te-100-C > ^ ^ -^'Te-59-N Te-59-N 10 (3.4A 1000) z Zero Bias I "\\Te-59-N PbS-I \ \ -9 PbS-I 10'2 3 4 81 1 1 PbS-II \ 10 10 10 10 1 2 3 4 5 6 FREQUENCY (cps) WAVELENGTH (Al) FIGURE 3. NOISE VOLTAGE SPECTRA FOR FIGURE 4. SPECTRAL DETECTIVITY FOR TWO TYPES OF TELLURIUM CELLS TELLURIUM, INDIUM ANTIMONIDE, AND LEAD SULFIDE PHOTOCONDUCTIVE CELLS 4

Institute of Science and Technology The University of Michigan At low temperatures the noise of the cell is determined by the fluctuations in the carrier concentration produced by the background divided by the associated time constant (i. e., fluctuations in the rate of absorption). The photoabsorption for both types of PbS cells is greater at 770K than at 1980K, and the time constant in the range from 770K to 1980K remains about the same for the type I cells but becomes considerably shorter for the type II cells. Thus, the rate of absorption (and also the noise) for the type I cells is greater at 770K than at 1980K whereas just the opposite is true for the type II cells. Since D* is inversely proportional to the rate of absorption, then for the type I cells D98o > D*7OK and for type II cells D7oK > D980K The difference in the long-wavelength cutoffs for type I and II cells is also explained by Spencer as due to the temperature dependence of the rate of absorption. The curve for the InSb cell shown in Figure 4 is for a photoconductive cell reported by Bratt et al. (see Reference 10). The cell temperature was 770K, and a cooled aperture was used to restrict the field of view to a 600 cone. The effect of the cooled aperture is to increase DA by about 1. 5 times. Roberts (see Reference 11) has reported DA values as great as 101 cm-cps /watt at X = 5.3 g for InSb photoconductive cells of similar design. From Figure 4it can be seen that cells Te-59-N and Te-100-C have very similar DA curves. The difference in the spectral peaks for these two cells is a surface effect as pointed out by Loferski (see Reference 3). The long-wavelength edge for Te-100-C and Te-59-N is almost identical with that of cell PbS-II. At X = 3. 4 /i the Di value for PbS-II is about 1. 5 times that of the Te cells and increases for shorter wavelengths. The time constant for the Te cells is about 60-120 isec compared with about 4000 gsec for the PbS-II cell. Thus, for applications where the shorter time constant is required and the increased DA for X < 3 a is unimportant, the Te cells should be superior to the PbS-II cell. Except for a narrow spectral region centered about 3. 6 i, the DA values are greater for the InSb cell than for the Te cells. The time constant for these InSb cells is of the order of I /isec. Thus the InSb cell appears to be superior to the Te cells in applications where rapid response times are important. By placing an optical filter having the long wavelength response of the Te cells in front of an InSb cell, one would have the advantages of the short time constant of the InSb cell and the spectral detectivity of the Te cell with little loss in DA at X = 3. 6 L. Also shown in Figure 4 is the DA curve for the tellurium cell, labeled Te-67-N, having the greatest detectivity measured so far. At the spectral peak, 3. 4 1L, the Di for Te-67-N is about 4 times that for Te-59-N and Te-100-C. The noise spectrum for cell Te-67-N is very similar to that for cell Te-59-N (Figure 3). Without an applied bias, the noise is approximately frequency independent and about equal to the thermal noise of the cell (1 mpv for 96 Q at 770K 5

