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19 Feb 1996

Volume 68, Issue 8, pp. 1031-1169

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Investigation of many‐body effects in one‐side modulation‐doped InP‐InGaAs heterostructure

A. J. C. Cardoso, P. C. Morais, and H. M. Cox

Appl. Phys. Lett. 68, 1105 (1996); http://dx.doi.org/10.1063/1.115727 (3 pages) | Cited 17 times

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A one‐side modulation‐doped quantum well of InGaAs lattice matched to InP has been used to investigate many‐body effects in a quasi‐two‐dimensional (2D) electron gas. The sample was grown by vapor levitation epitaxy (VLE). Low‐temperature photoluminescence (PL) measurements were carried out under different optical excitation intensities using 5145 Å line from an argon ion laser. By increasing the laser intensity over five orders of magnitude a 13.2 meV blue shift in the PL line was observed to occur for a single asymmetric quantum well having a 2D electron gas density as low as 0.9×1011 cm−2. The observed blue shift is explained in terms of the reduction of both band bending (of the order of 1.8 meV) and many‐body effects (of the order of 11.4 meV) due to the reduction of the 2D electron gas density in the quantum well. © 1996 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors

Organic field‐effect bipolar transistors

A. Dodabalapur, H. E. Katz, L. Torsi, and R. C. Haddon

Appl. Phys. Lett. 68, 1108 (1996); http://dx.doi.org/10.1063/1.115728 (3 pages) | Cited 77 times

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Organic field‐effect transistors (FETs) which employ two carefully selected active materials can function as n channel, p channel, or both n‐ and p‐channel devices. It is shown that under an appropriate set of bias conditions the channel current in FETs with α‐hexathienylene (α‐6T) and C60 active layers consist of electron and hole components that are injected from the source and drain contacts into the C60 and α‐6T layers, respectively. © 1996 American Institute of Physics.
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85.30.Pq Bipolar transistors
85.30.Tv Field effect devices

Ga0.25In0.75As/InP quantum wells with extremely high and anisotropic two‐dimensional electron gas mobilities

P. Ramvall, N. Carlsson, P. Omling, L. Samuelson, W. Seifert, M. Stolze, and Q. Wang

Appl. Phys. Lett. 68, 1111 (1996); http://dx.doi.org/10.1063/1.115729 (3 pages) | Cited 28 times

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Measurements of modulation‐doped Ga0.25In0.75As/InP quantum wells show, in the 〈−110〉 direction, a record electron mobility of 520 000 cm2/V s at 300 mK. A mobility difference of 15% between the 〈110〉 direction and the 〈−110〉 direction is observed. This anisotropy is tentatively attributed to an ordering effect. The mobilities at room temperature and at 77 K were 16 100 and 170 000 cm2/V s, respectively. By separating out the ionized impurity scattering from other scattering processes in the quantum well, we conclude that at low electron concentrations ionized impurity scattering is limiting the mobility, while alloy scattering has a strong influence on the mobility at high electron concentrations. From this result we determine the first experimental value of the alloy‐scattering potential as ΔV=0.3 eV. © 1996 American Institute of Physics.
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73.50.Bk General theory, scattering mechanisms
73.50.Dn Low-field transport and mobility; piezoresistance

Determination of the effective mass of GaN from infrared reflectivity and Hall effect

P. Perlin, E. Litwin‐Staszewska, B. Suchanek, W. Knap, J. Camassel, T. Suski, R. Piotrzkowski, I. Grzegory, S. Porowski, E. Kaminska, and J. C. Chervin

Appl. Phys. Lett. 68, 1114 (1996); http://dx.doi.org/10.1063/1.115730 (3 pages) | Cited 73 times

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Infrared reflectivity and Hall effect measurements were performed on highly conducting n‐type GaN (n≊6×1019 cm−3) bulk crystals grown by the high‐pressure high‐temperature method. Values of electron‐plasma frequency and free‐electron concentration were determined for each sample of the set of seven crystals. It enabled us to calculate the perpendicular effective mass of electrons in the wurtzite structure of GaN as m∗=0.22±0.02 m0. Effects of nonparabolicity and a difference between parallel and perpendicular components of the effective mass are small and do not exceed the experimental error. © 1996 American Institute of Physics.
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71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Nr Semiconductor compounds

