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10 Feb 1992

Volume 60, Issue 6, pp. 665-786

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Quasi‐continuous lasing from optically pumped CdZnTe/ZnTe multiple quantum wells at room temperature

D. Lee, A. M. Johnson, J. E. Zucker, C. A. Burrus, R. D. Feldman, and R. F. Austin

Appl. Phys. Lett. 60, 739 (1992); http://dx.doi.org/10.1063/1.106554 (3 pages) | Cited 4 times

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We demonstrate the first room‐temperature operation of optically pumped II‐VI quantum‐well lasers in a quasi‐continuous mode. This result shows promise for high repetition rate, short‐pulse operation, and cw operation of future wide‐gap II‐VI diode lasers at room temperature.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Suppressed photocurrent multiple‐quantum‐well optical modulators by proton implantation

T. K. Woodward, B. Tell, W. H. Knox, and J. B. Stark

Appl. Phys. Lett. 60, 742 (1992); http://dx.doi.org/10.1063/1.106555 (3 pages) | Cited 8 times

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We investigate the reduction of power dissipation in absorptive semiconductor optical modulators via reduction in photocurrent. We present experimental results for proton implantation of p‐i‐n‐multiple‐quantum‐well modulators to levels of 1×1012, 1×1013, and 1×1014 cm−2. We find that photocurrent can be significantly reduced with moderate reduction in modulation performance relative to the unimplanted device. Application to asymmetric self‐electro‐optic devices is demonstrated.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.61.Ey III-V semiconductors

GaAs p‐n junction formed in quantum wire crystals

Keiichi Haraguchi, Toshio Katsuyama, Kenji Hiruma, and Kensuke Ogawa

Appl. Phys. Lett. 60, 745 (1992); http://dx.doi.org/10.1063/1.106556 (3 pages) | Cited 84 times

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A p‐n junction is formed for the first time in a cross‐sectional area of a GaAs wire crystal with a diameter of about 100 nm. Ultrafine cylindrical growth by metalorganic vapor phase epitaxy is employed for the fabrication. Current‐voltage and capacitance‐voltage characteristics confirm the formation of the p‐n junction in a narrow area at the midpoint of a wire crystal. Intensive light emission by current injection is observed at 77 K and even at room temperature. These results suggest that ultrafine optoelectronic devices with quantum‐size p‐n junction are possible.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Pairing of noble metals with phosphorus

H. Zimmermann, N. Q. Khanh, G. Battistig, J. Gyulai, and H. Ryssel

Appl. Phys. Lett. 60, 748 (1992); http://dx.doi.org/10.1063/1.106557 (3 pages) | Cited 2 times

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Pairing of gold and platinum with phosphorus is examined. For this purpose, gold, respectively platinum, is diffused into silicon wafers, which contained phosphorus doped regions. A value of 1.0×1019 cm−3 at 900 °C is suggested for the equilibrium concentration of gold phosphorus pairs for a phosphorus concentration of 3.0×1020 cm−3. The pair‐forming capability of platinum with phosphorus is found to be much smaller. The equilibrium concentration of platinum phosphorus pairs is less than 3×1017 cm−3. Deep level transient spectroscopy measurements show that gold does not penetrate a 14 μm thick phosphorus layer in 2 h and that the platinum concentration in the bulk is a factor of four smaller than in reference samples without phosphorus doping.
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61.72.jd Vacancies
61.72.jj Interstitials
66.30.Lw Diffusion of other defects
81.65.-b Surface treatments

Negative persistent photoconductivity in the Al0.6Ga0.4Sb/InAs quantum wells

Ikai Lo, W. C. Mitchel, M. O. Manasreh, C. E. Stutz, and K. R. Evans

Appl. Phys. Lett. 60, 751 (1992); http://dx.doi.org/10.1063/1.106558 (3 pages) | Cited 29 times