Institute of Science and Technology The University of Michigan and 5-cycle bandwidth). With an applied bias, the noise power is 1/f semiconductor noise. The performance characteristics are given in Table I for the three tellurium cells, Te-100-C, Te-59-N, and Te-67-N. TABLE I. CHARACTERISTICS OF TELLURIUM SINGLECRYSTAL PHOTOCONDUCTIVE CELLS AT 770K Te-100-C Te-59-N Te-67-N D(c0 K 9p1/29 D*(500-K, 90) ( - 1.3x109 1.3x109 6.2x109 D*(5000K, 900 ) cmcp 4 x 109 4.7x109 1.7 x 1010 watt cm-cps1/2 10 10 D*(X, 90 ) 2 x 10 1.7 x 10 8.3 x 10 wamci'21tt0 2x101 8.3x DX (, 900) watt 6.4x 10 6.2x 10 2.3 x 1011 X (spectral peak) (/) 3.6 3.4 3.4 T (time constant) (tsec) ~60 ~ 120 ~ 120 R (resistance) (Q) 1000 199 96 2 A (area) (cm2) 0.02 x 0.02 0.05 x 0.05 0.05 x 0.05 Recently, several articles have been published (see References 12-14) that describe methods for calculating the ultimate detectivity of a cell assuming that the limitations are fluctuations of the background radiation. Petritz (see Reference 12) has simplified the problem to a relation between the intrinsic energy gap, E., and the spectral detectivity, DXo Taking the optical activation energy to be 0. 37 ev as given by Moss (see Reference 1), the ultimate detectivity would be DA = 6 x 101 cm-cps 1/2/watt, about 2. 5 times greater than the measured value for Te-67-N. One disadvantage of this method of estimating DA is that a knowledge of the intrinsic energy gap is required. In most cases, the value of the energy gap has been assigned somewhat arbitrarily. Moss takes the energy gap to be defined by the condition that the photocurrent is 50 percent of the peak photocurrent. Loferski (see Reference 3) takes the energy gap to be defined by the condition that the transmission is 5 percent of its value in the transparent region, i. e., E. = 0. 325 ev. This corresponds to a D = 3 x 10 cm-cps /watt. Another definition sometimes used is that the value of the energy gap corresponds to an absorption 6

Institute of Science and Technology The University of Michigan 3 coefficient 10 times the value in the transmission region. For this energy gap (E. = 0. 275 1/2 1 ev), D = 1. 6 x 101 cm-cps /watt. Other authors have used still different definitions for the energy gap. For the case of tellurium, the definition of the energy gap is further complicated by the fact that the crystal is dichroic. These difficulties can be bypassed to some extent by calculating the ultimate detectivity after the method of Moss (see Reference 13). Here a knowledge of the intrinsic energy gap is not necessary. By this method, the ultimate detectivity is estimated (see Reference 15) to be DA (3. 4, -) = 2.2 x 10 cm-cps2 /watt, compared with the measured value of D* (3.4 t, 1000) 2.3 x 10 cm-cps 2/watt. This excellent agreement between the measured and estimated DA values is somewhat fortuitous because of the simplifying approximations made in this method of calculation. It can be seen from both methods for estimating the theoretical DA value that the detectivity of cell Te-67-N is limited by the fluctuations of the background radiation. A possible explanation as to why the DX values of the other Te cells are less than that for Te-67-N is in the relative number of defects in the sensitive cell elements. From the study of whisker growth, it is known that the number of defects increases with the crystal diameter. One might then conclude that the Te-C elements cleaved from large crystals would intrinsically have a greater number of defects than the Te-N elements. Also, as pointed out earlier, tellurium can be easily deformed plastically, thereby introducing a large number of defects. The number of defects are intimately related to the time constant and thus to the detectivity (see Reference 9). Unfortunately, it was not possible to obtain estimates of the defect densities for any of the Te cell elements measured after they had been assembled. Investigations along this line are being continued. REFERENCES 1. T. S. Moss, Proc. Phys. Soc. London, 1949, Vol. A62, p. 264. 