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16 Oct 2000

Volume 77, Issue 16, pp. 2437-2616

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Improvement on epitaxial grown of InN by migration enhanced epitaxy

Hai Lu, William J. Schaff, Jeonghyun Hwang, Hong Wu, Wesley Yeo, Amit Pharkya, and Lester F. Eastman

Appl. Phys. Lett. 77, 2548 (2000); http://dx.doi.org/10.1063/1.1318235 (3 pages) | Cited 106 times

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Epitaxial growth of InN on (0001) sapphire with an AlN buffer layer was studied by migration-enhanced epitaxy, which is composed of an alternative supply of pure In atoms and N2 plasma. A series of samples were prepared with different substrate temperatures ranging from 360 to 590 °C. As-grown films were characterized by x-ray diffraction (XRD), reflective high-energy electron diffraction, atomic-force microscopy (AFM), and Hall measurements. Both XRD θ–2θ and ω scans show that the full width at half maximum of the (0002) peak nearly continuously decrease with increasing growth temperature, while InN grown at 590 °C shows the poorest surface morphology from AFM. It is suggested that three-dimensional characterization is necessary for an accurate evaluation of the quality of the InN epilayer. Hall mobility as high as 542 cm2/V s was achieved on film grown at ∼ 500 °C with an electron concentration of 3×1018 cm−3 at room temperature. These results argue against the common view that nitrogen vacancies are responsible for the high background n-type conductivity of InN. To illuminate the relationship between Hall mobility and carrier concentration, the electrical properties of all InN films grown recently were summarized. © 2000 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

E. Frayssinet, W. Knap, P. Lorenzini, N. Grandjean, J. Massies, C. Skierbiszewski, T. Suski, I. Grzegory, S. Porowski, G. Simin, X. Hu, M. Asif Khan, M. S. Shur, R. Gaska, and D. Maude

Appl. Phys. Lett. 77, 2551 (2000); http://dx.doi.org/10.1063/1.1318236 (3 pages) | Cited 47 times

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Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measurements performed in the 300 K–50 mK range show a low-temperature electron mobility exceeding 60 000 cm2/V s for an electron sheet density of 2.4×1012 cm−2. Magnetotransport experiments performed up to 15 T exhibit well-defined quantum Hall-effect features. The structures corresponding to the cyclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found the quantum and transport scattering times to be 0.4 and 8.2 ps, respectively. The high ratio of the scattering to quantum relaxation time indicates that the main scattering mechanisms, at low temperatures, are due to long-range potentials, such as Coulomb potentials of ionized impurities. © 2000 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Ea III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.43.-f Quantum Hall effects

Finite size effects in carbon nanotubes

Jian Wu, Wenhui Duan, Bing-Lin Gu, Jing-Zhi Yu, and Yoshiyuki Kawazoe

Appl. Phys. Lett. 77, 2554 (2000); http://dx.doi.org/10.1063/1.1318241 (3 pages) | Cited 17 times

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The low-energy theory for finite long carbon nanotube is derived and numerically examined. It shows that the electronic structure is dominated by the quantum confining, which determines the profile of wave functions as well as the eigen energies; while the details of the wave functions are resolved by the structure of the nanotubes. This behavior is attributed to the peculiar electronic structure of the nanotubes. Because of the slow variation of the profile of electron wave functions, the measured conductance is NOT independent of the position to measure it, which is evident in the multiprobe experiment. © 2000 American Institute of Physics.
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71.20.Tx Fullerenes and related materials; intercalation compounds
72.80.Rj Fullerenes and related materials

Conductive layer near the GaN/sapphire interface and its effect on electron transport in unintentionally doped n-type GaN epilayers

M. G. Cheong, K. S. Kim, C. S. Oh, N. W. Namgung, G. M. Yang, C.-H. Hong, K. Y. Lim, E.-K. Suh, K. S. Nahm, H. J. Lee, D. H. Lim, and A. Yoshikawa

Appl. Phys. Lett. 77, 2557 (2000); http://dx.doi.org/10.1063/1.1318728 (3 pages) | Cited 18 times

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Temperature-dependent Hall effect measurements on unintentionally doped n-type GaN epilayers show that, above room temperature, the Hall-mobility values of different samples vary parallel with each other with temperature. We demonstrate that this anomaly is mainly due to a conductive layer near the GaN/sapphire interface for thin samples with low carrier density. Through trapping electrons, threading edge dislocations (TEDs) debilitate the epilayer contribution in a two-layer mixed conduction model involving the epilayer and the near-interface layer. The trapping may, in part, explain low mobility and anomalous transport in pure GaN layers. Scattering by TEDs is important only at low temperatures. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Bk General theory, scattering mechanisms

Fowler–Nordheim hole tunneling in p-SiC/SiO2 structures

R. K. Chanana, K. McDonald, M. Di Ventra, S. T. Pantelides, L. C. Feldman, G. Y. Chung, C. C. Tin, J. R. Williams, and R. A. Weller

Appl. Phys. Lett. 77, 2560 (2000); http://dx.doi.org/10.1063/1.1318229 (3 pages) | Cited 22 times

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We report the confirmed occurrence of Fowler–Nordheim hole tunneling in p-4H–SiC metal-oxide-semiconductor capacitor structures. The effective mass for holes in the oxide is found to be in the range of 0.35m–0.52m, where m is the free electron mass. © 2000 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
73.20.-r Electron states at surfaces and interfaces
85.30.Tv Field effect devices
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Variable frequency photoconductive grating method

J. P. Nicholson

Appl. Phys. Lett. 77, 2563 (2000); http://dx.doi.org/10.1063/1.1318936 (3 pages) | Cited 1 time

