APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Jun 1992

Volume 60, Issue 24, pp. 2951-3065

Page 2 of 2 Pages Previous Page | Jump to Page

Reactive ion etching of ZnSe by gas mixture of ethane and hydrogen

K. Ohtsuka, M. Imaizumi, H. Sugimoto, T. Isu, and Y. Endoh

Appl. Phys. Lett. 60, 3025 (1992); http://dx.doi.org/10.1063/1.106797 (2 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
ZnSe epitaxial layers grown by gas source molecular beam epitaxy were etched by reactive ion etching (RIE) with a gas mixture of ethane and hydrogen (C2H6/H2). Smooth etching surfaces were obtained under the following RIE conditions: an ethane concentration (flow fraction) of 3%, total flow (C2H6+H2) of 55 sccm, total pressure of 15 Pa and radio frequency power density of 0.6 W/cm2. This ethane concentration is smaller than that in III–V semiconductors, 5%–7%. The etching rate of ZnSe was 21 nm/min and smaller than that of III–V semiconductors.
Show PACS
81.65.-b Surface treatments
61.80.Jh Ion radiation effects

Observation of a two‐dimensional electron gas in low pressure metalorganic chemical vapor deposited GaN‐AlxGa1−xN heterojunctions

M. Asif Khan, J. N. Kuznia, J. M. Van Hove, N. Pan, and J. Carter

Appl. Phys. Lett. 60, 3027 (1992); http://dx.doi.org/10.1063/1.106798 (3 pages) | Cited 78 times

Full Text: | Download PDF

Show Abstract
We have confirmed the presence of a two‐dimensional electron gas (2DEG) in a wide band‐gap GaN‐AlxGa1−xN heterojunction by observing steplike features in the quantum Hall effect. The 2DEG mobility for a GaN‐Al0.13Ga0.87N heterojunction was measured to be 834 cm2/V s at room temperature. It monotonically increased and saturated at a value of 2626 cm2/V s at 77 K. The 2DEG mobility remained nearly constant for temperatures ranging from 77 to 4.2 K. Using Shubnikov–de Haas (SdH) measurements the two‐dimensional carrier concentration was estimated to be 1×1011 cm−2. The peak mobility for the 2DEG was found to decrease with the heterojunction aluminum compositions in excess of 13%.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Impact ionization in Ga1−xAlxSb

L. Gouskov, B. Orsal, M. Pérotin, M. Karim, A. Sabir, P. Coudray, S. Kibeya, and H. Luquet

Appl. Phys. Lett. 60, 3030 (1992); http://dx.doi.org/10.1063/1.106799 (3 pages) | Cited 5 times

Full Text: | Download PDF

Show Abstract
We have measured impact ionization rates in Ga1−xAlxSb at x=0 and 0.08. For these Al contents, the ratio values of the spin‐orbit splitting energy Δ to the energy gap Eg are, respectively, greater and lower than unity. We have determined that the ratio of the ionization coefficients kp/kn is greater than unity for both compositions and that it is much lower (kp/kn≊2) than the value (≳10) determined on our layers for x=0.04. Multiplication noise measurements confirm these results. The comparison to other published data show that the ionization in these antimonide compounds is not yet elucidated.
Show PACS
79.20.Kz Other electron-impact emission phenomena
72.40.+w Photoconduction and photovoltaic effects
85.60.Dw Photodiodes; phototransistors; photoresistors

Growth and strain compensation effects in the ternary Si1−x−yGexCy alloy system

K. Eberl, S. S. Iyer, S. Zollner, J. C. Tsang, and F. K. LeGoues

Appl. Phys. Lett. 60, 3033 (1992); http://dx.doi.org/10.1063/1.106774 (3 pages) | Cited 181 times

