2900-197-R Memorandum of Project MICHIGAN EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND UNSTRAINED GERMANIUM DAVID F. ~ARDS VITO J. LAZAZZERA August 1960 SOLID -STATE PHYSICS LABORATORY T H E U N I V E'R S I T Y O F M I C H I G A N Ann Arbor, Michigan

DISTRIBUTION OF REPORTS 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 Willow Run Laboratories through The University of Michigan Research Institute.

WI LLOW 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 Willow Run Laboratories as part of The University of Michigan's service to various government agencies and to industrial organizations. Robert L. Hess Technical Director Project MICHIGAN 111

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND UNSTRAINED GERMANIUM' ABSTRACT Measurements have been made of the direct-transition magneto-optical effect in strained and unstrained germanium at 770K. The results indicate that the absorption peaks correspond to transitions to exciton levels associated with each Landau level in qualitative agreement with the theoretical calculations of Loudon (Reference 12) and of Howard and Hasegawa (Reference 13). INTRODUCTION As part of its program in basic research, Project MICHIGAN is carrying out experimental and theoretical investigations on the optical properties of semiconducting materials. Included in such materials is the monatomic semiconductor germanium, the subject of this memorandum. The direct-transition exciton and magneto-optical effect in germanium have been investigated in several recent experiments (References 1 and 2). The samples used were glued to a backing, usually of glass. However, it was subsequently pointed out by Macfarlane, MacLean, Quarrington, and Roberts (Reference 3, hereinafter referred to as MMQR) that samples mounted in this way become strained when cooled because of the difference in contraction of the sample and the backing. This group made transmission measurements without a magnetic field at 770K on the same germanium sample, first mounted free of any backing, and then glued to a glass substrate. They observed for the backed sample that the exciton absorption, Ex, shifted to'The authors wish to acknowledge their indebtedness to Dr. F. Blatt, Dr. R. R. Goodman, and Dr. G. Weinreich for their helpful discussions and advice, Dr. R. W. Terhune, Dr. C. W. Peters, and Mr. P. D. Maker for their assistance with the instrumentation, and G. Weinreich of the Bell Telephone Laboratories, Dr. R. Petritz of the Texas Instruments Incorporated, and Dr. W. C. Dunlap of Raytheon Manufacturing Company for supplying the intrinsic germanium crystals. 1

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM higher energies and that a second absorption appeared at an energy greater than E. They concluded that backing the samples on glass produced a compressional strain which distorted the energy band structure. As a further check of this theory, fused silica was used as the backing material to produce a tension on the sample when cooled. The result was a shift of Ex towards lower energy as expected. Edwards and Lazazzera (Reference 4) have also reported transmission measurements without a magnetic field for free-mounted germanium at 770K with approximately the same results as found by MMQR. The effect of the strain on the energy band structure has been examined by Kleiner and Roth (Reference 5) to obtain information about the deformation potential for the band edges. They concluded that the backing produces a shear strain that splits the valence band into two edges and also increases the energy gap. For the backed samples they associate an exciton level with each valence band edge and thus explain the second absorption. The shift in E is associated with the increased energy gap. These investigations make it clear that a sample must be mounted strain-free for an experiment to represent accurately the intrinsic characteristics of the specimen and not some property of the environment. The problem of a strain-free sample will arise, however, only for the case of the direct-transition magneto-optical effect. Here the samples must be thin (about 5 microns) for the effect to be observed. For the indirect transition, since the samples are several millimeters thick and self-supporting, the question of strain will not arise. The purpose of this paper is to report the results of direct-transition magneto-opticaleffect measurements on strained and unstrained germanium samples at 770K. An interpretation of these data is made in terms of transitions to exciton levels associated with each Landau level. The instrumentation and experimental technique are briefly described in Section 2. In Sections 3 and 4 are given the experimental results and analysis for the unstrained and strained specimens, respectively. 2 EXPERIMENTAL TECHNIQUE The germanium samples were made from either [ 100] or [ 110] wafers cut from intrinsic single crystals. The thin specimens were made by careful grinding and polishing techniques, and a special attempt was made to minimize the adverse surface effects of the grinding. Each wafer was cut to a square of about 2 cm on a side and a thickness of about 1 mm. The trimmings 2

