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2 Feb 1987

Volume 50, Issue 5, pp. 227-298


Edge‐ and surface‐emitting distributed Bragg reflector laser with multiquantum well active/passive waveguides

Keisuke Kojima, Susumu Noda, Kazumasa Mitsunaga, Kazuo Kyuma, Koichi Hamanaka, and Takashi Nakayama

Appl. Phys. Lett. 50, 227 (1987); http://dx.doi.org/10.1063/1.97668 (3 pages) | Cited 16 times

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A novel AlGaAs/GaAs distributed Bragg reflector laser utilizing a multiquantum well structure both as an active waveguide and as a low loss passive waveguide was fabricated. The threshold current was 102 mA at room temperature, and the differential quantum efficiency for the edge‐ and surface‐emitted light was 16% and 3.7%, respectively. No mode hopping was observed in a temperature range of 35 K. A 0.17°×17° far‐field pattern was obtained for the surface‐emitted light.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Gn Optical waveguides and couplers

cw phase‐locked array Ga0.25In0.75As0.5P0.5‐InP high power semiconductor laser grown by low‐pressure metalorganic chemical vapor deposition

M. Razeghi, R. Blondeau, M. Krakowski, B. de Cremoux, J. P. Duchemin, F. Lozes, M. Martinot, and M. A. Bensoussan

Appl. Phys. Lett. 50, 230 (1987); http://dx.doi.org/10.1063/1.97669 (3 pages) | Cited 8 times

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Continuous and pulsed phase‐locked operation of a high power GaInAsP‐InP semiconductor laser emitting at 1.3 μm has been achieved. The laser consists of a seven‐striped array of ridge‐island lasers fabricated by a two‐step low‐pressure metalorganic chemical vapor deposition growth technique. Linear output powers greater than 300 mW (pulsed) and 120 mW (cw) have been obtained with no facet coatings. The far‐field full widths at half power, both parallel and perpendicular to the junction plane, were 3° and 45°, respectively, at 10 mW (at 20 °C) which is evidence for strong stripe‐to‐stripe coupling.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

High power, AlGaAs buried heterostructure lasers with flared waveguides

D. F. Welch, P. S. Cross, D. R. Scifres, W. Streifer, and R. D. Burnham

Appl. Phys. Lett. 50, 233 (1987); http://dx.doi.org/10.1063/1.98237 (3 pages) | Cited 4 times

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High power, buried heterostructure laser with flared waveguide horns have been grown by a two‐step metalorganic chemical vapor deposition process. Powers up to 120 mW cw in a single longitudinal and transverse mode have been obtained from a single stripe laser. The flared waveguides decrease the lateral far‐field divergence from 25° to 11° while supporting only the lowest order transverse mode.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Gn Optical waveguides and couplers

Electro‐optical performance of a new, black‐white and highly multiplexable liquid crystal display

Martin Schadt and Frans Leenhouts

Appl. Phys. Lett. 50, 236 (1987); http://dx.doi.org/10.1063/1.98238 (3 pages) | Cited 34 times

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A new, low bias tilt field‐effect liquid crystal display (LCD) is presented with better image quality than supertwist or superbirefringence LCD’s at the same high level of multiplexing. In its positive contrast mode, the display image is black on white with virtually no inherent coloration and with a comparably large contrast as that of twisted nematic LCD’s. The viewing range of the display is as wide as that of superbirefringence LCD’s, whereas its image quality is an order of magnitude less dependent on cell gap variations. With specifically designed liquid crystal mixtures, multiplexing ratios of 1000:1 and response times below 300 ms result.
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85.60.Pg Display systems
78.20.Jq Electro-optical effects
42.30.Va Image forming and processing
61.30.-v Liquid crystals

Transverse instability of an electron beam in a beam‐induced ion channel

K. T. Nguyen, R. F. Schneider, J. R. Smith, and H. S. Uhm

Appl. Phys. Lett. 50, 239 (1987); http://dx.doi.org/10.1063/1.98239 (3 pages) | Cited 21 times

