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15 Sep 2003

Volume 83, Issue 11, pp. 2091-2291

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 2244 (2003); http://dx.doi.org/10.1063/1.1610259 (3 pages)

X.-M. Meng, Y. Jiang, J. Liu, C.-S. Lee, I. Bello, and S.-T. Lee
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Synthesis of ternary SiGeSn semiconductors on Si(100) via SnxGe1−x buffer layers

Matthew Bauer, Cole Ritter, P. A. Crozier, Jie Ren, J. Menendez, G. Wolf, and J. Kouvetakis

Appl. Phys. Lett. 83, 2163 (2003); http://dx.doi.org/10.1063/1.1606104 (3 pages) | Cited 31 times

Online Publication Date: 9 September 2003

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Single-phase Si1−x−yGexSny alloys with random diamond cubic structures are created on Si(100) via ultrahigh vacuum chemical vapor deposition reactions of SnD4 with SiH3GeH3 at 350 °C. Commensurate heteroepitaxy is facilitated by Ge1−xSnx buffer layers, which act as templates that can conform structurally and absorb the differential strain imposed by the more rigid Si and Si–Ge–Sn materials. The crystal structure, elemental distribution and morphological properties of the Si1−x−yGexSny/Ge1−xSnx heterostructures are characterized by high-resolution electron microscopy, including electron energy loss nanospectroscopy, x-ray diffraction (rocking curves) and atomic force microscopy. These techniques demonstrate growth of perfectly epitaxial, uniform and highly aligned layers with atomically smooth surfaces and monocrystalline structures that have lattice constants close to that of Ge. Rutherford backscattering ion channeling shows that the constituent elements occupy random substitutional sites in the same average diamond cubic lattice and the Raman shifts are consistent with the lattice expansion produced by the Sn incorporation into SiGe tetrahedral sites. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Li Other semiconductors
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.60.Bs Mechanical and acoustical properties
79.20.Uv Electron energy loss spectroscopy
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
78.30.Hv Other nonmetallic inorganics

Orientation dependent microwave dielectric properties of ferroelectric Ba1−xSrxTiO3 thin films

Seung Eon Moon, Eun-Kyoung Kim, Min-Hwan Kwak, Han-Cheol Ryu, Young-Tae Kim, Kwang-Yong Kang, Su-Jae Lee, and Won-Jeong Kim

Appl. Phys. Lett. 83, 2166 (2003); http://dx.doi.org/10.1063/1.1609658 (3 pages) | Cited 49 times

Online Publication Date: 9 September 2003

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The effects of anisotropic dielectric properties of ferroelectric Ba1−xSrxTiO3 (BST) films on the characteristics of the interdigital (IDT) capacitors have been studied in microwave regions at room temperature. Ferroelectric BST films with (001), (011), and (111) orientation were epitaxially grown on (001), (011), and (111) MgO substrates, respectively, by the pulsed laser deposition method. The microwave properties of orientation engineered BST films were investigated using interdigital capacitors. The calculated dielectric constant tunability with 40 V dc bias variation and the calculated dielectric quality factor values for IDT capacitors based on (001), (011), and (111) oriented BST films at 9 GHz with no dc bias were about 47%, 55%, 43%, and 12, 14, 21, respectively. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Electron dynamics in InNxSb1−x

I. Mahboob, T. D. Veal, and C. F. McConville

Appl. Phys. Lett. 83, 2169 (2003); http://dx.doi.org/10.1063/1.1611270 (3 pages) | Cited 6 times

Online Publication Date: 9 September 2003

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Electron transport properties in InNxSb1−x are investigated for a range of alloy compositions. The band structure of InNxSb1−x is modeled using a modified k⋅p Hamiltonian. This enables the semiconductor statistics for a given x value to be calculated from the dispersion relation of the E− subband. These calculations reveal that for alloy compositions in the range 0.001 ⩽ x ⩽ 0.02 there is only a small variation of the carrier concentration at a given plasma frequency. A similar trend is observed for the effective mass at the Fermi level. Measurements of the plasma frequency and plasmon lifetime for InNxSb1−x alloys enable the carrier concentration and the effective mass at the Fermi level to be determined and a lower limit for the electron mobility to be estimated. © 2003 American Institute of Physics.
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71.20.Nr Semiconductor compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.15.-m Methods of electronic structure calculations
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance

Chemistry and band offsets of HfO2 thin films for gate insulators

M. Oshima, S. Toyoda, T. Okumura, J. Okabayashi, H. Kumigashira, K. Ono, M. Niwa, K. Usuda, and N. Hirashita

Appl. Phys. Lett. 83, 2172 (2003); http://dx.doi.org/10.1063/1.1611272 (3 pages) | Cited 43 times

Online Publication Date: 9 September 2003

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Interfacial chemistry and band offsets of HfO2 films grown on Si(100) substrates are investigated using high-resolution angle-resolved photoelectron spectroscopy and are correlated with interfacial structures revealed by transmission electron microscope. Hf 4f and O 1s spectra show similar chemical shifts indicating the existence of a double layer structure consisting of a HfO2, upper layer and a SiO2-rich Hf1−xSixO2 lower layer. Two types of valence band offsets are clearly determined by a double subtraction method to be 3.0 and 3.8 eV that can be attributed to ΔEv1 for the upper layer HfO2/Si and ΔEv2 for the lower layer Hf1−xSixO2/Si, respectively. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Ct Interface structure and roughness