WI LLOW RUN LABORATORIES TECHNICAL MEMORAN DUM were then used as material to help maintain parallel surfaces and were termed blocking material. The 2-cm square was glued at the center of a 3-inch-diameter optical flat with an acetone-soluble thermosetting glue. The trimmings were glued adjacent to this piece in approximately the same position as before they were cut off. In addition, three or four blocks of the same thickness were glued equally spaced at the edge of the flat. To help insure parallel surfaces these eight or nine pieces were glued at the same time using a thin layer of glue and held under pressure until the glue hardened. The first surface was then ground lightly, using 3200-grit carborundum on an optical flat to remove any saw marks. A scratch-free, highly reflecting surface was then obtained by polishing with Linde As on a moist Metcloth4 stretched over an optical flat. About 25 microns of material were removed by the polishing to reduce any layer damaged by the grinding. The resulting surface was optically flat to less than a fringe over approximately the center 90% of the sample. For this first surface, no attempt was made to reduce the thickness of the germanium wafer. The wafer and blocks were then removed, either by gently heating, or by dissolving the glue in a solvent; and each piece was turned over and glued with the polished surface towards the optical flat. Sometimes a section of a microscope slide can be used-between the germanium pieces and the flat. The thickness of the wafer was then reduced to about 100 microns, using 400- or 600-grit carborundum. Periodic checks were made to insure that the wafer surfaces remained parallel. The wafer thickness was next reduced to about 25 to 30 microns using 3200 grit. The final 20 to 25 microns were removed using the Linde A polishing compound on Metcloth as before. Once the second surface has been polished the sample thickness can be checked from the interference fringes produced by multiple internal reflections in the transparent spectral region of the germanium. By careful polishing and frequent checking for parallel surfaces, fringes usually can be obtained for samples about 15 to 20 microns thick. The polishing was continued until the samples were about 5 microns thick. The wafer was then masked and cut, using a dental dust blast, into samples about 4 mm x 12 mm, along definite crystallographic directions. The samples were floated from the microscope slides by dissolving the glue in warm dichlorethylene. The crucial part of the direct-transition measurements was obtaining a sample that is strain-free at all temperatures. To help insure this the samples were mounted free from any backing in the holders of the type shown in Figure 1. The samples were placed between two 2NU-C-70, Hugh Courtright & Co., 7600 Greenwood Ave., Chicago 19, Ill. 3Linde A, Linde Company, Div. of Union Carbide Corp., New York, N. Y. 4Metcloth, Buehler, Ltd., Evanston, Ill. 3

WI LLOW RUN LABORATORIES TECHNICAL MEMORAN DUM microscope cover-glass slides and this sandwich was then slipped under the spring clips of the sample holder, as shown at the bottom of Figure 1. This arrangement permitted easy handling of the delicate samples and also permitted the free movement of the sample with respect to the cover glass when the holder was cooled. To insure that the sample was at the temperatures of the coolant, the entire holder, with sample in place, was immersed in the coolant. The sample end of the metal dewar (Reference 6) used for these measurements is shown in Figure 2. The nose piece is a Kovar metal-to-glass seal with the infrared beam passing through the glass. The tips of the pole pieces are part of the Dewar wall and magnetic fields up to 25 kilogauss are possible. MICROSCOPE COVER GLASS GERMANIUM HARD COPPER SLIDES SAMPLE SPRING WINDOW BRASS SAMPLE HOLDER FIGURE 1. SAMPLE HOLDER FOR FREE MOUNTED SAMPLES A high-resolution Fastie-Ebert grating spectrometer (References 7 and 8) with 3-meter focal-length optics, single pass, and a 127 x 203-mm (300 lines/mm) Bausch and Lomb grating operated in second order was used for these measurements. The detector was an Eastman lead sulfide detector cooled to 77~K. The entire optical path was evacuated to less than 50microns pressure with the exception of a short distance between the source and entrance to the evacuated spectrometer tank. This path was filled with dry nitrogen. The purpose of the 4

