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28 Nov 1988

Volume 53, Issue 22, pp. 2123-2240

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Boron profile changes during low‐temperature annealing of BF+2‐implanted silicon

Yudong Kim, Hisham Z. Massoud, and Richard B. Fair

Appl. Phys. Lett. 53, 2197 (1988); http://dx.doi.org/10.1063/1.100505 (3 pages) | Cited 10 times

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BF+2 ions were implanted in (100) silicon at room temperature with an energy of 40 keV through a 140‐Å‐thick SiO2 layer. Boron profiling by secondary‐ion mass spectrometry indicates that subsequent annealing in a conventional furnace in the 650–850 °C range for 30–240 min results in a pronounced secondary peak in the B and F profiles, in addition to the near‐surface primary peak located in the vicinity of the projected range of the implanted species. This phenomenon was also observed in BF+2 ‐implanted samples which were rapid thermal annealed at 900 °C for 15–60 s. The depths of the secondary peaks in the B and F profiles correspond to the depths of a damaged layer observed by cross‐sectional transmission electron microscopy. Isochronal furnace annealing revealed that there is no chemical interaction between B and F atoms during annealing. This is also supported by the observation of F atoms not affecting the B segregation coefficient during oxidation of the BF+2 ‐implanted samples. The end‐of‐range extended dislocations appear to be responsible for the gettering of B and F atoms during annealing.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
85.40.Hp Lithography, masks and pattern transfer

Stability of TaSix‐GaAs Schottky barriers in rapid thermal processing

T. E. Haynes, W. K. Chu, C. C. Han, S. S. Lau, and S. T. Picraux

Appl. Phys. Lett. 53, 2200 (1988); http://dx.doi.org/10.1063/1.100506 (3 pages) | Cited 7 times

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n‐type GaAs samples coated with TaSi2 and Ta5 Si3 Schottky barrier contacts were heated in a flashlamp rapid thermal processing (RTP) system to temperatures between 600 and 950 °C. We have measured the evaporation of gallium and arsenic through the contact overlayers which results from the decomposition of the GaAs substrate. These decomposition measurements have been correlated with the Schottky barrier behavior as determined from forward‐bias current‐voltage characteristics and selected capacitance‐voltage measurements. The high‐temperature stability against decomposition and electrical degradation was superior for Ta5 Si3 contacts relative to TaSi2 contacts. We observed for both contact compositions that the onset temperature for decomposition of GaAs was slightly lower than the maximum temperature for electrical stability. Thus, we found that in some cases substantial decomposition occurred with no effect on the current‐voltage characteristics. For example, Ta5 Si3 contacts maintained a stable barrier height of 0.78 eV through 10 s RTP treatments up to 900 °C, in spite of decomposition of at least ten equivalent monolayers of GaAs.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ei Rectification
73.40.Ns Metal-nonmetal contacts
68.60.Dv Thermal stability; thermal effects

Observation of carbon incorporation during gallium arsenide growth by molecular beam epitaxy

David M. Joseph, Rajappan Balagopal, Robert F. Hicks, Laurence P. Sadwick, and Kang L. Wang

Appl. Phys. Lett. 53, 2203 (1988); http://dx.doi.org/10.1063/1.100281 (2 pages) | Cited 5 times

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Carbon incorporation has been observed by infrared spectroscopy during the growth of a gallium arsenide film at 200 °C by molecular beam epitaxy. Infrared absorbances are observed at 2925 and 2855 cm−1 with a shoulder at 2950 cm−1. These frequencies are characteristic of the symmetric and asymmetric stretches of CH3 and/or CH2 groups.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.30.Fs III-V and II-VI semiconductors

A Monte Carlo study of electron‐hole scattering and steady‐state minority‐electron transport in GaAs

K. Sadra, C. M. Maziar, B. G. Streetman, and D. S. Tang

Appl. Phys. Lett. 53, 2205 (1988); http://dx.doi.org/10.1063/1.100282 (3 pages) | Cited 7 times

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We report the first bipolar Monte Carlo calculations of steady‐state minority‐electron transport in room‐temperature p‐GaAs including multiband electron‐hole scattering with and without hole overlap factors. Our results show how such processes, which make a significant contribution to the minority‐electron energy loss rate, can affect steady‐state minority‐electron transport. Furthermore, we discuss several other issues which we believe should be investigated before present Monte Carlo treatments of electron‐hole scattering can provide quantitative information.
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72.20.Dp General theory, scattering mechanisms
72.80.Ey III-V and II-VI semiconductors

Minimization of dopant‐induced random potential fluctuations in sawtooth doping superlattices

E. F. Schubert, T. D. Harris, and J. E. Cunningham

Appl. Phys. Lett. 53, 2208 (1988); http://dx.doi.org/10.1063/1.100283 (3 pages) | Cited 12 times

