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10 Oct 1994

Volume 65, Issue 15, pp. 1863-1972

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Experimental evidence of photoeffects in silicon rapid isothermal diffusion

J. Mavoori, R. Singh, S. Narayanan, and J. Chaudhuri

Appl. Phys. Lett. 65, 1935 (1994); http://dx.doi.org/10.1063/1.112822 (3 pages) | Cited 12 times

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Rapid isothermal processing (RIP) based on incoherent radiation as a source of optical and thermal energy is emerging as a key low thermal budget technique for the processing of semiconductor devices and circuits. The continuing development of RIP technique for the fabrication of electronic and optical devices requires a microscopic understanding of various phenomena associated with RIP. Junction formation by diffusion process is an integral part of all semiconductor devices. In this letter, we have shown that for identical thermal budget, different values of sheet resistivity are observed when the samples are irradiated from front or back. These results cannot be explained by the various process models and computer aided design tools available in the literature. We have offered a qualitative explanation of the observed results based on the role of photoeffects in RIP. The availability of high‐energy photons in the front irradiation configuration and consequent electronic excitation can lead to higher diffusion coefficients as well as higher activation of dopants, compared to the back irradiated case. © 1994 American Institue of Physics.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities
81.40.Gh Other heat and thermomechanical treatments

Empirical formula for the dielectric constant of cubic semiconductors

B. R. Nag

Appl. Phys. Lett. 65, 1938 (1994); http://dx.doi.org/10.1063/1.112823 (2 pages) | Cited 12 times

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Empirical formulae are presented relating the dielectric constants of cubic semiconductors with the average atomic number of the constituent atoms. The inverses of the constants are found to be linearly related to the average atomic number with a square foot mean percentage error of less than 0.25% for elemental semiconductors, 1.3% for gallium and indium compounds, 3.4% for aluminium compounds, 1.4% for II‐VI compounds, and 1.2% for lead compounds. Usefulness of the formulae is also illustrated for identifying incorrect values and for estimating unknown values. © 1994 American Institue of Physics.
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77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Fast growth of hydrogenated amorphous silicon from dichlorosilane

Masami Nakata and Sigurd Wagner

Appl. Phys. Lett. 65, 1940 (1994); http://dx.doi.org/10.1063/1.112966 (3 pages) | Cited 11 times

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We report the discovery of very high growth rates of hydrogenated amorphous silicon (a‐Si:H) from a glow discharge in dichlorosilane (SiH2Cl2) with small additions of silane (SiH4). The growth rate reaches ∼50 Å s−1 at substrate temperatures between 200 and 300 °C. The rate depends on substrate temperature and is correlated with the concentrations of hydrogen and chlorine in the films in a way that suggests a SiH4‐catalyzed mutual elimination of Cl and H from the growing surface. We observe no dust, and no growth on the cold walls of the chamber. The film properties suggest material close to device quality, with dark conductivities of ∼10−12 S cm−1 and photoconductivities of ∼10−7 S cm−1. We measured a midgap defect density of 3.3×1016 cm−3 in an as‐grown film, and 4.5×1016 cm−3 after 73 h of light soaking at 1 W cm−2. © 1994 American Institue of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Double two‐dimensional electron gas structure formed by molecular beam epitaxy regrowth on an ex situ patterned n+‐GaAs back gate

R. J. Evans, M. P. Grimshaw, J. H. Burroughes, M. L. Leadbeater, M. J. Tribble, D. A. Ritchie, G. A. C. Jones, and M. Pepper

Appl. Phys. Lett. 65, 1943 (1994); http://dx.doi.org/10.1063/1.112824 (3 pages) | Cited 1 time

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We have regrown two two‐dimensional electron gases (2DEGs) in a wide GaAs quantum well on a large area ex situ patterned n+‐GaAs back gate. The transport in these channels is controlled by this gate and a surface front gate. We present results showing the control that the patterned back gate has over the carrier concentration in the low mobility back 2 DEG and the very low leakage currents that are observed from the back gate to the source‐drain channel at 1.5 K. Using four terminal resistance and magnetoresistance data the transition from two conducting channels to conduction in the low mobility back 2DEG is shown. The implications of these results for the fabrication of velocity modulated transistors are discussed. © 1994 American Institue of Physics.
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85.40.Hp Lithography, masks and pattern transfer
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Empirical relationship between the low‐frequency noise spectral density and the transconductance of silicon‐on‐insulator n‐channel metal‐oxide‐semiconductor transistors

E. Simoen and C. Claeys

Appl. Phys. Lett. 65, 1946 (1994); http://dx.doi.org/10.1063/1.112825 (3 pages) | Cited 2 times

