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17 Jun 1991

Volume 58, Issue 24, pp. 2727-2856

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Hole‐dependent diffusion of implanted Mg in GaAs

Heyward G. Robinson, Michael D. Deal, and David A. Stevenson

Appl. Phys. Lett. 58, 2800 (1991); http://dx.doi.org/10.1063/1.104740 (3 pages) | Cited 14 times

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Magnesium implants in GaAs exhibit two types of diffusion during annealing: uphill diffusion in the peak of the implant and concentration‐dependent diffusion into the bulk. The uphill diffusion predominates at short times and low temperatures, while the concentration‐dependent diffusion is dominant at long times and high temperatures. By studying implants that were annealed at temperatures where no uphill diffusion occurs, diffused profiles could be modeled and an expression for the Mg diffusivity obtained. The activation energy for this process is 1.77 eV. Results from Fermi level experiments show that the diffusivity is hole dependent rather than concentration dependent. The hole‐dependent exponent is unity for Mg implanted into semi‐insulating substrates, but may change to two at high hole concentrations.
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66.30.J- Diffusion of impurities
61.72.U- Doping and impurity implantation

Simulation of intervalley mixing in double‐barrier diodes using the lattice Wigner function

Douglas R. Miller and Dean P. Neikirk

Appl. Phys. Lett. 58, 2803 (1991); http://dx.doi.org/10.1063/1.104741 (3 pages) | Cited 9 times

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We demonstrate that through the use of the lattice Wigner function, band structure effects can be included explicitly in quantum kinetic simulations of double‐barrier diodes. These band structure effects include Γ to X intervalley mixing and effective mass variations at the interface. In a simplified case which emphasizes the impact of broken translational symmetry, we have used this technique to calculate, for the first time, both Γ and X valley equilibrium Wigner functions for an AlAs/GaAs double‐barrier diode.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.15.-m Methods of electronic structure calculations

p‐i‐n HgCdTe photodiodes grown by molecular beam epitaxy

J. M. Arias, M. Zandian, R. Zucca, and R. E. DeWames

Appl. Phys. Lett. 58, 2806 (1991); http://dx.doi.org/10.1063/1.104742 (3 pages) | Cited 14 times

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We report the successful molecular beam epitaxy (MBE) growth of in situ arsenic‐ and indium‐doped p‐i‐n HgCdTe double heterostructures. High‐performance, short‐wavelength, infrared (2.09 μm) photodiodes operating at 300 K have been fabricated with these double heterostructures. The observed current‐voltage characteristics and quantum efficiency of these diodes can be explained by assuming that the current components are dominated by generation‐recombination currents. These photodetectors exhibit quantum efficiencies of 78%. Growth of this kind of in situ doped structures indicates that the HgCdTe MBE technology has matured to the point where doped HgCdTe multilayer heterostructures can be grown and used to fabricate advanced infrared electronic devices.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Schottky‐limit barrier heights for CO‐coated metal clusters on GaAs(110)

T. Komeda, F. Stepniak, and J. H. Weaver

Appl. Phys. Lett. 58, 2809 (1991); http://dx.doi.org/10.1063/1.104743 (3 pages) | Cited 3 times

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This letter discusses band bending induced by the deposition of metal clusters coated with onto GaAs(110). The layer of CO between the metallic clusters and the undisrupted semiconductor simulates a metal‐insulator‐semiconductor junction. The observed barrier height shows Schottky‐limit‐like dependence on the work function of the metal.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
79.60.Jv Interfaces; heterostructures; nanostructures

Monolithic, photoconductive impulse generator using a GaAs wafer

A. Kim, R. Zeto, R. Youmans, J. Conrad, C. Kondek, M. Weiner, H. Brisker, J. Agee, L. Jasper, and B. Lalevic

Appl. Phys. Lett. 58, 2812 (1991); http://dx.doi.org/10.1063/1.104744 (3 pages)

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A new technique for generating multikilovolt, nanosecond pulses was demonstrated. The technique relies on the use of a semi‐insulating GaAs substrate, which performs the dual functions of energy storage and switching. The energy storage was realized by fabricating disk‐shaped electrodes on a 7.5‐cm‐diameter GaAs wafer, thereby forming a radial transmission line. A mode‐locked Nd:YAG laser was used to activate the switch, which is vertically fabricated in the central region of the substrate. This device generated and delivered about a 2 MW pulse with a rise time of less than 500 ps to a 50 Ω load.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
85.60.-q Optoelectronic devices
72.40.+w Photoconduction and photovoltaic effects
84.30.Ng Oscillators, pulse generators, and function generators

