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4 Dec 2006

Volume 89, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 89, 233120 (2006); http://dx.doi.org/10.1063/1.2402115 (3 pages)

S. Yeo, Y. Horibe, S. Mori, C. M. Tseng, C. H. Chen, A. G. Khachaturyan, C. L. Zhang, and S.-W. Cheong
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Hole transport in p-type ZnO films grown by plasma-assisted molecular beam epitaxy

J. W. Sun, Y. M. Lu, Y. C. Liu, D. Z. Shen, Z. Z. Zhang, B. H. Li, J. Y. Zhang, B. Yao, D. X. Zhao, and X. W. Fan

Appl. Phys. Lett. 89, 232101 (2006); http://dx.doi.org/10.1063/1.2398908 (3 pages) | Cited 10 times

Online Publication Date: 4 December 2006

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The hole transport properties of nitrogen doped p-type ZnO grown on c-plane sapphire (c-Al2O3) were investigated by temperature-dependent Hall-effect measurements. The experimental Hall mobility was found to be considerably lower than the calculated mobility including ionized impurity scattering, acoustic-mode deformation potential scattering, piezoelectric potential scattering, and polar optical phonon scattering. Atomic force microscopy and x-ray diffraction measurements demonstrated that p-type ZnO on c-Al2O3 consisted of two kinds of 30°-rotated domains surrounded by grain boundaries. Thus, taking the effect of inhomogeneous microstructure on the mobility into account, the calculated mobility agreed favorably with the experimental data. This agreement indicates that besides ionized impurity and acoustic deformation potential scattering at low temperatures and the polar optical phonon scattering at high temperatures, the effects of the inhomogeneous microstructure in p-type ZnO films play a more important role in determining the hole mobility.
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73.61.Ga II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
77.65.-j Piezoelectricity and electromechanical effects
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
68.37.Ps Atomic force microscopy (AFM)

Influence of surface passivation on ultrafast carrier dynamics and terahertz radiation generation in GaAs

J. Lloyd-Hughes, S. K. E. Merchant, L. Fu, H. H. Tan, C. Jagadish, E. Castro-Camus, and M. B. Johnston

Appl. Phys. Lett. 89, 232102 (2006); http://dx.doi.org/10.1063/1.2398915 (3 pages) | Cited 21 times

Online Publication Date: 4 December 2006

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The carrier dynamics of photoexcited electrons in the vicinity of the surface of (NH4)2S-passivated GaAs were studied via terahertz emission spectroscopy and optical-pump terahertz-probe spectroscopy. Terahertz emission spectroscopy measurements, coupled with Monte Carlo simulations of terahertz emission, revealed that the surface electric field of GaAs reverses after passivation. The conductivity of photoexcited electrons was determined via optical-pump terahertz-probe spectroscopy and was found to double after passivation. These experiments demonstrate that passivation significantly reduces the surface state density and surface recombination velocity of GaAs. Finally, it was demonstrated that passivation leads to an enhancement in the power radiated by photoconductive switch terahertz emitters, thereby showing the important influence of surface chemistry on the performance of ultrafast terahertz photonic devices.
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81.05.Ea III-V semiconductors
68.47.Fg Semiconductor surfaces
72.80.Ey III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.70.Gq Microwave and radio-frequency interactions
73.25.+i Surface conductivity and carrier phenomena

Work function engineering using lanthanum oxide interfacial layers

H. N. Alshareef, M. Quevedo-Lopez, H. C. Wen, R. Harris, P. Kirsch, P. Majhi, B. H. Lee, R. Jammy, D. J. Lichtenwalner, J. S. Jur, and A. I. Kingon

Appl. Phys. Lett. 89, 232103 (2006); http://dx.doi.org/10.1063/1.2396918 (3 pages) | Cited 52 times

Online Publication Date: 4 December 2006

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A La2O3 capping scheme has been developed to obtain n-type band-edge metal gates on Hf-based gate dielectrics. The viability of the technique is demonstrated using multiple metal gates that normally show midgap work function when deposited directly on HfSiO. The technique involves depositing a thin interfacial of La2O3 on a Hf-based gate dielectric prior to metal gate deposition. This process preserves the excellent device characteristic of Hf-based dielectrics, but also allows the realization of band-edge metal gates. The effectiveness of the technique is demonstrated by fabricating fully functional transistor devices. A model is proposed to explain the effect of La2O3 capping on metal gate work function.
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85.30.Tv Field effect devices

