2900-80-R Memorandum of Project MICHIGAN PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe- In2Te3 LARS THOMASSEN DONALD R. MASON Department of Chemical and Metallurgical Engineering April 1960 THE UNIVERSITY OF MICHIGAN Ann Arbor, Michigan

Distribution control of Project MICHIGAN Reports has been delegated by the U. S. Army Signal Corps to: Commanding Officer U. S. Army Liaison Group Project MICHIGAN Willow Run Laboratories Ypsilanti, Michigan It is requested that information or inquiry concerning distribution of reports be addressed accordingly. Project MICHIGAN is carried on for the U. S. Army Signal Corps under Department of the Army Prime Contract Number DA-36-039 SC-78801, University contract administration is provided to the Willow Run Laboratories through The University of Michigan Research Institute.

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM PREFACE Documents issued in this series of Technical Memorandums are published by Willow Run Laboratories 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 Willow Run Laboratories as part of The University of Michigants service to various government agencies and to industrial organizations. Robert L. Hess Technical Director Project MICHIGAN 111

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM CONTENTS Preface........................... iii Lists of Figures and Tables....................... vi Abstract............................... 1 1. Introduction............................ 2 2. Sample Preparation...................... 2 3. Solid-Liquid Equilibrium...................... 3 3. 1. Differential Thermal Analysis Apparatus and Procedures 3 3. 2. Experimental Results from Differential Thermal Analysis 5 3. 3. The Phase Diagram 8 3. 4. Thermodynamic Characterization of the Liquidus Line 9 4. Crystal Structures........................ 9 4. 1. The CdTe (ca) Phase 12 4. 2. The CdIn2Te4 (3) Phase 12 4. 3. The Cd7In38Te64 (') Phase 14 4.4. The In2Te3 (6) Phase 14 4. 5. The In2Te3 (e) Phase 14 5. Solid-Solid Equilibria........................ 14 5. 1. Diffusion Couple 15 5. 2. The X-Ray Powder-Pattern Studies 15 5. 3. Photomicrograph Studies 15 6. Semiconductor Properties.. 18 6. 1. Preliminary Measurements 18 6. 2. Measurements on CdIn2Te4 19 7. Conclusion.................. 20 References............................ 21 Distribution List........................ 23

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM FIGURES 1. Schematic Diagram of Differential Thermal Analysis Equipment,... 4 2. Diagram of Differential Thermocouples and Sample Tubes... 4 3. Differential Thermal Analysis Curves for CdTe-In2Te3, Phase-Diagram Study..................... 6 4. Phase Diagram for CdTe-In2Te3 Binary System........... 8 5. Unit Cell Structure for CdIn2Te4.................. 13 6. Photomicrographs at 33. 3 Mol %oIn2Te3 in CdTe........... 15 7. Infrared Transmission for CdIn2Te4................ 20 TABLES I. Summary of DTA Results for CdTe-In2Te3 System........ 7 II. Tabulation of X-Ray Lines for Complex Compounds in CdTe-In2Te3 System.................... 10, 11 III. Properties of Compounds in CdTe-In2Te3 System......... 13 IV. Summary of X-Ray Studies Used to Define Phase Boundaries.... 16, 17 V. Energy Gaps of Compounds in CdTe-In2Te3 System........ 18 vi

WI ILLOW RUN LABORATORIES TECHNICAL MEMORANDUM Phase Diagram for the Binary System CdTe- In Te1 ABSTRACT The phase diagram for the binary system CdTe-In2Te3 has been obtained by correlating information from differential thermal analysis measurements, microscopic studies, diffusion couples, and X-ray powder patterns. In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melting point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. The first (f) is at 785~C and 50 mol% In2Te3; the second (y) is at about 7020C and 74 mol % In Te3; and the third (6') is at 6950C and about 83 mol % In Te. There is a large retrograde solubility of CdIn2Te4 in CdTe. The 6-phase transforms to an-c-phase at 6250C and 100% In2Te3. The addition of CdTe stabilizes the 6-phase, and it finally disappears to y + E in a eutectoid reaction at about 3600C and 83 mol % In2Te3. Some of the properties of the phases have been measured and are presented. There appear to be qualitatively significant monotonic relationships among the energy gap, the transition temperatures, and the compositions. 1This research was carried on at the Semiconductor Materials Research Laboratory, College of Engineering, The University of Michigan, Ann Arbor, Michigan. It was supported in part by Project MICHIGAN, and in part by grant NSF-G4127 from the National Science Foundation. Dr. David F. Edwards made the infrared measurements at Willow Run Laboratories. The authors would like to acknowledge the aid of many students who helped with the individual determinations. 1

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM 1 INTRODUCTION Since mixed crystals of binary, isomorphous, semiconductor compounds are formed from isoelectronic elements, the electrical properties appear to be monotonic functions between limits defined by the properties of the constituents. In some cases slight maxima or minima are observed, but these systems are exceptional. Since new ternary phases are formed by combining nonisomorphous binaries with nonisoelectronic elements, this functional variation of the electrical properties is not known. An additional degree of freedom should be present by virtue of the presence of the third element. With this freedom, it should be possible ultimately to improve the performance of many semiconductor devices, including those that are used as sensors in military electronic systems. A valid experimental determination of this functional relationship requires the preparation of pure, homogeneous test samples as a first step. Such samples cannot be prepared intelligently and reproducibly without a knowledge of the phase diagram of the system from which the ternary compounds are formed. This work was undertaken to ascertain the phase diagram of the system CdTe-In 2Te3 which produced a typical chalcopyritelike ternary compound, CdIn2Te4. It was obtained by correlating information from differential thermal analysis measurements, microsopic studies, X-ray powder patterns, and diffusion couples. Preliminary measurements on the physical properties of the five phases found in the system are also reported. This system is of interest since all compounds formed by mixing CdTe and In2Te3 are semiconductors. In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melting point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. At 7850C, the compound CdIn2Te4 is formed. This material has a tetragonal chalcopyritelike structure. At about 7020C and 74 mol % In2 Te3, a second peritectic forms which has a structure somewhat similar to the first peritectic. At 6950C and about 83 mol % In Te3, a third peritectic solidification creates a material which is isomorphous with In2Te3 in its zinc blende form. A large retrograde solubility of CdIn2Te4 in CdTe is apparent from the structures in the photomicrographs taken in the intermediate two-phase region. The 6-phase transforms to an E-phase at 6250C and 100 % In2Te3. The addition of CdTe stabilizes the 6-phase and it finally disappears to y + E in a eutectoid reaction at about 83 % In2Te3 between 350~C and 375~C. Some of the properties of these new phases have been measured. There appear to be qualitatively significant monotonic relationships 2