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Potential fluctuations due to random dopant distribution are estimated in a doping superlattice for different doping profiles. It is shown that statistical potential fluctuations are minimized by employing a doping profile consisting of a train of δ functions, which result in sawtooth‐shaped band edges. Clearly resolved quantum‐confined optical absorption and luminescence transitions are observed in this improved doping superlattice structure. The sawtooth superlattice provides the basis for a novel GaAs technology which is suited to operate in the minimum dispersion region of silica fibers at a wavelength of λ=1.3 μm.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Comparison of SiIII‐SiV and SiIII‐VIII diffusion models in III‐V heterostructures lattice matched to GaAs

D. G. Deppe, W. E. Plano, J. E. Baker, N. Holonyak, M. J. Ludowise, C. P. Kuo, R. M. Fletcher, T. D. Osentowski, and M. G. Craford

Appl. Phys. Lett. 53, 2211 (1988); http://dx.doi.org/10.1063/1.100284 (3 pages) | Cited 4 times

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The diffusion of SiIII‐SiV neutral pairs versus the diffusion of SiIII‐VIII complexes in III‐V crystals is compared in the light of experimental data showing the effect of Si diffusion on self‐diffusion of column III and column V lattice atoms. Secondary‐ion mass spectroscopy is used to compare the enhanced diffusion of column III or column V atoms in several different Si‐diffused heterostructures closely lattice matched to GaAs. Enhancement of the lattice‐atom self‐diffusion, via impurity diffusion, is found to occur predominantly on the column III lattice. Supporting the SiIII‐VIII diffusion model, these data indicate that the main native defects accompanying the Si diffusion are column III vacancies, which diffuse directly on the column III sublattice.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
66.30.Ny Chemical interdiffusion; diffusion barriers
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation

Dynamics of photoexcited carriers in micron‐size InP‐InGaAsP etched microstructures probed by picosecond photoluminescence spectroscopy

K. Kash, P. Grabbe, R. E. Nahory, A. Scherer, A. Weaver, and C. Caneau

Appl. Phys. Lett. 53, 2214 (1988); http://dx.doi.org/10.1063/1.100285 (3 pages) | Cited 4 times

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We report the first use of picosecond photoluminescence spectroscopy to probe carrier relaxation in etched semiconductor microstructures. 2‐μm‐diam posts etched from double‐heterostructure InP‐InGaAsP epitaxial layers show anomalous time‐dependent spectral broadening and blue shift of the quaternary layer band‐edge luminescence. This new effect may be a result of modification of recombination processes upon microstructuring.
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78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Reduction of defects and inhomogeneous strain in heteroepitaxial ZnSe

B. J. Skromme, M. C. Tamargo, J. L. de Miguel, and R. E. Nahory

Appl. Phys. Lett. 53, 2217 (1988); http://dx.doi.org/10.1063/1.100286 (3 pages) | Cited 8 times

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We present low‐temperature ZnSe photoluminescence spectra having very narrow bound exciton linewidths (0.55 meV), which demonstrate for the first time that thin, pseudomorphic ZnSe layers with minimal inhomogeneous strain can be grown directly on GaAs by molecular beam epitaxy. Similar characterization of ZnSe/AlAs/GaAs heterostructures shows that AlAs layers up to 4 μm thick exhibit only kinetically limited, partial lattice relaxation, which prevents the overgrowth of uniform, coherently strained ZnSe layers. However, pseudomorphic ZnSe/AlAs/GaAs structures with thin (≲0.5 μm) AlAs layers exhibit the narrowest bound exciton peaks (≲0.37 meV full width at half maximum) ever reported for heteroepitaxial ZnSe, indicating a high degree of structural perfection.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Et II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

New modulated structure in a Pb‐doped Bi‐Ca‐Sr‐Cu‐O superconductor

R. Ramesh, G. van Tendeloo, G. Thomas, S. M. Green, and H. L. Luo

Appl. Phys. Lett. 53, 2220 (1988); http://dx.doi.org/10.1063/1.100507 (3 pages) | Cited 37 times

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A new modulated structure has been observed in a Pb‐doped Bi‐Ca‐Sr‐Cu‐O superconductor (Tc,0=105 K) in addition to the incommensurate modulated structure reported by several researchers. This new modulation occurs in the b∗ direction and shows up as satellite spots to each of the original diffracted spots. Upon cooling to 88 K the diffraction spots due to the original modulation disappear, while the spots due to the new modulation remain. In the case of the undoped samples, the modulation does not disappear upon cooling to 30 K, which is below the Tc,0 of the sample (∼75 K).
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds

Magnetization and critical currents of Bi‐Sr‐Ca‐Cu‐O and Ba2YCu3O7 superconductors

E. M. Gyorgy, R. B. van Dover, S. Jin, R. C. Sherwood, L. F. Schneemeyer, T. H. Tiefel, and J. V. Waszczak

Appl. Phys. Lett. 53, 2223 (1988); http://dx.doi.org/10.1063/1.100508 (3 pages) | Cited 15 times

