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15 Mar 1995

Volume 77, Issue 6, pp. 2231-2849

Page 2 of 5 Pages Previous Page Next Page | Jump to Page

Codiffusion of arsenic and boron implanted in silicon

S. Solmi, S. Valmorri, and R. Canteri

J. Appl. Phys. 77, 2400 (1995); http://dx.doi.org/10.1063/1.358765 (7 pages) | Cited 15 times

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The codiffusion of As and B implanted in Si at high doses (1×1016 cm−2) and with energies corresponding to the same projected range has been investigated at 900 and 1000 °C on the basis of dopant and carrier profile measurements. The comparison of the codiffusion data with the corresponding ones obtained by the diffusion of each element alone revealed some anomalous effects which can be explained by assuming the formation of neutral donor–acceptor pairs. These complexes are mobile with a diffusion coefficient Dpair=17 exp(−4/kT) cm2/s, very close to the diffusion coefficient of As in intrinsic Si. Electrons are the majority carriers in the region where both dopants are present at high densities. On the basis of these features, a diffusion model that takes pairing into account is presented. A simulation program including this model allows one to foresee the anomalous phenomena occurring in the high‐concentration codiffusion of donors and acceptors in Si and in general shows a good agreement with experimental profiles. © 1995 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Rapid migration of silver on roughened glass surfaces in a methanol/air mixture near 500 °C

W. M. Sears and D. A. Love

J. Appl. Phys. 77, 2407 (1995); http://dx.doi.org/10.1063/1.358766 (8 pages) | Cited 1 time

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Experimental results presented here show that at elevated temperatures (about 500 °C) silver can be mobile on tin oxide, as well as other metal oxide surfaces. Because the migrating species seems to be Ag+ both diffusion and electrically assisted migration occurs. This movement is made visible in the form of tiny silver droplets on the glass surface by the presence of methanol vapor mixed in air. Without oxygen no migration occurs at all. It is clear that the movement requires a continuous or dynamic conversion of silver ions to silver oxide and back again, through the presence of both oxidizing and reducing agents. We show how it is possible to measure the diffusion constant and the electrical mobility constant by an appropriate analysis of the time evolution of a circular front of silver droplets measured with a video camera connected to a microscope zoom lens. Typical values on a roughened glass surface at 500 °C are for mobility, 42±13×10−6 cm2/V s, and for diffusion 12±6×10−6 cm2/s. Similar values for the electrical mobility on a smooth tin oxide surface have been measured. At this temperature diffusion on pure silica or even Pyrex glass powder is very slow, but the diffusion constant for MgO or CaO powder, annealed onto a sandblasted glass surface, is about 10−4 cm2/s. These oxides may be responsible for the movement seen on soda glass surfaces. The activation energy is about 4 eV and seems related to the work function of silver metal. © 1995 American Institute of Physics.
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66.30.Fq Self-diffusion in metals, semimetals, and alloys
68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Carbon impurity effects in Al‐Ga interdiffused GaAs/AlAs multiple quantum wells

Y. T. Oh, S. K. Kim, Y. H. Kim, T. W. Kang, C. Y. Hong, and T. W. Kim

J. Appl. Phys. 77, 2415 (1995); http://dx.doi.org/10.1063/1.358767 (4 pages) | Cited 3 times

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Photoluminescence (PL) measurements were performed in order to investigate the carbon impurity effects on the intermixing behavior of GaAs/AlAs multiple quantum wells (MQWs) grown by molecular‐beam epitaxy. The GaAs/AlAs MQWs were annealed with a carbon source in a furnace annealing system. The PL spectra show that the magnitude of the intermixing of Al and Ga induced by thermal annealing in GaAs/AlAs MQWs increases with depth. This behavior is not in agreement with the intermixing mechanism considering vacancy injection of the surface. The nonuniformity of the intermixing as a function of the depth originated from the carbon impurities which were injected during thermal treatment. © 1995 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Combined electron spin resonance and capacitance‐voltage analysis of hydrogen‐annealing induced positive charge in buried SiO2