Silicon epitaxial growth on Si‐TaSi2 eutectic composite substrates

M. Levinson, M. Tabasky, C. Sung, G. Hamill, D. H. Matthiesen, K. Ostreicher, and B. M. Ditchek

Appl. Phys. Lett. 58, 2815 (1991); http://dx.doi.org/10.1063/1.104745 (3 pages) | Cited 1 time

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Epitaxial layers of Si were grown by atmospheric chemical vapor deposition on two‐phase, Si‐TaSi2 eutectic composite substrates. Characterization by scanning electron microscopy, transmission electron microscopy, and x‐ray double‐crystal rocking curve analysis showed very good crystallographic and microstructural quality. Epilayer areas lying over the TaSi2 regions of the substrate in most cases showed no defect structures. In some cases, pores or dislocations originating at the Si‐TaSi2 interface were observed. Epilayers such as these should enable the integration of conventional silicon devices with the novel ones made possible by these unique composite structures.
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68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Si doping efficiency in GaAs grown at low temperatures

K. Winer, M. Kawashima, and Y. Horikoshi

Appl. Phys. Lett. 58, 2818 (1991); http://dx.doi.org/10.1063/1.104746 (3 pages) | Cited 8 times

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The doping efficiency of Si (≡[e−]/[Si]) has been measured as a function of substrate temperature Ts, beam‐equivalent As4‐to‐Ga fluence ratio R, and beam supply conditions to probe the kinetic limitations of low‐temperature GaAs homoepitaxy. The doping efficiency decreases strongly with increasing R at low Ts due, we suggest, to electron trapping at defects caused by excess As incorporation.
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61.72.U- Doping and impurity implantation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Electron transport of inhomogeneous Schottky barriers

R. T. Tung

Appl. Phys. Lett. 58, 2821 (1991); http://dx.doi.org/10.1063/1.104747 (3 pages) | Cited 92 times

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A novel approach is presented which leads to analytic solutions to the potential and the electron transport through inhomogeneous Schottky barriers. The existence of barrier height nonuniformities is shown to provide a simple explanation of the following abnormal experimental results, routinely observed from various Schottky barriers: greater‐than‐unity ideality factors, the T0 effect, the ‘‘soft’’ reverse characteristics, and the dependence of barrier height on the technique of measurement.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Bk General theory, scattering mechanisms

Photoreflectance of semi‐insulating InP: Resistivity effects on the exciton phase

Alok K. Berry, D. K. Gaskill, G. T. Stauf, and N. Bottka

Appl. Phys. Lett. 58, 2824 (1991); http://dx.doi.org/10.1063/1.104748 (3 pages) | Cited 9 times

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It is shown that photoreflectance (PR), a contactless form of modulation spectroscopy, can be used to measure the resistivity of semi‐insulating InP:Fe substrates. PR measurements of the substrates, obtained from various vendors and laboratories, were performed at 82 K and had line shapes dominated by excitonic transitions. The phase angle of the line shape was found to be a measure of the bulk resistivity of the substrate. The behavior of the line shape phase angle is explained by the exciton ionization model, where the electric field near the surface of the sample is sufficient to ionize excitons. The extent of this ionizing electric field corresponds to an optical path length which enters additively into the exciton line shape phase. Samples with higher resistivities have ionizing electric fields of larger extent, increasing the phase angle of the exciton line shape.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Jq Electro-optical effects
73.20.At Surface states, band structure, electron density of states

Avoiding preamorphization damage in MeV heavy ion‐implanted silicon

R. J. Schreutelkamp, J. S. Custer, J. R. Liefting, and F. W. Saris

Appl. Phys. Lett. 58, 2827 (1991); http://dx.doi.org/10.1063/1.105228 (3 pages) | Cited 5 times