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In this letter, the relationship between the input‐referred low‐frequency noise spectral density SVG and the transconductance gm of a large number of similar silicon‐on‐insulator n‐channel metal‐oxide‐semiconductor transistors is investigated. As will be shown, a large, two orders of magnitude dispersion is observed in the noise, which corresponds with a factor two variation in gm. It is demonstrated that the average SVG depends exponentially on the corresponding transconductance. This holds both for linear operation—in strong and weak inversion—and for saturation. The practical implications of these findings are discussed. © 1994 American Institue of Physics.
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72.70.+m Noise processes and phenomena
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Evolution of surface topography during metalorganic vapor phase epitaxy of InP/InGaAs/InP quantum well heterostructures

J. E. Epler, J. Söchtig, and H. C. Sigg

Appl. Phys. Lett. 65, 1949 (1994); http://dx.doi.org/10.1063/1.112826 (3 pages) | Cited 5 times

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The evolution of surface topography during epitaxial growth of lattice matched InP/InGaAs/InP on (100) InP substrate is observed using in situ elastic light scattering supported by ex situ atomic force microscopy. A topographically smooth growth transition from InP to InGaAs is observed. However, the InP‐on‐InGaAs interface exhibits three‐dimensional nucleation followed by planarization and two‐dimensional epitaxy. The three‐dimensional phase is a result of the high surface energy of InP relative to InGaAs. A growth pause after the InGaAs QW increases the transient roughness of the InP surface and increases the thickness of InP required for planarization. © 1994 American Institue of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.35.Md Surface thermodynamics, surface energies

High‐spatial‐resolution photoluminescence measurements on AlxGa1−xAs grown on a nonplanar substrate by metalorganic vapor phase epitaxy

S. M. Olsthoorn, M. M. G. Bongers, and L. J. Giling

Appl. Phys. Lett. 65, 1952 (1994); http://dx.doi.org/10.1063/1.112827 (3 pages) | Cited 3 times

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High‐spatial‐resolution photoluminescence measurements are reported of AlxGa1−xAs grown on nonplanar substrates by metalorganic vapor phase epitaxy. The aluminum fractions are determined of the various facets of three grooves with varying widths. The (111)A facets on the side walls of the grooves have an aluminum fraction 6.3% higher than that of the unpatterned area. The narrowest groove is exactly V‐shaped showing only these (111)A facets. Higher index facets in the corners of the bottom of the two broader grooves show a 27.8% reduction in aluminum fraction as compared with the unpatterned area. The aluminum fractions of the (100) facets at the bottom of the grooves depend strongly on the groove widths. © 1994 American Institue of Physics.
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78.55.Cr III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Nq Composition and phase identification

Structural and electrical properties of BaTiO3 grown on p‐InP (100) by low‐pressure metalorganic chemical vapor deposition at low temperature

T. W. Kim and S. S. Yom

Appl. Phys. Lett. 65, 1955 (1994); http://dx.doi.org/10.1063/1.112828 (3 pages) | Cited 8 times

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Metalorganic chemical vapor deposition of BaTiO3 using Ba(tmhd)2, Ti(OC3H7)4, and N2O via pyrolysis at relatively low temperature (∼300 °C) was performed in order to produce high‐quality BaTiO3/p‐InP (100) interfaces and BaTiO3 insulator gates with dielectric constants of high magnitude. Scanning electron microscopy showed that the surfaces of the BaTiO3 films had very smooth morphologies. Auger electron spectroscopy measurements showed that the compositions of the as‐grown films consisted of barium, titanium, and oxygen. Transmission electron microscopy showed that the BaTiO3 films had interdiffusion and local epitaxial formations near the BaTiO3/p‐InP (100) interfaces. Room‐temperature current‐voltage and capacitance‐voltage (C‐V) measurements clearly revealed metal‐insulator‐semiconductor behavior for the BaTiO3 insulator gates, and the interface state densities at the BaTiO3/p‐InP interfaces were approximately low 1011 eV−1 cm−2 at an energy about 0.6 eV below the conduction‐band edge. The dielectric constant of the BaTiO3 thin film determined from C‐V measurements was as large as 78. © 1994 American Institue of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Enhancement in thermal shock resistance of melt‐textured YBa2Cu3Ox superconductors by hot isostatic pressing

A. Satpathy, D. F. Lee, C. Partsinevelos, K. Salama, and V. Selvamanickam

Appl. Phys. Lett. 65, 1958 (1994); http://dx.doi.org/10.1063/1.112829 (3 pages) | Cited 1 time