Full Text: | Download PDF

Show Abstract
Strain compensation is an important aspect of heterostructure engineering. In this letter, we discuss the synthesis of pseudomorphic Si1−yCy and Si1−x−yGexCy alloy layers on a silicon (100) substrate by molecular beam epitaxy using solid sources and the controlled strain compensation that results from the introduction of the ternary system. The introduction of C into substitutional sites in the crystal lattice is kinetically stabilized by low‐temperature growth conditions (400–550 °C) against thermodynamically favored silicon‐carbide phases. The lattice constant in Ge is about 4% larger than in Si, whereas in diamond it is 52% smaller. Consequently, the compressive strain caused by 10.8% Ge in a pseudomorphic Si1−xGex alloy can be compensated by adding about 1% carbon into substitutional lattice sites of the film assuming Vegard’s law of linear change of the lattice constant in the alloy as a function of the composition. Using x‐ray diffraction, we observe a partial strain compensation in Si0.75−yGe0.25Cy alloys on Si depending on the amount of carbon in the layer, with no observable misfit dislocation generation. The Raman spectra from Si1−yCy and Si1−x−yGexCy alloys show a substitutional carbon vibration mode at about 600 wavenumbers. No indication of silicon‐carbide precipitation is observed in transmission electron microscopy and Raman spectroscopy.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.66.Dk Alloys

Large blueshifting of InGaAs/InP quantum‐well band gaps by ion implantation

J. E. Zucker, B. Tell, K. L. Jones, M. D. Divino, K. F. Brown‐Goebeler, C. H. Joyner, B. I. Miller, and M. G. Young

Appl. Phys. Lett. 60, 3036 (1992); http://dx.doi.org/10.1063/1.106775 (3 pages) | Cited 17 times

Full Text: | Download PDF

Show Abstract
We demonstrate that phosphorous ion implantation in InGaAs/InP quantum wells can be used to produce large (from 1550 to 1200 nm) blueshifts of the band edge. This reproducible technique of lateral band‐gap control can be used in quantum‐well photonic integrated circuits to produce regions of low‐loss waveguide, e.g., for interconnects or large passive cavities. Phosphorous implants with subsequent p‐type InP regrowth produces blueshifted quantum‐well diodes with good reverse‐bias characteristics and low‐loss p‐i(multiple quantum well)‐n waveguides.
Show PACS
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
61.80.Jh Ion radiation effects
42.82.Ds Interconnects, including holographic interconnects

High‐quality Nb/HfOx‐Hf/Nb Josephson junction

Shin’ichi Morohashi, Takeshi Imamura, and Shinya Hasuo

Appl. Phys. Lett. 60, 3039 (1992); http://dx.doi.org/10.1063/1.106776 (3 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
We fabricated a niobium (Nb) Josephson junction with a hafnium (Hf) overlayer. The Hf native oxide (HfOx), formed by thermal oxidation, was used as the new tunneling barrier. Hf was selected as an overlayer because of its good affinity to Nb and strong oxygen affinity. The junction was fabricated the same way as Nb/AlOx‐Al/Nb junctions. The junction showed excellent I‐V characteristics (Vm=40 mV and Vg=3.0 mV). The critical current of the junction did not change with annealing up to 250 °C.  
Show PACS
85.25.-j Superconducting devices
74.25.-q Properties of superconductors
81.40.Rs Electrical and magnetic properties related to treatment conditions

Effect of thermal history on the transport properties and the location of Fe in YBa2Cu3O7 thin films

Frank Bridges, J. B. Boyce, and R. I. Johnson

Appl. Phys. Lett. 60, 3042 (1992); http://dx.doi.org/10.1063/1.106777 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Epitaxial Fe‐substituted YBa2Cu3O7 films on LaAlO3 substrates prepared by pulsed‐laser deposition exhibit a large variation in Tc with changes in the cooldown rate of the films in an O2 environment immediately after deposition. A rapid cooldown rate (200 °C/min) yields surprisingly high‐Tc films with Tc≳75 K for 13% of the Cu replaced by Fe, while a slow cooldown of 10 °C/min results in low‐Tc films with Tc→0 at 11% Fe, a greater suppression than reported for bulk materials. In addition, post‐deposition anneals in O2 affect Tc significantly, even for anneal temperatures as low as 370 °C. These results are interpreted in terms of isolated‐ and clustered‐Fe atoms substituted on the Cu chains sites.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
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
81.40.Rs Electrical and magnetic properties related to treatment conditions

