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16 Mar 1992

Volume 60, Issue 11, pp. 1277-1404

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Refractive index determination of SiGe using reactive ion etching/ellipsometry: Application of the depth profiling of the GE concentration

G. M. W. Kroesen, G. S. Oehrlein, E. de Frésart, and G. J. Scilla

Appl. Phys. Lett. 60, 1351 (1992); http://dx.doi.org/10.1063/1.107314 (3 pages) | Cited 10 times

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The complex refractive index at a wavelength of 632.8 nm of strained epitaxial SiGe layers on silicon substrates has been determined as a function of the germanium content using in situ ellipsometry during reactive ion etching. The germanium concentration was obtained from Rutherford backscattering. These index values are used to invert the ellipsometry equations. Using this principle, the Ge concentration depth profile of an unknown SiGe structure can be determined from an in situ ellipsometry measurement sequence that is taken while the unknown sample is being etched  
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Nq Composition and phase identification
68.35.Dv Composition, segregation; defects and impurities
07.60.Fs Polarimeters and ellipsometers

Photoluminescence‐dark‐spot‐free AlGaAs grown on Si substrate

Naoki Wada, Koichi Iwabu, Shiro Sakai, and Masuo Fukui

Appl. Phys. Lett. 60, 1354 (1992); http://dx.doi.org/10.1063/1.107315 (3 pages) | Cited 1 time

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GaAs and AlGaAs are grown on an UCGAS (undercut GaAs on Si) in which a part of the GaAs layer grown on Si substrate is separated from the substrate by the post‐growth processing. The grown layers are characterized by the high‐magnification (×1600) photoluminescence image which is capable of visualizing the very small (less than 1 μm) dark spots in the AlGaAs layer. No dark spot is found in the layer grown on the UCGAS. A planar AlGaAs on Si, on the other hand, has the dark‐spot density (DSD) of more than 108 cm−2. The DSDs of the layers grown on planar GaAs on Si and on the mesa are more than 108 cm−2 and in the order of 107 cm−2, respectively. The dark‐spot‐free region exactly corresponds to the UCGAS part, showing that the UCGAS is quite effective to eliminate the defects in AlGaAs on Si. The two factors, the reduced stress and the absence of the GaAs/Si interface in the UCGAS, are thought to be responsible for this improvement.
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68.55.-a Thin film structure and morphology
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors

Application of scanning electron acoustic microscopy to the characterization of n‐type and semi‐insulating GaAs

B. Meńdez and J. Piqueras

Appl. Phys. Lett. 60, 1357 (1992); http://dx.doi.org/10.1063/1.107485 (3 pages) | Cited 5 times

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A series of GaAs wafers with different doping levels and electrical resistivity has been used to investigate the scanning electron acoustic microscopy (SEAM) application to the characterization of this material. It has been found that SEAM is particularly useful to characterize semi‐insulating GaAs as compared with n‐type material. The SEAM signal generation mechanisms in GaAs are discussed.
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71.55.Eq III-V semiconductors
79.20.Kz Other electron-impact emission phenomena
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

High‐resolution electron microscopy of growth interruption effect on AlAs/GaAs interfacial structure during molecular beam epitaxy

Nobuyuki Ikarashi, Masaaki Tanaka, Hiroyuki Sakaki, and Koichi Ishida

Appl. Phys. Lett. 60, 1360 (1992); http://dx.doi.org/10.1063/1.107291 (3 pages) | Cited 19 times

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Step structures at an AlAs/GaAs interface grown by molecular beam epitaxy (MBE) and the effects of growth interruption were investigated by high‐resolution transmission electron microscopy (HRTEM) of the interface in the [110] imaging orientation. In order to accomplish this, we developed a new TEM specimen preparation technique and determined an observation condition for HRTEM of the interface. Atomic steps were clearly observed at the AlAs‐on‐GaAs interface grown by conventional MBE, and the step intervals ranged from a few nm to several tens of nm. When 120 s growth interruption was employed, the interfacial steps were smoothed out and the step intervals become larger than several tens of nm.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology

Ga adatom diffusion on an As‐stabilized GaAs(001) surface via missing As dimer rows: First‐principles calculation

Kenji Shiraishi

Appl. Phys. Lett. 60, 1363 (1992); http://dx.doi.org/10.1063/1.107292 (3 pages) | Cited 47 times