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We have measured the Shubnikov–de Haas (SdH) effect in the Al0.6Ga0.4Sb/InAs quantum wells under the negative persistent photoconductivity (NPPC) conductions. By illuminating the sample at low‐temperature, the carrier concentration of the two‐dimensional electron gas in the InAs well was reduced from 5.8 to 3.6×1011 cm−2 and the corresponding quantum lifetime increases from 0.16 to 0.21 ps. The electrons which escaped from the InAs well were captured by the ionized deep donors in the Al0.6Ga0.4Sb layers. The effective mass is equal to (0.0317±0.0005)m0. We also propose, based on the SdH data, that the illumination of the sample with the ionized deep donors at low temperature will exhibit the NPPC effect.
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73.50.Pz Photoconduction and photovoltaic effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Gated photoluminescence method for interface state density determination

R. Iyer and D. L. Lile

Appl. Phys. Lett. 60, 754 (1992); http://dx.doi.org/10.1063/1.106559 (3 pages) | Cited 4 times

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We have investigated the use of gated photoluminescence (PL) to estimate interface state density in III–V metal‐insulator‐semiconductor (MIS) structures. Low‐temperature PL measurements have been recorded as a function of bias applied to the semi‐transparent gate of a MIS diode. An analysis of these data resulted in surface state densities in the low 1010/cm2 eV range on sulfur passivated SiO2 coated InP. The present technique is more sensitive than the conventional 1 MHz capacitance‐voltage (C‐V) method, and less dependent on low leakage currents in the dielectric, when compared to the quasi‐static C‐V technique.  
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.55.Cr III-V semiconductors
77.55.-g Dielectric thin films
85.30.De Semiconductor-device characterization, design, and modeling

Origins of reverse bias leakage currents in hydrogenated amorphous silicon p‐i‐n detector structures

J. K. Arch and S. J. Fonash

Appl. Phys. Lett. 60, 757 (1992); http://dx.doi.org/10.1063/1.106560 (3 pages) | Cited 17 times

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The transport‐simulation computer program amps has been used to explore the origin and behavior of dark leakage currents in hydrogenated amorphous silicon p‐i‐n detector structures. A comparison of simulated and experimental data reveals that the experimentally observed voltage dependence of the reverse bias current‐voltage characteristics can be explained by a varying defect density through the i layer, due either to dopant permeation or to Fermi‐level‐driven defect densities, as well as by the previously suggested field‐enhanced generation. amps simulations indicate that the dependence of these reverse leakage currents on i‐layer thickness would be useful in determining the relative importance of each possible mechanism.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Kk Junction diodes

Activity and diffusivity of oxygen in a liquid Yb1Ba2Cu3 high temperature superconducting precursor alloy

H. Chou, H. S. Chen, W. C. Fang, F. A. Thiel, and M. K. Wu

Appl. Phys. Lett. 60, 760 (1992); http://dx.doi.org/10.1063/1.106561 (3 pages) | Cited 2 times

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The activity and diffusivity of oxygen in a liquid Yb1Ba2Cu3 high temperature superconducting precursor alloy have been measured by modified coulometric titration method in a temperature range from 913 to 957 °C. The standard Gibbs formation energies and the diffusivity of oxygen in liquid Yb1Ba2Cu3 for 1/2O2 (1 atm)→O (1 at. %) are determined to be ΔG=−655.20+0.335T(K) (±1.5) kJ/mol and D=1.8×10−2 exp(−48 100/RT) (cm2/s) where R=8.314 J/deg×mol. Despite very strong bonding of oxygen to the liquid alloys, the diffusion coefficient of oxygen is relatively high in the order of 10−4 cm2/s. The solubility of oxygen in the liquid alloy is low, of about 0.0145 and 0.017 at. % at 913 and 935 °C, respectively.
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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
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Surface resistance of epitaxial YBa2Cu3O7 thin films on CeO2 diffusion barriers on sapphire