K. Vanheusden, A. Stesmans, and V. V. Afanas’ev

J. Appl. Phys. 77, 2419 (1995); http://dx.doi.org/10.1063/1.359571 (6 pages) | Cited 6 times

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A novel charge sensing technique, based on monitoring donor defects in near‐interfacial Si by electron spin resonance (ESR), has been applied to measure positive charge in buried oxide (BOX) layers of separation by implantation of oxygen material. This positive charge is introduced into the BOX layer by annealing in hydrogen in the temperature range 450–700 °C. Standard capacitance‐voltage (C‐V) analysis of the areal BOX‐charge densities was used as a crucial test for this ESR‐based method, yielding good agreement between the two techniques. Photoinjection of charges, optical excitation, and C‐V and ESR etchback experiments have been performed on BOX layers subsequent to the hydrogen charging treatment leading to additional information on location, nature, and stability of the hydrogen‐induced positive centers. The results show that these centers are very stable (not even affected by electron injection) and that they are located near the two Si/BOX interfaces (within a layer of ≤20 nm). © 1995 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
76.30.Da Ions and impurities: general
81.65.-b Surface treatments

Switching mechanisms in layered CoCrPt thin films

G. J. Sinclair, G. A. Jones, P. J. Grundy, K. O’Grady, and M. el Hilo

J. Appl. Phys. 77, 2425 (1995); http://dx.doi.org/10.1063/1.358768 (4 pages) | Cited 1 time

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A series of thin CoCrPt layered structures has been studied with a view to understanding the nature and extent of any interactions present, both within and between the various constituent layers. In this investigation, we have utilized the principal remanence curves and their derivatives to characterize the bulk magnetic properties of the samples. In addition, we have employed a low energy broad beam Kaufman‐type ion source to sputter etch some of the layers, enabling unambiguous determination of the reversal fields of the various constituent layers. For each layered sample the magnetic layer grown on the thick Cr underlayer has the highest in‐plane coercivity. The second layer grown on a 100 Å Cr spacer has the next largest coercivity. All additional layers reverse at the same applied field strength. The coercivity of the layers is also insensitive to thickness reduction from 200 Å down to 80 Å. © 1995 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Structural analysis of ZnS/GaAs heterostructures grown by hydrogen transport vapor‐phase epitaxy

C. Giannini, T. Peluso, C. Gerardi, L. Tapfer, N. Lovergine, and L. Vasanelli

J. Appl. Phys. 77, 2429 (1995); http://dx.doi.org/10.1063/1.358769 (6 pages) | Cited 3 times

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The structural characterization of ZnS epilayers grown by hydrogen transport vapor‐phase epitaxy on (100)‐oriented GaAs substrates is reported. X‐ray‐diffraction measurements in both double‐axis (DA) and single‐axis modes were performed to determine the residual strain tensor and the strain temperature dependence of the epilayer in the range between 25 and 650 °C. From the analysis of the data obtained by DA measurements of several symmetric Bragg reflections at different azimuth angles and several asymmetric reflections recorded in different geometries, an orthorhombic distortion of the ZnS lattice was found. The crystallographic symmetry could be explained by an asymmetric distribution of the misfit dislocation density in the interface plane along the [011] and [011] directions. The temperature dependence measurements of the strain tensor components between room temperature and the growth temperature (650 °C) allowed determination of the thermal misfit between ZnS and GaAs and the linear thermal‐expansion coefficient of ZnS. Finally, triple‐crystal diffractometry and secondary‐ion‐mass spectrometry were used to investigate the chemical nature of the ZnS‐GaAs interface. The results indicate the presence of an interdiffused ZnS‐GaAs interface region, whose occurrence turns out to be associated with the initial defect structure of the substrate surface before the growth. © 1995 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Formation of thin films of CoSi2 on GaAs