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM among the energy gap, the transition temperatures, and the compositions. The experimental work can be conveniently classified into five categories: the preparation of the compounds; the determinations of the solid-liquid equilibria; the determination of the structural properties of the various components in the system; the determination of the solidsolid equilibria; and the determination of the semiconducting properties of the various components in the system. 2 SAMPLE PREPARATION All compounds used in the sutdy were made by direct fusion from commercially available high purity elements. Indium of 99. 999+% purity was obtained from the Indium Corporation of America. Cadmium of 99. 99+% purity and tellurium of 99. 999+% purity were obtained from the American Smelting and Refining Company. Stoichiometric amounts of the elements were weighed into clear fused silica ampoules, evacuated to a pressure below 10 mm Hg, and sealed. The fusions were carried out over a period of several hours in such a way that the heat of reaction was evolved gradually, so as not to break the ampoules by any sudden increases in the vapor pressures. The content of each ampoule was homogenized by maintaining it above its liquidus temperature in an agitating furnace. After fusion each sample was removed from its original container, crushed, and transferred to a new fused silica tube containing a deep thermocouple well concentric with the tube axis. Each sample was annealed for at least 24 hours below the lowest transition temperature before the DTA (differential thermal analysis) measurements. 3 SOLID-LIQUID EQUILIBRIUM The solid-liquid equilibrium lines have been determined primarily from DTA measurements. In the following section the experimental apparatus and procedures are described first, and the experimental results next. The available information from the literature will be reported and combined with our results to synthesize a phase diagram for the system CdTe-In 2Te3. The liquidus line is examined thermodynamically. 3. 1. DIFFERENTIAL THERMAL ANALYSIS APPARNALYSISTUS APPARATUS AND PROCEDURES A schematic diagram of the DTA apparatus is shown in Figure 1. The power input to the 3

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM DTA furnace is controlled by means of an automatically programmed motor-driven autotransformer. The furnace is purged with dry nitrogen in order to prevent corrosion of the nickel sample holder, which is provided with three sample wells spaced at 1200 intervals. Two specimens may be measured at one time, the third well being occupied by the reference material. Each sample temperature is measured by means of a chromel-alumel thermocouple, the output of which is measured on a Leeds and Northrup precision potentiometer. The output of the differential thermocouple (Figure 2) is amplified and recorded with a Leeds and Northrup Speedomax recorder. The thermocouples were calibrated against standards of indium (1560C), lead (3270C), and silver (9610C) and found to agree within 10C. POWER SUPPLY Cu WIRE it + Ca TURN. FLO 22Ov I o-22ovl O-6 O, 8Nz I PROGRAMMED ASUREMENT SYSTEM l\=,_,,Ts.-Tr 1 tC L H2o DAMPLE TEMP. B IaN NICKEL FIGURE 1. SCHEMATIC DIAGRAM OF DIFFERENTIAL THERMAL ANALYSIS EQUIPMENT 5gm lOmmD. SAMPLSAMPLE REFERENCE, HOLDER NITROGEN M.P. 156 PURGE Ts TTr FIGURE 2.SCI DIAGRAM OF DIFFERENTIAL THERMOCOUPLES AND SAMPLE TUBES

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM The samples were heated and cooled inside the nickel block with a liquid indium standard, at a rate of 2. 50C/minute from room temperature to a maximum temperature well above that of the highest transition, and back to room temperature. Although the DTA sample tubes sometimes cracked at low temperatures as the sample contracted around the thermocouple well, they were not wet significantly by the sample and no apparent oxidation occurred. A continuous record was taken as a function of time for both the sample temperature and the differential emf, and the data were replotted to show the differential emf as a function of sample temperature. Each sample was subsequently reannealed and cooled before photomicrographs were taken and the X-ray determinations made. In some instances, X-ray samples were removed prior to the DTA runs. 3.2. EXPERIMENTAL RESULTS FROM DIFFERENTIAL THERMAL ANALYSIS More than 50 samples covering the composition range from pure CdTe to pure In2Te were prepared in this system, and representative results from differential thermal analysis measurements are shown in Figure 3. Differential emf is plotted against temperature for several different compositions. In the interpretation of the experimental DTA curves, the liquidus temperature on the heating curves was chosen as the point where the differential emf completed its last deviation. On the cooling cycle, considerable supercooling sometimes occurred, as indicated by a large initial differential emf which sometimes indicated an increase in the sample temperature. This effect was particularly noticeable in the high cadmium region, as is apparent in Figure 3. The liquidus temperature was taken as the point where the deviation in the differential emf was initiated, or attained its maximum value. The agreement between the two liquidus temperatures derived in this way was not always good. This ambiguity in interpreting the DTA results was particularly large over the range from 0 to 63 mol % In2Te3. The peritectic transformations agreed well on both heating and cooling. The solidus lines were obtained from the heating curves by choosing the point where the first deviation in the differential emf was initiated. The data are tabulated in Table I. In checking the terminal points for this diagram, the melting point for CdTe was found to be 1098 ~ 30C (Reference 1), which represents a considerable deviation from the widely reported value of 10450C (Reference 2). The variation can be attributed to the differences in purity of the tellurium which was available to Kobayashi in 1910 (mp 4370C), and that which is available today (mp 454 C), as well as to differences in experimental techniques. Lawson, 5

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM MO I 0. I 30 oi 785.' 20 -o`0 ------ 0 0 0 55 —-- ----- 63 1, 70 o 1 75 i__________________ 80 o 0.s. 85 o0r 90 0 15I. SAMPLESr. S ALED UNDER VACUU IN FU3ED "ILICA TUBES SAMPLES HEATED AND COOLED AT 2.30C/MIN. 95 o \ 0. SAMPLES MEASURED IN31DE NICKEL BLOCK. N LIQUID INDIUM USED AS STANDARD ~~~~~~~~~~0 2 t ~HEATING CURVES 0.... 667I COOLING CURVES 0. 100 I 0 - -- VOG 700 )00 000 "000 1100 1O0 TEMPERATURE -~C FIGURE 3. DIFFERENTIAL THERMAL ANALYSIS CURVES FOR CdTe-In Te PHASE-DIAGRAM STUDY 2 3 6