W I LLOW RU N LABORATORIES TEC H NICAL MEMORAN DU M evacuation and dry nitrogen was to remove all water vapor and CO2 from the optical path. A combination of an ADP (ammonium dihydrogen phosphate) crystal and a coated silicon crystal were used in the fore optics to remove the unwanted orders of radiation from the incoming beam. A Polaroid type-HR polarizer was also used in the fore optics for the polarized-light experiments. The sample was placed in the aft optics to avoid possible heating by the source. The resolving power of the instrument was not used to its fullest because of the broad nature of the absorption lines. For a resolving power of about 13, 000 the spectral slit width was about 1/15 the width of the narrowest line and gave a signal-to-noise ratio of about 100 with the sample in the beam. COPPER LIQUID HELIUM RADIATION SHIELD CONTAINER KOVAR SEAL M MAGNET x ~<;POLE TIPS PYREX FLUORITE WINDOW NOSE PIECE FIGURE 2. SAMPLE END OF LIQUID HELIUM METAL DEWAR SHOWING GLASS NOSEPIECE AND MAGNET POLE TIPS 5

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM 3 UNSTRAINED SAMPLE In our laboratory we have repeated the zero-field exciton transmission measurements of MMQR at 770K and the results for an unstrained sample are shown as curve TI-91, Figure 3. The exciton absorption line, Ex = 0. 88171 ~ 0. 00002 ev, represents the excitation of an electron from the valence band to the ground state of the direct transition exciton. The spectral -5 slit width for this measurement was 7 x 10 ev. For comparison, curve RRE-2 is the data of MMQR for a free-mounted sample at 770K. They give the position of the exciton as E = 0. 8820 ~ 0. 0001 ev. It should be noted for both curves that there is just the single absorption, Ex, followed by the monotonically decreasing transmission; no other absorptions are present.6 Elliott (Reference 9) has investigated theoretically the direct transition between spherical energy bands including the coulombic effect between the hole and electron. He showed that one should expect a sharp absorption peak for the exciton followed by a region of continuous absorption beginning at the energy gap, Eo, of the form x e sinh x where (E - Ex 1/2 x =K hv- E (1) By fitting the experimental data of Figure 3 with the theoretical curve, Equation 1, the direct transition energy gap, Eo, can be evaluated. MMQR have done this and find Eo = 0. 8832 ~ 0. 0001 ev. For sample TI-91 the direct transition energy gap was estimated to be Eo = 0. 8834 + 0. 0001 ev. With the application of a magnetic field the continuous absorption for hv > E becomes a series of lines or oscillations, and is called the magneto-absorption effect. The results of magneto-absorption measurements on the unstrained sample, TI-91 are shown in Figure 4. Here is plotted the energy of each absorption for various values of applied magnetic field. From Figure 4 several points should be noted. First, for zero field only the single absorption, Ex, is observed as was shown in Figure 3. Second, the lowest absorption behaves quadratically 6For sample RRE-2 the deviation in the region of 0. 8855 ev might be due to a slightly strained sample (see Figure 6) and would thus account for the difference in the E value.

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM I I I l.- S, - CI 0 C>o~~~~~~~~ 5 \8 < 50 gauss ven~~~~~ I ~~~~T = 77' K Sz4 SPECTRAL SLIT r)4 WIDTH t' 7 X I0' ev. Mt.88171 3+ 3 ~.00002 ev I I Eo +-. 0001 ev E.:.8820 ~.000 1 ev 880.882.884.886.888 PHOTON ENERGY (ev) FIGURE 3. ZERO-FIELD EXCITON TRANSMISSION FOR STRAIN-FREE GERMANIUM AT 770K. See Reference 3. with magnetic field and can be traced to zero field. The second level is also quadratic in B and appears to originate from the region of Ex, but the absorption peaks are not well defined for fields less than 8 kilogauss. The third point to note is that the higher levels appear to be linear with B. However, if the same change of curvature in going from the lowest to the second level is extended to the higher levels, it is reasonable to believe that any curvature above the second level would not be discernible. If we assume that these higher levels depend linearly on magnetic field, i. e., assume the absorption lines correspond to transitions between Landau levels, then the energy separation between two levels, n and n', will be of the form (References 10 and 11): Enn =E +(n+)hwc + (n' 2)hwc2 (2)