Mikael Hult, Leif Persson, Mohamed El Bouanani, Harry J. Whitlow, Margaretha Andersson, Mikael Östling, Nils Lundberg, Carina Zaring, Kristina Georgsson, David D. Cohen, Nick Dytlewski, Peter N. Johnston, and Scott R. Walker

J. Appl. Phys. 77, 2435 (1995); http://dx.doi.org/10.1063/1.358770 (9 pages)

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CoSi2 exhibits the features of low resistivity and stability at elevated temperatures which make it interesting to employ for metallization on GaAs. The interfacial reactions in GaAs samples with thin film overlayers of Si and Co [Si(220 nm)/Co(50 nm)/(〈100〉‐GaAs)] were studied using x‐ray diffraction, scanning electron microscopy, x‐ray photoelectron spectroscopy, and mass and energy dispersive recoil spectrometry. Samples were vacuum furnace annealed for time periods between 1 and 8 h at temperatures ranging from 300 to 700 °C. It was found that a CoSi2 layer formed without observable reaction with the substrate at 500 °C and above. The excess Si (Si/Co atomic ratio of 2.41) remained near the surface as elemental Si and as SiO2 for the 500 and 600 °C annealings. For the 700 °C annealing the excess near‐surface Si was not observed. © 1995 American Institute of Physics.
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68.55.Nq Composition and phase identification
85.40.Ls Metallization, contacts, interconnects; device isolation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Calculation of strain distributions in multiple‐quantum‐well strained‐layer structures

James Downes and David A Faux

J. Appl. Phys. 77, 2444 (1995); http://dx.doi.org/10.1063/1.358771 (4 pages) | Cited 21 times

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We present a simple method for calculating strain distributions in structures containing an arbitrary number and combination of strained layers of finite length buried in an infinite medium. This method is used to calculate the strain distributions for a quantum‐well stack containing four compressive layers separated by barriers of different thicknesses and states of strain. It is found that the in‐plane strain is relaxed along a significant length of each compressive layer if the barriers are unstrained. In contrast, if the barriers are in tension, the compressive strain is retained over most of the length of the layer. It is concluded that the judicial use of compressive and tensile layers in device structures would substantially reduce the region over which the strain is relaxed and possibly minimize the adverse effects of modified band structure or atomic diffusion arising due to the relaxation of strain. It is also confirmed that strain relaxation reduces the average strain within the square cross section of a single quantum wire to about one tenth of the misfit strain. © 1995 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Theoretical consideration of equilibrium dissociation geometries of 60° misfit dislocations in single semiconductor heterostructures

J. Zou and D. J. H. Cockayne

J. Appl. Phys. 77, 2448 (1995); http://dx.doi.org/10.1063/1.358772 (6 pages) | Cited 14 times

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Equilibrium geometries of 60° dissociated misfit dislocations are considered theoretically using elasticity theory. The prediction of equilibrium dissociation width and the position of each partial with respect to the interface is given. The experimental results are in excellent agreement with the theory. © 1995 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Lk Linear defects: dislocations, disclinations

Interfacial energy calculation at interconnect‐metal/barrier‐metal interfaces for grain orientation control

Yasushi Nakasaki, Gaku Minamihaba, Kyoichi Suguro, and Hitoshi Itow

J. Appl. Phys. 77, 2454 (1995); http://dx.doi.org/10.1063/1.358773 (8 pages) | Cited 1 time

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The interfacial energy of interconnect‐metal/barrier‐metal interfaces in ultralarge‐scale integrations have been investigated numerically by assuming a simple additive interaction potential within a rigid‐lattice approximation. The calculation gave some noteworthy results: Al prefers the (111) orientation on a TiN(111) plane, but Cu did not have such a strong preference. Al(111) can be expected to show strong epitaxial growth on VNx(111), as did Cu on Nb(110). On the basis of the calculations, a Cu/Nb bilayered structure was sputter deposited sequentially by dc magnetron sputtering and examined for crystalline orientation by x‐ray‐diffraction analysis. Cu exhibited strong (111) orientation preference, and a narrow full width at half‐maximum in (111) rocking angle around the substrate normal. © 1995 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation

Growth and thermal decomposition of ultrathin ion‐beam deposited C:H films

A. Schenk, B. Winter, J. Biener, C. Lutterloh, U. A. Schubert, and J. Küppers

J. Appl. Phys. 77, 2462 (1995); http://dx.doi.org/10.1063/1.358774 (12 pages) | Cited 29 times

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Several monolayers thick hydrogenated carbon films, C:H, were prepared by ion beam deposition from hydrocarbon process gases onto Pt and monolayer C covered Pt single crystal surfaces and investigated with Auger electron and thermal desorption spectroscopies in an UHV environment. Efficient deposition was achieved at ion energies in the 160–300 eV range. The deposited thickness and H/C ratio of the films depend on both, target temperature and H/C ratio of the process gas. It is shown that the C monolayer is crucial for efficient on‐top deposition. Irrespective of the process gas used for deposition, the films grow as a C network and assume a constant H/C ratio at thicknesses greater than ∼ 3 monolayers. The H/C ratio of the films scale with the H content of the hydrocarbon process gas, a H/C ratio of 0.4 was obtained for ethane at 350 K substrate temperature. Upon thermally activated decomposition the films release molecular hydrogen as the major gaseous species and various hydrocarbons as minority species. The latter products signal chemical erosion of the film. It is shown that the rate determining step towards erosion via methane is a C–C bond breaking event which releases methyl radicals from the C network in the film. The activation energies for this step are determined as a 10 kcal/mol wide Gaussian distribution centered at 56 kcal/mol. Transport through the film is found to be so fast that it does not contribute to the observed gas release rates. © 1995 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Interaction in the Cr/amorphous‐silicon system

Yuichi Masaki, Shuichi Nonomura, Takashi Kurokawa, Takahiro Sakimoto, Hidenori Kawai, Roderick A. G. Gibson, and David I. Jones

J. Appl. Phys. 77, 2474 (1995); http://dx.doi.org/10.1063/1.358775 (5 pages) | Cited 3 times

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The kinetics of a low‐temperature silicide formation have been investigated in experiments on the solid‐phase interaction between Cr and amorphous Si (a‐Si). For the Cr/plasma‐enhanced chemical‐vapor‐deposited a‐Si:H system, it was found that amorphous interlayer was formed at the interface at RT. The compositional ratio of Cr to Si in the amorphous interlayer formed at RT was found to be about 5%. On the other hand, for the Cr/sputtered a‐Si system at RT, an interfacial amorphous layer with negligible thickness seemed to exist. From the experimental results and from the results previously reported, the kinetics of the low‐temperature interaction were discussed and a new model of an internal‐field‐assisted interaction was proposed. © 1995 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Al and B ion‐implantations in 6H‐ and 3C‐SiC

Mulpuri V. Rao, Peter Griffiths, O. W. Holland, G. Kelner, J. A. Freitas, David S. Simons, P. H. Chi, and M. Ghezzo

J. Appl. Phys. 77, 2479 (1995); http://dx.doi.org/10.1063/1.358776 (7 pages) | Cited 55 times

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Low (keV) and high (MeV) energy Al and B implants were performed into n‐type 6H‐ and 3C‐SiC at both room temperature and 850 °C. The material was annealed at 1100, 1200, or 1400 °C for 10 min and characterized by secondary ion mass spectrometry, Rutherford backscattering (RBS), photoluminescence, Hall and capacitance‐voltage measurement techniques. For both Al and B implants, the implant species was gettered at 0.7 Rp (where Rp is the projected range) in samples implanted at 850 °C and annealed at 1400 °C. In the samples that were amorphized by the room temperature implantation, a distinct damage peak remained in the RBS spectrum even after 1400 °C annealing. For the samples implanted at 850 °C, which were not amorphized, the damage peak disappeared after 1400 °C annealing. P‐type conduction is observed only in samples implanted by Al at 850 °C and annealed at 1400 °C in Ar, with 1% dopant electrical activation. © 1995 American Institute of Physics.
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61.72.up Other materials