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM Nielsen, Putley, and Young (Reference 3) have recently reported the melting point of CdTe as 11060C, and deNobel has reported a melting point of 10900C (Reference 4). TABLE I. SUMMARY OF DTA RESULTS FOR CdTe-In2Te3 SYSTEM Sample In 2Te3 Heating Cooling Solidus Peritectic Temperature Code No. Liquidus Liquidus 1st 2nd 3rd (mol %) (oc) (oC) (oc) (Oc) (Oc) (oC) 354 0. 0 1098 1098 1098 - 333 5. 0 1075 1065 1045 - 324 12.5 1030 - 955 - - 332 20. 0 975 960 840 - 319 25.0 955 930 805 - 346 30.0 930 900 - 784 - 355 33.3 925 885 - 784 - - 345 37. 0 910 870 - 785 - 309 40. 0 885 865 - 785 - - 344 45.0 860 840 - 784 - - 307 50.0 840 825 - 783 - - 352 55. 0 820 805 784 725 - 308 60. 0 805 790 - 785 720 - 349 63. 0 805 783 - - 715 - 310 66.7 800 775 - - 715 - 350 70.0 785 775 - - 700 - 371 75.0 770 765 - - 704 696 367 77.5 760 755 - - 702 696 351 80. 0 755 750 - - 702 695 368 82.5 745 740 - - 700 696 356 85.0 740 735 - - 704 695 366 87.5 725 725 692 - 702 - 357 90.. 0 715 711 690 - 702 - 369 92.5 710 705 684 - - 695 348 95. 0 702 690 680 370 97.5 690 685 - - 303 100. 0 667 667 667 7

WILLOW RUN LABORATORIES TECHNI*CAL MEMORANDUM Other important transition points, at 7850C, 7020C, 6950C, and 6670C, can also be seen in Figure 3. Note also the transition in the pure In2Te at about 6250C. Hahn (Reference 5), Inuzuka and Sugaike (Reference 6), and Woolley, Pamplin, and Holmes (Reference 7) have characterized a structure of In2Te3 which forms from the zinc blende structure after long annealing, which would indicate the presence of a transition somewhere below the melting point. Gasson, Holmes, Parrott, and Penn (Reference 8) have reported a transition at 615 ~ 50C. Hahn et al. (Reference 9) have also investigated the crystal structures of the compounds formed in this system, and reported the existence of the CdIn2Te4 phase. 3.3. THE PHASE DIAGRAM With this data, supplemented by diffusion couples, photomicrographs, and X-ray studies on quenched samples, it is possible to hypothesize the broad outline of the phase diagram shown in Figure 4. Both the heating and cooling liquidus points are plotted, as discussed above. This diagram shows that cadmium telluride (CdTe = a) and indium telluride (In Te3 6) are congruently melting. In addition, there are three peritectic points, a eutectoid, and a o000c o o,110 o098C 900 0 -DO00~- oa + L LIQUID 800.- 7850C 30 l _+ L ~t 0 1o 3 00 70209o FIGURE 4. PHASE DIAGRAM FOR CdTe-InTe a / Cd Te InpTe3 heating; 0 from DTA on cooling; 0 from photomicrographs.

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM transformation in the In2Te3 structure, from 6 to E. The peritectics occur at about 50 mol % In2Te3 (CdIn2Te4 = 13) and 7850C, at about 74 mol% In2Te3 (CdIn6Te10 or Cd7In38Te64 = y) and 7020C, and at about 83 mol% In2Te3 (CdIn10Tel6 = 6') and 6950C. No congruently melting compounds form along this particular line in the ternary system cadmium-indium-tellurium. The 6-phase is stabilized by adding CdTe, but it finally disappears to y + e in an eutectoid reaction at about 83 mol % In2Te3 between 3500C and 3750C. 3.4. THERMODYNAMIC CHARACTERIZATION OF THE LIQUIDUS LINE The liquidus line comprises four separate and distinct segments: (a) from 0 to 63 mol % In2Te3; (b) from 63 to 93 mol % In Te; (c) from 93 to 95 mol %lo In2Te; and (d) from 95 to 100 mol % In2Te3. Prigogine and Defay (Reference 10) show that in general the liquidus curve is actually a composite of several separate relationships. In this particular case, four separate relationships would be required. The regions (c) and (d) are too short to yield to an intelligible thermodynamic analysis with the data available. The large solid solubility in region (a) makes thermodynamic analysis difficult since the solidus curve is not precisely defined. However, by assuming negligible solid solubility in the 3 phase, the region (b) can be approximated by an ideal solution through the Schroeder-vanLaar equation ln x3 =H 19, 400 070 T (1) where x = mol fraction 3 phase in 6 phase = 2(1 - y) y = mol fraction In Te3 = abscissa in Figure 4 AH = "apparent" latent heat of fusion of 13 phase = 38, 550 cal/gm mol R = gas constant = 1. 987 cal/gm mol OK T1 = "apparent" melting point of 1 phase = 10700K = 7970~C T = temperature, 0K, of liquidus line at composition x/ over region (b) defined above CRYSTAL STRUCTURES The differential thermal analysis runs gave erratic results below about 6000C and could not be relied on to clarify the solid-solid transformations which were found particularly at the high indium end of the diagram. X-ray powder-pattern studies, microscopic examinations, and diffusion couples were used. 9

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM TABLE II. TABULATION OF X-RAY LINES FOR COMPLEX COMPOUNDS IN CdTe-In2Te3 SYSTEM~ #810 #371 #303 50% In2Te3 (3)* 75% In2Te3 (y)* 100% In2Te3 (E)** N2 I 0 sin2 0 I 0 sin2 O I 0 sin2 0 3 10 12.58 0. 0474 10 12.62 0. 0480 10 12.69 0. 0482 3.25 2 13.05 0. 0507 1 13.81 0. 0565 4.0 1 14.43 0. 0621 1 14.61 0. 0638 1 14.59 0. 0630 4.25 1 15.34 0.0700 5. 2 16.29 0. 0786 2 16. 19 0. 0778 5.25 3 16.70 0. 0825 2 16.84 0. 0838 5.75 2 17.41 0.0895 6.0 2 17.85 0. 0939 1 17.96 0.0954 3 18.34 0.0991 6.25 1 18.64 0.1022 7.25 3 19.63 0. 1138 1 19.81 0.1147 4 18.85 0.1045 8 10 20.63 0. 1241 10 20.88 0. 1271 10 20.88 0. 1280 9 1 21.99 0.1402 1 22.07 0.1411 9.25 2 22.32 0. 1442 3 22.45 0. 1460 9.75 2 23.90 0. 1641 11 9 24.43 0. 1711 9 24.66 0. 1741 10 24.61 0. 1743 14 1 27.73 0.2165 15.25 3 29.07 0. 2366 2 29.35 0.2410 4 28.85 0.2328 16 4 29.86 0.2480 5 30.12 0.2521 3 30.61 0.2594 17 3 31.08 0.2666 1 31.28 0.2691 3 31.44 0.2721 18 1 31.86 0. 2786 2 32.40 0. 2871 19 8 32.86 0. 2945 8 33.03 0. 2972 6 33.27 0. 3006 21 1 34.80 0. 3257 2 34.06 0.3135 22 1 35.71 0.3406 23 1 36.79 0.3586 1 36.30 0.3505 23.25 1 36.45 0.3529 24 8 37.56 0.3716 9 37.91 0.3778 7 37.96 0.3782 25 2 38.65 0. 3891 25.25 2 38.93 0. 3948 1 38.98 0. 3953 26 2 39.60 0.4018 1 39.64 0.4077 27 5 40.21 0.4168 5 40.64 0.4231 4 40.57 0.4230 27.25 2 41.42 0.4376 29 3 42.46 0.4577 1 42.38 0.4542 29.25 4 42.20 0.4512 1 43.83 0.4793 *Heat treated at 500~C for 100 hours, water quenched. **100'% In2 Te3 was slowly cooled to room temperature. ~All measurements made from Cu-Ka radiation through nickel filter. 10