Electrical detection of hybridization and threading intercalation of deoxyribonucleic acid using carbon nanotube network field-effect transistors

Ee-Ling Gui, Lain-Jong Li, P. S. Lee, Anup Lohani, S. G. Mhaisalkar, Qing Cao, Seong Jun Kang, John A. Rogers, N. C. Tansil, and Zhiqiang Gao

Appl. Phys. Lett. 89, 232104 (2006); http://dx.doi.org/10.1063/1.2399355 (3 pages) | Cited 18 times

Online Publication Date: 4 December 2006

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The authors study deoxyribonucleic acid (DNA) sensing characteristics of carbon nanotube network field-effect transistors (CNNFETs) by monitoring their electrical responses upon immobilization with a DNA probe, hybridization with DNA analytes, and intercalation with a N,N′-bis(3-propylimidazole)-1,4,5,8-naphthalene diimide modified with Os(2,2′-bipyridine)2Cl+ pendants. The CNNFETs immobilized by single-stranded DNA molecules demonstrate the selective sensing of its complementary and single-base mismatched DNA (difference of ∼ 16% in reduction of normalized drain current Id). Subsequent intercalation demonstrates a further sensitivity enhancement (difference of ∼ 13% in Id reduction) due to specific binding between hybridized DNA and intercalators, corroborated by the x-ray photoelectron spectroscopy study.
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79.60.Fr Polymers; organic compounds
87.80.-y Biophysical techniques (research methods)
85.30.Tv Field effect devices
85.35.Kt Nanotube devices
87.14.G- Nucleic acids
87.15.-v Biomolecules: structure and physical properties

Hole capture into self-organized InGaAs quantum dots

M. Geller, A. Marent, E. Stock, D. Bimberg, V. I. Zubkov, I. S. Shulgunova, and A. V. Solomonov

Appl. Phys. Lett. 89, 232105 (2006); http://dx.doi.org/10.1063/1.2400059 (3 pages) | Cited 19 times

Online Publication Date: 4 December 2006

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Hole capture into and emission from self-organized InGaAs/GaAs quantum dots (QDs) are studied by means of charge-selective deep level transient spectroscopy. The authors observe hole capture and determine activation energies and apparent capture cross sections for emission and capture. The experimental findings indicate that the capture process into the QDs in the presence of an applied electric field is controlled by phonon-assisted tunneling. An apparent capture cross section (at infinite values of temperature T and electric field F) σF,T = ∞ ≈ 7×10−12 cm2 and an average time tc ≈ 0.3 ps (T = 300 K) for hole capture and relaxation are obtained.
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73.63.Kv Quantum dots
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Gk Tunneling
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Strong suppression of the yellow luminescence in C-doped GaN in air ambient

M. A. Reshchikov

Appl. Phys. Lett. 89, 232106 (2006); http://dx.doi.org/10.1063/1.2400074 (3 pages) | Cited 7 times

Online Publication Date: 4 December 2006

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The authors observed a drastic reduction of the yellow luminescence (YL) intensity in carbon-doped semi-insulating GaN in air or oxygen ambient as compared to the intensity in vacuum. The YL intensity dropped about 300 times while the exciton emission remained almost unchanged. The authors assume that the donor-acceptor-pair transitions involving a gallium vacancy complex in a thin near-surface region cause the strong YL. Oxygen molecules or ions induce the surface states acting as a very efficient channel of nonradiative recombination. The results indicate that carbon may not be involved in the acceptor responsible for the YL band in GaN:C.
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78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena
61.72.J- Point defects and defect clusters
73.20.At Surface states, band structure, electron density of states

Electron dephasing in wurtzite indium nitride thin films

Z. W. Jia, W. Z. Shen, H. Ogawa, and Q. X. Guo

Appl. Phys. Lett. 89, 232107 (2006); http://dx.doi.org/10.1063/1.2400097 (3 pages) | Cited 6 times

Online Publication Date: 4 December 2006

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The authors present magnetotransport measurements of electron dephasing characteristics in wurtzite indium nitride thin films grown by metal-organic vapor phase epitaxy. Pronounced weak antilocalization effects have been observed at low magnetic fields due to the presence of strong spin-orbit interactions at the top of the valence band. With the aid of the weak localization theory, they are able to demonstrate that the dephasing is connected to three separate processes of the spin-orbit, electron-phonon, and extended structural defect scatterings. The spin-orbit splitting has been determined to be 5.7 meV. They have also shown that both the magnetoresistivity and resistivity can be explained using the same temperature-dependent dephasing times.
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73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.20.Nr Semiconductor compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Liquid-state semiconductor p-n junction at 903 K