Observation of double cyclotron resonance in modulation‐δ‐doped In0.52Al0.48As/In0.53Ga0.47As heterostructure by optical detection

Y. F. Chen, Y. T. Dai, and I. Lo

Appl. Phys. Lett. 68, 1117 (1996); http://dx.doi.org/10.1063/1.115731 (3 pages) | Cited 5 times

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We report an investigation of optical and electronic properties of a two‐subband populated electron gas confined at a δ‐doped Al0.48In0.52As/Ga0.47In0.53As heterostructure by the technique of far‐infrared optically detected cyclotron resonance (ODCR). Oscillatory characteristics are observed in the ODCR spectrum, and interpreted in terms of the crossing between the Landau levels of the two‐dimensional electron gas and the Fermi level from which the electron concentration and effective mass of the first and second subbands can be determined. Quite different effective masses associated with these subbands are obtained, reflecting the strong effects of conduction band nonparabolicity as well as polaron coupling in Ga0.47In0.53As quantum well. © 1996 American Institute of Physics.
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71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Adatom migration effects during molecular beam epitaxial growth of InGaAs/GaAs quantum wells on patterned substrates with vertical sidewalls: Blue shift in luminescence spectra

J. Phillips, K. Kamath, J. Singh, and P. Bhattacharya

Appl. Phys. Lett. 68, 1120 (1996); http://dx.doi.org/10.1063/1.115732 (3 pages)

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We have studied the blue shift in photoluminescence emission energy of pseudomorphic InGaAs/GaAs quantum wells grown on patterned (001) GaAs substrates with grooves and trenches having vertical sidewalls made by dry etching. Dependence of the blue shift, which can be as large as 51 meV, on the direction, feature size, and the etch depth of the patterns as well as the thickness of the buffer layer was observed, and is explained by the altered migration behavior of the adatoms. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Properties of Schottky contact of Al on SiGe alloys

R. L. Jiang, J. L. Liu, J. Li, Y. Shi, and Y. D. Zheng

Appl. Phys. Lett. 68, 1123 (1996); http://dx.doi.org/10.1063/1.115733 (3 pages) | Cited 13 times

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Electrical properties of Schottky contacts of Al on p‐Si1−xGex alloys were investigated. The Si1−xGex strained layers were grown on p‐Si substrates by using rapid thermal process/very low pressure‐chemical vapor deposition. Low reverse currents were obtained. It was found that the Schottky barrier height of Al/p‐Si1−xGex contacts decreased with increasing Ge fraction. The decrement is in accordance with the decrement of the band gap of the strained Si1−xGex. The Fermi level at the interface is pinned at about 0.43 eV below the conduction band. The influence of strain relaxation for SiGe alloy layers and the Si sacrificial cap layers on the properties of Schottky contacts were also investigated. © 1996 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Cg Contact resistance, contact potential

Electroluminescence from forward‐biased Er‐doped GaP p‐n junctions at room temperature

G. M. Ford and B. W. Wessels

Appl. Phys. Lett. 68, 1126 (1996); http://dx.doi.org/10.1063/1.115734 (3 pages) | Cited 3 times

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The electroluminescent properties of Er‐doped GaP light emitting diodes are reported. Diodes were prepared by metalorganic vapor phase epitaxy and zinc diffusion. Strong characteristic Er3+ emission at 0.80 eV (1.54 μm) under forward bias is detected at room temperature. Minimal thermal quenching of the electroluminescence was observed. The luminescence intensity depended linearly on current density for low applied current densities, and saturated at a current density of 17 A/ cm2 © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Deposition of high quality wurtzite GaN films over cubic (111) MgAl2O4 substrates using low pressure metalorganic chemical vapor deposition

C. J. Sun, J. W. Yang, Q. Chen, M. Asif Khan, T. George, P. Chang‐Chien, and S. Mahajan

Appl. Phys. Lett. 68, 1129 (1996); http://dx.doi.org/10.1063/1.115735 (3 pages) | Cited 18 times