WI LOW RUN LABORATORIES TECHNICAL MEMORANDUM TABLE II. TABULATION OF X-RAY LINES FOR COMPLEX COMPOUNDS IN CdTe-In2Te3 SYSTEM (Continued) #810 #371 #303 50% In2Te3 (3) 75% In2Te3 (y)* 100%In2Te3 (E)*' N2 I e sin2 e I e sin2 U I 0 sin2 e 31 2 43.93 0.4813 32 4 44.62 0. 4943 5 45. 13 0. 5038 1 45.85 0. 5145 34 1 46.32 0.5230 35 5 47.26 0. 5394 6 47.73 0. 5482 4 47.78 0. 5486 37 1 48.55 0.5618 37.25 1 49.23 0. 5735 38.25 1 49.84 0.5841 39 39.25 1 50.99 0.6038 1 51.90 0.6193 40 6 52.22 0.6272 3 52.37 0.6270 40.25 4 51.66 0.6152 41.25 1 52.63 0.6315 43 3 54.50 0.6628 4 54. 17 0.6743 2 55.06 0.6719 45 3 56.31 0.6919 1 56.16 0.6894 45.25 2 58.45 0. 7262 2 56.95 0. 7029 47.25 2 59.24 0.7395 48 1 59.22 0.7381 1 59.89 0.7502 3 59.64 0.7443 49.25 3 60.36 0.7555 50.25 1 61. 14 0.7670 52 5 62.26 0.7834 3 62.71 0.7892 53 1 64.79 0.8189 53.25 1 64.58 0.8157 54.25 1 65.66 0.8302 55.25 1 67.95 0.8590 55.5 2 66.99 0.8473 56 6 67.80 0.8568 6 68.64 0.8710 57 3 68. 19 0. 8622 59 5 72.33 0. 9081 61 2 75.66 0. 9387 62 2 76.81 0. 9479 *Heat treated at 5000C for 100 hours, water quenched. **100% In2Te3 was slowly cooled to room temperature. ~All measurements made from Cu-Ka radiation through nickel filter. 11

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM In order to interpret the results of these studies, it was necessary first to characterize all the phases in the system which were known to exist as a result of the DTA measurements and the literature survey. All phases were carefully analyzed by X-ray powder techniques. The diffraction patterns of the i, y, and e compounds all contain the zinc blende lines characteristic of the a and 6 phases. However, the distribution of the additional weaker lines are distinctive, although it requires very careful measurements to separate them. The results of the powder-pattern analyses are shown in Table II. The sin 0 values were taken from the films, which were made in 57. 3-mm-diameter cameras with Cu-Ka radiation through a nickel filter to eliminate the Cu-K1 radiation. The X-ray film was covered with an aluminum foil to reduce spurious radiation effects which arise from scattering. The N values listed were calculated by assuming that the structures are tetragonal with c/a = 2. 00; hence 2 2 2 N =h +k + — (2) 4 The tabulated values of sin 0 were quite reproducible from sample to sample. However, more recent diagrams on a 114. 6-mm-diameter camera indicated poorer reproducibility; hence we are not certain as to the accuracy of the lines reported in Table II, but their precision was good. More careful structure studies are in progress and will be reported later. The structure studies in this system have been based solely on X-ray powder patterns and are quite difficult to interpret. It is almost impossible to distinguish the atom positions from X-ray intensity measurements alone. Since Cd, In, and Te have atomic numbers 48, 49, and 52, respectively, they have almost identical X-ray scattering factors. However, since all these structures seem to be derived from the basic zinc blende structure, we have adopted the assumption of Hahn et al, (Reference 9) that the tellurium atoms alone form a face-centered cubic lattice, with the metallic atoms disposed in the tetrahedral interstices. The results of the measurements on each phase are discussed below, and summarized in Table III. 4. 1. THE CdTe (a) PHASE The a-phase (CdTe) has a zinc blende structure with lattice constant a = 6. 488 ~ 0. 002 A. Zachariasen (Reference 11) reported that a = 6. 477 kX. 4. 2. THE CdIn2Te4 (13) PHASE The first peritectic compound (CdIn2Te4) has been characterized by Hahn et al. (Reference 9) as a tetragonal, chalcopyritelike structure with space group S4 or I4 (Figure 5). Our X-ray 12

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM TABLE III. PROPERTIES OF COMPOUNDS IN CdTe-In2Te3 SYSTEM Transition Phase Composition Temperature Structure Lattice Constants (~C) (A) ra CdTe 1098 Td F43m a = 6. 488 ~ 0. 002 1106 (3)* a = 6. 477 kX (11) 1090 (4) 1B CdIn Te 785 S I4 (9) a = 6. 235 ~ 0. 002 2 4 4 c = 12.47 ~ 0. 002 a = 6. 192 (9) c = 12. 38 (9) Cd7In38Te64 702 6' CdIn 10 16 695 Td F43m a = 6. 16 (9) 6 In Te667 Td F43m a = 6. 171 ~ 0. 002 a = 6. 146 (12) 2 In Te 625 Td F43m (6) a = 18.40 ~ 0.04 (6) 2 3 625 d Imm2 (7) P42/mnm (7) *Numbers in parentheses refer to "References" section, at the end of the text. FIGURE 5. UNIT CELL STRUCTURE FOR CdIn2Teq. Black = tellurium atoms; white = indium atoms; gray = cadmium atoms. 13