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Transverse oscillations of a relativistic electron beam propagating in a beam‐induced ion channel have been theoretically investigated and experimentally observed. Good agreement between experimental observations and theoretical calculations strongly suggests that these oscillations may be caused by the ion hose (ion resonance) instability.
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52.40.Mj Particle beam interactions in plasmas
52.70.Ds Electric and magnetic measurements
41.75.Ht Relativistic electron and positron beams
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Dependence of radiation‐induced interface traps on silicide gate stoichiometry in silicide/SiO2/Si devices

S. Buchner, M. Natan, K. Kang, and D. Gill

Appl. Phys. Lett. 50, 242 (1987); http://dx.doi.org/10.1063/1.98240 (3 pages)

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The density of radiation‐induced traps at the Si/SiO2 interface in TiSix and WSix gate metal‐oxide‐semiconductor capacitors is shown to depend on the stoichiometry (x value) of the silicide. The dependence is such that capacitors with metal‐rich silicide gates exhibit a smaller increase in interface traps than do capacitors with silicon‐rich gates. These results can be qualitatively explained by the dependence of the silicide stress on stoichiometry—metal‐rich films are under large tensile stress that inhibits the generation of radiation‐induced interface traps.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Ed γ-ray effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.40.Rs Electrical and magnetic properties related to treatment conditions

Infrared Raman probing of deep‐lying damaged layers in hydrogen‐implanted GaAs

E. Anastassakis and J. Tatarkiewicz

Appl. Phys. Lett. 50, 245 (1987); http://dx.doi.org/10.1063/1.98241 (3 pages) | Cited 4 times

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We report on the use of a cw Nd:yttrium aluminum garnet infrared laser to probe by Raman scattering the damaged layers of GaAs implanted with high‐energy(∼2 MeV) protons and deuterons. Such layers are too deep into the material to be probed by visible light. As the implanted area is approached laterally, we observe a gradual decrease in the scattering intensity of the longitudinal optical and transverse optical phonons and a downward shift of their frequencies. These effects are attributed to defect‐induced absorption and lattice strains. The results demonstrate the advantages of the technique for studying the damage in deeply buried layers of radiation‐modified materials.
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78.30.Fs III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
63.50.-x Vibrational states in disordered systems

Observation of valence‐band discontinuity of hydrogenated amorphous silicon/hydrogenated amorphous silicon carbide heterojunction by photocurrent‐voltage measurements

Yoshinobu Okayasu, Keitaro Fukui, and Mitsuo Matsumura

Appl. Phys. Lett. 50, 248 (1987); http://dx.doi.org/10.1063/1.98242 (2 pages) | Cited 2 times

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Photocurrent‐voltage measurements at different wavelengths exhibit the valence‐band discontinuity of a hydrogenated amorphous silicon/hydrogenated amorphous silicon carbide heterojunction. A band discontinuity of ∼100 meV is deduced based on a tunneling model for a hole barrier. This energy gap is relatively small compared to that for the conduction band, but significantly affects the characteristics of heterojunction p‐i‐n solar cells.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
84.60.Jt Photoelectric conversion
72.80.Ng Disordered solids
73.50.Pz Photoconduction and photovoltaic effects

Correlation of interface composition and barrier height for model AuGeNi contacts to GaAs

J. R. Waldrop and R. W. Grant

Appl. Phys. Lett. 50, 250 (1987); http://dx.doi.org/10.1063/1.98215 (3 pages) | Cited 19 times

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Model contacts to GaAs that include nonalloyed layered structures of Au, Ge, and Ni in various combinations are used to establish a correlation between interface composition and large changes in barrier height ϕB. The interface Fermi level EiF and chemistry during initial contact formation were investigated by x‐ray photoemission spectroscopy; the corresponding ϕB for the thick contact was obtained by current‐voltage (I‐V) measurement. The circumstances under which a thin (∼10 Å) Ge layer at the GaAs interface can produce ϕB =∼0.25–0.4 eV (as measured by I‐V) are described. For all model contacts examined a ϕB range from ∼0.25 to 0.9 eV is observed. This result questions the usual assumption of a relatively fixed ϕB of ∼0.8 eV for the alloyed AuGeNi contact and offers an alternative explanation for the mechanism of ohmic contact formation. The conditions that define the exceptionally low ϕB contacts provide a guide for the design of nonalloyed tunnel ohmic contacts.
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73.40.Ns Metal-nonmetal contacts
68.35.Dv Composition, segregation; defects and impurities
73.30.+y Surface double layers, Schottky barriers, and work functions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Effects of reactive ion etching on chemical vapor deposition

