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21 Nov 1988

Volume 53, Issue 21, pp. 1999-2113

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In situ thermal oxidation for surface cleaning and mask generation prior to selective area epitaxy

Stephen H. Jones and Kei May Lau

Appl. Phys. Lett. 53, 2068 (1988); http://dx.doi.org/10.1063/1.100321 (3 pages) | Cited 2 times

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Dry thermal oxidation of GaAs and AlAs has been carried out in an organometallic chemical vapor deposition system. This in situ process performed either before or after an epitaxial growth serves the purposes of surface cleaning and mask generation for selective area epitaxy of various III‐V semiconductors. AlAs oxidized immediately after growth and patterned for the next regrowth provides better oxide‐semiconductor interfaces and minimizes wafer handling. Pre‐epitaxy oxidation at 435 °C on a patterned wafer with AlAs/GaAs areas resulted in a selective oxide mask. Since thermal oxides of GaAs sublime at temperatures >600 °C, a 700 °C pregrowth annealing thus thermally cleans the oxidized GaAs areas while the oxides of AlAs remain as a mask for the following regrowth. Photoluminescence results indicate that high quality regrown interfaces have been obtained.
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81.65.-b Surface treatments
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ensemble Monte Carlo simulation of Te‐induced intermixing of AlGaAs‐based interfaces

K. B. Kahen

Appl. Phys. Lett. 53, 2071 (1988); http://dx.doi.org/10.1063/1.100322 (3 pages) | Cited 4 times

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An ensemble Monte Carlo simulation has been used to model the enhanced disordering of AlGaAs‐based interfaces in the presence of high concentrations of Te atoms. The model is based on the experimental finding that the thermal interdiffusion process is similar to the self‐diffusion of Ga in GaAs. The model agrees well with the experimental data for both the Ga self‐diffusion and intermixing. The intermixing is found to be caused by the enhanced solubility of the Ga vacancy acceptors in the presence of the donor Te atoms, and not as a result of the diffusion of the Te atoms. The activation energy of the process is found to be approximately 2.7 eV.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.jd Vacancies
61.72.jj Interstitials
66.30.J- Diffusion of impurities

Electrical properties of ytterbium‐doped InP grown by metalorganic chemical vapor deposition

Peter S. Whitney, Kunihiko Uwai, Hiroshi Nakagome, and Ke’ichiro Takahei

Appl. Phys. Lett. 53, 2074 (1988); http://dx.doi.org/10.1063/1.100305 (3 pages) | Cited 68 times

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A study has been carried out on the electrical properties of ytterbium‐doped InP grown by metalorganic chemical vapor deposition for the purpose of clarifying the electrical behavior of ytterbium impurities in InP. The epilayers were characterized by Hall effect measurements and by deep level transient spectroscopy. The results strongly suggest that ytterbium introduces an acceptor‐like level 0.03±0.01 eV below the conduction band which is related to isolated ytterbium atoms or single ytterbium atoms complexed with native defects. No signs of precipitation or clustering of ytterbium are observed for concentrations below 1018 cm−3 . Contrary to previous hypotheses, no evidence has been found for the existence of an ytterbium‐related acceptor level in the lower half of the band gap.
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73.61.Ey III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

(111) oriented (GaAs)n(AlAs)n superlattices are direct band‐gap materials for all n’s

Su‐Huai Wei and Alex Zunger

Appl. Phys. Lett. 53, 2077 (1988); http://dx.doi.org/10.1063/1.100415 (3 pages) | Cited 19 times

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Total energy calculations show that the (111) (AlAs)n(GaAs)n superlattice has a lower formation enthalpy (i.e., is stabler) than either the (001) or (110) superlattices. Self‐consistent band structure calculations further show that while the (001) superlattice is direct only for n>7, the (111) superlattice has (i) a smaller and (ii) a direct (not pseudodirect) gap for all n’s. Contrary to the expectations based on particle in a box models, the confined states at the zone center are strongly localized even for the monolayer superlattice.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Two‐dimensional electron system with extremely low disorder

