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30 Mar 1992

Volume 60, Issue 13, pp. 1529-1639

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Evidence for heavy ion channeling in AlGaAs at low energies

N. G. Stoffel, S. A. Schwarz, M. A. A. Pudensi, K. Kash, L. T. Florez, J. P. Harbison, and B. J. Wilkens

Appl. Phys. Lett. 60, 1603 (1992); http://dx.doi.org/10.1063/1.107239 (3 pages) | Cited 14 times

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We used a new molecular dynamics simulation program to model the scattering of low‐energy ions into the relatively open 〈011〉 axial channels of zinc‐blende crystals. We also implanted 1–5 keV Si ions into GaAs/AlGaAs multiple‐quantum well samples and used secondary ion mass spectrometry and photoluminescence to search for the deep ion penetration and optical damage which are characteristic of this ion channeling. Both the simulated and measured Si depth distributions have exponential tails extending at least 20 times further than the mean ion range. The photoluminescence efficiencies are severely degraded in the quantum wells which are overlapped by the observed Si profile tails. These results suggest that unintentional ion channeling is a major factor in the extensive degradation of optical and electrical properties of semiconductor surfaces which are exposed to low‐energy ion bombardment during device fabrication.
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61.80.Jh Ion radiation effects
81.65.-b Surface treatments

Growth of GaAs on hydrogen‐fluoride treated Si (100) surfaces using migration‐enhanced epitaxy

T. Sudersena Rao, K. Nozawa, and Y. Horikoshi

Appl. Phys. Lett. 60, 1606 (1992); http://dx.doi.org/10.1063/1.107240 (3 pages) | Cited 1 time

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Heteroepitaxial growth of GaAs has been successfully achieved for the first time using migration‐enhanced epitaxy (300 °C) on HF treated Si substrates which have been subjected to an initial in situ pre‐heat treatment in the range of 350–620 °C and without the customary high‐temperature Si oxide desorption step. High quality GaAs on Si exhibiting double‐crystal x‐ray rocking curve full‐width at half‐maximum value of 280 arcsec was obtained by using two‐step growth technique MEE(300 °C)/MBE (580 °C). Secondary‐ion mass spectrometry studies indicated 0.05 (monolayer) ML of oxygen at the interface of GaAs and HF treated Si substrate. The photoluminescence spectra at 10 K for GaAs grown on HF treated Si substrates was dominated by sharp excitonic related peaks and no carbon acceptor related emission could be detected.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Photoluminescence topography of shallow impurities in GaAs epilayers grown by metalorganic vapor phase epitaxy

Z. M. Wang, D. J. As, J. Windscheif, K. H. Bachem, and W. Jantz

Appl. Phys. Lett. 60, 1609 (1992); http://dx.doi.org/10.1063/1.107216 (3 pages) | Cited 4 times

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Spectrally and spatially resolved low‐temperature photoluminescence topography has been applied to investigate the lateral variation of impurities in nominally undoped epitaxial GaAs layers. The concentrations of both shallow donors and acceptors exhibit lateral variations. The donor variation pattern appears to be arbitrary, but the fluctuation of shallow acceptor carbon clearly reproduces the well‐known cellular structure of the liquid encapsulated Czochralski GaAs substrate dislocation density distribution, suggesting that the carbon incorporation into the epitaxial layer is influenced by the substrate during the growth of metalorganic vapor phase epitaxy.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors

Time dependence of recombination‐enhanced impurity diffusion in GaAs

Masashi Uematsu and Kazumi Wada

Appl. Phys. Lett. 60, 1612 (1992); http://dx.doi.org/10.1063/1.107217 (3 pages) | Cited 9 times

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The time dependence of recombination‐enhanced impurity diffusion (REID) has been investigated. The decrease in the peak current density of tunnel diodes was simulated based on the analysis in terms of the kinetics of the decay of the recombination center. The present results suggest that in the REID the energy released on minority‐carrier injection at the recombination center enhances the annihilation of the recombination center, in which a group III point defect that enhances the Be diffusion is emitted.
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66.30.J- Diffusion of impurities
61.72.-y Defects and impurities in crystals; microstructure
71.55.Eq III-V semiconductors