P. Merchant, R. D. Jacowitz, K. Tibbs, R. C. Taber, and S. S. Laderman

Appl. Phys. Lett. 60, 763 (1992); http://dx.doi.org/10.1063/1.106535 (3 pages) | Cited 42 times

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Epitaxial thin films of YBa2Cu3O7 (YBCO) have been deposited by off‐axis sputtering onto substrates of r‐plane sapphire coated with a CeO2 diffusion barrier which had been previously deposited by metalorganic chemical vapor deposition process. The YBCO films display excellent superconducting properties, with critical current densities and microwave surface resistances comparable to state of the art YBCO films deposited directly onto LaAlO3 or MgO substrates. The volume fraction of YBCO with large‐angle in‐plane misalignment relative to the underlying layers is comparable to, or smaller than that obtained for YBCO directly deposited onto MgO substrates.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Phase coherence and disorder in Josephson‐junction arrays

M. Octavio, C. B. Whan, and C. J. Lobb

Appl. Phys. Lett. 60, 766 (1992); http://dx.doi.org/10.1063/1.106513 (3 pages) | Cited 28 times

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We present simulations of one‐ and two‐dimensional Josephson‐junction arrays to study the effects of disorder on the coherent oscillation of such arrays. For uniformity in the critical currents comparable to that which can be achieved with present technology, two‐dimensional arrays are much more stable against disorder than one‐dimensional arrays. Both systems are particularly sensitive to disorder when biased near the critical current, with stability increasing at currents farther above the critical current.
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74.50.+r Tunneling phenomena; Josephson effects
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
85.25.Dq Superconducting quantum interference devices (SQUIDs)
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

In‐plane aligned YBa2Cu3O7−x thin films deposited on polycrystalline metallic substrates

Y. Iijima, N. Tanabe, O. Kohno, and Y. Ikeno

Appl. Phys. Lett. 60, 769 (1992); http://dx.doi.org/10.1063/1.106514 (3 pages) | Cited 363 times

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C‐axis oriented YBa2Cu3O7−x thin films are conventionally obtained on polycrystalline substrates, but a‐ and b‐axes are randomly distributed. Due to the weak links at the high‐angle grain boundaries in the a–b plane, the critical current density (Jc) are comparatively low, from 103 to 104 A/cm2 (77 K, 0 T), and the Jc decreases in magnetic field in a manner similar to bulk YBa2Cu3 O7−x samples. To reduce weak links at the high‐angle grain boundaries, biaxially oriented buffer layers of yttrium stabilized zirconia (YSZ) were formed on polycrystalline, Ni‐based alloy by ion‐beam assisted deposition (IBAD), and subsequently the a–b plane aligned YBa2Cu3 O7−x film was deposited by laser ablation. Jc of 2.5×105 A/cm2 (77 K, 0 T) and 2.2×104 A/cm2 (77 K, 8.0 T) were obtained. A new method to prevent intergranular weak links has been developed for potential applications using practical polycrystalline substrates.  
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
61.80.Jh Ion radiation effects

Low‐temperature formation of epitaxial Tl2Ca2Ba2Cu3O10 thin films in reduced O2 pressure

W. Y. Lee, S. M. Garrison, M. Kawasaki, E. L. Venturini, B. T. Ahn, R. Boyers, J. Salem, R. Savoy, and J. Vazquez

Appl. Phys. Lett. 60, 772 (1992); http://dx.doi.org/10.1063/1.106515 (3 pages) | Cited 33 times