Magnetic properties of heavily Mn-doped quaternary alloy ferromagnetic semiconductor (InGaMn)As grown on InP

Shinobu Ohya, Hideo Kobayashi, and Masaaki Tanaka

Appl. Phys. Lett. 83, 2175 (2003); http://dx.doi.org/10.1063/1.1610788 (3 pages) | Cited 20 times

Online Publication Date: 9 September 2003

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See Also: Publisher's Note

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We have studied magnetic properties of heavily Mn-doped [(In0.44Ga0.56)0.79Mn0.21]As thin films grown by low-temperature molecular-beam epitaxy on InP substrates. (InGaMn)As with high Mn content (21%) was obtained by decreasing the growth temperature to 190 °C. When the thickness of the [(In0.44Ga0.56)0.79Mn0.21]As layer is equal or thinner than 10 nm, the reflection high-energy electron diffraction pattern and transmission electron microscopy show no MnAs clustering, indicating that a homogeneous single crystal was grown. Magnetic circular dicroism characterizations, as well as transport and magnetization measurements, indicate that the Curie temperature is 125–130 K. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Determination of the electronic conductivity of polybithiophene films at different doping levels using in situ electrochemical impedance measurements

Germà Garcia-Belmonte, Juan Bisquert, and George S. Popkirov

Appl. Phys. Lett. 83, 2178 (2003); http://dx.doi.org/10.1063/1.1609657 (3 pages) | Cited 4 times

Online Publication Date: 9 September 2003

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This letter presents in situ electronic conductivity measurements of polybithiophene films using a twin working electrode in an electrochemical configuration. A twin electrode is made of two metallic stripes which are separated by a few micrometers by an insulating gap. As the polymer doping level depends on the bias potential maintained between counter- and working electrodes, changes of electronic density of many orders of magnitude (from 1016 up to 1020 cm−3 in the potential window investigated) can be achieved using this experimental technique. A simple impedance model based on electronic (polaronic) diffusion between absorbing contacts accounts for the measured impedance spectra. The dependence of low-frequency conductivity σdc with bias potential E at low doping levels follows the relationship ln σdc∝E/2kBT, which allows one to regard it as a double contribution, simultaneously electronic and ionic, to the thermodynamics of doping. It has also been possible to calculate the electronic chemical diffusion coefficient from the diffusion characteristic frequency ωd, which results within the range of De ∼ 4–1×10−3 cm2 s−1. © 2003 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
71.20.Rv Polymers and organic compounds

Spin splitting in narrow InAs quantum wells with In0.75Ga0.25As barrier layers

C. H. Möller, Ch. Heyn, and D. Grundler

Appl. Phys. Lett. 83, 2181 (2003); http://dx.doi.org/10.1063/1.1610790 (3 pages) | Cited 15 times

Online Publication Date: 9 September 2003

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Using two independent magnetotransport experiments, i.e., thermal activation and the coincidence method in tilted fields, we determine the g factor in a two-dimensional electron system in a 4-nm-wide InAs quantum well. From these independent techniques we deduce consistently an absolute value ∣gexp∣ ≅ 6. This is considerably smaller if compared to ∣g∣ = 14.8 for bulk InAs. Nonparabolicity in InAs cannot fully explain the reduced g factor. We argue that the penetration of the wave function into the In0.75Ga0.25As barriers and into the In0.75Al0.25As spacer layer plays an additional role. © 2003 American Institute of Physics.
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73.63.Hs Quantum wells
73.21.Fg Quantum wells
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Probing carriers in two-dimensional systems with high spatial resolution by scanning spreading resistance microscopy

K. Maknys, O. Douhéret, and S. Anand

Appl. Phys. Lett. 83, 2184 (2003); http://dx.doi.org/10.1063/1.1611619 (3 pages) | Cited 16 times

Online Publication Date: 9 September 2003

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In this work, cross-sectional scanning spreading resistance microscopy (SSRM) is used to profile carriers in quantum wells (QWs). The investigated structures consist of InGaAs wells of different widths sandwiched between Si-doped InP barriers. It is demonstrated that SSRM is indeed capable of detecting electrons in the quantum wells with high lateral resolution and that the SSRM signal shows a systematic trend for the different wells. Clear dips in the resistance signal are observed at the quantum wells and imply accumulated electron densities higher than in the surrounding barriers. Carrier density in the QW is found by using the calibration curve obtained from the resistance measurements on reference layers sample. It is also shown that only at certain appropriate tip-sample bias conditions the depletion regions in the barriers adjacent to the wells are resolved. Finally, we demonstrate that under very low forward biases the full width at half maximum of the observed resistance dips in SSRM data is nearly equal to the geometric QW widths. © 2003 American Institute of Physics.
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73.63.Hs Quantum wells
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
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