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM with the condition An =n' - n =0, -2 where n and n' refer to the Landau quantum numbers, and coc = eB/mlc is the cyclotron frequency for band 1, and similarly for band 2. For zero mnagnetic field, E nn = Eo; thus the extension of the higher levels in Figure 4 to zero field would give the direct transition energy gap E' = 0. 88047 ~ 0. 00047 ev, a value less than the exciton energy, E. But it is not possible 0 x for the energy of the bound electron-hole of the exciton to have a higher energy than the free carriers in the conduction bands. In other words, if the higher levels corresponded to Landau transitions the exciton would have a negative binding energy which is contradictory to the usual definition of an exciton..930 l I l I / SAMPLE TI-91 [1i1] 77 K E.=,0. 88171 ~.00002 ev E' 0. 88047 ~.00047 ev E, O. 8834 ~.0001 ev - o' Ex-E, 0.0017 *v.920 UNSTRAINED 8 4 S / /.900 E X, MAGNETIC FIELD (kg) FIGURE 4. MAGNETO-ABSORPTION SPECTRUM FOR STRAIN-FREE GERMANIUM AT 770K. Levels Exi correspond to exciton transitions and ELi correspond to Landau transitions determined from Equation 2. 8~~~~~~~L

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM Loudon (Reference 12) has extended the theoretical calculations of Elliott (Reference 9) to the case of optical absorption in the presence of a magnetic field taking into account the effect of the exciton. He concludes that there is an exciton level associated with each Landau level in the conduction band, and that the most important absorption peaks in the magneto-absorption spectrum correspond to transitions to these exciton levels, with the Landau absorption an insignificant shoulder. This same conclusion was arrived at independently by Howard and Hasegawa (Reference 13), who examined the magneto-absorption spectrum of impurity states. Thus, the conclusion for Figure 4 is that the higher levels, as well as the two lowest levels, correspond to exciton transitions with a nonlinear field dependence, and originate from the region of Ex. The model of this energy band structure is illustrated in Figure 5. For zero x magnetic field the exciton absorption, Ex(0), is the strong absorption peak followed by the smooth direct transition absorptions for hv > E. For B 0 O the strong absorptions of the magneto-absorption spectrum are for transitions to the exciton levels, Ei (B), (i = 1, 2,...), associated with each Landau level ELi (B). The position of the Landau levels can be estimated using Equation 2 and the cyclotron resonance effective masses, m* = 0. 33m (heavy hole) and v O m* = 0. 034m. They are shown in Figure 4 by the dashed lines and are labeled L. (i = 1, 2,...). C 0 1 We have arbitrarily considered only transitions between the heavy holes and the conduction band with An = -2. The difference between the Landau level and the corresponding exciton level represents the exciton binding energy. At zero field the exciton binding energy, Eexi = ELi - Exi, is 0. 0017 ev and increases quadratically with magnetic field in qualitative agreement with B:O BO EXCITON CONDUCTI ON BAND EDGE EXCITON _ UJI Ex(O) Eo(O) Ex (B) EL i wHevy holes Light holes FIGURE 5. ENERGY BAND STRUCTURE FOR STRAIN-FREE GERMANIUM WITH AND WITHOUT A MAGNETIC FIELD 9

WILLOW W RUN LABORATORIES TECHNICAL MEMORANDUM the calculations of Yafet, Keyes, and Adams (Reference 14). For a given magnetic field the Eexi values increase with the index i. This may be fortuitous, however, because of the manner used in selecting the Landau levels. 4 STRAINED SAMPLES The zero-field exciton transmission is shown in Figure 6 for a few strained samples at 770K. The curve TI-91 is for the unstrained sample of Figure 3 and is included for comparison. Curve BTL-61 is the transmission of the sample displaying the greatest shift of Ex and presumably greatest strain that we measured. The strain in sample BTL-61 was accidental and was probably produced by localized binding between the sample and the cover-glass slides. Unfortunately, the strain in the samples could not be measured. The curve at the extreme right is that of Zwerdling, Lax, Roth, and Button (Reference 1, hereinafter referred to as ZLRB), and is for a sample glued to a glass substrate. The strain in each of these samples is compressional and is produced by the difference in the contraction of the substrate and the sample when cooled. These curves have been adjusted vertically to avoid confusion. The general 725 04 C E,- E817.8869 ev Og' \ Br-61-[110]'2 UJE,=.88253 ev.J LL E,=.88171 ev 880 882 884 886 888 890 892 894 ENERGY (ev) FIGURE 6. ZERO-FIELD EXCITON TRANSMISSION FOR STRAINED GERMANIUM SAMPLES AT 77~K. See Reference 1. 10