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We have investigated the microscopic processes of Ga adatom diffusions on an As‐stabilized GaAs(001) surface by the first‐principles pseudopotential method. The results show that Ga adatoms diffuse on the surface by passing through the missing As dimer rows. Comparison with the results of scanning tunneling microscopy (STM) experiments during molecular beam epitaxy (MBE) growth suggests that low As pressure increases the surface Ga adatom diffusion by a formation of the continuous Ga adatom diffusion path. This is consistent with the fact that low temperature growth is possible by migration enhanced epitaxy (MEE), in which As and Ga sources are supplied alternately.
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68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.20.At Surface states, band structure, electron density of states

Atomic layer epitaxy of GaN over sapphire using switched metalorganic chemical vapor deposition

M. Asif Khan, R. A. Skogman, J. M. Van Hove, D. T. Olson, and J. N. Kuznia

Appl. Phys. Lett. 60, 1366 (1992); http://dx.doi.org/10.1063/1.107484 (3 pages) | Cited 42 times

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In this letter we report the first switched atomic layer epitaxy (SALE) of single crystal GaN over basal plane sapphire substrates. A low pressure metalorganic chemical vapor deposition (LPMOCVD) system was used for the epilayer depositions. In contrast to conventional LPMOCVD requiring temperatures higher than 700 °C, the SALE process resulted in single crystal insulating GaN layers at growth temperatures ranging from 900 to 450 °C. The band‐edge transmission and the photoluminescence of the films from the SALE process were comparable to the best LPMOCVD films. To the best of our knowledge this is the first report of insulating GaN films which show excellent band‐edge photoluminescence.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Characterization of epitaxial and oxidation‐induced stacking faults in silicon: The influence of transition‐metal contamination

V. Higgs, M. Goulding, A. Brinklow, and P. Kightley

Appl. Phys. Lett. 60, 1369 (1992); http://dx.doi.org/10.1063/1.107293 (3 pages) | Cited 43 times

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Photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and defect etching have been used to characterize epitaxial stacking faults (ESF) in silicon epilayers grown by low‐pressure chemical vapor deposition (LPCVD) and oxidation‐induced stacking faults (OISF) in high‐purity float‐zone (FZ) Si. No dislocation‐related luminescence was observed from either ESFs or OISFs grown under clean conditions. Deliberate surface contamination, followed by annealing with Cu, Fe, Ni, Ag, or Au in the range 4×1012–2×1016 atoms cm−2 introduced dislocation luminescence features, with a maximum intensity at ≊4×1012 atoms cm−2. TEM examination revealed that there was no evidence for precipitation at low levels of contamination but as the contamination level increased metal‐related precipitates were observed on the bounding partial dislocations.
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78.55.Hx Other solid inorganic materials
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Origin of dual epitaxy in the growth of CdTe on (211) GaAs

Y. Nakamura, N. Otsuka, M. D. Lange, R. Sporken, and J. P. Faurie

Appl. Phys. Lett. 60, 1372 (1992); http://dx.doi.org/10.1063/1.107294 (3 pages) | Cited 7 times

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The atomic structure of the (133)CdTe/(211)GaAs interface is analyzed by high resolution transmission electron microscopy in order to elucidate the origin of the dual epitaxy in the growth of CdTe on (211)GaAs by molecular beam epitaxy. The analysis shows that the lattice mismatch at the interface is accommodated by a novel mechanism, which occurs with the combination of the 14.6% lattice mismatch between CdTe and GaAs and one wurtzite type bond sequence on the (211) substrate surface.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Photoluminescence studies on porous silicon

Z. Y. Xu, M. Gal, and M. Gross

Appl. Phys. Lett. 60, 1375 (1992); http://dx.doi.org/10.1063/1.107295 (3 pages) | Cited 111 times

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We have measured the temperature dependence of the photoluminescence of porous silicon and have found that it disagrees with the expected behavior of crystalline or amorphous silicon. We also found that soaking the samples in oxygen and simultaneously illuminating them with light results in the quenching of the photoluminescence. We propose that luminescence in porous silicon may actually be luminescence from molecules attached to the Si surface, rather than any previously assumed quantum size effect.
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78.55.Hx Other solid inorganic materials
81.65.-b Surface treatments
73.20.Hb Impurity and defect levels; energy states of adsorbed species

High Q YBa2Cu3Ox cavities

T. W. Button and N. McN. Alford

Appl. Phys. Lett. 60, 1378 (1992); http://dx.doi.org/10.1063/1.107296 (3 pages) | Cited 15 times