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Epitaxial Tl2Ca2Ba2Cu3O10 films on (100) LaAlO3 are prepared by post‐annealing 2Tl:2Ca:2Ba:3Cu precursor films at 830–860 °C in ≂0.03–0.15 atm of O2. These films (0.2–1.1 μm thickness) are smooth and shiny to the eye, and have a sharp zero resistance and onset diamagnetic transition temperature of 117–121 K. Transport critical current densities of 1.6×106 A/cm2 at 77 K and ≂105 A/cm2 at 100 K are obtained for a 0.38‐μm‐thick film in magnetic fields up to 100 Oe. Strong flux pinning at low temperatures is inferred from the weak‐field dependence of the critical current density calculated from magnetic hysteresis loops. At 5 K, the best film has a magnetic critical current density of 9×106 A/cm2 in zero field, decreasing gradually to 1.5×106 A/cm2 in a 5‐T field.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Fully connected bulk Pb1−xSnxMo6S7.6 samples made by hot isostatic pressing

L. Le Lay, T. C. Willis, and D. C. Larbalestier

Appl. Phys. Lett. 60, 775 (1992); http://dx.doi.org/10.1063/1.106516 (3 pages) | Cited 8 times

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High‐density bulk Pb1−xSnxMo6S7.6 (0≤x≤1) samples have been made by hot isostatic pressing at the relatively low temperatures of 800 and 900 °C. Critical current densities, computed from magnetization data taken at various magnetic fields and temperatures, show excellent temperature scaling indicating that a single pinning mechanism is present. The magnetization of all samples scales with size, showing that full density samples are not granular. Samples sintered without pressure at higher temperatures did not achieve full density and did not exhibit good size scaling of the magnetization, thus indicating only percolation connections across the sample in this case. We conclude that there is no intrinsic granularity in these Chevrel phases even though their coherence length is short.
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74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.-q Properties of superconductors
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

New crucible made of Y2O3 for preparing yttrium based high Tc superconducting films by molecular beam epitaxy

H. S. Wang, D. Eissler, Y. Kershaw, W. Dietsche, A. Fischer, K. Ploog, and D. Brunner

Appl. Phys. Lett. 60, 778 (1992); http://dx.doi.org/10.1063/1.106517 (3 pages) | Cited 5 times

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A new kind of crucible made of Y2O3 has been used for the first time to evaporate yttrium for the preparation of YBa2Cu3O7−y films by MBE. Problems related to the purity and thermal stability of the crucible and the evaporating stability of yttrium were investigated. The results imply that this crucible can be used for yttrium evaporation. Purity was high and the evaporating stability was good in spite of some interdiffusion and reaction between Y and Y2O3. YBa2Cu3O7−y films with Tcon of 77 K and Tco of 52 K have been obtained in situ using this crucible.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Excimer laser‐ablated bismuth titanate thin films

N. Maffei and S. B. Krupanidhi

Appl. Phys. Lett. 60, 781 (1992); http://dx.doi.org/10.1063/1.106518 (3 pages) | Cited 27 times

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Bismuth titanate thin films were deposited by the excimer laser ablation technique. Process parameters such as substrate temperature, laser fluence, and gas pressure were investigated and correlated to the resulting film properties. Results suggest an intrinsic bombardment effect on the growing film. The permittivity and dissipation factor measured at 100 kHz were 150 and 0.01, respectively. The ferroelectric properties exhibited a dependence on film orientation and films with preferred c‐axis orientation yielded fully saturated hysteresis loops with Pr=7 μC/cm2 and Ec=20 kV/cm.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
42.55.Lt Gas lasers including excimer and metal-vapor lasers
77.55.-g Dielectric thin films

Electron holographic study of ferroelectric domain walls

X. Zhang, T. Hashimoto, and D. C. Joy

Appl. Phys. Lett. 60, 784 (1992); http://dx.doi.org/10.1063/1.106519 (3 pages) | Cited 39 times

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Electron holography performed in a transmission electron microscope, has been used to measure the width of 90° domain walls in tetragonal BaTiO3, and to determine the magnitude and distribution of the polarization across these walls. The walls are found to be between 15 and 25 Å in width. The polarization and its measured variation are in good agreement with other estimates. Fringe splitting has been observed in some holograms and it is suggested that this is due to the presence of charged oxygen vacancies on the walls.
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77.80.Dj Domain structure; hysteresis
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
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