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM properties of the strained samples as compared to the unstrained sample are the following: (1) the position of the absorption Ex is shifted towards higher energies; and (2) additional absorptions are evident at energies greater than E x. These effects have been attributed (Reference 5) to the shear strain which splits the valence band edge into two edges and also increases the energy gap. The magneto-absorption effect has been measured for a few strained samples, and the results are shown in Figures 7 and 8. Both samples have the same general characteristics as for the unstrained sample, Figure 4, with the exception of the shift in energies produced by the strains. The two lowest levels of Figures 7 and 8 behave quadratically with magnetic field, with the lowest level being traced to zero field. The higher levels appear to be linear and extrapolate to a point, the energy of which is less than Ex. It should be noted that sample TI-91A is under a slight tension as demonstrated by the fact that E has shifted towards energy lower than for the unstrained sample, Figure 3. Thus it is evident from Figures 7 and 8 that 930 I SAMPLE TI-91A [111] 77BK E, (0):.88159 E' (0):.88007 920 _ EI,.00152 ev [110 E NOT POLARIZED 910 L so / / // 880 0 4 8 12 16 20 24 MAGNETIC FIELD (kg) FIGURE 7. MAGNETO-ABSORPTION SPECTRUM FOR A SAMPLE UNDER A SLIGHT COMPRESSIONAL STRAIN 11

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM for samples accidentally strained, at least up to a certain amount, the intense transitions are to exciton levels associated with each Landau level the same as for the unstrained sample. For sample BTL-61 the magneto-absorption measurements were made using polarized radiation. Within the limits of the experiment no difference could be detected in the positions of the absorptions for E I B and E B, where E is the electric vector of the polarized beam. The strain was compressional and presumably along a [110] crystallographic direction. 930 SAMPLE BTL-61- [110] -77 K [,,0] 920 [lhO [100] E,.88253etv. Eo.88032 /v. 910 CE e LLJ~/ / 88032l l 900 4 1 _/ / / 0 _ / // / II, / // / / // // TENSIONAL STRAIN 12

WI LLOW RUN LABORATORIES TECH NICAL M.EMORAN DU M the exciton level associated with each Landau level, and that the Landau absorption is an insignificant shoulder. These experimental results are in qualitative agreement with the theoretical calculations of Loudon and of Howard and Hasegawa. For a sample glued to a glass substrate the strain is relatively large, and the magneto-absorption spectrum becomes rather complicated. An example of this can be seen from the measurements of ZLRB where at 77~K at least three zero-field absorptions are observed. A definitive experiment that would verify that the intense absorptions were due to excitons would be to measure the photoconductivity at hv = Exi (B-# 0). For a true exciton no photoconductive effect should appear. Although this should verify that the absorption is due to an exciton, it may be a difficult measurement to make because of effects such as impact ionization. REFERENCES 1. S. Zwerdling, B. Lax, L. Roth, and K. Button, Phys. Rev., 1959, Vol. 114. 2. D. F. Edwards, R. W. Terhune, M. Bruemmer, and C. W. Peters, Bull. Am. Phys. Soc., 1959, Ser. II, Vol. 4, p. 154. 3. G. G. Macfarlane, T. P. McLean, J. E. Quarrington, and V. Roberts, Phys. Rev. Letters, 1959, Vol. 2, p. 252. 4. D. Edwards, and V. Lazazzera, Bull. Am. Phys. Soc., 1960, Ser. II, Vol. 5, p. 177. 5. W. H. Kleiner, and L. M. Roth, Phys. Rev. Letters, 1959, Vol. 2, p. 334. 6. D. F. Edwards, R. W. Terhune, and V. J. Lazazzera, Rev. Sci. Instr., 1958, Vol. 29, p. 1049. 7. W. G. Fastie, J. Opt. Soc. Am., 1954, Vol. 44, p. 641. 8. W. G. Fastie, J. Opt. Soc. Am., 1953, Vol. 43, p. 1174. 9. R. Elliott, Phys. Rev., 1957, Vol. 108, p. 1384. 10. E. Burstein, G. S. Picus, R. F. Wallis, and F. Blatt, Phys. Rev., 1959, Vol. 113, p. 15. 11. L. Roth, B. Lax, and S. Zwerdling, Phys. Rev., 1959, Vol. 114, p. 90. 12. R. Loudon, The Theory of the Absorption Edge in Semiconductors, unpublished doctoral dissertation, Oxford University, 1959. 13. R. E. Howard, and H. Hasegawa, Bull. Am. Phys. Soc., 1960, Ser. II, Vol. 5, p. 178. 14. Y. Yafet, R. W. Keyes, and E. N. Adams, J. Phys. Chem. Solids, 1956, Vol. 1, p. 137. 13