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM results for the 3-phase as tabulated in Table II agree with those reported by Hahn. We have accepted his structure designation without repeating the intensity calculations. We find a slight difference in lattice constants, with a = 6. 235 ~ 0. 002 A, and c = 12. 47 i~ 0. 002 A, whereas Hahn et al. (Reference 9) report that a = 6. 192 A, and c = 12. 38 A. 4.3. THE Cd7In38 Te64 (y) PHASE The second peritectic (Cd7In38Te64), or y-phase, also seems to be a chalcopyritelike structure very similar to the 13-phase. However, this phase has only about half as many powderpattern lines as the 3-phase, as indicated in Table II. The distances between the diffracting planes in the: and -y phases also seem to be substantially identical, so that it is extremely difficult to distinguish them from each other on the X-ray powder pictures in the region from 50 mol % to 75 mol % In2Te3. Hence it is not surprising that Hahn et al. (Reference 9) have not defined the existence of the y-phase, since their survey relied only on X-ray analyses and no samples were run between 66. 7 mol % In Te and 80 mol % In2Te3~ 4. 4. THE In2Te3 (6) PHASE The 6-phase extends from CdIn10Te16 to pure In2Te3, and shows again the zinc blende structure, with some metal positions randomly vacant. At the pure In Te3 side of the phase field we have found that a = 6. 171 ~ 0. 002 A whereas Hahn and Klinger (Reference 12) reported a = 6. 146 A. 4. 5. THE In2Te3 (e) PHASE The e phase apparently forms from pure In2Te3 in the 6 structure, by transformation in the solid state at about 6250C. Our line measurements are tabulated in Table II. Inuzuka and Sugaike (Reference 6) report the structure to be F43m with a = 18. 40 ~ 0. 04 A. Woolley and Pamplin (Reference 7), and Holmes (Reference 7) have also considered the structure of low-temperature modification of In2Te3. Holmes suggests a tetragonal structure of P4 /mcm or P42/mnm, comprising basically nine cubic unit cells of a fluorite lattice with about two-thirds of the sites vacant. Woolley and Pamplin (Reference 7), on the other hand, suggest an orthorhombic structure, Imm2, derived from the zinc blende configuration with selected vacancies. SOLID -SOLID EQUILIBRIA With the individual phases characterized, several additional studies were then conducted to ascertain the solid-solid equilibria boundaries. These studies comprised one diffusioncouple experiment, X-ray powder-pattern studies, and photomicrograph studies. 14

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM 5. 1. DIFFUSION COUPLE A diffusion couple was run at 6500C between CdIn 2Te4 and In2Te3, and only one intermediate constituent was found. It appeared that the intermediate phase was formed exclusively on the In2Te3 side of the interface, suggesting that the cadmium diffused through the structure at a much more rapid rate than the other constituents. 5.2. THE X-RAY POWDER-PATTERN STUDIES Four separate series of X-ray powder-pattern pictures were taken. Two series were taken at 2. 5% intervals over most of the range between 75 mol % and 100 mol % In2Te. Series I was quenched from 650~C and showed only -y and 6 phases. The 6-phase was pure above 82. 5 mol % In2Te3. Series II was quenched from 500~C and showed that the pure 6-phase region extended only from 82. 5 mol % to 92. 5 mol % In Te3. In order to ascertain the position of the eutectoid, Series III was run. Samples of 87.5 mol% In2Te3 were annealed at temperatures of 2000C, 2500C, 3000C, 3500C, 3750C, 4000C, 4260C, 5050C, and 6500C. It was observed from these measurements that, at 3500C and below, the X-ray lines are characteristic of a mixture containing both the y and e phases. At 3750C and above, the y-phase lines are replaced by 6-phase lines, and we conclude that the eutectoid is between 3500C and 3750C. Series IV comprises miscellaneous X-ray determinations which were run to corroborate the conclusions from the microscopic and differential thermal analysis experiments. The results of the X-ray phase studies are summarized in Table IV. 5.3 PHOTOMICROGRAPH STUDIES The retrograde solubility of CdIn Te in CdTe was established by annealing samples in the a and (ca + 3) range at 6000C and observing a Widmanstatten structure in microscopic examinations. A typical photomicrograph taken at 33. 3 mol % In2Te is shown in Figure 6. The pure 1 crystallites show up as a single phase material, whereas the a crystallites contain small platelets of precipitated 1 phase. The relative amount of the a phase observed in the photomicrographs decreased as the percentage of In2Te3 in the composition of the sample was increased towards the 50 mol % point. The solubility of In Te in FIGURE 6. PHOTOMICROGRAPHS 3 AT 33. 3 mol %- In2Te3 IN CdTe. Clear CdTe at the 785~C peritectic is more than 25 mol 3-phase region (CdInTe) and Widmanstatten structure in a-phase (CdTe). Magnification = 100X, 15

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM TABLE IV. SUMMARY OF X-RAY STUDIES USED TO DEFINE PHASE BOUNDARIES Sample No. In2Te3 Heat Treatment* Phases Present (%) (0c) Series I 371 75.0 650 AQ y 351 80.0 650 AQ 6 +368 82.5 650 AQ 6 356 85. 0 650 AQ 6 366 87.5 650 AQ 6 357 90.0 650 AQ 6 348 95.0 650 AQ 6 370 97.5 650 AQ 6 303 100.0 650 AQ 6 Series II 371 75.0 500 AQ -y 351 80.0 500 AQ Ty+6 368 82.5 500 AQ 6 356 85.0 500 AQ 6 815 87.5 500 AQ 6 357 90.0 500 AQ 6 369 92.5 500 AQ 6 348 95.0 500 AQ 6 +E 370 97.5 500 AQ 6 +e 303 100.0 500 AQ e Series III 817 87.5 200 AQ y +e 817 87.5 250 AQ y +E 817 87.5 300 AQ y + 817 87.5 350 AQ y +E 817 87.5 375 AQ 6 +E 817 87.5 400 AQ 6+e 817 87.5 426 AQ 6 815 87.5 505 AQ 6 366 87.5 650 A4 6 *AQ = Air quenched; FC = furnace cooled at 2. 5~C/minute; WQ = water quenched. 16

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM TABLE IV. SUMMARY OF X-RAY STUDIES USED TO DEFINE PHASE BOUNDARIES (Continued) Sample No. In2Te3 Heat Treatment"'- Phases Present (%) (~C) Series IV 805 0.0 600 FC c 333 5.0 600 FC c 332 20.0 600 FC +13 319 25.0 600 FC c +13 346 30.0 600 FC c + 355 33.3 600 FC c +13 330 37.0 600 FC a + 340 45.0 600 FC 1 + a 810 50.0 600 FC 1 810 50.0 650 AQ 1 810 50.0 660 WQ 13 308 60.0 600 FC 3 308 60.0 695 WQ 1 + y 349 63.0 600 FC 1 + y 809 63.0 770 WQ 1+~ 310 66.7 600 FC 3+T 350 70.0 600 FC 13+Y 350 70.0 695 WQ 13+ 318 75.0 600 FC y 318 75.0 695 WQ y 811 80.0 570 AQ y+6 811 80.0 684 AQ 6 356 85.0 600 FC 6 357 90.0 525 AQ 6 357 90.0 600 FC 6 357 90.0 684 AQ 6 303 100.0 665 AQ 6 808 100.0 665 AQ 6 303 100.0 500 AQ e 808 100.0 500 AQ E *AQ = Air quenched; FC = furnace cooled at 2. 50C/minute; WQ = water quenched. 17