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We report the deposition of high quality single‐crystal wurtzite GaN films on cubic (111) spinel (MgAl2O4) substrates. The room‐temperature electron mobility and the optically pumped stimulated emission threshold for these films are nearly identical to those of films deposited on basal plane sapphire. Using cross sectional high resolution TEM we have determined the following orientation relationship between the film and the substrate: [0001]GaN//[111]MgAl2O4 and [1120]GaN//[110]MgAl2O4. This should provide a common cleavage plane for (111) spinel and the wurtzite GaN films over it. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
73.61.Ey III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Selectivity of growth on patterned GaAs (311)A substrates

Richard Nötzel, Johann Menniger, Manfred Ramsteiner, Ana Ruiz, Hans‐Peter Schönherr, and Klaus H. Ploog

Appl. Phys. Lett. 68, 1132 (1996); http://dx.doi.org/10.1063/1.115736 (3 pages) | Cited 35 times

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We report on the selectivity of growth on patterned GaAs (311)A substrates by solid‐source molecular beam epitaxy. For mesa stripes oriented along the [01‐1] direction, the selectivity of growth is qualitatively different from that on patterned GaAs (100) substrates with a higher growth rate on one of the side facets of the stripes. This growth mode develops a convex curved surface profile enclosing thicker wirelike regions of GaAs due to preferential migration of Ga atoms from both sides toward the sidewall leaving behind thinner regions on the adjacent mesa top and bottom areas. A mechanism for the formation of the surface profile is proposed. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Coimplantation of carbon and group II acceptors in GaAs

R. Morton, S. S. Lau, D. B. Poker, and P. K. Chu

Appl. Phys. Lett. 68, 1135 (1996); http://dx.doi.org/10.1063/1.115737 (3 pages) | Cited 2 times

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Coimplantation of carbon and one of the group II acceptors Mg, Zn, or Cd, was performed in GaAs using doses of 5×1014 cm−2, and the resulting p‐type electrical activity was studied. Carbon and group II coimplantation offers a means of maintaining the III–V stoichiometry, which is known to be beneficial for both carbon and group II activation. The group II implantation profiles show reduced diffusivity from the balance in stoichiometry the carbon coimplantation provides. The group II elements Zn and Cd create substantial implantation damage and therefore help assist carbon activation by supplying the necessary abundance of As vacancies. The Mg coimplantation, because of the light mass of the ion, does not create a significant amount of lattice damage at this dose and consequently the implanted carbon remains inactive, which results in reduced conductivity. This investigation differs from past group III and carbon coimplantation studies because both of the coimplanted species, the group II and carbon, contribute to p‐type conductivity as well as help to maintain the stoichiometry. © 1996 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
71.55.Eq III-V semiconductors

Carrier profile for In0.35Ga0.65As/GaAs multiquantum well lasers from capacitance–voltage measurements

J. Arias, I. Esquivias, J. D. Ralston, E. C. Larkins, S. Weisser, J. Rosenzweig, A. Schönfelder, and M. Maier

Appl. Phys. Lett. 68, 1138 (1996); http://dx.doi.org/10.1063/1.115738 (3 pages) | Cited 7 times

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The carrier profile for MBE grown In0.35Ga0.65As/GaAs multiquantum well laser structures with nominally undoped and beryllium‐doped active regions was determined by using the capacitance–voltage (C–V) technique at room temperature. A simple theoretical model was used to extract the impurity concentration and the quantum‐well carrier density from the experimental profiles. We obtained a high carrier concentration in nominally undoped devices caused by a strong growth temperature dependent Be diffusion from the p‐cladding layer, and no difference between doped samples with different nominal dopant location. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Structural properties of GaN films grown on sapphire by molecular beam epitaxy

Q. Zhu, A. Botchkarev, W. Kim, Ö. Aktas, A. Salvador, B. Sverdlov, H. Morkoç, S.‐C. Y. Tsen, and David J. Smith

Appl. Phys. Lett. 68, 1141 (1996); http://dx.doi.org/10.1063/1.115739 (3 pages) | Cited 26 times

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The structural characteristics of GaN films grown on sapphire substrates by molecular beam epitaxy have been investigated using high‐resolution synchrotron x‐ray diffraction and electron microscopy. We find remarkable correspondence between the in‐plane structural order (coherence length and mosaic spread) and the electrical and optical properties. Contrary to common belief, our observations show unequivocally that the out‐of‐plane structural features, which are considerably better developed than the in‐plane counterparts, cannot be used for determining the material quality with respect to their optical and electrical activity. In particular, the (00l) mosaic spread is not a good indicator of film quality. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Photoluminescence of polycrystalline CuInSe2 thin films