C. Y. Wong and P. E. Batson

Appl. Phys. Lett. 50, 253 (1987); http://dx.doi.org/10.1063/1.98216 (3 pages)

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Silicon surfaces were exposed to reactive ion etching with CCl2F2, followed by low pressure chemical vapor deposition of silicon nitride. Examination with transmission electron microscopy shows a 5‐nm homogeneous layer with interfacial roughness about the order of the layer thickness between the nitride and the silicon substrate. Analysis with spatially resolved electron energy loss scattering indicates that this phase is Si2N2O. The causes for the formation of this layer and its implication on very large scale integration technology are discussed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Bh Computer-aided design of microcircuits; layout and modeling
81.65.-b Surface treatments
68.55.Nq Composition and phase identification

Unpinning of the Fermi level on GaAs by flowing water

N. A. Ives, G. W. Stupian, and M. S. Leung

Appl. Phys. Lett. 50, 256 (1987); http://dx.doi.org/10.1063/1.98217 (3 pages) | Cited 31 times

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Unpinning of the Fermi level on GaAs (100) surfaces by photochemical reactions resulting from simultaneous exposure of specimens to flowing water and light was recently reported. We discuss here a series of experiments carried out to provide further information on the changes in surface electronic structure responsible for unpinning of the Fermi level under these conditions. The present work supports the conclusion that the surface states which pin the Fermi level are associated with elemental arsenic and arsenic sesquioxide (As2O3). Effects of each of these two species on pinning are distinguished experimentally. We find that, in addition to photochemical reactions, exposure to flowing water alone can result in Fermi level unpinning under certain conditions. The oxygen content of the wash water and the specimen preparation are shown to be important variables.
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73.20.At Surface states, band structure, electron density of states

Formation of epitaxial NiSi2 of single orientation on (111) Si inside miniature size oxide openings

C. S. Chang, C. W. Nieh, and L. J. Chen

Appl. Phys. Lett. 50, 259 (1987); http://dx.doi.org/10.1063/1.98218 (3 pages) | Cited 25 times

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Epitaxial NiSi2 of single orientation was grown on (111) Si inside miniature size oxide openings. Striking oxide opening size effects on the growth of NiSi2 epitaxy were observed. The formation temperature of NiSi2 on (111) Si was found to be as low as 550 °C inside oxide openings 1.8 μm or smaller in size. Epitaxial NiSi2 of single orientation which is identical to that of (111) Si substrate was formed inside oxide openings of or smaller than 1.8, 1, and 0.8 μm in size in samples annealed at 550–750, 800, and 850–900 °C, respectively. The results are discussed in terms of the variation in tensile stress exerted by oxide near the silicon surface and small free‐energy difference between type A and type B NiSi2 epitaxy inside small size oxide openings.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Nondestructive measurement of indium content in semi‐insulating GaAs substrates and ingots

D. Kirillov, M. Vichr, and R. A. Powell

Appl. Phys. Lett. 50, 262 (1987); http://dx.doi.org/10.1063/1.98219 (3 pages) | Cited 2 times

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We report the use of room‐temperature photoluminescence to determine low levels of indium in semi‐insulating GaAs intended for use as low dislocation material for substrates of integrated circuits. We have compared this technique with other optical methods such as low‐temperature (4.2 K) photoluminescence and Raman scattering and find it more convenient for this application. Room‐temperature photoluminescence easily allows measurement of In content in InxGa1−xAs in the range of 0.1–2% with a standard deviation of 0.1%, which is sufficient for most practical applications. The technique is nondestructive and rapid. The measurement can be done on polished, sawed, or etched surfaces, or on side surfaces of as‐grown ingots without any treatment. To illustrate its use, we have measured variations in the In content of semi‐insulating GaAs due to segregation of In in the melt during liquid encapsulated Czochralski growth.
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61.72.U- Doping and impurity implantation
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
78.55.Cr III-V semiconductors
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Silicon diffusion into AlxGa1−xAs (x=0–0.4) from a sputtered silicon film