2. T. S. Moss, Photoconductivity in the Elements, Thornton Butterworth, Ltd., London, England, 1952. 3. J. J. Loferski, Phys. Rev., 1954, Vol. 93, p. 707. 4. G. H. Suits, "A Single-Crystal Photoconductive Tellurium Detector," Report Number 2144-240-T, Willow Run Laboratories, The University of Michigan, Ann Arbor, Mich., 1957. 5. C. D. Butter and L. D. McGlauchlin, "A New Single-Crystal Tellurium Infrared Detector," Proc. IRIS, July 1960, Vol. 5, No. 3, p. 103. 6. T. J. Davis, J. Appl. Phys., 1957, Vol. 28, p. 1217. 7

Institute of Science and Technology The University of Michigan 7. J. S. Blakemore, J. D. Heaps, K. C. Nomura, and L. P. Beardsley, Phys. Rev., 1960, Vol. 117, p. 687. 8. A. P. deCarvalho, Compt. rend., 1956, Vol. 242, p. 745. 9. H. E. Spencer, J. Appl. Phys., 1960, Vol. 31, p. 505. 10. P. Bratt, W. Engeler, H. Levinstein, A. MacRae, and J. Pehek, Final Report Germanium and Indium Antimonide Infrared Detectors, Syracuse University, Syracuse, New York, February 1960, Contract Number AF 33(616)-3859. 11. V. Roberts, paper presented at a meeting of International Commission for Optics, Stockholm, Sweden, August 24, 1959. 12. R. L. Petritz, Proc. IRE, 1959, Vol. 47, p. 1458. 13. T.S. Moss, J. Opt. Soc. Am., 1950, Vol. 40, p. 603. 14. R. A. Smith, F. E. Jones, and R. P. Chasmar, The Detection and Measurement of Infrared Radiation, Oxford University Press, London 1957. 15. D. F. Edwards and M. Mercado, Infrared Physics, Pergamon Press, Ltd., New York, 1961, Vol. 1. 8

Institute of Science and Technology The University of Michigan PROJECT MICHIGAN DISTRIBUTION LIST 5 1 March 1961-Effective Date Copy No. Addressee Copy No. Addressee 1 Army Research Office, ORCD, DA 47-48 Commander, Army Rocket & Guided Missile Agency Washington 25, D. C. Redstone Arsenal, Alabama ATTN: Research Support Division ATTN: Technical Library, ORDXR-OTL 2 Office, Assistant Chief of Staff for Intelligence 49 Commanding Officer Department of the Army, Washington 25, D. C. U. S. Army Transportation Research Command ATTN: Chief, Research & Development Branch Fort Eustis, Virginia ATTN: Research Reference Center 3 Commanding General, U. S. Continental Army Command Fort Monroe, Virginia 50 Commanding General ATTN: ATSWD-G Ordnance Tank-Automotive Command, Detroit Arsenal 28251 Van Dyke Avenue 4-5 Commanding General Centerline, Michigan U. S. Army Combat Surveillance Agency ATTN: Chief, ORDMC-RRS 1124 N. Highland Street Arlington 1, Virginia 51 Commanding Officer, Ordnance Weapons Command Rock Island, Illinois 6-8 Office of the Chief Signal Officer Department of the Army, Washington 25, D. C. ATTN: ORDOW-GN 52 Commanding Officer (6) ATTN: Chief, Combat Development Commanding Officer Branch, Research & Devel t D n U. S. Army Diamond Ordnance Fuze Laboratories Branch, Research & Development DivisionC. (7-8) ATTN: Chief, Signal Research Office Research & Development Division 53-55 Director, U. S. Army Engineer 9-37 Commanding Officer Research & Development Laboratories U. S. Army Signal Research & Development Laboratory Fort Belvoir, Virginia Fort Monmouth, New Jersey (53) ATTN: Chief, Topographic, Engineer Department ATTN: SIGRA/SL-ADT (54) ATTN: Chief, Electrical Engineering Department 38-39 Commanding General (55) ATTN: Technical Documents Center U. S. Army Electronic Proving Ground U. S. Army Electronic Proving Ground 56 Director, Human Engineering Laboratory Fort Huachuca, Arizona Aberdeen Proving Ground, Aberdeen, Maryland ATTN: Technical Library 57 