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WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM PROJECT MICHIGAN DISTRIBUTION LIST 5 1 August 1960-Effective Date Copy No. Addressee Copy No. Addressee 59 Department of the Air Force 94 The RAND Corporation Headquarters, USAF 1700 Main Street Washington 25, D. C. Santa Monica, California ATTN: Directorate of Requirements ATTN: Library 60 Commander, Air Technical 95 Chief, U. S. ArmyArmor Intelligence Center Human Research Urit Wright-Patterson Air Force Base, Ohio Fort Knox, Kentucky 61-70 ASTIA (TIPCR) ATTN: Administrative Assistant Arlington Hall Station Arlington Hall Station 96 Director of Research, U. S. Army Infantry Human Research Unit 71-75 Commander, Wright Air Development P. O. Box 2086, FortBenning, Georgia Center ~~C ~~~~enter 9 ~97 Chief, U. S. Army Leadership Wright-Patterson Air Force Base, Ohio Hi sarm L Human Research Unit ATTN: WCLROR P. O. Box 787 Presidio of Monterey, California 76 Commander, Wright AirDevelopment ATTN: Librarian Center Wright-Patterson Air Force Base, Ohio 98 Chief Scientist, Research &Development ATTN: WCLDRFV Division, Office of the Chief Signal Officer 77 Commander, Wright Air Development Department of the Army, Washington 25, D. C. Center 99 Stanford Research Institute Wright-Patterson Air Force-Base, Ohio Safr ee Document Center ATTN: WCOSI-Library Menlo Park, California ATTN: Acquisitions 78 Commander, Rome Air Development Center Griffiss Air Force Base, New York 100 Operations Research Office ATTN: RCVSL-1 The Johns Hopkins University 6935 Arlington Road 79 Commander, Rome Air Development Center Bethesda, Maryland, Washington 14, D. C. Commander, Rome Air Development Center Griffiss Air Force Base, New York ATTN: Chief, Intelligence Division ATTN: RCVH 101-102 Cornell Aeronautical Laboratory, 80-81 Incorporated 80-81 Commander, Air Force Incorporated Cambridge Reseairch Center 4455 Genesee Street, Buffalo 21,New York Cambridge Research Center Laurence G. Hanscom Field ATTN: Librarian Bedford, Massachusetts VIA: Bureau of Aeronautics ATTN: CRES, Stop 36 Representative 4455 Genesee Street 82-85 Central Intelligence Agency Buffalo 21, New York 2430 E. Street, N. W., Washington 25, D. C. 103-104 Control Systems Laboratory ATTN: OCR Mail Room University of Illinois Urbana, Illinois 86-90 National Aeronautics & Space Administration 1520 H. Street, N. W. Washington 25, D. C. VIA: ONR Resident Representative 1209 W. Illinois Street 91 U. S. Army Air Defense Human Urbana, Illinois Research Unit FoResearch Unit ex105-106 Director,Human Resources Research Office The George Washington University ATTN: Library P. O. Box 3596, Washington 25, D. C. ATTN: Library 92-93 Combat Surveillance Project Cornell Aeronautical Laboratory, 107 Massachusetts Institute of Technology, Incorporated Research Laboratory of Electronics Box 168, Arlington 10, Virginia Cambridge 39, Massachusetts ATTN: Technical Library ATTN: Document Room 26-327 15

WI LLOW RU N LABORATORI ES TECH N ICAL MEMO RAN DU M PROJECT MICHIGAN DISTRIBUTION LIST 5 1 August 1960-Effective Date Copy No. Addressee Copy No. Addressee 108 The U. S. Army Aviation HRU 116-118 Assistant Commandant P. O. Box428, Fort Rucker, Alabama U. S. Army Air Defense School Fort Bliss, Texas 109-110 Visibility Laboratory, Scripps Institution of Oceanography of Oceanography 119-120 Mitre Corporation University of California P. O. Box 208 San Diego 52, California Lexington 73, Massachusetts VIA: Commander Air Defense Systems Integration 111-113 Bureau of Aeronautics Division Department of the Navy, Washington 25, D. C. United States Air Force Laurence G. Hanscom Field ATTN: RAAV-43 Lexington 73, Massachusetts 114 Office of Naval Research 121 U. S. Continental Army Command Liaison Department of the Navy Officer 17th & Constitution Ave., N. W. Project MICHIGAN, Willow Run Washington 25, D. C. Laboratories Ypsilanti, Michigan ATTN: Code 461 122 Commanding Officer 115 Director, Electronic Defense Group U. S. Army Liaison Group U of M Research Institute Project MICHIGAN, Willow Run The University of Michigan Laboratories Ann Arbor, Michigan Ypsilanti, Michigan 16