E. Omura, X. S. Wu, G. A. Vawter, E. L. Hu, L. A. Coldren, and J. L. Merz

Appl. Phys. Lett. 50, 265 (1987); http://dx.doi.org/10.1063/1.98220 (2 pages) | Cited 8 times

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Silicon diffusion into AlxGa1−xAs (x=0–0.4) from a sputtered Si film is described. It is shown that both the diffusion rate and the surface concentration of Si decrease with increasing Al mole fraction. The diffusion behavior of Si in AlxGa1−xAs is discussed in terms of the binding energy of the Al–As bond and mixed crystal disorder.
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66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
68.35.Dv Composition, segregation; defects and impurities

Electron spin resonance studies on buried oxide silicon‐on‐insulator

T. Makino and J. Takahashi

Appl. Phys. Lett. 50, 267 (1987); http://dx.doi.org/10.1063/1.98221 (3 pages) | Cited 7 times

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Electron spin resonance is used to study defects in high‐dose oxygen‐ion implanted Si substrates. By this implantation, a crystalline Si/buried SiO2/crystalline Si structure is created. Two kinds of defect centers are found; one is assigned to the amorphous center, and the other, the Pb0 center, which has been observed at thermally grown SiO2/(111) Si interfaces. The observed Pb0 center appears to exist near precipitated SiO2/crystalline Si interfaces, rather than crystalline Si/buried SiO2 interfaces. When annealed at 1150 °C, spin density decreases due to oxygen outdiffusion from the crystalline Si.
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76.30.Mi Color centers and other defects
61.80.Jh Ion radiation effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.-y Defects and impurities in crystals; microstructure

Interactions between bombardment‐induced defects in GaAs

Sherif Makram‐Ebeid, Pierre Boher, and Michel Lannoo

Appl. Phys. Lett. 50, 270 (1987); http://dx.doi.org/10.1063/1.98222 (3 pages) | Cited 9 times

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Interdefect electron hopping is shown to play an important role in the physical manifestations of radiation induced defects in GaAs. In fast electron irradiated n‐GaAs, we are led to attribute the observed high‐temperature deep level transient spectroscopy (DLTS) peaks to defect pairs each including an antisite AsGa related midgap level defect together with a VAs vacancy related shallower level defect. In contrast with recent publications, we show that one can consistently interpret DLTS, electrical conductivity, and electron paramagnetic resonance experimental data in terms of the same irradiation induced defects.
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61.80.Fe Electron and positron radiation effects
61.72.Yx Interaction between different crystal defects; gettering effect
71.55.Eq III-V semiconductors
63.20.kp Phonon-defect interactions

Strong 8.2 μm infrared intersubband absorption in doped GaAs/AlAs quantum well waveguides

B. F. Levine, R. J. Malik, J. Walker, K. K. Choi, C. G. Bethea, D. A. Kleinman, and J. M. Vandenberg

Appl. Phys. Lett. 50, 273 (1987); http://dx.doi.org/10.1063/1.98223 (3 pages) | Cited 205 times

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We have measured the infrared intersubband absorption at 8.2 μm in doped GaAs/AlAs quantum well superlattices. Waveguide geometry experiments demonstrate strong absorption with 95% of the incident infrared energy being absorbed.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Gn Optical waveguides and couplers

Optical and electronic properties of reactively sputtered amorphous GeNx:H

I. Honma, K. Kawai, H. Komiyama, and K. Tanaka

Appl. Phys. Lett. 50, 276 (1987); http://dx.doi.org/10.1063/1.98268 (3 pages) | Cited 13 times