Commandant, U. S. Army Command & General Staff College 40 Director, Weapons Systems Evaluation Group Fort Leavenworth, Kansas Room 1E880, The Pentagon ATTN: Archives Washington 25, D. C. 58 Commandant, U. S. Army Infantry School 41 Chief of Engineers Fort Benning, Georgia Department of the Army, Washington 25, D. C. ATTN: Combat Developments Office ATTN: Research & Development Division dant 59-60 Assistant Commandant U. S. Army Artillery & Missile School 42 Chief, Chief of Ordnance, Research& Development Division Fort Sill, Oklahoma Department of the Army, Washington 25, D. C. 61 Assistant Commandant, U. S. Army Air Defense School ATTN: ORDTB, Research & Special Projects Fort Bliss, Texas 43 Commanding Officer, Army Map Service, Corps of Engineers 62 Commandant, U. S. Army Engineer School U. S. Army, Washington 25, D. C. Fort Belvoir, Virginia ATTN: Document Library ATTN: ESSY-L 63 President, U. S. Army Infantry Board 44 Commanding General Fort Benning, Georgia Quartermaster Research & Engineering Command U. S. Army, Natick, Massachusetts 64 President, U. S. Army Artillery Board Fort Sill, Oklahoma 45-46 Chief, U. S. Army Security Agency 65 President, U. S. Army Air Defense Board Arlington Hall Station, Arlington 12, Virginia Fort Bliss, Texas 9

Institute of Science and Technology The University of Michigan Distribution List 5, 1 March 1961-Effective Date Copy No. Addressee Copy No. Addressee 66 President, U. S. Army Aviation Board 103-106 Central Intelligence Agency Fort Rucker, Alabama 2430 E Street, N. W. Washington 25, D. C. 67-68 President, U. S. Army Intelligence Board ATTN: OCR Mail Room Fort Holabird, Baltimore 19, Maryland 69 Office, Deputy Chief of Naval Operations 107-112 National Aeronautics & Space Administration Department of the Navy 1520 H Street, N. W. The Pentagon, Washington 25, D. C. Washington 25, D. C. ATTN: Op-07T 113 Combat Surveillance Project 70-73 Office of Naval Research, Department of the Navy Cornell Aeronautical Laboratory, Incorporated 17th & Constitution Avenue, N. W. Box 168, Arlington 10, Virginia Washington 25, D. C. Washington 25, D. C. ATTN: Technical Library (70-71) ATTN: Code 463 114 The RAND Corporation (72-73) ATTN: Code 461 The RAND Corporation 1700 Main Street 74-76 Chief, Bureau of Ships California Department of Navy, Washington 25, D. C. ATTN: Library (74) ATTN: Code 335 ~~~~~(74) ATTN: Code 335 ~115-116 Cornell Aeronautical Laboratory, Incorporated (75) ATTN: Code 684C 4455 Genesee Street (76) ATTN: Code 690 Buffalo 21, New York ATTN: Librarian 77 Director, U. S. Naval Research Laboratory VIA: Bureau of Naval Weapons Representative Washington 25, D. C. 4455 Genesee Street ATTN: Code 2027 Buffalo 21, New York 78 Commanding Officer U. S.78 Comma Offirdcer Labor y 117-118 Director, Human Resources Research Office U Corona California LaborThe George Washington University P. 0. Box 3596, Washington 7, D. C. ATTN: Library ATTN: Library 79 Commanding Officer & Director U. S. Navy Electronics Laboratory San Diego 52, California USan Diego 52EClectrnicLba tr 119 Chief Scientist, Department of the Army Office of the Chief Signal Officer ATTN: Library Research & Development Division, SIGRD-2 Washington 25, D. C. 80-81 Department of the Air Force, Headquarters, USAF Washington 25, D. C. 120 Columbia University, Electronics Research Laboratories 632 W. 125th Street (81) ATTN: AFOIN-1B1 New York 27, New York ATTN: Technical Library 82 Aerospace Technical Intelligence Center, U. S. Air Force Wright-Patterson AFB, Ohio VIA: Commander, Rome Air Development Center Griffiss AFB, New York ATTN: AFCIN-4Bla, Library ATTN: RCKCS 83-92 ASTIA (TIPCR) Arlington Hall Station, Arlington 