Size quantization by faceting in (110)‐oriented GaAs/AlAs heterostructures

R. Nötzel, L. Däweritz, N. N. Ledentsov, and K. Ploog

Appl. Phys. Lett. 60, 1615 (1992); http://dx.doi.org/10.1063/1.107218 (3 pages) | Cited 13 times

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On GaAs (110) substrates a distinct step structure exists on the surface during molecular beam epitaxy of GaAs/AlAs multilayer structures which is monitored in situ by reflection high‐energy electron diffraction. This peculiar surface structure results in thicker GaAs (AlAs) channels associated with the step planes giving rise to pronounced redshifts of the luminescence. The observation of hot exciton luminescence indicates increased exciton stability and exciton phonon interaction due to strong lateral localization of the excitons in the GaAs channels. The measured optical anisotropy is in agreement with the lateral potential introduced by the faceting of the GaAs/AlAs interface.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
71.35.-y Excitons and related phenomena

Variable width and electron density quantum wires in GaAs/AlGaAs with ion‐implanted gates and a surface Schottky gate

R. J. Blaikie, J. R. A. Cleaver, H. Ahmed, and K. Nakazato

Appl. Phys. Lett. 60, 1618 (1992); http://dx.doi.org/10.1063/1.107481 (3 pages) | Cited 5 times

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Beryllium implants have been used to form p‐n junctions which confine electrons laterally in a GaAs/AlGaAs heterostructure to make high‐mobility quasi‐one‐dimensional wires whose electrical width can be varied by biasing the implanted regions. Incorporation of an additional surface Schottky gate enables the electron density within the wires to be controlled independently. Magnetoresistance measurements have been performed at 1.7 K and the weak‐field boundary‐scattering maxima used to determine the width as a function of both the bias applied to the implanted regions and to the surface gate. The mobility is also calculated and is comparable to that reported for wires of similar dimensions fabricated using high energy ion damage.  
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Epitaxial YBa2Cu3O7−δ on GaAs(001) using buffer layers

D. K. Fork, K. Nashimoto, and T. H. Geballe

Appl. Phys. Lett. 60, 1621 (1992); http://dx.doi.org/10.1063/1.107219 (3 pages) | Cited 39 times

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Epitaxy of YBa2Cu3O7−δ (YBCO) on GaAs substrates has been demonstrated using epitaxial buffer layers. Recently developed methods for growing epitaxial YBCO thin films on Si have been adapted to achieve similar results on GaAs. MgO thin films were grown epitaxially on GaAs at below 400 °C. This layer provides a suitable template for the growth of YBCO or YBCO on BaTiO3. All materials are deposited in situ by pulsed laser deposition in a single growth process. The in‐plane crystallography of MgO on GaAs is [100] parallel to [100], accommodating a lattice mismatch of −25.5%. Zero resistance at temperatures as high as 87 K and transition widths as narrow as 1.5 K are reported. Critical current densities as high as 9×106 A/cm2 at 4.2 K and 1.5×105 A/cm2 at 77 K have been measured.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Superconducting properties and normal‐state resistivity of single‐crystal NbN films prepared by a reactive rf‐magnetron sputtering method

A. Shoji, S. Kiryu, and S. Kohjiro

Appl. Phys. Lett. 60, 1624 (1992); http://dx.doi.org/10.1063/1.107220 (3 pages) | Cited 22 times

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In this letter, we report some superconducting properties and normal‐state resistivities of single‐crystal NbN films prepared by a reactive rf‐magnetron sputtering method. It was found that the prepared single‐crystal NbN films have Tc’s above 16 K, normal‐state resistivities in the range from 12.2 to 14.3 μΩ cm (at 20 K), and magnetic penetration depths in the range from 93 to 100 nm (at 4.2 K). From a temperature dependence of the upper critical magnetic field for a single‐crystal NbN film, the zero‐temperature Ginzburg–Landau coherence length ξGL(0) for the film was calculated to be 6.9 nm.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering

Controlled preparation of oxygen deficient YBa2Cu3Ox films

E. Osquiguil, M. Maenhoudt, B. Wuyts, and Y. Bruynseraede

Appl. Phys. Lett. 60, 1627 (1992); http://dx.doi.org/10.1063/1.107221 (3 pages) | Cited 47 times

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We describe a simple method based on the oxygen pressure‐temperature phase diagram to prepare oxygen deficient YBa2Cu3Ox thin films. Systematic critical temperature and x‐ray diffraction experiments clearly show that films with different oxygen contents (6.6≤x≤7) are obtained in a controlled, reproducible, and reversible way.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Nq Composition and phase identification
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Oxygen content and disorder in a‐axis oriented YBa2Cu3O7−δ thin films

Erik Sodtke and Herbert Münder

Appl. Phys. Lett. 60, 1630 (1992); http://dx.doi.org/10.1063/1.107222 (3 pages) | Cited 13 times

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Using results of Raman spectroscopy, it is shown that the transition temperature Tc (R=0) of a‐axis oriented YBa2Cu3O7−δ thin films strongly depends on the disorder in the oxygen sublattice. Regardless of deposition temperature Td, the films have an oxygen deficiency δ<0.1. However, at low Td, films show Tc≊50 K and a significant disorder in the distribution of chain and/or apex oxygen atoms. Using a template growth procedure we show that, at a sufficiently high Td, the oxygen disorder vanishes and Tc≳80 K, although the crystalline disorder, measured by the width of the (200) x‐ray rocking curve, is increasing with Td.
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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
74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering

Ambient gas effects on debris formed during KrF laser ablation of polyimide

Stephan Küper and James Brannon

Appl. Phys. Lett. 60, 1633 (1992); http://dx.doi.org/10.1063/1.107223 (3 pages) | Cited 18 times

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The surface debris that results from KrF excimer laser ablation of polyimide has been investigated as a function of the pressure, and atomic or molecular weight of several ambient gases: H2, He, Ne, air, Ar, Kr, and Xe. A linear relation between the measured debris radius and the inverse third root of the ambient pressure was found to exist, consistent with the predictions of blast wave theory. No measurable debris could be observed using helium or hydrogen gases up to 1 atm, similar to previous reports on helium. The derived value of the blast energy, equal to about 5% of the incident pulse energy, was used to estimate a nascent blast pressure of approximately 150 atm. By making the assumption that surface debris will form if the ablation fragments are confined in a ‘‘small’’ volume for a ‘‘sufficient’’ time, conclusions from blast wave theory suggest how to decrease the amount of generated debris.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Nanosecond laser‐driven reflection high energy electron diffraction system providing digital imaging in real time

D. Kitriotis, K. Ozasa, T. Meguro, S. Shimoda, K. Nishi, and Y. Aoyagi

Appl. Phys. Lett. 60, 1636 (1992); http://dx.doi.org/10.1063/1.107224 (3 pages)

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See Also: Erratum

Show Abstract
High current densities of 1940 A/cm2 have been produced by a Cu/Be alloy photocathode, activated by 355 nm Q‐switched laser pulses. The transient photocurrent, 7 ns full width, is utilized for the development of a pulsed reflection high energy electron diffraction (RHEED) system. Digital imaging and storage of single shot, two‐dimensional diffraction patterns are achieved in real time with good spatial and intensity resolution.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
FREE

Erratum: Time response of a tunable‐electron‐density quantum well and reservoir structure [Appl. Phys. Lett. 59, 2709 (1991)]

Jin Wang and J. P. Leburton

Appl. Phys. Lett. 60, 1639 (1992); http://dx.doi.org/10.1063/1.107445 (1 page)

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Abstract Unavailable
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
42.79.Hp Optical processors, correlators, and modulators
99.10.Cd Errata
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