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We have measured the critical currrent density Jc as a function of temperature for a Bi‐Sr‐Ca‐Cu‐O sample containing a substantial fraction of a phase with Tc≊110 K and for a Ba2YCu3O7 sample (TTc≊92 K). The behavior of Jc was deduced from magnetization measurements. For both samples the magnetization at fixed temperature and field decayed logarithmically with time. The values of Jc so derived, allowing for the decay to occur, went to zero for temperatures above 35 K for the Bi‐Sr‐Ca‐Cu‐O ceramic and to zero above 70 K for the Ba2YCu3O7 sample. These values are substantially lower than those deduced from dynamic M‐H loops.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena

Planar weak‐link devices from YBaCuO and BiSrCaCuO films

I. S. Gergis, J. A. Titus, P. H. Kobrin, and A. B. Harker

Appl. Phys. Lett. 53, 2226 (1988); http://dx.doi.org/10.1063/1.100509 (3 pages) | Cited 11 times

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Weak‐link devices were fabricated from polycrystalline thin films of YBaCuO and BiSrCaCuO. Two distinct types of weak links have been found in these devices. The first type, found in all of the YBaCuO and most of the BiSrCaCuO devices, has relatively low dynamic resistances and critical currents with nearly linear temperature dependences. The second type of weak links, found in some BiSrCaCuO films, has much larger dynamic resistances and critical current temperature dependences similar to that of a tunnel junction. Superconductivity quantum interference devices (SQUID’s) fabricated from BiSrCaCuO showed a periodic response to applied fields that is consistent with the magnitude of the flux enclosed by the SQUID loop. Significant hysteresis was found in the SQUID response, apparently indicating flux penetration into the films at relatively low fields.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

High Tc superconducting thin films by rapid thermal annealing of Cu/BaO/Y2O3 layered structures

Q. Y. Ma, T. J. Licata, X. Wu, E. S. Yang, and Chin‐An Chang

Appl. Phys. Lett. 53, 2229 (1988); http://dx.doi.org/10.1063/1.100510 (3 pages) | Cited 13 times

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Superconducting thin films of YBaCuO have been formed using rapid thermal annealing of Cu/BaO/Y2 O3 layered structures, which were deposited on MgO substrates by electron beam evaporation. The best film has an onset temperature of 94 K and zero resistance at 84 K. The dependence of the film characteristics and superconducting transition temperature on the annealing conditions has been studied. Auger depth profiling was used to examine the interdiffusion between the film and the MgO substrate.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Rs Electrical and magnetic properties related to treatment conditions

Epitaxial growth of YBa2Cu3O7−x thin films on (110) SrTiO3 single crystals by activated reactive evaporation

T. Terashima, Y. Bando, K. Iijima, K. Yamamoto, and K. Hirata

Appl. Phys. Lett. 53, 2232 (1988); http://dx.doi.org/10.1063/1.100511 (3 pages) | Cited 39 times

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The orientation of YBa2Cu3O7−x thin films grown on (110) planes of SrTiO3 by activated reactive evaporation was investigated by means of reflection high‐energy electron diffraction. The orientation of the films depended on the substrate temperature. The films with (110) planes parallel to the substrate surface grew in a narrow range of substrate temperatures around 530 °C, while the films with (103) planes parallel to the surface grew at temperatures above 600 °C. The change of the epitaxial orientation with the substrate temperature is discussed in terms of the temperature dependence of the lattice mismatch between YBa2Cu3O7−x and SrTiO3.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Synthesis of LaBa2Cu3O7−y through tetragonal to orthorhombic phase transition at high oxygen deficiency

Stephen G. Brass and Mohammad H. Ghandehari

Appl. Phys. Lett. 53, 2235 (1988); http://dx.doi.org/10.1063/1.100512 (3 pages) | Cited 5 times

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Superconductive LaBa2Cu3O7−y materials which achieve zero resistivity at temperatures above 90 K have been synthesized using the appropriate sintering and annealing conditions. We find it necessary to sinter our samples in an inert atmosphere and to cool our samples from a high temperature to below the tetragonal to orthorhombic transition temperature in an inert atmosphere before the sample is further exposed to oxygen. We conclude that in order to produce amounts of orthorhombic LaBa2Cu3O7−y material sufficient to achieve zero resistivity at temperatures of 90 K or above, it is necessary to prevent the material from incorporating too much oxygen while it is at temperatures in excess of its tetragonal to orthorhombic transition temperature.
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74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
64.70.K- Solid-solid transitions

Magnetization measurements of single levitated grains of Ba2YCu3O7

G. S. Grader, A. F. Hebard, and R. H. Eick

Appl. Phys. Lett. 53, 2238 (1988); http://dx.doi.org/10.1063/1.100513 (3 pages) | Cited 7 times

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An electrodynamic balance has been constructed in which the perturbative forces from applied magnetic fields are used to probe the superconducting properties of single levitated charged grains of high Tc superconductors with diameters ≲10 μm. The low‐temperature magnetization of selected Ba2YCu3O7 grains has been observed to exhibit a flux exclusion near 80% of the theoretical maximum. Hysteresis, flux creep, and the lower critical field are identified.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
84.71.Ba Superconducting magnets; magnetic levitation devices
74.25.Op Mixed states, critical fields, and surface sheaths
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