12, Virginia 121 Coordinated Science Laboratory, University of Illinois 93-100 Urbana, Illinois 93-100 Commander, WrightAir Development Division Urbana, Illinois Wright-Patterson AFB, Ohio ATTN: Librarian (93-96) ATTN: WWDE VIA: ONR Resident Representative ~(97) ATTN-~:~ ~ WWAD -DIST^T ^605 S. Goodwin Avenue (97) ATTN: WWAD-DIST Urbana, Illinois Urbana, Illinois (98-100) ATTN: WWRNOO (Staff Physicist) 122 Polytechnic Institute of Brooklyn 101 Commander, Rome Air Development Center Polyhn nttte r n Griffiss AFB, New York B rookyn 1 New Yor Brooklyn 1, New York ATTN: RCOIL-2 ATTN: Microwave Research Institute Library 102 APGC (PGTRI) VIA: Air Force Office of Scientific Research Eglin Air Force Base, Florida Washington 25, D. C. 10

Institute of Science and Technology The University of Michigan Distribution List 5, 1 March 1961-Effective Date Copy No. Addressee Copy No. Addressee 123 Visibility Laboratory, Scripps Institution of Oceanography 129 The Ohio State University Antenna Laboratory University of California 2024 Neil Avenue San Diego 52, California Columbus 10, Ohio VIA: ONR Resident Representative ATTN: Security Officer University of California Scripps Institution of Oceanography, Bldg. 349 W A eeomen on ~~~~La Jol~~~~la, CaliforniaWright Air Development Division Wright-Patterson AFB, Ohio 124-125 Bureau of Naval Weapons ATTN: WWKSC Department of the Navy, Washington 25, D. C. (124) ATTN: RTPA-31 (124) ATTN: RTPA-31 130 Cooley Electronics Laboratory ~(125 ) AI IJ~TTN: RKAAV ~-323 ~University of Michigan Research Institute Ann Arbor, Michigan 126 Headquarters, Tactical Air Command ATTN: Director Langley AFB, Virginia ATTN: TPL-RQD (Requirements) 131 U. S. Continental Army Command 127 Headquarters, Tactical Air Command Liaison Officer, Project MICHIGAN Langley AFB, Virginia The University of Michigan P. O. Box 618, Ann Arbor, Michigan ATTN: TOCE (Communications-Electronics) 128 Office of the Director 132 Commanding Officer, U. S. Army Defense Research & Engineering Liaison Group, Project MICHIGAN Technical Library The University of Michigan Department of Defense, Washington 25, D. C. P. O. Box 618, Ann Arbor, Michigan 11

AD Div. 25/2 UNCLASSIFIED AD Div. 25/2 UCASFE Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN Institute of Science and Technology, U. of Michigan, Ann Arbor 1 il:PoetMCIA PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C. D., Butter, C. D., PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by I.EdasCDButrC.., D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of adM~acln.D Project MICHIGAN. Mar 61. 7 pp. incl.illus., table, 15 refs. III. U. S. Army Signal Corps Project MICHIGAN. Mar 61. 7 pp. incl. illus..table, 15 refs. II.USAryigaCop (Rept. no. 2900-248-R) IV. Contract DA-36-039 SC-78801 (Rept. no. 2900-248-R)IVCotatD-609S781 (Contract DA-36-039 SC-78801) Unclassified report (Contract DA-36-039 SC-78801) Unclassified report Measurements are reported of the photoconductive properties of Measurements are reported of the photoconductive properties of tellurium crystals grown from the vapor phase as well as from tellurium crystals grown from the vapor phase as well as from the melt. The results are compared with measurements of other the melt. The results are compared with measurements of other types of photoconductive cells and with theoretical estimates of types of photoconductive cells and with theoretical estimates of the cell detectivity. For the "best" tellurium cell the measured the cell detectivity. For the "best" tellurium cell the measured detectivity at the spectral peak was D* (3.4 p., 900) = 2. 3x1011cm- detectivity at the spectral peak was D* (3. 4 A, 900) = 2. 