+ + AD Div. 25/6 UNCLASSIFIED AD Div. 25/6 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metals- EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metals UNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium UNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy- Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy14 refs. Absorption 14 refs. Absorption (Memo. no. 2900-197-R) 3. Optics and spectroscopy- (Memo. no. 2900-197-R) 3. Optics and spectroscopy(Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation (Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation Measurements have been made of the direct-transition magneto- Title: Project MI CHIGAN. Title: Project MICHIGANeto-. Ttle: Pr H Edwards, David F., ~~~Measurements have been made of the direct-transition magneto- I il:PoetMCIA optical effect in strained and unstrained germanium at 77~ K. The. wLazazzera, Vito. optical effect in strained and unstrained germanium at 77~ K. The II. Ewars, avid F., to trnsitons o Il. U.Lazazzera, Vito J.o Lzze results indicate that the absorption peaks correspond to transitions to Army Signal Corps results indicate that the absorption peaks correspond to transitions to Lazazzera, Vito J. exciton levels associated with each Landau level in qualitative agree- IV. Contract DA-36-039 exciton levels associated with each Landau level in qualitative agree- III. C S. Ar — 09 ment with the theorectical calculations of Loudon (Reference 12) and of SC-7801 ment with the theorectical calculations of Loudon (Reference 12) and of IV. Contract Howard and Hasegawa (Reference 13). Howard and Hasegawa (Reference 13). SC-7880 (over) Armed Services (over) Armed Services Technical Information Agency Technical Information Agency UNCLASSIFIED UNCLASSIFIED + AD Div. 25/6 UNCLASSIFIED AD Div. 25/6 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metals- EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metalsUNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium UNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy- Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy14 refs. Absorption 14 refs. Absorption (Memo. no. 2900-197-R) 3. Optics and spectroscopy- (Memo. no. 2900-197-R) 3. Optics and spectroscopy(Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation (Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation Measurements have been made of the direct-transition magneto- I Title: Project MICHIGAN Measurements have been made of the direct-transition magneto- I. Title: Project MICHIGAN optical effect in strained and unstrained germanium at 77~ K. The La azea Vit J. opticaleffectinstrainedandunstrainedgermaniumat770K. The. Edwards, i. results indicate that the absorption peaks correspond to transitions to zzzer,. results indicate that the absorption peaks correspond to transitions toV JA exciton levels associated with each Landau level in qualitative agree- III. U. S. Army Signal Corps exciton levels associated with each Landau level in qualitative agree- III. U. S. Ary A IV. Contract DA-36-039 exciton levels associated with each Landau level in qualitative agree- I.Cnrc A3-3 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~IV. Contract DA-36-039 I.Cnrc ment with the theorectical calculations of Loudon (Reference 12) and of SC-78801 ment with the theorectical calculations of Loudon (Reference 12) and of SC-7880 Howard and Hasegawa (Reference 13). Howard and Hasegawa (Reference 13). S-8 (over) Armed Services (over) Armed Services Technical Information Agency Technical Information Agency UNCLASSIFIED UNCLASSIFIED +~~~~~~~~~~

AD UNCLASSIFIED AD UNCLASSIFIED UNITERMS UNITERMS Germanium Germanium Absorption peaks Absorption peaks Magneto-optical effects Magneto-optical effects Direct transitions Direct transitions Landau level Landau level Exciton Exciton UNCLASSIFIED UNCLASSIFIED AD UNCLASSIFIED AD UNCLASSIFIED UNITERMS UNITERMS Germanium Germanium Absorption peaks | Absorption peaks Magneto-optical effects Magneto-optical effects Direct transitions Direct transitions Landau level Landau level Exciton Exciton UNCLASSIFIED UNCLASSIFIED