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM 6 SEMICONDUCTOR PROPER TIES All these compounds should be semiconductors according to the rules promulgated by Mooser and Pearson (Reference 13), as long as there are neither tellurium-to-tellurium bonds nor intermetallic bonds between indium and/or cadmium. These restrictions are fulfilled in the postulated structures. 6. 1. PRELIMINARY MEASUREMENTS A series of samples was prepared for infrared transmission measurements, and the preliminary results of optical energy gaps in electron volts, shown in Table V, were found. Since reasonably high transmissions of the order of 30% to 40% were obtained in these samples, the indication is that they were quite pure. The gap values were obtained by measuring the infrared transmission. The region of steepest slope on the cutoff edge of the short wavelength was projected to zero transmission. TABLE V. ENERGY GAPS OF COMPOUNDS IN CdTe-In2Te3 SYSTEM Phase Composition Energy Gap Authors' Results Other Reported Results (ev) (ev) (Reference) ua CdTe 1.32 1.42 (14) 1.51 (15) 1.51 (4) 1. 55 (3) 2 CdIn2Te4 1.077 0.9 (16) Cd7In38Te64 1.06 6 In Te -- 2.4 (15) 21.04 (8) I2 Te3 1.04 0. 93 (15) 1. 12 (8) 18

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM In order to evaluate their significance, the results must first be compared with the measurements reported in the literature. The magnitude of the energy gap in CdTe at room temperature has been reported by Bube (Reference 14) to be 1. 42 ev. Lawson, Nielsen, Putley and Young (Reference 3) report an infrared transmission edge of 0. 8,u, or 1. 55 ev. DeNobel (Reference 4) reports a gap of 1. 51 ev using both infrared transmission and photo emf measurements. Appel and Lautz (Reference 15) measured differences in the activation energies of CdTe and In2Te3 by measuring resistivity vs. temperature from room temperature to their melting points. They report an average gap of 1. 51 ev for CdTe. Busch, Mooser and Pearson (Reference 16) report a gap of 0. 9 ev for CdIn2Te4 using resistivity vs. temperature measurements. Appel and Lautz (Reference 15) report that the low-temperature form of In2Te3 shows an average gap value of 0. 93 ev, whereas the high-temperature average value is 2. 4 ev. Of three samples measured, one never showed the high-temperature form; of the other two, one showed the transition at 2500C and the other at 600 0C, which is in moderately good agreement with the transition at 620~ 50C reported in Section 4. 5. Gasson, Holmes, Parrott, and Penn (Reference 8) have reported a gap of 1. 04 ev for the 6 phase and 1. 12 ev for the e phase of In2Te3. In view of the evidence, we feel that our preliminary gap values are qualitatively significant. There appear to be monotonic relationships among the energy gap, the transition temperatures, and the compositions of the compounds in this system. Although our energy-gap measurements are only approximate, and the agreement with the literature is poor in many instances, the internal consistency of the data is qualitatively significant. 6. 2. MEASUREMENTS ON CdIn Te4 More careful infrared transmission measurements were made on two samples from a particular ingot of CdIn2Te4 (cadmium indium telluride), which was felt to be better in quality than the other materials, and the results are shown in Figure 7. The transmission was measured at room temperature by an in-the-beam, out-of-the-beam technique on samples of thicknesses 0. 121 mm and 0. 533 mm at the indicated points. The energy gap was taken as the intersection of the sharp band edge with the abscissa, corresponding to AE300oK = 1. 077 ev. The refractive index is 3. 08 in the region of the band edge and decreases to 2. 83 at 2 u; it then decreases continuously to 2. 72 at 14. 5,. The index of refraction was calculated for the region between 7. 5, and 14. 5 p from the interference fringes produced by multiple internal reflections. Over the region from 1. 1 pu to 8. 0,u, it was calculated from essentially reflection measurements, with good agreement in the overlap region. The drop in transmission at long wavelengths can probably be attributed to free carrier absorption. 19

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM 80 REFRACTIVE n370....0n = 3.01.... 20. 7 5m 2 6,o I: 1 2 3 4 5 6 7 8 9 I 0 11 12 13 14 15 WAVELENGTH (I) FIGURE 7. INFRARED TRANSMISSION FOR CdIn2Te4. CdIn2Te4, No. 1004; AE3000K = 1. 077 ev; P3000K = 292cm. CONCLUSION It seems apparent that the problems which must be defined and solved before a large number of ternary compounds can be investigated intelligently are even greater than we thought a year ago. This is particularly true for the types of compounds with which we have been working. However, we feel that the potential flexibility in optimizing the semiconductor properties for many applications by using ternary compounds makes continued efforts in this direction desirable and necessary, and that ultimate results will be significant. A. M. G. D. 20

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM REFERENCES 1. D. R. Mason and B. M. Kulwicki, The Phase Diagram for the Binary System Cadmium-Tellurium, Report Number 2900-139-R, Willow Run Laboratories, The University of Michigan, Ann Arbor, Mich. In preparation. 2. M. Kobayashi, "Uber die Legierungen des Tellurs mit Cadmium and Zinn," Z. anorg, u. allgem. Chem., 1911, Vol. 69, pp. 1-9. 3. W. D. Lawson, S. Nielsen, E. H. Putley, A. S. Young, "Preparation and Properties of HgTe and Mixed Crystals of HgTe and CdTe, " J. Phys. Chem. Solids, 1959, Vol. 9, pp. 325-329. 4. D. deNobel, "Phase Equilibria and Semiconducting Properties of Cadmium Telluride," Phillips Res. Repts., 1959, Vol. 14, pp. 361-399; cf. D. deNobel, Phase Equilibria and Semiconducting Properties of Cadmium Telluride, Thesis, University of Leiden, May 1958. 5. H. Hahn, "Zur Struktur der Galliumchalkogenide", Angew. Chem., 1952, Vol. 64, p. 203. 6. H. Inuzuka and S. Sugaike, "On In2Te3, Its Preparation and Lattice Constant, " Proc. Japan Acad., 1954, Vol. 30, pp. 383-386. 7. J. C. Woolley, B. R. Pamplin, P. J. Holmes, "The Ordered Crystal Structure of In2Te3, " J. of Less-Common Metals, Vol. 1, p. 360-376, 1959. 8. D. Gasson, P. Holmes, J. Parrott, A. Penn, "In2Te3 and Its Alloys with InAss, " presented before the Electrochemical Society, Columbus, Ohio, October 22, 1959, replacing paper No. 105. 9. H. Hahn, G. Frank, W. Klinger, A. D. Storger, G. Storger, "On the Ternary Chalcopyrites of Aluminum, Gallium, and Indium with Zinc, Cadmium, and Mercury," Z. anorg. u. allgem. Chem., 1955, Vol. 279, pp. 241-270. 10. I. Prigogine and R. Defay, Chemical Thermodynamics, Longmans, Green & Company, New York, N.Y., p. 379. 11. W. Zachariasen, "Uber die Kristallstruktur der Telluride von Beryllium, Zink, Cadmium und Quecksilber, " Z. physik Chem., 1926, Vol. 124, pp. 277-284. 12. H. Hahn and W. Klinger, "Uber die Kristallstrukturen des In2S3 und In2Te3, " Z. anorg. u. allgem, Chem., 1949, Vol. 260, pp. 97-109. 13. E. Mooser and W. B. Pearson, "The Chemical Bond in Semiconductors, " J. Electronics, 1956, Vol. 1, pp. 629-643. 14. R. H. Bube, "Photoconductivity of the Sulfide, Selenide and Telluride of Zinc or Cadmium," Proc. I. R. E., 1955, Vol. 43, pp. 1836-1850. 21