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Basic photoelectronic properties of hydrogenated amorphous germanium nitride (a‐GeNx:H) are presented for the first time. Amorphous‐GeNx:H films were prepared by an rf reactive sputtering of a Ge target using Ar+N2+H2 mixed gases and their optical band gaps were controlled continuously in the range from 1.0 to 3.3 eV by varying the compositional ratio of nitrogen to germanium. In contrast to H‐free a‐GeNx, the temperature dependence of the dark conductivity of a‐GeNx:H shows that thermally activated band conduction prevails in the carrier transport over a wide temperature range at least down to 180 K. The photo‐to‐dark conductivity ratio under AM1 light of unoptimized a‐GeNx:H amounts to 40.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.66.-w Optical properties of specific thin films
68.55.-a Thin film structure and morphology

High efficiency indium oxide/cadmium telluride solar cells

T. Nakazawa, K. Takamizawa, and K. Ito

Appl. Phys. Lett. 50, 279 (1987); http://dx.doi.org/10.1063/1.98224 (2 pages) | Cited 17 times

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Solar cells have been fabricated by reactive deposition of thin‐film n‐In2O3 onto single‐crystal p‐CdTe. The cell has a total area solar power conversion efficiency of 13.4% which corresponds to an active area efficiency of 14.4% at air mass 1.5 without antireflection coatings. The cell consists of a buried homojunction structure with low dark saturation current density.
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84.60.Jt Photoelectric conversion
73.50.Pz Photoconduction and photovoltaic effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Process dependence of AlAs/GaAs superlattice mixing induced by silicon implantation

S. A. Schwarz, T. Venkatesan, D. M. Hwang, H. W. Yoon, R. Bhat, and Y. Arakawa

Appl. Phys. Lett. 50, 281 (1987); http://dx.doi.org/10.1063/1.98225 (3 pages) | Cited 26 times

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Silicon implantation induced mixing of a 400‐Å period AlAs/GaAs superlattice grown by organometallic chemical vapor deposition is examined using secondary ion mass spectrometry and transmission electron microscopy. The depth dependence of Al and Si diffusion for a 180‐kV 3×1015 cm−2 Si+ implant is measured as a function of implantation temperature, annealing temperature, and annealing time. The room‐temperature implanted sample exhibits a near‐surface mixing inhibition following anneal. No mixing inhibition is observed in samples implanted at higher temperatures. Si segregates rapidly into the GaAs layers during the anneal. Si diffusion is inhibited near the peak of the implant. Mixing depths and defect distributions are strongly dependent on the processing conditions employed. The results are consistent with a divacancy model for Al diffusion.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.J- Diffusion of impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Use of tertiarybutylarsine in the metalorganic chemical vapor deposition growth of GaAs

R. M. Lum, J. K. Klingert, and M. G. Lamont

Appl. Phys. Lett. 50, 284 (1987); http://dx.doi.org/10.1063/1.98226 (3 pages) | Cited 52 times

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Epitaxial films of GaAs have been grown by metalorganic chemical vapor deposition using a new arsenic source, tertiarybutylarsine (TBAs). Films with excellent surface morphology were obtained for low V/III values over a wide temperature range (600–800 °C), and relatively strong free‐exciton emission was observed in the photoluminescence spectra. Hall measurements indicate carrier concentrations as low as 5×1015 cm−3 and mobilities μ300=4000 cm2/V s. These are equivalent or better than results obtained with trimethylarsenic. In contrast to growth with arsine, the layers were found to be n type for all values of V/III ratio investigated (2–20). Higher quality layers can be expected with source repurification of synthesis via a purer chemical process.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors

Nb/GaAs and NbN/GaAs Schottky barriers

X. W. Wu, L. C. Zhang, P. Bradley, D. K. Chin, and T. Van Duzer

Appl. Phys. Lett. 50, 287 (1987); http://dx.doi.org/10.1063/1.98227 (3 pages) | Cited 2 times