++ AD Div. 25/6 UNCLASSIFIED AD Div. 25/6 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metals- EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metalsUNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium UNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanum Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy- Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 inl. illus., 2. Optics and spectroscopy14 refs. Absorption 14 refs. Absorption (Memo. no. 2900-197-R) 3. Optics and spectroscopy- (Memo. no. 2900-197-R) 3. Optics and spectroscopy(Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation (Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation Measurements have been made of the direct-transition magneto- I. Title Project MICHIGAN Measurement have been made of the direct-transition magneto- I. Title: Project MICHIGAN optical effect in strained and unstrained germanium at 77~K. The II. Edwards, David F., optical effect in strained and unstrained germanium at 77K. Th II. Edwards, Davd F., results indicate that the absorption peaks correspond to transitions to III Lazazzera, Vito J. results indicate that the absorption peaks correspond to transtions to Lazazzera, Vito J. ~~~~~~~~~~~~~~~~~II.US.AmSinlCrsresults indicate that the absorption peaks correspond to transitions to II.S rySga op exciton levels associated with each Landau level in qualitative agree- V.. o rmy a gnal D ops exciton levels associated with each Landau level in qualitative agree III. U. S.CnrcD men wih te teoectcalcalulaios o Lodon(Reernce12)andof IV. Contract DA-36-039IVCot mwi t Heo a c r SC-7801 ment with the theorectical calculations of Loudon (Reference 12) and of SC~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Howard and Hasegawa (Reference 13). Howard and Hasegawa (Reference 13). Howard and Hasegawa (Reference 13). SC-78801 (over) Armed Services (over) Armed Services Technical Information Agency Technical Information Agency UNCLASSIFIED UNCLASSIFIED AD Div. 25/6 UNCLASSIFIED AD Div. 25/6 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Metallic elements and EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metals- EXCITON AND MAGNETO-OPTICAL EFFECT IN STRAINED AND structural metalsUNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium UNSTRAINED GERMANIUM by David F. Edwards and Vito J. Germanium Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy- Lazazzera. Memo. of Proj. MICHIGAN. Aug 60. p. 13 incl. illus., 2. Optics and spectroscopy14 refs. Absorption 14 refs. Absorption (Memo. no. 2900-197-R) 3. Optics and spectroscopy- (Memo. no. 2900-197-R) 3. Optics and spectroscopy(Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation (Contract DA-36-039 SC-78801) Unclassified memorandum Magneto-optic rotation Measurements have been made of the direct-transition magneto- I Title: Project MICHIGAN Measurements have been made of the direct-transition magneto- I. Title: II dadDvdFMaueet aebe aeo h iettasto ant-I. Title: Project MICHIGAN optical effect in strained and unstrained germanium at 77~0K. The La azera, Vito. opticaleffect n strainedandunstrainedgermaniumat770K. The II. Edwards, David F., results indicate that the' absorption peaks correspond to transitions to zaz results indicate that theabsorption peaks correspond to transitions to La zer, exciton levels associated with each Landau level in qualitative agree- III... rmy Signal Corps exciton levels associated with each Landau level in qualitative agree- III. U. S. Army Signal Corps I.Contract DA-36-039 ecto eesascae ihec adulvli ulttv ge VCnrc A3-3 ment with the theorectical calculations of Loudon (Reference 12) and of SC-78801 ment with the theorectical calculations of Loudon (Reference 12) and of IV. Contract DA-36-039 Howard and Hasegawa (Reference 13). Howard and Hasegawa (Reference 13). SC-78801 (over) Armed Services (over) Armed Services Technical Information Agency Techical Information Agency Technica SSIfiAe UNCLASSIFIED + +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~UCASFE

AD UNCLASSIFIED AD UNCLASSIFIED UNITERMS UNITERMS Germanium Absorption peaks Absorption peaks Absorption peaks Magneto-optical effects Magneto-optical effects Direct transitions Direct transitions Landau level Landau level Lan Exciton Exciton UNCLASSIFIED AD | UNCLASSIFIED AD UNITERMS ) Germanium Germanium GeAbsorption peaks Absorption peaks Absorption peaks Magneto-optical effects M Magneto-optical effects Direct transitions Direct transitions Direct transitions Landau level Landau level Exciton Exciton UNCLASSIFIED UNCLASSIFIED