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Implantation of 1.0 MeV 115In in Si results in secondary‐defect formation during subsequent 900 °C annealing if the total number of displaced Si atoms is greater than 1.6×1017/cm2, achieved with a dose near 1.5×1013/cm2. We demonstrate, though, that higher total In doses can be introduced without forming secondary defects by repetitive subthreshold implants each followed by an anneal to remove the implant damage. While a single 6×1013 In/cm2 implant results in a high density of dislocation loops after annealing, instead using four separate 1.5×1013 In/cm2 implants each followed by an anneal leads to the formation of only a few partial dislocations.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.Bb Theories and models of crystal defects
61.72.jd Vacancies
61.72.jj Interstitials

Anisotropy of critical current density in textured Bi2Sr2Ca1Cu2Ox tapes

H. Kumakura, K. Togano, H. Maeda, J. Kase, and T. Morimoto

Appl. Phys. Lett. 58, 2830 (1991); http://dx.doi.org/10.1063/1.104749 (3 pages) | Cited 27 times

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Anisotropy in Jc with respect to field direction for a textured Bi2Sr2Ca1Cu2Ox tape was measured at various temperatures and magnetic fields. Anisotropy at 4.2 K was small enough for practical applications in fields up to 25 T. However, the anisotropy increases rapidly with increasing temperature. Angular dependence of Jc shows a history effect, which is characteristic of ceramic superconductors.
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates

Dependence of the magnetization in YBa2Cu3O7−x thin films on the applied magnetic field direction

H. Teshima, A. Oishi, H. Izumi, K. Ohata, T. Morishita, and S. Tanaka

Appl. Phys. Lett. 58, 2833 (1991); http://dx.doi.org/10.1063/1.104750 (3 pages) | Cited 9 times

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The dependence of the magnetization on the applied magnetic field direction was investigated at 5 K on superconducting thin films of YBa2Cu3O7−x prepared by ArF laser ablation with the c axis perpendicular to the film plane. The difference of the magnetic moment between the increasing and decreasing branches of the hysteresis curves at zero field depends on the angle θ between the film normal and the magnetic field as ‖cos θ‖. This result can be attributed to the magnetic moment perpendicular to the film plane.
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74.25.N- Response to electromagnetic fields
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Processing of a TlBa2Ca2Cu3Oy superconducting film by liquid‐gas solidification

H. Chou, H. S. Chen, A. R. Kortan, L. C. Kimerling, F. A. Thiel, and M. K. Wu

Appl. Phys. Lett. 58, 2836 (1991); http://dx.doi.org/10.1063/1.104751 (3 pages) | Cited 9 times

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We succeed for the first time in growing a superconducting TlBa2Ca2Cu3Oy film on MgO〈100〉 substrate using a liquid‐gas solidification process (LGS). The films are grown in situ; they are deposited by LGS. There is no post‐anneal or compensation of Tl applied after the initial deposition. The as‐grown film shows a flat and uniform morphology with the c axis perpendicular to the MgO〈100〉. It exhibits a resistant transition onset of 117 K and zero resistance at 103 K.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Compositional effects on plasma‐enhanced metalorganic chemical vapor deposition of YBa2Cu3O7−x thin films

J. Zhao, C. S. Chern, Y. Q. Li, P. Norris, B. Gallois, B. Kear, X. D. Wu, and R. E. Muenchausen

Appl. Phys. Lett. 58, 2839 (1991); http://dx.doi.org/10.1063/1.104752 (3 pages) | Cited 23 times

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Epitaxial YBa2Cu3O7−x superconducting thin films with a zero resistance transition temperatures of about 90 K have been prepared, in situ, on LaAlO3 by a plasma‐enhanced metalorganic chemical vapor deposition process at a substrate temperature of 670 °C in 1 Torr partial pressure of N2O. The composition of the films was varied systematically to investigate the effect of changes in the Ba/Y and Cu/Y ratio on the film properties. The results indicated that superconducting current densities exceeding 106 A/cm2, measured at 77 K by a transport method, could be obtained on films with an anomalously wide range of film compositions. Excess Cu (up to 60%) and deficiency in Ba (down to 30%) from their stoichiometric values did not significantly degrade the superconducting properties of the films. As the composition approached the Y‐Ba‐Cu ratio of 1‐2‐3, an improvement in surface morphology and a decrease in superconducting transition temperature were found.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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

Magneto‐optical recording by short pulses

T. Ohtsuki, S. Owa, and F. Yamada

Appl. Phys. Lett. 58, 2842 (1991); http://dx.doi.org/10.1063/1.104753 (3 pages)