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Niobium and niobium nitride films have been deposited on n‐GaAs substrates using dc magnetron sputtering to form Nb/GaAs and NbN/GaAs Schottky diodes. Current‐voltage(I‐V) measurements were made on the diodes and the metal/GaAs interfaces were studied by Rutherford backscattering spectrometry. For the Nb/GaAs Schottky diodes, without rapid thermal annealing and after annealing for 10 s at temperatures up to 600 °C, the ideality factor and the Schottky barrier height as measured by the current‐voltage technique vary slightly from 1.01 to 1.03 and from 0.75 to 0.78 V, respectively. For annealing above 750 °C, evidence of interdiffusion between Nb and GaAs is observed. In contrast to the Nb/GaAs diodes, the NbN/GaAs Schottky diodes have poor characteristics without high‐temperature annealing; however, after annealing at 800 °C, the diodes show excellent forward I‐V characteristics with an ideality factor of 1.06 and a barrier height of 0.73 V. No trace of interdiffusion between NbN and GaAs is found after annealing up to 800 °C.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
68.35.Fx Diffusion; interface formation

Subthreshold model of a polycrystalline silicon thin‐film field‐effect transistor

Brian Faughnan

Appl. Phys. Lett. 50, 290 (1987); http://dx.doi.org/10.1063/1.98228 (3 pages) | Cited 25 times

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A model is presented for the subthreshold current versus gate voltage of a polycrystalline silicon thin‐film field‐effect transistor. It utilizes the experimentally observed exponential density of states of polycrystalline silicon grain boundaries and is based on an earlier model of M. Shur and M. Hack [J. Appl. Phys. 55, 3831 (1984)] which they applied to hydrogenated amorphous silicon. Experimental subthreshold curves are presented along with the corresponding curves predicted by the model. In addition current activation data are shown to fit the model. The primary fitting parameter is the density of states at the valence band.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Quasiparticle trapping and the quasiparticle multiplier

N. E. Booth

Appl. Phys. Lett. 50, 293 (1987); http://dx.doi.org/10.1063/1.98229 (3 pages) | Cited 99 times

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Superconductors and in particular superconducting tunnel junctions can be used to detect phonons, electromagnetic radiation, x rays, and nuclear particles by the mechanism of Cooper‐pair breaking to produce excess quasiparticles and phonons. We show that the sensitivity can be increased by a factor of 100 or more by trapping the quasiparticles in another superconductor of lower gap in the region of the tunnel junction. Moreover, if the ratio of the gap energies is >3 a multiplication process can occur due to the interaction of the relaxation phonons. This leads to the concept of the quasiparticle multiplier, a device which could have wider applications than the Gray effect transistor or the quiteron.
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74.50.+r Tunneling phenomena; Josephson effects
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
72.15.Lh Relaxation times and mean free paths
29.40.-n Radiation detectors

Unexpected unidirectional anisotropy in amorphous Tb‐Fe/Ni‐Fe‐Mo bilayer films

F. Hellman, R. B. van Dover, and E. M. Gyorgy

Appl. Phys. Lett. 50, 296 (1987); http://dx.doi.org/10.1063/1.98230 (3 pages) | Cited 15 times

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The exchange interaction between amorphous Tb‐Fe (a‐Tb‐Fe) and crystalline Ni‐Fe‐Mo produces a unidirectional anisotropy in the magnetically soft Ni‐Fe‐Mo layer. This anisotropy appeared anomalous because the magnetizations of the layers were previously believed to be orthogonal to each other. The magnitude of the unidirectional anisotropy is quite large by comparison to values quoted in the literature for Permalloy of a comparable thickness exchange coupled to an in‐plane antiferromagnet. Precise measurement of the direction of the easy axis in a‐Tb‐Fe shows that it is in fact tilted at a small angle with respect to the normal to the Ni‐Fe‐Mo moment which lies in the film plane. An expression relating the unidirectional anisotropy to measured properties of the a‐Tb‐Fe layer fits the experimental results. The tilt appears to be the consequence of a nonperpendicular incident angle of deposition and depends critically on deposition parameters such as substrate temperature, Tb‐Fe layer thickness and composition, and the incident angles of the Tb and Fe vapor beams.
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75.30.Et Exchange and superexchange interactions
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Gw Magnetic anisotropy
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