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The theoretical treatment of the steady-state photocarrier grating method is extended to include the frequency dependence of the chopping frequency, ω. It is shown that measurements of the characteristic parameter, β, as a function of ω yield both the ambipolar diffusion length, L, as well as the carrier lifetime, τ, for a fixed angular setting. An alternative experimental setup using a Pockel cell and polarizing cube as beam splitter is suggested to facilitate measurements at higher frequencies. © 2000 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects
42.79.Dj Gratings
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
85.60.Bt Optoelectronic device characterization, design, and modeling

Role of inversion layer formation in producing low effective surface recombination velocities at Si/liquid contacts

William J. Royea, David J. Michalak, and Nathan S. Lewis

Appl. Phys. Lett. 77, 2566 (2000); http://dx.doi.org/10.1063/1.1318935 (3 pages) | Cited 3 times

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Photoconductivity decay lifetimes have been obtained for NH4F(aq)-etched Si(111) and for air-oxidized Si(111) surfaces in contact with solutions of CH3OH or tetrahydrofuran (THF) containing either ferrocene+/0 (Fc+/0), bis(pentamethylcyclopentadienyl) Fe+/0, or I2. Si surfaces in contact with electrolytes having Nernstian redox potentials >0 V versus the standard calomel electrode exhibited low effective surface recombination velocities regardless of the different surface chemistries, whereas those exposed only to N2(g) ambients or to electrolytes containing mild oxidants showed differing rf photoconductivity decay behavior depending on their different surface chemistry. The data reveal that formation of an inversion layer, and not a reduced density of electrical trap sites on the surface, is primarily responsible for the long charge-carrier lifetimes observed for Si surfaces in contact with CH3OH or THF electrolytes containing I2 or Fc+/0. © 2000 American Institute of Physics.
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73.40.Mr Semiconductor-electrolyte contacts
73.25.+i Surface conductivity and carrier phenomena
72.40.+w Photoconduction and photovoltaic effects
82.45.-h Electrochemistry and electrophoresis
73.20.-r Electron states at surfaces and interfaces
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation

Ultrashallow junctions in silicon formed by molecular-beam epitaxy using boron delta doping

Phillip E. Thompson and Joe Bennett

Appl. Phys. Lett. 77, 2569 (2000); http://dx.doi.org/10.1063/1.1319189 (3 pages) | Cited 12 times

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Low-temperature molecular-beam epitaxy was used to form highly conductive, ultrashallow layers in silicon using boron delta doping. Junction depths, determined with secondary ion mass spectrometry, ranged from 7 to 18 nm. A minimum resistivity of 3×10−4 Ω cm was obtained when the delta-doped layers were spaced 2.5 nm apart. The sheet resistances of the epitaxial layers, plotted as a function of junction depth, followed the theoretical curve for a box-doped layer having a boron doping concentration equal to the solid solubility limit, 6×1020/cm3. At a specific thickness, the minimum sheet resistance obtained by B delta doping was more than a factor of 5 less than that achieved by ion implantation. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.61.Cw Elemental semiconductors

Metal-assisted chemical etching in HF/H2O2 produces porous silicon

X. Li and P. W. Bohn

Appl. Phys. Lett. 77, 2572 (2000); http://dx.doi.org/10.1063/1.1319191 (3 pages) | Cited 176 times

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A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H2O2, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts. © 2000 American Institute of Physics.
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81.05.Rm Porous materials; granular materials
78.55.Mb Porous materials
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Ap Elemental semiconductors

Thin film semiconductor deposition on free-standing ZnO columns

R. Könenkamp, K. Boedecker, M. C. Lux-Steiner, M. Poschenrieder, F. Zenia, C. Levy-Clement, and S. Wagner

Appl. Phys. Lett. 77, 2575 (2000); http://dx.doi.org/10.1063/1.1319187 (3 pages) | Cited 66 times

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We report the deposition of a-Si:H on thin films of free-standing single crystalline ZnO columns. The ZnO columns have a height of several μm and a diameter between 100 and 200 nm. The ZnO films are prepared in electrodeposition and have considerable potential for use in photoelectric thin film devices. Morphology, electronic parameters, and basic optical behavior, such as reflectance and light trapping efficiency, are reported. Amorphous silicon is deposited on the columns as a continuous smooth film with conformal coverage. Some possibilities of using these films in devices are discussed. © 2000 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
78.30.Fs III-V and II-VI semiconductors
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Pq Electrodeposition, electroplating
78.66.Jg Amorphous semiconductors; glasses
84.60.Jt Photoelectric conversion

Aharonov–Bohm phase effects and inelastic scattering in transport through a parallel tunnel-coupled symmetric double-dot device

Anatoly Yu. Smirnov, Norman J. M. Horing, and Lev G. Mourokh

Appl. Phys. Lett. 77, 2578 (2000); http://dx.doi.org/10.1063/1.1317542 (3 pages) | Cited 8 times

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We have examined the effects of inelastic phonon scattering on the lead-to-lead current through a parallel-quantum-double-dot device to determine the persistence of coherence within the device. The tunnel-coupled double-dot system is taken to be symmetric and is threaded by Aharonov–Bohm magnetic flux. We show that at resonant values of the magnetic flux, when only the bonding or antibonding state is involved in transport through the double dot, the current–voltage characteristic changes drastically and the electron–phonon interaction has a pronounced effect on the level populations. However, it does not destroy coherence during the tunneling process through the system. © 2000 American Institute of Physics.
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85.35.Ds Quantum interference devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
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