Yasushi Sasaki, Yoshihiko Hirano, Manabu Iguchi, and Kuniyoshi Ishii

Appl. Phys. Lett. 89, 232108 (2006); http://dx.doi.org/10.1063/1.2400119 (3 pages)

Online Publication Date: 4 December 2006

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A liquid-state semiconductor p-n junction has been fabricated by applying the liquid phase separation of the monotectic Sb-Sb2S3 system at 903 K. Electrical conduction types of liquid semiconductor of Sb–S alloy and S2S3-x consisting of the immiscible system are found to be p and n types, respectively, from measured absolute Seebeck coefficients. The p-n junction was formed by the liquid Sb–-S alloy and Sb2S3−x; this is confirmed from the asymmetric current-voltage characteristics or its behavior is rectified. The formation of the liquid-state p-n junction in liquid semiconductors has great prospects in the next-generation direct thermal-to-electrical energy conversion materials.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Ei Rectification
72.80.Ph Liquid semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
64.75.-g Phase equilibria

High spatial resolution picosecond cathodoluminescence of InGaN quantum wells

S. Sonderegger, E. Feltin, M. Merano, A. Crottini, J. F. Carlin, R. Sachot, B. Deveaud, N. Grandjean, and J. D. Ganière

Appl. Phys. Lett. 89, 232109 (2006); http://dx.doi.org/10.1063/1.2397562 (3 pages) | Cited 24 times

Online Publication Date: 5 December 2006

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The authors have studied InxGa1−xN/GaN (x ≈ 15%) quantum wells (QWs) using atomic force microscopy (AFM) and picosecond time resolved cathodoluminescence (pTRCL) measurements. They observed a contrast inversion between monochromatic CL maps corresponding to the high energy side (3.13 eV) and the low energy side (3.07 eV) of the QW luminescence peak. In perfect correlation with CL images, AFM images clearly show regions where the QW thickness almost decreases to zero. Pronounced spectral diffusion from high energy thinner regions to low energy thicker regions is observed in pTRCL, providing a possible explanation for the hindering of nonradiative recombination at dislocations.
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78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
68.37.Ps Atomic force microscopy (AFM)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Photoexcitation dynamics in thin films of insulated molecular wires

M. H. Chang, M. J. Frampton, H. L. Anderson, and L. M. Herz

Appl. Phys. Lett. 89, 232110 (2006); http://dx.doi.org/10.1063/1.2398914 (3 pages) | Cited 12 times

Online Publication Date: 5 December 2006

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A study is presented on how encapsulation of conjugated polymer chains affects the motion of photoexcitations and the formation of interchain aggregates in solid films. It is shown that threading of a poly(diphenylene vinylene) backbone inside insulating cyclodextrins (rotaxination) and/or complexation of the chains with poly(ethylene oxide) are effective means of preventing the diffusion of excitons to nonradiative defect sites. Ultrafast time-resolved photoluminescence data reveal that excitation transfer between encapsulated chains is still possible and, for the case of rotaxination, is likely to be facilitated through close packing of end groups belonging to adjacent chains.
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78.66.Nk Insulators
78.66.Qn Polymers; organic compounds
78.47.-p Spectroscopy of solid state dynamics
78.55.Kz Solid organic materials
71.35.-y Excitons and related phenomena

Electron-beam-induced dissociation of B–D complexes in diamond

J. Barjon, J. Chevallier, F. Jomard, C. Baron, and A. Deneuville

Appl. Phys. Lett. 89, 232111 (2006); http://dx.doi.org/10.1063/1.2400201 (3 pages) | Cited 12 times