M. Shayegan, V. J. Goldman, M. Santos, T. Sajoto, L. Engel, and D. C. Tsui

Appl. Phys. Lett. 53, 2080 (1988); http://dx.doi.org/10.1063/1.100306 (3 pages) | Cited 15 times

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We report on the growth of modulation‐doped GaAs/AlxGa1−x As heterostructures with extremely low disorder by molecular beam epitaxy. In growing these structures we employed the atomic plane doping technique and ultrathick (>1000 Å) spacer layers with graded composition. The structures have mobilities (μ) on the order of 1×106 cm2/V s (at 4.2 K) for areal densities (ns) as low as 4×1010 cm−2. Quantum transport measurements in these structures exhibit new fractional quantum Hall states and demonstrate their exceptionally high quality.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

X‐ray topography of the coherency breakdown in GexSi1−x/Si(100)

D. J. Eaglesham, E. P. Kvam, D. M. Maher, C. J. Humphreys, G. S. Green, B. K. Tanner, and J. C. Bean

Appl. Phys. Lett. 53, 2083 (1988); http://dx.doi.org/10.1063/1.100288 (3 pages) | Cited 24 times

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An x‐ray topography study is presented of the coherency breakdown in GexSi1−x/Si(100) strained epilayers. Finite dislocation densities (in excess of 103 cm−2) are observed at compositions in the range 12–13 at. % Ge for an epilayer thickness of h≊180 nm. Above 13 at. % Ge the dislocation density starts to change rapidly and this composition is identified as critical for h≊180 nm, a thickness which is almost a factor of 4 lower than the accepted ‘‘critical’’ thickness for this lattice mismatch. The result suggests that in low‐mismatched GexSi1−x alloys the dislocation density will increase continuously at the ‘‘critical’’ thickness, as opposed to exhibiting a sharp onset. The implications of these results to the various models of the critical thickness transition are discussed.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Behavior of Ga on Si(100) as studied by scanning tunneling microscopy

J. Nogami, Sang‐il Park, and C. F. Quate

Appl. Phys. Lett. 53, 2086 (1988); http://dx.doi.org/10.1063/1.100289 (3 pages) | Cited 62 times

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The behavior of gallium on the Si(100) surface has been studied with scanning tunneling microscopy at low metal coverages. The Ga atoms are more mobile on Si(100) than on Si(111) under the same conditions. At less than 0.1 monolayer, the Ga atoms line up in rows parallel to the Si dimerization direction with a two unit cell periodicity. At higher metal densities, these rows are organized into areas of 3×2 two‐dimensional order. The relevance of these results to studies of the initial stages of growth of GaAs on Si is discussed.
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68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Femtosecond intervalley scattering in GaAs

P. C. Becker, H. L. Fragnito, C. H. Brito Cruz, J. Shah, R. L. Fork, J. E. Cunningham, J. E. Henry, and C. V. Shank

Appl. Phys. Lett. 53, 2089 (1988); http://dx.doi.org/10.1063/1.100290 (2 pages) | Cited 66 times

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We report the measurement of intervalley scattering rates for optically excited carriers in GaAs. The measurements were performed using optical pulses of 6 fs duration and an energy distribution centered at 2.0 eV. The average rates for Γ→X and Γ→L intervalley scattering were separately estimated by varying the sample temperature.
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72.20.Dp General theory, scattering mechanisms
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

AlGaInP/GaAs red edge‐emitting diodes for polymer optical fiber applications

B. V. Dutt, J. H. Racette, S. J. Anderson, F. W. Scholl, and J. R. Shealy

Appl. Phys. Lett. 53, 2091 (1988); http://dx.doi.org/10.1063/1.100497 (2 pages) | Cited 5 times