Layer‐by‐layer deposition of La1.85Sr0.15CuOx films by pulsed laser ablation

M. Y. Chern, A. Gupta, and B. W. Hussey

Appl. Phys. Lett. 60, 3045 (1992); http://dx.doi.org/10.1063/1.106778 (3 pages) | Cited 27 times

Full Text: | Download PDF

Show Abstract
Reflection high‐energy electron diffraction (RHEED) has been used to monitor the growth of La1.85Sr0.15CuOx (LSCO) thin films on (100) SrTiO3 substrates by pulsed laser deposition. The films are grown using a combination of pulsed molecular oxygen and a continuous source of atomic oxygen, with the average background pressure maintained as low as 1 mTorr. The RHEED pattern is sharp and streaky, and the intensity of the specular beam oscillates during the deposition, indicating a two‐dimensional layer‐by‐layer epitaxial growth. The film thickness measured by x‐ray small‐angle interference is consistent with the thickness determined by the RHEED oscillation period with a growth unit of half a unit cell. Thin films of YBa2Cu3O7−δ (YBCO) with good RHEED oscillations have also been grown under similar oxygenation conditions. The low‐pressure‐grown LSCO and YBCO films are superconducting, with zero‐resistance temperatures of 15 and 80 K, respectively.
Show PACS
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
74.70.-b Superconducting materials other than cuprates
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Low 1/f noise single‐layer YBa2Cu3Ox dc SQUID at 77 K

G. Friedl, M. Vildić, B. Roas, D. Uhl, F. Bömmel, M. Römheld, B. Hillenbrand, B. Stritzker, and G. Daalmans

Appl. Phys. Lett. 60, 3048 (1992); http://dx.doi.org/10.1063/1.106752 (3 pages) | Cited 25 times

Full Text: | Download PDF

Show Abstract
Autonomous single‐layer dc superconducting quantum interference devices (SQUIDs) have been prepared from epitaxial, laser‐deposited YBa2Cu3Ox films on step edge SrTiO3 and LaAlO3 substrates. For device patterning, a SiOx inhibit technique as well as conventional ethylenediaminetetraacetic wet etch was used. The Josephson junctions are of grain boundary type. Their widths are 5 μm. The SQUID hole is a square of about 5 μm; the SQUID inductance is estimated to be about 20 pH. We obtained a very regular, nonhysteretic flux to voltage modulation over more than 100 flux quanta (Φ0). The maximum voltage signal is of the order of 15 μV peak to peak and the maximum transfer function dV/dΦ at the appropriate flux bias is 50 μV/Φ0 at 77 K. The best value of the equivalent flux noise as measured in the flux locked loop mode is 1.4×10−5 Φ0/Hz1/2 at 1 Hz and 1×10−5 Φ0/Hz1/2 in the white noise region for f≳5 Hz. This results in an energy resolution ϵn,w(f≳5 Hz)=1×10−29 J/Hz in the white noise region and 2×10−29 J/Hz at 1 Hz.
Show PACS
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates

Plasma nitridation of Nb wiring sidewalls to improve annealing stability

Tetsuyoshi Shiota, Takeshi Imamura, and Shinya Hasuo

Appl. Phys. Lett. 60, 3051 (1992); http://dx.doi.org/10.1063/1.106753 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The superconductivity of Nb wiring used in Josephson circuits deteriorates after annealing due to oxygen diffusion from the surface oxide. We previously reported that plasma nitridation of the Nb film surface improves the annealing stability of wiring. To further improve the annealing stability, we developed a new method that includes nitridation of Nb wiring sidewalls. We compared critical currents of the Nb wiring before and after annealing. The critical current with nitridation on both the sidewalls and the top surface did not decrease after annealing at 300 °C, while the critical current with nitridation on the top surface only dropped to less than 70% of its preannealing value. This indicates that the nitridation on the sidewalls is a very effective way to maintain the superconductivity of Nb wiring during annealing in the case of a small linewidth.
Show PACS
85.25.-j Superconducting devices
66.30.J- Diffusion of impurities
81.05.Bx Metals, semimetals, and alloys

Preparation of YBa2Cu3O7−δ thin films with thickness gradients and investigations of growth stages by scanning tunneling microscopy