Stark effect and Stark‐ladder effect in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells

S. J. Kim, Y. T. Oh, S. K. Kim, T. W. Kang, and T. W. Kim

J. Appl. Phys. 77, 2486 (1995); http://dx.doi.org/10.1063/1.358777 (9 pages) | Cited 5 times

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Photoluminescence (PL) measurements at 10 K were performed in order to investigate the influence of electric fields on the exciton states in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells (ACMQW) grown by molecular‐beam epitaxy. The coupling of the electronic energy levels in the wells led to an enhancement of the quantum‐confined Stark effect. The PL intensity decreased as the electric field increased. Calculated values of the intersubband transition energies were in good agreement with the experimental values for the ACMQW, and these values showed a similar behavior as those for the step quantum well. When the external applied field was very strong, Stark‐ladder transitions were observed, and the measured dependence of the field‐induced energy shifts of the Stark‐ladder transitions for the ACMQW agreed with theory. These results indicate that the Stark effect and the Stark‐ladder transitions in a unique ACMQW based on the AlxGa1−xAs/GaAs structure were observed simultaneously. © 1995 American Institute of Physics.
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71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Electrical and optical properties of ruthenium‐related defects in silicon

H. Pettersson, H. G. Grimmeiss, K. Schmalz, A. Knecht, and R. Pässler

J. Appl. Phys. 77, 2495 (1995); http://dx.doi.org/10.1063/1.358778 (6 pages) | Cited 2 times

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The electrical and optical properties of defects due to ion implantation of ruthenium in silicon have been studied by means of junction space‐charge techniques. Two energy levels were observed with energy positions at Ec−0.184 eV (A‐level) and EV+0.265 eV (B‐level), respectively, at 77 K. The changes in enthalpy due to the capture of electrons and holes were −8 meV (A‐level) and 1 meV (B‐level). Gibb’s free energies at different temperatures were calculated for both levels. Good agreement with the corresponding optical threshold energy was found for the B‐level suggesting a small Frank–Condon shift. A tentative model for the origin of the observed defects is discussed. © 1995 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.uf Ge and Si

Electric and photoelectric properties of diode structures in porous silicon

V. Pačebutas, A. Krotkus, I. Šimkienė, and R. Viselga

J. Appl. Phys. 77, 2501 (1995); http://dx.doi.org/10.1063/1.358779 (7 pages) | Cited 10 times

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Diode properties of structures containing a porous silicon layer have been investigated. The structures have been fabricated by depositing metal or indium‐tin‐oxide layers either directly on the ‘‘as‐anodized’’ silicon wafer or on the wafers with upper, nanocrystalline part of the porous layer removed. Different behavior was observed in both cases: (1) The photovoltaic effect is absent in diodes from as‐anodized wafers but appears in diodes from the cleaned wafers; (2) the diode ideality factor is close to 2 for ‘‘cleaned’’ diodes and increases in diodes containing an upper porous silicon layer. Energy‐band diagrams for the structures are proposed and it is concluded that the electrical transport in those structures is limited by the carrier recombination in the depletion layer. © 1995 American Institute of Physics.  
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72.40.+w Photoconduction and photovoltaic effects
85.60.Dw Photodiodes; phototransistors; photoresistors

Dependence of giant magnetoresistance on the number of valence electrons in the ferromagnetic constituent of granular alloys: Precipitates of face‐centered cubic Fe–Co, Co–Ni, and Ni–Cu alloys in Ag matrices