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It was experimentally demonstrated that a laser pulse with a duration of less than 10 ns gives a steep temperature distribution in the film plane with little thermal diffusion out of the irradiated area. This results in the writing of domains whose sizes closely fit the cross sections of the laser power profile, and a reduction in the amount of laser energy needed for writing. The experimental results agree well with thermal analysis in which the thermal conductivity adopted for the film is one order of magnitude smaller than that of the bulk material. The advantages of short pulse writing in high‐density recording are described.
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85.70.Sq Magnetooptical devices

Universal elastic scattering cross sections for electrons in the range 1–100 keV

R. Browning

Appl. Phys. Lett. 58, 2845 (1991); http://dx.doi.org/10.1063/1.104754 (3 pages) | Cited 8 times

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For high atomic numbers the total cross section for electron‐atom elastic scattering calculated using the partial‐wave method is found to fall into two regimes over the range 1–100 keV. The cross section in the higher energy regime scales as E−1, and in the lower energy regime as E−0.5. An empirical equation has been drawn up that describes these trends, and can give a universal expression for the cross sections over the Periodic Table to allow economical Monte Carlo simulation of electron scattering over a wide range of energies and materials.
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34.10.+x General theories and models of atomic and molecular collisions and interactions (including statistical theories, transition state, stochastic and trajectory models, etc.)
41.75.Fr Electron and positron beams
34.80.Bm Elastic scattering
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Electronic structure of Sb in perovskite superconducting compounds

M. Eibschütz, W. M. Reiff, R. J. Cava, J. J. Krajewski, and W. F. Peck

Appl. Phys. Lett. 58, 2848 (1991); http://dx.doi.org/10.1063/1.104755 (3 pages) | Cited 1 time

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The Mössbauer effect of the 37.2 keV γ transition of 121Sb has been employed to study the electronic configuration of Sb ions in perovskite superconducting materials. The isomer shift (IS) changes with Sb content and falls in the region of the Sb(V) valence state. The IS increases from 7.00 mm/s for BaPb0.75Sb0.25O3 to 7.25 mm/s for BaPb0.75Bi0.25O3 and to 7.70 mm/s for (Ba0.6K0.4)BiO3 compounds, indicating a high degree of covalency, corresponding to changes in the 5sm5pn hybridization.
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74.70.-b Superconducting materials other than cuprates
71.20.-b Electron density of states and band structure of crystalline solids
74.25.-q Properties of superconductors

Role of bubbles in laser‐assisted wet etching

B. W. Hussey, B. Haba, and A. Gupta

Appl. Phys. Lett. 58, 2851 (1991); http://dx.doi.org/10.1063/1.104756 (3 pages) | Cited 5 times

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Evidence is presented to explain laser‐based aqueous salt etching in terms of vapor bubble growth conditions at the irradiated surface of a substrate. The effect of pulse and frequency modulation of a cw laser is investigated to determine growth behavior for adhering bubbles in pure water. The role of salt in solution (such as KOH, NaOH, or CaCl2) is discussed in terms of its function as a diffusion barrier for growing vapor bubbles. Etching data are presented for the case of a Cu‐vapor laser applied to a Mn‐Zn‐ferrite substrate, comparing results with and without KOH in the etching solution.
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68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.20.Hf Product distribution
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Noninductive detection of single‐proton magnetic resonance

J. A. Sidles

Appl. Phys. Lett. 58, 2854 (1991); http://dx.doi.org/10.1063/1.104757 (3 pages) | Cited 108 times

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The presence of nuclear magnetic resonance can be detected noninductively by coupling the nuclear spin to the motion of a mechanical oscillator. The coupling is obtained by applying a large‐gradient magnetic field, which exerts a mechanical force on the particle by virtue of its magnetic moment. The coupling increases in strength as the oscillator mass is decreased and the gradient length scale is made shorter. Oscillator‐based detection is thus only marginally effective for macroscopic samples, but can be quite effective for single protons interacting with a micron‐scale oscillator. This letter describes the physics of devices in which single‐nucleon magnetic resonance is detected by monitoring the excitation of a mechanical oscillator.
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76.60.-k Nuclear magnetic resonance and relaxation
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
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