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11 Mar 2002

Volume 80, Issue 10, pp. 1683-1849

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Simultaneous measurements of Seebeck coefficient and thermal conductivity across superlattice

B. Yang, J. L. Liu, K. L. Wang, and G. Chen

Appl. Phys. Lett. 80, 1758 (2002); http://dx.doi.org/10.1063/1.1458693 (3 pages) | Cited 37 times

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A method is developed to simultaneously measure the Seebeck coefficient and thermal conductivity in the cross-plane direction of thin films and applied to an n-type Si/Ge quantum-dot superlattice. In this method, an Au/Cr pattern serves as both a heater and a thermometer, and a microprobe is prepared between the heater and the thin film to extract the Seebeck voltage. Using a differential measurement between the thin films with different thickness, the temperature and voltage drops across the thin film are determined to deduce its cross-plane thermal conductivity and Seebeck coefficient. At room temperature, the cross-plane Seebeck coefficient and thermal conductivity are 312 μV/K and 2.92 W/mK, respectively, for the n-type Si(75 Å)/Ge(15 Å) quantum-dot superlattice doped to 8.7×1019 cm−3. © 2002 American Institute of Physics.
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73.63.Kv Quantum dots
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.20.-n Thermal instruments and apparatus

Electron transport measurements of Schottky barrier inhomogeneities

L. E. Calvet, R. G. Wheeler, and M. A. Reed

Appl. Phys. Lett. 80, 1761 (2002); http://dx.doi.org/10.1063/1.1456257 (3 pages) | Cited 25 times

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We report nonmonotonicities in the low-temperature current versus gate voltage characteristics of PtSi/Si Schottky Barrier metal–oxide–semiconductor field-effect transistors. Direct tunneling through the Schottky barrier is shown to limit the current and be superimposed with resonant peaks and oscillations. These structures are attributed to resonant tunneling through impurities located close to the interface and nonuniformities of the heterojunction. We thus demonstrate barrier height variations in electron transport through a relatively large metal/semiconductor contact area. The inhomogeneities result in different average Schottky barrier heights between devices, and cause height variations as a function of carrier concentration within a metal/semiconductor interface. © 2002 American Institute of Physics.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Tv Field effect devices
73.40.Ns Metal-nonmetal contacts
73.40.Gk Tunneling
73.61.Cw Elemental semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Band discontinuity in the GaAs/AlAs interface studied by in situ photoemission spectroscopy

J. Okabayashi, K. Ono, T. Mano, M. Mizuguchi, K. Horiba, K. Nakamura, A. Fujimori, and M. Oshima

Appl. Phys. Lett. 80, 1764 (2002); http://dx.doi.org/10.1063/1.1455695 (3 pages) | Cited 1 time

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In order to investigate the valence-band discontinuity of the GaAs/AlAs interface, the thickness dependence of the photoemission spectra of a GaAs layer in situ deposited on AlAs by molecular-beam epitaxy has been studied. Although the interface is atomically abrupt, the electronic structure in the interface region displays Al1−xGaxAs alloy-like behaviors. The valence-band maximum as well as the Ga 3dcore level show a gradual shift as a function of GaAs layer thickness of less than 2 nm (8 monolayers), which indicates that interface formation needs about 2 nm thickness for the electronic structure of the GaAs layer to become that of bulk GaAs. © 2002 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
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
79.60.Dp Adsorbed layers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Thermal quenching effect of an infrared deep level in Mg-doped p-type GaN films

Keunjoo Kim and Sang Jo Chung

Appl. Phys. Lett. 80, 1767 (2002); http://dx.doi.org/10.1063/1.1456547 (3 pages) | Cited 6 times

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The thermal quenching of an infrared deep level of 1.2–1.5 eV has been investigated on Mg-doped p-type GaN films, using one- and two-step annealing processes and photocurrent measurements. The deep level appeared in the one-step annealing process at a relatively high temperature of 900 °C, but disappeared in the two-step annealing process with a low-temperature step and a subsequent high-temperature step. The persistent photocurrent was residual in the sample including the deep level, while it was terminated in the sample without the deep level. This indicates that the deep level is a neutral hole center located above a quasi-Fermi level, estimated with an energy of EpF = 0.1–0.15 eV above the valence band at a hole carrier concentration of 2.0–2.5×1017/cm3. © 2002 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.66.Fd III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing

Current transport in InP/In0.5(Al0.6Ga0.4)0.5P self-assembled quantum dot heterostructures using ballistic electron emission microscopy/spectroscopy

C. V. Reddy, V. Narayanamurti, J. H. Ryou, and R. D. Dupuis

Appl. Phys. Lett. 80, 1770 (2002); http://dx.doi.org/10.1063/1.1458689 (3 pages) | Cited 4 times

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Ballistic electron emission microscopy/spectroscopy (BEEM/S) has been employed to image, inject, and investigate the current transport through self-assembled InP quantum dots embedded in InAlGaP barriers. The spectroscopy performed on the dot and off the dot revealed that the charge confinement within the dots is more effective than the leakage through the quasibound states. Evidence for the charge accumulation in the quantum dots is presented with the help of BEEM imaging as a function of the tip bias. © 2002 American Institute of Physics.
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73.63.Kv Quantum dots
73.21.La Quantum dots
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Improving SiO2/SiGe interface of SiGe p-metal–oxide–silicon field-effect transistors using water vapor annealing

T. Ngai, X. Chen, J. Chen, and S. K. Banerjee

Appl. Phys. Lett. 80, 1773 (2002); http://dx.doi.org/10.1063/1.1445806 (3 pages) | Cited 3 times

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SiGe p-metal–oxide–silicon field-effect transistors (p-MOSFETs) were fabricated with ultrathin thin (∼20 Å) remote plasma chemical vapor deposition gate oxides deposited directly on SiGe. A low temperature water vapor annealing was used to improve the SiO2/SiGe interface and performance of SiGe p-MOSFETs. After the wet annealing, dangling Si and Ge bonds at the interface are passivated by atomic hydrogen, the threshold voltage of SiGe p-MOSFETs decreases from −0.39 to −0.20 V, the subthreshold slope from 117 to 87 mV/dec, and more than 20% output current enhancement is observed in these SiGe p-MOSFETs compared with Si control devices. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing
81.65.Rv Passivation
71.55.Ht Other nonmetals
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