D. J. Kubinski and H. Holloway

J. Appl. Phys. 77, 2508 (1995); http://dx.doi.org/10.1063/1.359542 (6 pages) | Cited 4 times

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The dependence of giant magnetoresistance on the composition of ferromagnetic face‐centered cubic precipitates in an Ag matrix grown epitaxially on MgO {100} is described. These compositions were chosen from the alloy ranges Ni0.6Cu0.4→Ni→NixCo1−x→ Co→Fe0.2Co0.8 to give a number of valence electrons per atom, n=n3d+n4s, in the ferromagnetic precipitates that ranged from 8.8 to 10.4. This corresponds to a decrease of the saturation magnetization from ∼1500 emu/cm3 to approximately zero. To reduce the influence of other variables the concentration of the precipitates was kept constant (at 23.5 vol %) and their size approximately so. Corrections are applied to adjust for some remaining variation in precipitate size. With other factors held constant, there is a steady increase in both the magnetoresistance ratio and the magnetic‐field‐dependent resistivity with increase in the saturation magnetization of the alloys, i.e., with increase in the spontaneous magnetization of the single‐domain precipitates. © 1995 American Institute of Physics.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
81.30.Mh Solid-phase precipitation

Semiconducting rhenium silicide thin films on Si(111)

T. A. Nguyen Tan, J. Y. Veuillen, P. Muret, S. Kennou, A. Siokou, S. Ladas, F. Lahatra Razafindramisa, and M. Brunel

J. Appl. Phys. 77, 2514 (1995); http://dx.doi.org/10.1063/1.358780 (5 pages) | Cited 12 times

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The crystallographic, electronic, and optical properties of thin ReSi2 films (∼20–300 Å) have been investigated in situ by low energy electron diffraction (LEED) and photoelectron spectroscopy (XPS and UPS), ex situ by glancing incidence x‐ray diffraction (GIXD), and optical absorption measurements. Thin Re layers were evaporated under ultrahigh vacuum on Si(111) (7×7) surfaces, maintained at room temperature, or heated at 650 °C. The films were subsequently annealed at increasing high temperature and the silicide formation was followed by in situ surface techniques. For very thin films (≲35 Å) LEED shows a faint (1×1) pattern after annealing at 750 °C, which improves slightly up to ∼900 °C. For thick films (∼50–300 Å) only a bright background is observed. XPS indicates that the ReSi2 composition is attained upon annealing at 600 °C. In the Re‐Si bonding the charge transfer is negligible: the energy positions of the corelevels (Si 2p and Re 4f) are the same in the compound and in the elements. As the energy shift of the Si KLL Auger is negligible also, the extra‐atomic relaxation energy for Si atoms is the same in silicide as in silicon, indicating that ReSi2 has a semiconducting character. UPS results confirm this assumption: the density of states near EF decreases strongly upon ReSi2 formation and at the same time the valence band edge shifts from EF to lower binding energy. GIXD gives sharp diffraction peaks, characteristic of ReSi2 (110) in epitaxy on Si(111). This technique also reveals that the films present an additional orientation near the interface. Optical absorption measurements performed on ReSi2 films of ∼300 Å thick indicate that this silicide is a semiconductor with an indirect energy gap of 0.15 eV, in agreement with previous studies. © 1995 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.55.Ht Other nonmetals
81.15.Np Solid phase epitaxy; growth from solid phases
78.66.Li Other semiconductors

Miniature electrical filters for single electron devices

D. Vion, P. F. Orfila, P. Joyez, D. Esteve, and M. H. Devoret

J. Appl. Phys. 77, 2519 (1995); http://dx.doi.org/10.1063/1.358781 (6 pages) | Cited 39 times

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In experiments on single electron devices, the electromagnetic noise from parts of the apparatus at temperatures higher than that of the device can dramatically increase the tunnel rates out of the Coulomb‐blocked state and therefore increase the device error rate. The electrical lines must therefore be filtered adequately. We derive simple expressions for calculating the required attenuation coefficient. We describe a wide‐band miniature dissipative filter functioning at cryogenic temperatures. The effective thermalization of an experiment at 30 mK can be obtained by placing four of these filters in series at temperatures ranging from 4 K to 30 mK. © 1995 American Institute of Physics.
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73.40.Gk Tunneling
73.40.Rw Metal-insulator-metal structures
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Electrical transport in (100)CoSi2/Si contacts