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Melt‐processed YBa2Cu3Ox thick film components for resonant cavities have been produced on yttria stabilized zirconica substrates. A variety of cavities have been constructed incorporating both copper and superconducting components and the TE011 modes have been examined. The highest unloaded Q factor measured was 715 688 for the TE011 mode of an all superconducting cavity at 77 K and 5.66 GHz in the Earth’s magnetic field. This corresponds to a surface resistance of 1.09 mΩ over a total surface area in excess of 230 cm2. Cooling this cavity within a mumetal shield increased the unloaded Q factor by approximately 5%.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
84.40.Az Waveguides, transmission lines, striplines
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Creation of 45° grain‐boundary junctions by lattice engineering

X. D. Wu, L. Luo, R. E. Muenchausen, K. N. Springer, and S. Foltyn

Appl. Phys. Lett. 60, 1381 (1992); http://dx.doi.org/10.1063/1.107297 (3 pages) | Cited 24 times

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The in‐plane, orientational relationships between LaAlO3, SrTiO3, yttria‐stabilized zirconia, MgO, CeO2, BaZrO3, and YBa2Cu3O7−δ(YBCO) are studied. Using a idea of continuous lattice match and photolithographic technique, a 45° YBCO grain‐boundary junction can be created on most substrates. The key element of the process is the utilization of a bridge layer. In addition to MgO bridge material, BaZrO3 was found to work functionally well. The crystallinity of the bridge layer is critical to obtain a clean boundary junction.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.20.-n Methods of materials synthesis and materials processing
85.25.-j Superconducting devices

Low‐temperature formation of YBa2Cu3O7−x superconducting films from molecular Cu‐Ba‐Y precursors

M. W. Rupich, Y. P. Liu, and J. Ibechem

Appl. Phys. Lett. 60, 1384 (1992); http://dx.doi.org/10.1063/1.107298 (3 pages) | Cited 10 times

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Highly oriented superconducting YBa2Cu3O7−x films were prepared on (100) LaAlO3 and (100) yttria‐stabilized ZrO2 (YSZ) substrates by sequential thermolysis and oxidation of Cu‐Ba‐Y μ‐oxo alkoxide precursor films at 730 °C. The precursor films were deposited by standard spin‐coating techniques. The electrical properties and surface morphology of the YBa2Cu3O7−x films are determined primarily by the thermolysis conditions. YBa2Cu3O7−x films processed at 730 °C show metallic behavior in the normal state and sharp resistive superconducting transitions with Tc (R=0) at 89.5 K. Critical current densities of 2×105 A/cm2 at 77 K were obtained with YBa2Cu3O7−x films on YSZ substrates. X‐ray diffraction analysis shows a preferential c‐axis alignment normal to the substrate plane.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Electrical anisotropy in Bi‐Sr‐Ca‐Cu‐O thin films prepared on (110) SrTiO3 by metalorganic chemical vapor deposition

Tsunemi Sugimoto, Nobuhiko Kubota, Yuh Shiohara, and Shoji Tanaka

Appl. Phys. Lett. 60, 1387 (1992); http://dx.doi.org/10.1063/1.107299 (3 pages) | Cited 9 times

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Highly (119) oriented Bi‐Sr‐Ca‐Cu‐O thin films with the transition temperature as high as 70 K on (110) and 5° off (110) SrTiO3 substrates were prepared by metalorganic chemical vapor deposition. The normal state resistivity along the [110] direction (tilted about 45° to the a‐b plane of the film) was 200 times larger than that measured along the [001] direction (parallel to the a‐b plane of the film) for the film prepared on a 5° off oriented (110) SrTiO3 substrate. The anomalous drop of the resistivity near the Tc,0 was observed in the film prepared on a (110) SrTiO3 substrate.
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74.70.-b Superconducting materials other than cuprates
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.78.-w Superconducting films and low-dimensional structures

Parametric amplification using superconductor‐insulator‐superconductor junctions: A study carried out on an electronic simulator

J. H. Zhou, H. F. Xu, S. Z. Yang, and P. H. Wu

Appl. Phys. Lett. 60, 1390 (1992); http://dx.doi.org/10.1063/1.107300 (3 pages)