Online Publication Date: 5 December 2006

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The diffusion of deuterium in boron-doped homoepitaxial diamond films leads to the passivation of boron acceptors via the formation of B–D complexes. In this letter, the stability of B–D pairs is investigated under the stress of a low-energy (10 keV) electron-beam irradiation at low temperature ( ∼ 100 K). The dissociation of the complexes is evidenced by cathodoluminescence spectroscopy and is shown to result in the reactivation of most acceptors. The dissociation yield per incident electron is found to be strongly dependent on the e-beam current, which suggests a dissociation involving a vibrational excitation of the complexes by hot electrons.
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61.80.Fe Electron and positron radiation effects
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.66.Db Elemental semiconductors and insulators
78.60.Hk Cathodoluminescence, ionoluminescence
81.05.Cy Elemental semiconductors
73.61.Cw Elemental semiconductors

Determination at 300 K of the hole capture cross section of chromium-boron pairs in p-type silicon

S. Dubois, O. Palais, and P. J. Ribeyron

Appl. Phys. Lett. 89, 232112 (2006); http://dx.doi.org/10.1063/1.2402261 (3 pages) | Cited 1 time

Online Publication Date: 6 December 2006

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Measurement of dissolved chromium concentration in p-type crystalline silicon by means of the change in carrier lifetime due to chromium-boron pair dissociation requires precise knowledge of the recombination parameters of dissolved chromium in silicon. This work, based on quasi-steady-state carrier lifetime measurements, aims to determine the value at 300 K of the hole capture cross section of the chromium-boron pairs in p-type silicon, which is the only recombination parameter still unknown at this temperature. The complete knowledge of the recombination parameters allows the determination of dissolved chromium concentrations in p-type silicon as low as 1010 cm−3, even when chromium atoms do not dominate carrier recombination.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
64.75.-g Phase equilibria
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Single wall carbon nanotube double quantum dot

H. I. Jørgensen, K. Grove-Rasmussen, J. R. Hauptmann, and P. E. Lindelof

Appl. Phys. Lett. 89, 232113 (2006); http://dx.doi.org/10.1063/1.2402887 (3 pages) | Cited 18 times

Online Publication Date: 6 December 2006

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The authors report on two top-gate defined, coupled quantum dots in a semiconducting single wall carbon nanotube, constituting a tunable double quantum dot system. The single wall carbon nanotubes are contacted by titanium electrodes and gated by three narrow top-gate electrodes as well as a back gate. The authors show that a bias spectroscopy plot on just one of the two quantum dots can be used to extract the addition energy of both quantum dots. Furthermore, honeycomb charge stability diagrams are analyzed by an electrostatic capacitor model that includes cross capacitances, and they extract the coupling energy of the double quantum dot.
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85.35.Kt Nanotube devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.De Semiconductor-device characterization, design, and modeling

Ultrafast carrier thermalization in InN

Yu-Chieh Wen, Cheng-Ying Chen, Chang-Hong Shen, Shangjr Gwo, and Chi-Kuang Sun

Appl. Phys. Lett. 89, 232114 (2006); http://dx.doi.org/10.1063/1.2402899 (3 pages) | Cited 17 times

Online Publication Date: 6 December 2006

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Carrier thermalization dynamics in heavily doped n-type InN was investigated at room temperature with a femtosecond transient transmission measurement. The dependence of hot carrier cooling time on the total electron density indicates that the plasma screening of electron-LO phonon interactions is responsible for the reduction in energy-loss rate. Under low excitation, the carriers with different excess energies can be found to cool down with a fixed thermalization time of 1.4 ps. Intensity dependent study suggests that this relatively slow carrier cooling time could be attributed to the screening effect by high-background-doping plasma rather than the hot phonon effect.
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72.30.+q High-frequency effects; plasma effects
72.80.Ey III-V and II-VI semiconductors
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Large cone angle magnetization precession of an individual nanopatterned ferromagnet with dc electrical detection

M. V. Costache, S. M. Watts, M. Sladkov, C. H. van der Wal, and B. J. van Wees

Appl. Phys. Lett. 89, 232115 (2006); http://dx.doi.org/10.1063/1.2400058 (3 pages) | Cited 15 times

Online Publication Date: 8 December 2006

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The on-chip resonant driving of large cone-angle magnetization precession of an individual nanoscale Permalloy element is demonstrated. Strong driving is realized by locating the element in close proximity to the shorted end of a coplanar strip waveguide, which generates a microwave magnetic field. A frequency modulation method is used to accurately measure resonant changes of the dc anisotropic magnetoresistance. Precession cone angles up to 9° are determined with better than 1° of resolution. The resonance peak shape is well described by the Landau-Lifshitz-Gilbert equation.
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75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.Np Metals and alloys
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