S. Zott, K. Leo, M. Ruckh, and H.‐W. Schock

Appl. Phys. Lett. 68, 1144 (1996); http://dx.doi.org/10.1063/1.115704 (3 pages) | Cited 26 times

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The photoluminescence of CuInSe2 thin films grown by multisource physical vapor deposition is investigated over a wide composition range with a specially designed sample. Measurements as a function of excitation intensity, and temperature are correlated with the Cu/In ratio x of the films ranging from 1.47≤x≤0.46. All the Cu–rich samples (x≳1.0) show well‐defined peak positions independent of the composition. In the slightly In‐rich region (x=0.90) where the best absorber layers for high efficiency CuInSe2 solar cells are expected, two broad emission lines are ascribed to donor‐acceptor pair transitions. For very In‐rich samples (x<0.67), a blue shift of the dominant transition is observed. © 1996 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
84.60.Jt Photoelectric conversion

Study of double barrier superlattice by synchrotron radiation and double‐crystal x‐ray diffraction

Y. Zhuang, Y. T. Wang, D. S. Jiang, X. P. Yang, X. M. Jiang, J. Y. Wu, L. S. Xiu, and W. L. Zheng

Appl. Phys. Lett. 68, 1147 (1996); http://dx.doi.org/10.1063/1.115705 (3 pages) | Cited 3 times

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An (AlAs/GaAs/AlAs/AlGaAs)/GaAs(001) double‐barrier superlattice grown by molecular beam epitaxy (MBE) is studied by combining synchrotron radiation and double‐crystal x‐ray diffraction (DCD). The intensity of satellite peaks is modulated by the wave function of each sublayer in one superlattice period. Simulated by the x‐ray dynamical diffraction theory, it is discovered that the intensity of the satellite peaks situated near the modulating wave node point of each sublayer is very sensitive to the variation of the layer structural parameters. The accurate layer thickness of each sublayer is obtained with an error less than 1 Å. Furthermore, x‐ray kinematical diffraction theory is used to explain the modulation phenomenon. © 1996 American Institute of Physics.
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61.05.C- X-ray diffraction and scattering
68.55.-a Thin film structure and morphology

Role of C and B clusters in transient diffusion of B in silicon

N. E. B. Cowern, A. Cacciato, J. S. Custer, F. W. Saris, and W. Vandervorst

Appl. Phys. Lett. 68, 1150 (1996); http://dx.doi.org/10.1063/1.115706 (3 pages) | Cited 30 times

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Transient diffusion of ion‐implanted B is inhibited in the presence of high C or B concentrations, due to the formation of interstitial clusters stabilized by impurity atoms. Comparison between experiments and simulations suggests that the number of self‐interstitials trapped per clustered impurity atoms is ≊1.15 for C and ∼1 for B, consistent with a volume compensation mechanism. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities

C‐axis oriented (Hg,Ti)‐based superconducting films with Tc≳125 K

F. Foong, B. Bedard, Q. L. Xu, and S. H. Liou

Appl. Phys. Lett. 68, 1153 (1996); http://dx.doi.org/10.1063/1.115707 (3 pages) | Cited 25 times

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Thin films with mostly (Hg,Tl)1Ba2Ca3Cu2O8+δ [(Hg,Tl)‐1223] phase have been fabricated by radio frequency magnetron sputtering of precursor films and post‐annealing method. The doping of a small amount of thallium in the film is helpful to the formation of the three‐layer CuO2 compound. These films have a highly oriented structure with the c‐axis perpendicular to the film surface. Resistivity measurements show that the films after annealing at 300 °C for 1 h in O2 have the superconducting transition temperature of Tc(onset)=133 K and Tc(zero)=127 K. Scanning electron micrographs of the film reveal platelike micrometer‐size grains coalesce to cover the substrate surface. © 1996 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures

Superconducting quantum interference devices based on YBaCuO nanobridges

M. V. Pedyash, D. H. A. Blank, and H. Rogalla

Appl. Phys. Lett. 68, 1156 (1996); http://dx.doi.org/10.1063/1.115708 (3 pages) | Cited 10 times

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Direct current SQUIDs based on YBaCuO thin film nanobridges have been investigated. Critical current densities Jc of the devices are up to 3×106 A/cm2 at T=77 K and show a temperature dependence of (1−T/Tc)1.6±0.1. High values of the voltage‐flux modulation are observed (8 μV peak to peak at 77 K, 45 μV at 4.2 K). The temperature dependence of the SQUID modulation is found to be essentially different from the one of the conventional weak link SQUID. We discuss our results by considering degradation of the nanobridge area during structuring, which leads to a transition from SNS to SS′S type junction with decreasing temperature. © 1996 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)

Induced magnetic anisotropy in Fe80B20 metallic glass by mechanical milling

G. J. Fan, M. X. Quan, and Z. Q. Hu

Appl. Phys. Lett. 68, 1159 (1996); http://dx.doi.org/10.1063/1.115709 (3 pages) | Cited 3 times

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By means of transmission Mössbauer spectroscopy, the effect of mechanical milling on the magnetic anisotropy of Fe80B20 metallic glass has been studied. On the basis of variation of the areal ratio R21 of the second to the first Mössbauer line with milling time, it was found that a rotation of the average magnetic‐moment directions from the in‐plane to an out‐of‐plane orientation may take place by mechanical milling without onset of bulk crystallization, and that the distribution of the magnetic‐moment directions becomes random after the bulk crystallization has occurred. The induced out‐of‐plane magnetic anisotropy by mechanical milling can be attributed to the occurrence of the chemical short‐range order and surface crystallization in the Fe80B20 metallic glass. The latter effect may cause the formation of compressive stresses in the bulk and therefore a rotation of magnetic‐moment directions in the Fe80B20 metallic glass. © 1996 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Low field giant magnetoresistance in sputtered permalloy/Au multilayers

S. S. P. Parkin and T. Rabedeau

Appl. Phys. Lett. 68, 1162 (1996); http://dx.doi.org/10.1063/1.115710 (3 pages) | Cited 13 times

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Polycrystalline permalloy/Au multilayers exhibit oscillatory variations in saturation magnetoresistance as a function of increasing Au layer thickness. The change in resistance is saturated in fields as low as a few Oe at room temperature leading to changes in resistance per unit field of more than 1%/Oe. These are the largest room temperature magnetic field sensitivities yet reported in simple magnetic multilayers. © 1996 American Institute of Physics.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Generation of a frequency agile modulated intense relativistic electron beam

M. Friedman, J. Pasour, and D. Smithe

Appl. Phys. Lett. 68, 1165 (1996); http://dx.doi.org/10.1063/1.115711 (3 pages)

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A new mechanism for self‐modulation of an annular intense relativistic electron beam is being described. The frequency of modulation can be tuned 10% by magnetically compressing the diameter of the electron beam. © 1996 American Institute of Physics.
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41.75.Fr Electron and positron beams
41.85.-p Beam optics
FREE

Erratum: ‘‘Growth of germanium‐carbon alloys on silicon substrates by molecular beam epitaxy’’ [Appl. Phys. Lett. 67, 1865 (1995)]

J. Kolodzey, P. A. O’Neil, S. Zhang, B. A. Orner, K. Roe, K. M. Unruh, C. P. Swann, M. M. Waite, and S. Ismat Shah

Appl. Phys. Lett. 68, 1168 (1996); http://dx.doi.org/10.1063/1.116796 (2 pages)

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Abstract Unavailable
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81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
99.10.Cd Errata
FREE

Erratum: ‘‘Defect‐free band‐edge photoluminescence and band gap measurement of pseudomorphic Si1−x−yGexCy alloy layers on Si (100)’’ [Appl. Phys. Lett. 67, 3915 (1995)]

A. St. Amour, C. W. Liu, J. C. Sturm, Y. Lacroix, and M. L. W. Thewalt

Appl. Phys. Lett. 68, 1169 (1996); http://dx.doi.org/10.1063/1.116797 (1 page)

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Abstract Unavailable
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
99.10.Cd Errata
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