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An ideal superconductor‐insulator‐superconductor (SIS) junction biased below the gap voltage is a purely reactive device based on which reflection parametric amplifier can be built. Using an electronic simulator to model the junction, we have observed gain as high as 10 dB and have shown that the quantum reactance of the simulator are on the same orders of magnitudes as those of a SIS junction, thus demonstrating, for the first time, the feasibility of this new type of parametric amplifier.
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85.25.Cp Josephson devices
07.50.Ek Circuits and circuit components
74.50.+r Tunneling phenomena; Josephson effects

Magnetic and magneto‐optic properties of epitaxial ferromagnetic τ‐MnAl/(Al,Ga)As heterostructures

T. L. Cheeks, M. J. S. P. Brasil, T. Sands, J. P. Harbison, D. E. Aspnes, V. G. Keramidas, and S. J. Allen

Appl. Phys. Lett. 60, 1393 (1992); http://dx.doi.org/10.1063/1.107301 (3 pages) | Cited 11 times

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We have investigated the magnetic and magneto‐optic properties of epitaxial τ MnAl/AlAs/GaAs heterostructures grown by molecular beam epitaxy. The ferromagnetic τ phase of MnAl was observed, and perpendicular anisotropy was confirmed by the nearly square hysteresis loops. The polar magneto‐optic Kerr rotation of thin 10 nm τ MnAl films is nearly constant at 0.11° from 220 to 820 nm.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Gas‐exposure enhanced Na∗ emission from Na‐rich surfaces

Jun Xu, Royal Albridge, Alan Barnes, Xinxing Yang, and Norman Tolk

Appl. Phys. Lett. 60, 1396 (1992); http://dx.doi.org/10.1063/1.107302 (3 pages)

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The optical emission attributed to electronically desorbed excited sodium atoms from NaCl and Na‐evaporated surfaces is shown to be enhanced by exposure of the surface to gaseous CO2 and N2. This is the first observation of enhancement of electron‐stimulated desorption of substrate atoms caused by the exposure of surfaces to gaseous molecules which do not contain the desorbed atoms. The large amount of excited‐sodium yield at 60 K provides evidence for nonexistence of the secondary‐electron excitation of thermally desorbed ground sodium.
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79.20.Kz Other electron-impact emission phenomena
61.80.Fe Electron and positron radiation effects
81.65.-b Surface treatments

Optical absorption in plasma‐deposited silicon oxynitride films

C. Ance, F. de Chelle, J. P. Ferraton, G. Leveque, P. Ordejón, and Félix Ynduráin

Appl. Phys. Lett. 60, 1399 (1992); http://dx.doi.org/10.1063/1.107303 (3 pages) | Cited 19 times

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We present an experimental and theoretical study of the optical absorption of amorphous silicon oxynitride films. The optical absorption coefficient α in the energy range from 4 to 10 eV has been measured for SiOxNyHz films between the nitride and oxide compositions grown by plasma‐enhanced chemical vapor deposition. We have also calculated the coefficient α for SiOxNy alloys assuming a random mixture of Si—N and Si—O bonds within the disordered alloy. The variation of the optical gap Eg with the composition and the appearance of steps in the optical absorption for oxygen‐rich samples are discussed.
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78.66.-w Optical properties of specific thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals

Laser‐assisted organometallic chemical vapor deposition of films of rhodium and iridium

Judson S. Cohan, Haojie Yuan, R. Stanley Williams, and Jeffrey I. Zink

Appl. Phys. Lett. 60, 1402 (1992); http://dx.doi.org/10.1063/1.107304 (2 pages) | Cited 12 times

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High purity (less than 1% carbon) thin films of rhodium and iridium metal have been obtained by laser‐assisted organometallic chemical vapor deposition. Gaseous (η5‐C5H5)M(C2H4)2 (M=Rh,Ir) was the organometallic precursor. Depositions were carried out in an atmosphere of He and H2 at room temperature and atmospheric pressure. Wavelength dependence studies of the rhodium precursor have shown that only irradiation into the compound’s charge transfer band causes deposition. Deposits can also be obtained thermally. The films were analyzed by x‐ray diffraction and x‐ray photoelectron spectroscopy.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.50.-m Photochemistry
FREE

Comment on ‘‘Occupancy of the DX Center in N‐Al0.32Ga0.68As under uniaxial stress’’

Ming‐fu Li, Peter Y. Yu, and E. R. Weber

Appl. Phys. Lett. 60, 1404 (1992); http://dx.doi.org/10.1063/1.107305 (1 page)

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A discussion is given on the various DX center models in connection wi some recent experiments concerning DX centers in n−AlGaAs under uniaxial stresses. (AIP)
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71.55.Eq III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
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