3xlI0 Icmcps'/2/watt compared with the estimated value of D,* (3. 4 p)=cpsl/2/watt compared with the estimated value of D* (3.4p.= 2.2 x 101cm-cpsl//watt. This is evidence that the tellurium Are.erie 2.2 x1011cm-cpsl//watt. This is evidence that the tellurium. photoconductive cell may be constructed to be background-radia- Technical Information Agency photoconductive cell may be constructed to be background-radia- Tcn^ oao~ec tion limited. (oer UNCLASSIFIED tion limited. (ovNCLSSIIE AD Div. 25/2 UNCLASSIFIED AD Div. 25/2 UCASFE Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN Institute of Science and Technology, U. of Michigan, Ann Arbor LTil:PoetMCIA PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C. D., Butter, C. D., PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by I.EdasCDButrC.., D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of adM~acln.D Project MICHIGAN. Mar 61. 7 pp. incl. illu-s., table, 15 refs. III. U. S. Army Signal Corps Project MICHIGAN. Mar 61. 7 pp. incl. illus..table, 15 refs. II.USAryigaCop (Rept. no. 2900-248-R) IV. Contract DA-36-039 SC-78801 (Rept. no. 2900-248-R)IVCotatD-609S781 (Contract DA-36-039 SC-78801) Unclassified report (Contract DA-36-039 SC-78801) Unclassified report Measurements are reported of the photoconductive properties of Measurements are reported of the photoconductive properties of tellurium crystals grown from the vapor phase as well as from tellurium crystals grown from the vapor phase as well as from the melt. The results are compared with measurements of other the melt. The results are compared with measurements of other types of photoconductive cells and with theoretical estimates of types of photoconductive cells and with theoretical estimates of the cell detectivity. For the "best" tellurium cell the measured the cell detectivity. For the "best" tellurium cell the measured detectivity at the spectral peak was D* (3. 4 a, 900) = 2. 3 x I01Icm- detectivity at the spectral peak was DX* (3. 4 t, 900) = 2. 3 xl10^1cm cpsl//watt compared with the estimated value of D* (3.4 p)=cps^/atcmae ihteetmtdvleo ^(.. 2..2 x101cm-cpsl//watt. This is evidence that the tellurium Arme Sevie 2.2 x 011cm-cpsV/2/watt. This is evidence that the tellurium. photoconductive cell may be constructed to be background-radia- Tehia nomto gnyphotoconductive cell may be constructed to be background-radia- Tcnc~fr o~ec tion limited. Tehnca UNforASSIonIAEnc tion limited. UCASFE +~~~~~~~~~~~~~~~~~~~~(vr UNLSSFE4-vr

pbSCOGO \ 5spOYS \scanckvotv$ AD \ \FSCRLP t^g^tz?YPOtOCO ^ss \ \^- \~~~~~~~~~~~~~~~~~~~~~~~~~~~ul~aS~C \^ - \.C^~~~~~~~~~~~~~~~~~~~T~ ^ \~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~pooodc~SPPf~t \ ^^~~~~~~~~~~~~~~~~~~~~~~~~~~yt~

AD Div. 25/2 UNCLASSIFIED AD Div. 25/2 UNCLASSIFIED Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C. D., Butter, C. D., PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C. D., Butter, C. D., D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. Project MICHIGAN. Mar 61. 7 pp. incl. illus., table, 15 refs. III. U.S. Army Signal Corps Project MICHIGAN. Mar 61. 7 pp. incl. illus., table, 15 refs. IH. U.S. Army Signal Corps (Rept. no. 2900-248-R) IV. Contract DA-36-039 SC-78801 (Rept. no. 2900-248-R)IV. Contract DA-36-039 SC-78801 (Contract DA-36-039 SC-78801) Unclassified report (Contract DA-36-039 SC-78801) Unclassified report Measurements are reported of the photoconductive properties of Measurements are reported of the photoconductive properties of tellurium crystals grown from the vapor phase as well as from tellurium crystals grown from the vapor phase as well as from the melt. The results are compared with measurements