H. Haefke, H. P. Lang, G. Leemann, and H.‐J. Güntherodt

Appl. Phys. Lett. 60, 3054 (1992); http://dx.doi.org/10.1063/1.106754 (3 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
The growth of (001) oriented YBa2Cu3O7−δ films on LaAlO3(100) has been studied by scanning tunneling microscopy. Using a special half‐shadow technique different growth stages have been obtained simultaneously on a single substrate crystal: nucleation and spreading of two‐dimensional islands, their coalescence and growth, formation of well‐developed growth hills and finally of a continuous film. The growth steps were determined to be one unit cell spacing in height regarding the crystallographic c‐axis.
Show PACS
74.70.-b Superconducting materials other than cuprates
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

New 100 K TlSr2(Ca,Cr)Cu2O7 superconducting films

Y. Q. Tang, Z. Z. Sheng, Z. Y. Chen, Y. F. Li, and D. O. Pederson

Appl. Phys. Lett. 60, 3057 (1992); http://dx.doi.org/10.1063/1.106755 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
New TlSr2(Ca,Cr)Cu2O7 superconducting films on MgO(100) substrates have been prepared and characterized. The superconducting films were fabricated via a two‐step process. Precursor SrCaCrCuO films were first deposited by spray pyrolysis at temperature of 350–400 °C, and thallium was then incorporated by heating the precursor films between unfired TlSrCaCrCuO bulk pellets at 880–900 °C in an oxygen atmosphere. The films were then cooled down to room temperature in an oxygen or argon atmosphere. The superconducting films were single 1212 phase with c‐axis perpendicular to the surface of the MgO(100) substrates. Onset temperatures up to 110 K and zero‐resistance temperatures up to 100 K were achieved. The critical transport currents (Jc) of the films were about 7×103 A/cm2 at 77 K.
Show PACS
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Exchange anisotropy in coupled films of Ni81Fe19 with NiO and CoxNi1−xO

M. J. Carey and A. E. Berkowitz

Appl. Phys. Lett. 60, 3060 (1992); http://dx.doi.org/10.1063/1.106756 (3 pages) | Cited 113 times

Full Text: | Download PDF

Show Abstract
Shifted hysteresis loops were used to investigate exchange anisotropy in 500 Å CoxNi1−xO/300 Å Ni81Fe19 polycrystalline bilayer couples. Bilayers of Ni81Fe19 with NiO have a room‐temperature exchange field, He, of 30 Oe in the as‐deposited state. A maximum in the exchange field at room temperature was observed near x=0.4, indicating an optimal alloying of the properties of the high anisotropy CoO and the high Néel temperature NiO. The blocking temperatures of the exchange couples vary linearly with x, suggesting a linear dependence of the oxide Néel temperature with x.
Show PACS
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
81.15.Cd Deposition by sputtering

Rapid thermal chemical vapor deposition of thin silicon oxide films using silane and nitrous oxide

X. L. Xu, R. T. Kuehn, J. J. Wortman, and M. C. Öztürk

Appl. Phys. Lett. 60, 3063 (1992); http://dx.doi.org/10.1063/1.106757 (3 pages) | Cited 19 times

Full Text: | Download PDF

Show Abstract
Thin (80–200 Å) silicon dioxide (SiO2) films have been deposited by low pressure rapid thermal chemical vapor deposition (RTCVD), using silane (SiH4) and nitrous oxide (N2O) as the reactive gases for the first time. A deposition rate of 55 Å/min has been achieved at 800 °C with a SiH4/N2O flow rate ratio of 2%. Auger electron spectroscopy (AES) and Rutherford back scattering spectroscopy (RBS) have shown a uniform and stoichiometric composition throughout the deposited oxide films. Electrical characterization of the films have shown an average catastrophic breakdown field of 13 MV/cm and a midgap interface trap density (Dit) of equal to or less than 5×1010 eV−1 cm−2. The results suggest that the deposited RTCVD SiO2 films using SiH4‐N2O gas system may have the potential to be used as the gate dielectric in future low‐temperature metal oxide semiconductor (MOS) device processes for ultralarge scale integration (ULSI).
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
85.40.Hp Lithography, masks and pattern transfer
Page 2 of 2 Pages Previous Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close