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM 15. J. Appel and G. Lautz, "Uber Einige Elektrische Eigenschaften der Halbleitenden Tellurverbindungen In2Te3, CdTe und Ag2Te, " Physica, 1954, Vol. 20, pp. 1110-1114. 16. G. Busch, E. Mooser, W. B. Pearson, "New Semiconducting Compounds with Diamond-Like Structures, " Helv. Phys. Acta, 1956, Vol. 29, pp. 192-193. 22

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WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM DISTRIBUTION LIST 5 1 April 1960- Effective Date Copy No. Addressee Copy No. Addressee 108 The U. S. Army Aviation HRU 115 Director, Electronic Defense Group P. O. Box 428, Fort Rucker, Alabama U of M Research Institute The University of Michigan Ann Arbor, Michigan 109-110 Visibility Laboratory, Scripps Institution ATTN: Dr. H. W. Ferris of Oceanography University of California 116-118 Assistant Commandant San Diego 52, California U. S. Army Air Defense School Fort Bliss, Texas 111-113 Bureau of Aeronautics 119 U. S. Continental Army Command Liaison Department of the Navy, Washington 25, D. C. Officer ATTN: RAAV-43 Project MICHIGAN, Willow Run Laboratories Ypsilanti, Michigan 114 Office of Naval Research 120 Commanding Officer Department of the Navy U. S. Army Liaison Group 17th & Constitution Ave., N. W. Project MICHIGAN, Willow Run Washington 25, D. C. Laboratories ATTN: Code 461 Ypsilanti, Michigan 25

AD Div. 4/4 UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties Lars Tbomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science (Memo no. 2900-80-R) Foundation (Memo no. 2900-80-R) Foundation (Contract DA-36-039 SC-78801} Unclassified memorandum III. Thomassen, Lars; (Contract DA-36-039 SC-78801) Unclassified memorandum III. Thomassen, Lars; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Mason, DonaldMaoDnl The phase diagram for the binary system CdTe-In2Te3 has been Mason, Donald 2 ~~~~IV. U. S. Army Signal Corps IV U.SAryig IV. U. S. Army Signal CorpsThe phase diagram for the binary system CdTe-In2Te3 has been obtained by correlating information from differential thermal anal- V. Contract DA-36-039 obtained by correlating information from differential thermal anal-. U.tS. Ar S a p Contract DA-36-039 ~~~~~~~~~~~~~~~~~~V. Contract DA-36-039 ysis measurements, microscopic studies, diffusion couples, and SC-78801 ysis measurements, microscopic studies, diffusion couples, and SC-781 X-ray powder patterns. X-ray powder patterns. In establishing the terminal points for this diagram, the melting In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melt- point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melting point of 1098 ~ 30C was indicated. ing point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. The In going across the diagram, three peritectics are apparent. The first (/} is at 7850C and 50 mol % In2Te3; the second (Y) at about first (f} is at 7850C and 50 mol % In2Te3; the second (TY at about 7020C and 74 mol %In2Te3; and the third (6'( is at 6950C and 7020C and 74 mol % In2Te3; and the third (6' ( is at 6950C and about 83 mol % In2Te3. There is a large retrograde solubility of about 83 mol % In2Te3. There is a large retrograde solubility of CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services CdIn2Te4 in CdTe. The 6-phase transforms to an E-phase at Armed Services 6250C and 100%In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency 6250C and l00tIn2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency (over UNCLASSIFIED (over UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED Willow Run LaB~ratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. H. Title: National Science MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science (Memo no. 2900-80-R( Foundation (Memo no. 2900-80-R( Foundation (Contract DA-36-039 SC-78801} Unclassified memorandum III. Thomassen, Lars; (Contract DA-36-039 SC-78801} Unclassified memorandum III. Thomassen, Lars; The phase diagram for the binary system CdTe-In Te3 has been Mason, Donald The phase diagram for the binary system has been Mason, Donald 2 IV. U. S. Army Signal Corps 2 IV. U. S. Army Signa obtained by correlating information from differential thermal anal- V. obtained by correlating information from differential thermal analV.Contract DA-36-039 V. Contract DA-36-039 ysis measurements, microscopic studies, diffusion couples, and SC-78801 ysis measurements, microscopic studies, diffusion couples, and ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~SC-80 S-78801 X-ray powder patterns. X-ray powder patterns. In establishing the terminal points for this diagram, the melting In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melt- point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melting point of 1098 ~ 30C was indicated. ing point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. The In going across the diagram, three peritectics are apparent. The first (0} is at 7850C and 50 mol % In2Te3; the second (T( at about first (P} is at 7850C and 50 mol % In2Te3; the second ('Y at about 7020C and 74 mol % In2Te3; and the third (6'( is at 6950C and 702~C and 74 mol %In2Te3; and the third (6'( is at 6950C and about 83 mol % In2Te3. There is a large retrograde solubility of about 83 mol % In2Te3. There is a large retrograde solubility of CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services 6250C and 100l In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency 6250C and 100lt In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency (over UNCLASSIFIED (over UNCLASSIFIED

AD UNCLASSIFIED AD UNCLASSIFIED and it finally disappears to'y + e in a eutectoid reaction at about UNITERMS and it finally disappears to y + e in a eutectoid reaction at about UNITERMS 3600C and 83 mol JoIn2Te3. Differential thermal analysis 3600C and 83 mol %In2Te3. Differential thermal analysis Some of the properties of the phases have been measured and are Diffusion couples Some of the properties of the phases have been measured and are Diffusion couples presented. There appear to be qualitatively significant monotonic X-ray powder patterns presented. There appear to be qualitatively significant monotonic X-ray powder patterns relationships among the energy gap, the transition temperatures, Phase diagram relationships among the energy gap, the transition temperatures, Phase diagram and the compositions. Cadmium telluride and the compositions. Cadmium telluride Indium telluride Indium telluride Semiconductor Semiconductor Ternary compounds Ternary compounds UNCLASSIFIED UNCLASSIFIED AD UNCLASSIFIED AD UNCLASSIFIED and it finally disappears to T' + E in a eutectoid reaction at about UNITERMS and it finally disappears to' + E in a eutectoid reaction at about UNITERMS 3600C and 83 mol %In2Te3. Differential thermal analysis 360C and 83 mol %In2Te3. Differential thermal analysis Some of the properties of the phases have been measured and are Diffusion couples Some of the properties of the phases have been measured and are Diffusion couples presented. There appear to be qualitatively significant monotonic X-ray powder patterns presented. There appear to be qualitatively significant monotonic X-ray powder patterns relationships among the energy gap, the transition temperatures, Phase diagram relationships among the energy gap, the transition temperatures, Phase diagram and the compositions. Cadmium telluride and the compositions. Cadmium telluride Indium telluride Indium telluride Semiconductor Semiconductor Ternary compounds Ternary compounds UNCLASSIFIED UNCLASSIFIED