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Pulsed and cw operation of AlGaInP/GaAs graded refractive index separate confinement heterostructure edge light‐emitting diodes fabricated from epitaxial structures grown by organometallic vapor phase epitaxy is reported. The device consists of an active region of a single 100 Å quantum well of ternary Ga0.5In0.5P and 1600‐Å‐thick lattice‐matched confining layers of quaternary (AlxGa1−x)0.5In0.5P. A coupled power of −10 dBm at 100 mA into a 500 μm polymer optical fiber of 0.48 NA is realized in a package consisting of a graded refractive index lens with uncoated facets from a 60×300 μm mesa‐shaped stripe geometry diode. The 10–90% rise and fall times at 100 mA with a 5 mA prebias were measured to be 5 ns. Higher launched powers are expected to result from improvements in the materials growth, facet coatings, and packaging techniques.
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85.60.Jb Light-emitting devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
81.15.Kk Vapor phase epitaxy; growth from vapor phase

High‐temperature resistance behavior of Bi2Sr2CaCu2O8+y and YBa2Cu3O7−x superconductors

T. K. Bansal, Sadhana Bansal, R. L. McGreevy, S. H. Smith, and G. Garton

Appl. Phys. Lett. 53, 2093 (1988); http://dx.doi.org/10.1063/1.100498 (3 pages) | Cited 2 times

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High‐ and low‐temperature resistance measurements have been carried out on Bi2Sr2CaCu2O8+y and YBa2Cu3O7−x in air and in vacuum. Both the ceramics exhibit a significant change in oxygen content during annealing between 350 and 450 °C. The Bi2Sr2CaCu2O8+y sample exhibits an increase in resistance with increased oxygen content resulting in deterioration of superconductivity, whereas YBa2Cu3O7−x shows improvement in superconducting behavior with increase in oxygen content. Consequently Bi2Sr2CaCu2O8+y prepared by fast cooling from the sintering temperature possesses a higher Tc , whereas slow cooling of YBa2Cu3O7−x produces a higher Tc .
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74.10.+v Occurrence, potential candidates
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
81.40.Rs Electrical and magnetic properties related to treatment conditions

Radiation damage effects in ion‐implanted Bi‐Sr‐Ca‐Cu‐O superconducting thin films

S. Matsui, H. Matsutera, T. Yoshitake, and T. Satoh

Appl. Phys. Lett. 53, 2096 (1988); http://dx.doi.org/10.1063/1.100499 (3 pages) | Cited 13 times

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Transition temperature (Tc) control and annealing effects of Bi2.0Sr1.4Ca1.8Cu2.2Oy superconducting thin films implanted by 200 keV Ne+ have been investigated. Tc end points for 0.4‐μm‐thick Bi2.0Sr1.4Ca1.8Cu2.2Oy films for 0, 1×1012, and 1×1013 ions/cm2 doses are 78, 76, and 54 K, respectively. The ion dose, to achieve a nonsuperconductor for Bi2.0Sr1.4Ca1.8Cu2.2Oy films, is two or more orders of magnitude lower than that for YBa2Cu3O7−x films. The c‐lattice constant increases were observed for the implanted films. Moreover, it was confirmed that the superconducting characteristics for the implanted films are recovered by annealing in O2 atmosphere.
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74.78.-w Superconducting films and low-dimensional structures
61.80.Jh Ion radiation effects
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

Correlation of superconductivity with ‘‘oxygen dimer’’ peak in photoelectron spectra from YBa2Cu3−xCoxO7−y

C. C. Chang, M. S. Hegde, J. M. Tarascon, T. Venkatesan, A. Inam, X. D. Wu, and W. L. McLean

Appl. Phys. Lett. 53, 2099 (1988); http://dx.doi.org/10.1063/1.100500 (3 pages) | Cited 6 times

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X‐ray photoelectron spectroscopy of YBa2Cu3−xCoxO7−y (0<x<0.4) shows a systematic change in the O 1s and Cu 2p3/2 regions as a function of x. Three peaks in the O 1s spectra at 528.5, 531, and 532.7 eV are seen for x=0 which are assigned to O2−, O1−, and O2−2 ions, respectively. As x is increased, the relative intensity of the O2−2 or O1− to the O2− peak decreases and the Cu2+ fraction increases showing a correlation with the decrease in the superconducting transition temperature. The result is interpreted in terms of Co ions substituting for the Cu ions in the chain with the Co ion in octahedral coordination.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.65.-b Surface treatments