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Thermal shock resistance of melt‐textured YBa2Cu3Ox superconductors has been investigated by thermal cycling between 77 and 350 K. The current carrying capability of as‐melt‐textured specimens is found to drop in three stages by a factor of up to 50% after 60 cycles. To rectify this degradation, a hot isostatic pressing (Hipping) method has been developed to close the microcracks generated during thermal cycling. The critical current (Ic) of specimens that were thermally cycled followed by Hipping is found to increase even above the initial Ic value of its as‐melt‐textured state. More importantly, Ic of the Hipped specimens is found to be completely insensitive to thermal cycling even after 60 cycles. Indentation measurements revealed that Hipping strengthens the basal plane platelet boundaries in addition to closing the microcracks. © 1994 American Institue of Physics.
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74.72.-h Cuprate superconductors
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.25.Sv Critical currents
81.40.Rs Electrical and magnetic properties related to treatment conditions

High current YBa2Cu3O7−δ thick films on flexible nickel substrates with textured buffer layers

X. D. Wu, S. R. Foltyn, P. Arendt, J. Townsend, C. Adams, I. H. Campbell, P. Tiwari, Y. Coulter, and D. E. Peterson

Appl. Phys. Lett. 65, 1961 (1994); http://dx.doi.org/10.1063/1.112830 (3 pages) | Cited 95 times

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High current YBa2Cu3O7−δ (YBCO) thick films on flexible nickel substrates with textured buffer layers were fabricated. Highly textured yttria‐stabilized‐zirconia buffer layers were deposited by using ion beam assisted deposition (IBAD). Pulsed laser deposited YBCO films were not only c‐axis oriented with respect to the film surface but also strongly in‐plane textured. The in‐plane mosaic spread of YBCO films was ∼10°. A critical current density of 8×105 A/cm2 was obtained at 75 K and zero field for thin YBCO films. It was also demonstrated that thick YBCO films with a high critical current and excellent magnetic field dependence at liquid nitrogen temperature can be obtained on flexible nickel substrates by using the textured buffer layers. The result indicates that thick film technology in combination with IBAD buffer layers could be a viable method for fabricating YBCO tapes in long lengths. © 1994 American Institue of Physics.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Fg Pulsed laser ablation deposition
74.25.Sv Critical currents

Epitaxial orientation and magnetic properties of MnAs thin films grown on (001) GaAs: Template effects

M. Tanaka, J. P. Harbison, M. C. Park, Y. S. Park, T. Shin, and G. M. Rothberg

Appl. Phys. Lett. 65, 1964 (1994); http://dx.doi.org/10.1063/1.112831 (3 pages) | Cited 116 times

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We have studied template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates. When As2 flux was first supplied without Mn flux on the (001) GaAs prior to the MnAs growth, the surface reconstruction was disordered c(4×4), a more As‐rich surface than c(4×4). The growth direction of the MnAs thin film grown on this surface is [1100] and the easy magnetization axis was found to be along the [1120] of MnAs and the [110] of GaAs. In contrast, when one monolayer of Mn was first deposited on the c(4×4) GaAs surface and then As2 flux was supplied to grow MnAs, the growth direction of the MnAs thin film was found to be mainly [1101], and the easy magnetization axis was along the [1120] of MnAs and the [110] of GaAs, 90° different with respect to the substrate. These results indicate the importance of the very first monolayer in controlling the epitaxial orientation and magnetic properties of epitaxial ferromagnetic MnAs thin films. © 1994 American Institue of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Magnetic properties of exchange coupled NiFe/CoO/NiFe trilayers

T. Ambrose and C. L. Chien

Appl. Phys. Lett. 65, 1967 (1994); http://dx.doi.org/10.1063/1.112836 (3 pages) | Cited 32 times

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A trilayer system consisting of an antiferromagnet (CoO) sandwiched by two ferromagnetic (NiFe=Ni81Fe19) layers of unequal thicknesses has been studied. Four different spin structures have been observed. The temperature dependencies of the exchange fields (HE) and coercivity (Hc) have been determined. The layer order between the antiferromagnet and the ferromagnet dictates the exchange field temperature behavior. © 1994 American Institue of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Formation of artificial BaTiO3/SrTiO3 superlattices using pulsed laser deposition and their dielectric properties

Hitoshi Tabata, Hidekazu Tanaka, and Tomoji Kawai

Appl. Phys. Lett. 65, 1970 (1994); http://dx.doi.org/10.1063/1.112837 (3 pages) | Cited 215 times

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We have formed strained dielectric superlattices of BaTiO3 (BTO) and SrTiO3 (STO) by a pulsed laser deposition technique. A large strain of 400–500 MPa is introduced at the interface between the BTO and STO layers. A large dielectric constant of 900 was observed with a stacking periodicity of 2 unit cells/2 unit cells. The superlattices show drastically different electrical behavior from that of the solid solution (Sr,Ba)TiO3 films. Broad maxima of the dielectric constants occur around 40–50 °C and the values remain large even for a temperature above 200 °C. © 1994 American Institue of Physics.
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81.15.Fg Pulsed laser ablation deposition
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.-d Dielectric properties of solids and liquids
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