A. Lauwers, K. Kyllesbech Larsen, M. Van Hove, R. Verbeeck, K. Maex, M. Van Rossum, A. Vercaemst, R. Van Meirhaeghe, and F. Cardon

J. Appl. Phys. 77, 2525 (1995); http://dx.doi.org/10.1063/1.358782 (12 pages) | Cited 13 times

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A detailed investigation of the electrical transport in (100) CoSi2/Si contacts is presented. The transport properties of epitaxial CoSi2 films, obtained both by ion‐beam synthesis and by solid‐state reaction of a Ti/Co bimetallic layer, are compared with the transport properties of conventional polycrystalline CoSi2 layers. The electrical resistivity, the magnetoresistance, and the Hall effect are measured on Hall bars for temperatures ranging from 1.2 to 300 K and magnetic fields up to 5 T. Very high values of the order parameter kFL0 are observed, indicating that the investigated samples are of very high purity and crystalline order. In addition, the electric transport at the CoSi2/Si interface is studied by current‐voltage and capacitance‐voltage measurements on Schottky diode structures for temperatures ranging from 173 to 333 K. Ideality factors close to unity are observed for the highest temperatures, for the lower temperatures the ideality factors are found to increase with decreasing temperatures. The observed temperature dependence of the ideality factor and the Schottky barrier height can be attributed to Schottky barrier inhomogeneities. © 1995 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Tunneling assisted thermionic emission in double‐barrier quantum well structures

S. Ehret, H. Schneider, E. C. Larkins, and J. D. Ralston

J. Appl. Phys. 77, 2537 (1995); http://dx.doi.org/10.1063/1.358783 (7 pages) | Cited 3 times

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We report on experimental and theoretical investigations of the dark current behavior in n‐type GaAs/AlAs/Al0.3Ga0.7As double‐barrier quantum wells (DBQW). The dark current perpendicular to the 50‐period DBQW structures shows evidence of tunneling through the 2‐nm‐wide AlAs tunnel barriers and thermionic emission across the 25‐nm‐wide AlGaAs layers. The temperature dependence is in good agreement with our numerical simulations, using an effective escape rate of 2.2×1014 s−1. The dark current is further modified by internal electric fields caused by an asymmetric dopant distribution, which partially arises from a dopant segregation during epitaxial growth. We also present a theoretical simulation showing how the dark current versus voltage dependence is influenced by these space‐charge fields. © 1995 American Institute of Physics.
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73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.40.+z Thermionic emission

Modified sheet resistance of ohmic contacts to p‐type In0.47Ga0.53As/InP

Patrick W. Leech

J. Appl. Phys. 77, 2544 (1995); http://dx.doi.org/10.1063/1.358784 (5 pages)

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The parameter known as the modified sheet resistance Rsk has been used in the modeling of ohmic contacts to define the region of alloying/reaction immediately below the metallization. In this study, the value of Rsk has been measured for Pd/Zn/Pd/Au, Pd/Au, Zn/Pd/Au, Au/Zn/Au, Ni/Zn/Ni/Au, Cr/Au, and Pd/Mn/Sb/Pd/Au contacts to In0.47Ga0.53As/InP as a function of the annealing temperature to 500 °C. In the as‐deposited contacts, the measured value of Rsk was lower than the sheet resistance outside of the contact, Rsh, by a factor of ∼2 to 3. This reduction in Rsk from Rsh has been attributed to (a) the formation of low‐resistivity phases at the interface and (b) the creation of a doped region by indiffusion of the Zn. In addition, in the Pd/Zn/Pd/Au contacts, the effect of varying the thickness of the layer of Zn between 0 and 400 Å on Rsk was examined. A thickness of Zn≥50 Å was required in order to produce a significant reduction in Rsk from the value for the Pd/Au (Zn=0 Å) contacts. This effect was enhanced by annealing at 500 °C, which produced a value of Rsk lower than Rsh by a factor of ∼10. The reduction in Rsk by annealing treatment was consistent with an enhanced formation of the interfacial phases and an increase in the rate of indiffusion of the Zn. The exceptions to these trends were in the Pd/Mn/Sb/Pd/Au contacts which showed an approximately constant value of Rsk and Pd/Au which showed a minor reduction in Rsk with increase in annealing temperature. © 1995 American Institute of Physics.  
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts

Characteristics of the electromechanical response and polarization of electric field biased ferroelectrics

Q. M. Zhang, J. Zhao, T. Shrout, N. Kim, L. E. Cross, A. Amin, and B. M. Kulwicki

J. Appl. Phys. 77, 2549 (1995); http://dx.doi.org/10.1063/1.358785 (7 pages) | Cited 11 times

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The electromechanical and dielectric responses of ferroelectric materials near paraelectric–ferroelectric (PF) phase transitions are examined both experimentally and theoretically. It is shown that the type of PF transition, i.e., first order and continuous transitions, and diffused phase transition found in relaxor ferroelectrics, has marked effect on the electromechanical and dielectric response behavior for materials under electric field bias. It is demonstrated that an exceptionally large piezoelectric and electromechanical response can be achieved in materials with a first order PF transition. For example, in Ba1−xSrxTiO3 (x∼0.35) ceramics at room temperature, a piezoelectric d33 larger than 1500 pm/V with very little frequency dispersion can be obtained. © 1995 American Institute of Physics.
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77.65.-j Piezoelectricity and electromechanical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Ab initio studies on the electronic structures of strained‐layer superlattices (InAs)n(InP)n(001), (n=1–5)

San‐huang Ke, Ren‐zhi Wang, and Mei‐chun Huang

J. Appl. Phys. 77, 2556 (1995); http://dx.doi.org/10.1063/1.358717 (8 pages) | Cited 5 times

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We report ab initio studies on the electronic structures of strained‐layer superlattices (SLSs) (InAs)n(InP)n(001), (n=1–5) under three different strain conditions via a linearized muffin‐tin‐orbital method with two treatments for d states. The effects of In 4d orbitals on the band structure and the valence band offset (VBO) are investigated. The hydrostatic pressure behavior and the Γ–X mixture in these SLS systems are also discussed. It is found that the band gap of the InP/InAs system is insensitive to its layer thickness. The VBO values at the SLS’s under the three strain conditions are determined by a frozen potential approach. Our results demonstrate that for the InP/InAs system the bulklike property is almost recovered in the molecular layer next to the interface. This behavior may be due to the common cation on both sides of the interface. This makes the frozen‐potential approach converge very fast with the layer thickness. Our results of band structure for the (1+1) SLS under a free‐standing mode are consistent with those given by a more elaborate full‐potential linearized augmented‐plane‐wave (FLAPW) calculation. The present results of VBO are about 0.07–0.09 eV larger than the data from an x‐ray photoelectron spectroscopy measurement and the FLAPW method, while in good agreement with the results given by the model solid theory. © 1995 American Institute of Physics.  
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

Quantum bound states in a double‐bend quantum channel

Chuan‐Kui Wang, K.‐F. Berggren, and Zhen‐Li Ji

J. Appl. Phys. 77, 2564 (1995); http://dx.doi.org/10.1063/1.358718 (8 pages) | Cited 7 times

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By use of the mode‐matching technique the quantum bound states in a double‐bend quantum channel of finite length connecting to two 2D electron gas reservoirs have been investigated in detail. The conductance G of the quantum system is calculated as a function of Fermi energy and the electron density associated with bound states. It is found that there exists one resonant peak in G corresponding to resonant tunneling via one quasibound state below the first conductance plateau for the quantum channel with double‐bend continuity and two resonant peaks in G corresponding to resonant tunneling via two quasibound states which are symmetric and antisymmetric superposition of two local bound states localized at two right‐angle bends below the first conductance plateau for the quantum channel with double‐bend discontinuity. At finite temperature the results are compared with experimental results and are found to explain them well. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.Dp General theory, scattering mechanisms
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