of other the melt. The results are compared with measurements of other types of photoconductive cells and with theoretical estimates of types of photoconductive cells and with theoretical estimates of the cell detectivity. For the "best" tellurium cell the measured the cell detectivity. For the "best" tellurium cell the measured detectivity at the spectral peak was D* (3.4 g, 900) = 2.3 x lOl1cm- detectivity at the spectral peak was D; (3.4 p, 900) = 2.3 x 1Olcmcpsl/2/watt compared with the estimated value of D* (3.4 ) = cpsl/2/watt compared with the estimated value of D* (3.4 4) = 2. 2 x 10I1cm-cpsl/2/watt. This is evidence that the tellurium Armed Services 2. 2 x 101Ocm-cpsl/2/watt. This is evidence that the tellurium S i photoconductive cell may be constructed to be background-radia- Technical Information Agency photoconductive cell may be constructed to be background-radia- Technical Information Agency tion limited. (over) UNCLASSIFIED tion limited. (Over) tion limited. ^^ ~~~~~~~~UNCLASSIFIED ^ ^(over) UNCLASSIFIED + 4 AD Div. 25/2 UNCLASSIFIED AD Div. 25/2 UNCLASSIFIED Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN Institute of Science and Technology, U. of Michigan, Ann Arbor I. Title: Project MICHIGAN PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C.D., Butter, C. D., PHOTOCONDUCTIVITY IN SINGLE-CRYSTAL TELLURIUM by II. Edwards, C.D., Butter, C D., D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. D. F. Edwards, C. D. Butter, and L. D. McGlauchlin. Rept. of and McGlauchlin, L. D. Project MICHIGAN. Mar 61. 7 pp. incl. illus., table, 15 refs. III. U.S. Army Signal Corps Project MICHIGAN. Mar 61. 7 pp. incl. illus., table, 15 refs. III. U.S. Army Signal Corps (Rept. no. 2900-248-R) IV. Contract DA-36-039 SC-78801 (Rept. no. 2900-248-R) IV. Contract DA-36-039 SC-78801 (Contract DA-36-039 SC-78801) Unclassified report (Contract DA-36-039 SC-78801) Unclassified report Measurements are reported of the photoconductive properties of Measurements are reported of the photoconductive properties of tellurium crystals grown from the vapor phase as well as from tellurium crystals grown from the vapor phase as well as from the melt. The results are compared with measurements of other the melt. The results are compared with measurements of other types of photoconductive cells and with theoretical estimates of types of photoconductive cells and with theoretical estimates of the cell detectivity. For the "best" tellurium cell the measured the cell detectivity. For the "best" tellurium cell the measured detectivity at the spectral peak was D* (3.4 p, 900) = 2.3 x 101 l cm- detectivity at the spectral peak was D* (3.4 p., 900) = 2.3 x 01lcmcpsl/2/watt compared with the estimated value of D* (3. 4 ) = cps1/2/watt compared with the estimated value of D* (3.4.) = 2.2 x 1011cm-cpsl/2/w~~~~~~~~~~~~~at Thisis e d n c t h t heeluumP 2.2 x 0I1cm-cpsl/2/watt. This is evidence that the tellurium Are evcs2.2 x 1011cm-cpsl/2/watt. This is evidence that the tellurium S photoconductive cell m~~~ ~ ~ ~~Aybcosruced toSebakrudrvice s Armed Services photoconductive cell may be constructed to be background-radia- Technical Information Agency photoconductive cell may be constructed to be background-radia- Technic foraoAgency tion limited. (over) UNCLASSIFIED tion limited. UNCLASSIFIED + (

AD UNCLASSIFIED AD UNCLASSIFIED DESCRIPTORS DESCRIPTORS Photoconductivity Photoconductivity Tellurium Tellurium Single crystals Single crystals UNCLASSIFIED UNCLASSIFIED AD UNCLASSIFIED AD UNCLASSIFIDo DESCRIPTORS DESCRIPTORS Photoconductivity Photoconductivity ____ Tellurium Tellurium Single crystals Single crystals UNCLASSIFIED UNCLASSIFIED