Superconducting Tl‐Ba‐Ca‐Cu‐O films by sputtering

M. Hong, S. H. Liou, D. D. Bacon, G. S. Grader, J. Kwo, A. R. Kortan, and B. A. Davidson

Appl. Phys. Lett. 53, 2102 (1988); http://dx.doi.org/10.1063/1.100501 (3 pages) | Cited 26 times

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Superconducting Tl‐Ba‐Ca‐Cu‐O thin films 0.2–1.0 μm thick have been prepared on MgO(100) and SrTiO3(100) substrates by dc diode sputtering using a single oxide target. Films containing primarily the Tl2Ba2Ca1Cu2O8 phase were obtained with a Tc (R=0) at 102 K and a transport Jc of 104 A/cm2 at 90 K. For the nearly pure phase Tl2Ba2Ca2Cu3O10 films, the Tc’s (R=0) are higher at 116 K and the transport Jc’s at 100 K are of 105 A/cm2. Both types of films show a strong preferred orientation with the c axis perpendicular to the film plane. The rocking curve of the Tl2Ba2Ca2Cu3O10 films is 0.32° wide and the typical grain size is over 10 μm.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology
74.25.Sv Critical currents

Correlation of grain boundary defect structure with boundary orientation in Ba2YCu3O7−x

S. Nakahara, G. J. Fisanick, M. F. Yan, R. B. van Dover, and T. Boone

Appl. Phys. Lett. 53, 2105 (1988); http://dx.doi.org/10.1063/1.100502 (3 pages) | Cited 15 times

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Correlations between observed defect structures and the orientation of planes involved in grain boundary formation in single phase, nearly ideal density Ba2YCu3O7−x are presented. Three types of grain boundary structures are observed: (1) coherent boundaries with only a low‐energy network of dislocations at the interface, which are associated with boundaries not involving a basal plane face, (2) semicoherent boundaries surrounded by a 50–1500 Å wide band of dislocation loops on the c‐axis side of the basal‐plane‐faced boundary, and (3) incoherent boundaries where severe local strain has produced substantial plastic deformation and generation of small voids, again associated with basal‐plane‐faced boundaries. These results are interpreted using a model for local stress based on the known highly anisotropic thermal contraction of the material during cooling from sintering temperatures.
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74.70.-b Superconducting materials other than cuprates
61.72.Mm Grain and twin boundaries
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Low‐noise modular microsusceptometer using nearly quantum limited dc SQUIDs

D. D. Awschalom, J. R. Rozen, M. B. Ketchen, W. J. Gallagher, A. W. Kleinsasser, R. L. Sandstrom, and B. Bumble

Appl. Phys. Lett. 53, 2108 (1988); http://dx.doi.org/10.1063/1.100291 (3 pages) | Cited 47 times

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A flexible combination of superconducting integrated circuits was used to construct a low‐temperature magneto‐optic microsusceptometer utilizing a dc superconducting quantum inteference device (SQUID) detector operating near the quantum limit (coupled energy sensitivity of 1.7ℏ). Miniature pick‐up loop assemblies on transparent substrates were joined by superconducting interchip connections to a thin‐film dc SQUID, which is in turn read out by a second dc SQUID connected to room‐temperature electronics. Measurements on an 8.5‐μm‐diam titanium dot evaporated directly into the pick‐up loop demonstrate a spin sensitivity of ∼103 spins/(Hz)1/2 at T=290 mK.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
85.40.Hp Lithography, masks and pattern transfer
85.70.Sq Magnetooptical devices
07.55.-w Magnetic instruments and components

Laser‐induced selective copper deposition on polyimide

H. S. Cole, Y. S. Liu, J. W. Rose, and R. Guida

Appl. Phys. Lett. 53, 2111 (1988); http://dx.doi.org/10.1063/1.100292 (3 pages) | Cited 19 times

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Laser irradiation of organometallic palladium compounds with an argon ion laser at 351 nm is used to selectively deposit catalytic amounts of palladium on polyimide. Subsequent immersion of the irradiated samples in an electroless copper solution results in copper deposition. Since a few monolayers of palladium are sufficient to catalyze the electroless copper process, fast writing speeds of several centimeters per second are obtained.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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