AD Div. 4/4 UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science (Memo no. 2900-80-R) Foundation (Memo no. 2900-80-R) Foundation (Contract DA-36-039 SC-78801) Unclassified memorandum III. Thomassen, Lars; (Contract DA-36-039 SC-78801) Unclassified memorandum III. Thomassen, Lars; Mason, Donald Mason, Donald The phase diagram for the binary system CdTe-In2Te3 has been Mason, Donald C The phase diagram for the binary system CdTe-In Te3 has been Mason, Donald 2 ~~~~IV. U. S. Army Signal Corps2IV U.SAryig obtained by correlating information from differential thermal anal- V. Contract DA-36-039 obtained by correlating information from differential thermal anal- V U. S Army Sgna Corps Y.Contract DA-36-039 V. Contract DA-36-039 ysis measurements, microscopic studies, diffusion couples, and SC78801 ysis measurements, microscopic studies, diffusion couples, and SC-78801 SC-78801 SC -78811 X-ray powder patterns. X-ray powder patterns. In establishing the terminal points for this diagram, the melting In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~ 1~C. For CdTe, a melt- point for In2Te3 was found to be 667 ~ 1~C. For CdTe, a melting point of 1098 ~ 30C was indicated. ing point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. The In going across the diagram, three peritectics are apparent. The first (X) is at 785~C and 50 mol % In2Te3; the second (?) at about first (X) is at 785~C and 50 mol % In2Te3; the second (T) at about 702~C and 74 mol %In2Te3; and the third (6') is at 695~0C and 702~C and 74 mol %In2Te3; and the third (6') is at 695~0C and about 83 mol % In2Te3. There is a large retrograde solubility of about 83 mol % In2Te3. There is a large retrograde solubility of CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services 625~C and 100% In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency 625~C and 100% In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency (over UNCLASSIFIED (over UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED AD Div. 4/4 UNCLASSIFIED Willow Run Labratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Semiconductors-Physical PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties PHASE DIAGRAM FOR THE BINARY SYSTEM CdTe-In2Te3 by Properties Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN Lars Thomassen and Donald Mason. Memorandum of Project I. Title: Project MICHIGAN MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science MICHIGAN. Apr 60. 22 p. incl. illus. tables, 16 refs. II. Title: National Science (Memo no. 2900-80-R) Foundation (Memo no. 2900-80-R) Foundation (Contract DA-36-039 SC-78801) Unclassified memorandum III. Thomassen, Lars; (Contract DA-36-039 SC-78801) Unclassified memorandum III. Thomassen, Lars; Mason, Donald Mason, Donald The phase diagram for the binary system CdTe-In2Te3 has been IV. U. S. Army Signal C The phase diagram for the binary system CdTe-In2Te3 has been nal obtained by correlating information from differential thermal anal- V. Contract DA-36-039 obtained by correlating information from differential thermal anal- V Contract DA-36-S ysis measurements, microscopic studies, diffusion couples, and SC-781 ysis measurements, microscopic studies, diffusion couples, and X-ray powder patterns. X-ray powder patterns. In establishing the terminal points for this diagram, the melting In establishing the terminal points for this diagram, the melting point for In2Te3 was found to be 667 ~f 10C. For CdTe, a melt- point for In2Te3 was found to be 667 ~ 10C. For CdTe, a melting point of 1098 ~ 30C was indicated. ing point of 1098 ~ 30C was indicated. In going across the diagram, three peritectics are apparent. The In going across the diagram, three peritectics are apparent. The first (,B) is at 7850C and 50 mol %6 In2Te3; the second (T) at about first (11) is at 7850C and 50 mol % In2Te3; the second (y) at about 7020C and 74 mol %In2Te3; and the third (6') is at 6950C and 7020C and 74 mol %In2Te3; and the third (6') is at 6950C and about 83 mol % In2Te3. There is a large retrograde solubility of about 83 mol % In2Te3. There is a large retrograde solubility of CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services CdIn2Te4 in CdTe. The 6-phase transforms to an e-phase at Armed Services 6250C and l00%In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency 6250C and 100% In2Te3. The addition of CdTe stabilizes the 6-phase Technical Information Agency (over UNCLASSIFIED (over UNCLASSIFIED i n g ~ ~ ~ pon+f19 o a niae.igpito 08~3cwsidctd

AD UNCLASSIFIED AD UNCLASSIFIED and it finally disappears to y + e in a eutectoid reaction at about UNITERMS and it finally disappears to y + e in a eutectoid reaction at about UNITERMS 3600C and 83 mol %In2Te3. Differential thermal analysis 360C and 83 mol %In2Te3. Differential thermal analysis Some of the properties of the phases have been measured and are Diffusion couples Some of the properties of the phases have been measured and are Diffusion couples presented. There appear to be qualitatively significant monotonic X-ray powder patterns presented. There appear to be qualitatively significant monotonic X-ray powder patterns relationships among the energy gap, the transition temperatures, Phase diagram relationships among the energy gap, the transition temperatures, Phase diagram and the compositions. Cadmium telluride and the compositions. Cadmium telluride Indium telluride Indium telluride Semiconductor Semiconductor Ternary compounds Ternary compounds (D~z UNCLASSIFIED UNCLASSIFIED AD UNCLASSIFIED AD UNCLASSIFIED and it finally disappears to y + e in a eutectoid reaction at about UNITERMS and it finally disappears to, + ~ in a eutectoid reaction at about UNITERMS 3600C and 83 mol %In2Te3. Differential thermal analysis 3600C and 83 mol oIn2Te3. Differential thermal analysis Some of the properties of the phases have been measured and are Diffusion couples Some of the properties of the phases have been measured and are Diffusion couples presented. There appear to be qualitatively significant monotonic X-ray powder patterns presented. There appear to be qualitatively significant monotonic X-ray powder patterns relationships among the energy gap, the transition temperatures, Phase diagram relationships among the energy gap, the transition temperatures, Phase diagram and the compositions. Cadmium telluride and the compositions. Cadmium telluride Indium telluride Indium telluride Semiconductor Semiconductor Ternary compounds Ternary compounds UNCLASSIFIED UNCLASSIFIED