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22 Dec 2003

Volume 83, Issue 25, pp. 5121-5321

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 5310 (2003); http://dx.doi.org/10.1063/1.1635070 (3 pages)

Z. G. Chiragwandi, O. Nur, M. Willander, and N. Calander
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Quantum conductance of carbon nanotube peapods

Young-Gui Yoon, Mario S. C. Mazzoni, and Steven G. Louie

Appl. Phys. Lett. 83, 5217 (2003); http://dx.doi.org/10.1063/1.1633680 (3 pages) | Cited 11 times

Online Publication Date: 17 December 2003

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We present a first-principles study of the quantum conductance of hybrid nanotube systems consisting of single-walled carbon nanotubes (SWCNTs) encapsulating either an isolated single C60 molecule or a chain of C60 molecules (nanotube peapods). The calculations show a rather weak bonding interaction between the fullerenes and the SWCNTs. The conductance of a (10,10) SWCNT with a single C60 molecule is virtually unaffected at the Fermi level, but exhibits quantized resonant reductions at the molecular levels. The nanotube peapod arrangement gives rise to high density of states for the fullerene highest occupied molecular orbital and lowest unoccupied molecular orbital bands. © 2003 American Institute of Physics.
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73.63.Fg Nanotubes
73.23.-b Electronic transport in mesoscopic systems
72.80.Rj Fullerenes and related materials
73.22.-f Electronic structure of nanoscale materials and related systems
71.20.Tx Fullerenes and related materials; intercalation compounds
71.15.-m Methods of electronic structure calculations

Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

P. Murzyn, C. R. Pidgeon, P. J. Phillips, M. Merrick, K. L. Litvinenko, J. Allam, B. N. Murdin, T. Ashley, J. H. Jefferson, A. Miller, and L. F. Cohen

Appl. Phys. Lett. 83, 5220 (2003); http://dx.doi.org/10.1063/1.1635659 (3 pages) | Cited 8 times

Online Publication Date: 17 December 2003

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We have made direct pump-probe measurements of spin lifetimes in intrinsic and degenerate n-InAs at 300 K. In particular, we measure remarkably long spin lifetimes (τs ∼ 1.6 ns) for near-degenerate epilayers of n-InAs. For intrinsic material, we determine τs∼20 ps, in agreement with other workers. There are two main models that have been invoked for describing spin relaxation in narrow-gap semiconductors: the D’yakonov–Perel (DP) model and the Elliott–Yafet (EY) model. For intrinsic material, the DP model is believed to dominate in III–V materials above 77 K, in agreement with our results. We show that in the presence of strong n-type doping, the DP relaxation is suppressed both by the degeneracy condition and by electron–electron scattering, and that the EY model then dominates for the n-type material. We show that this same process is also responsible for a hitherto unexplained lengthening of τs with n-type doping in our earlier measurements of n-InSb. © 2003 American Institute of Physics.
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72.25.Rb Spin relaxation and scattering
72.25.Dc Spin polarized transport in semiconductors
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
76.30.-v Electron paramagnetic resonance and relaxation
71.20.Nr Semiconductor compounds
71.55.Eq III-V semiconductors

Charge detrapping in HfO2 high-κ gate dielectric stacks

E. P. Gusev and C. P. D’Emic

Appl. Phys. Lett. 83, 5223 (2003); http://dx.doi.org/10.1063/1.1633332 (3 pages) | Cited 34 times

Online Publication Date: 17 December 2003

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We investigated the kinetics of charge detrapping in high-κ gate stacks fabricated with ultrathin HfO2 dielectric films grown by atomic layer deposition and a polycrystalline silicon gate electrode. It was observed that charge trapped after electron injection in the high-κ stack was unstable and slowly decayed over time. The decay does not follow a simple first-order exponential law suggesting complex detrapping mechanism(s), possibly involving more than one type of trap present in the stack. The detrapping rate was found to depend strongly on gate voltage, temperature, and light illumination. © 2003 American Institute of Physics.
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73.61.Ng Insulators

Bandgap states in transition-metal (Sc, Y, Zr, and Nb)-doped Al2O3

Ranju Jung, Jae-Cheol Lee, Ye-Won So, Tae-Won Noh, S.-J. Oh, Jong-Cheol Lee, and Hyun-Joon Shin

Appl. Phys. Lett. 83, 5226 (2003); http://dx.doi.org/10.1063/1.1635656 (3 pages) | Cited 9 times

Online Publication Date: 17 December 2003

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We have investigated the electronic structure of transition-metal (TM = Sc, Y, Zr, and Nb)-doped Al2O3 by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS). In valence bands of these TM-doped Al2O3 measured by XPS, the highest occupied levels and the shapes of valence bands are almost unchanged from the pure alumina. On the other hand, XAS spectra obtained at the oxygen K-edge show that Nb- and Zr-doped Al2O3 show localized d states in the bandgap below the conduction band minimum, while Y- and Sc-doped Al2O3 have d states inside the conduction band of the original Al2O3. This implies that Y- and Sc-doped Al2O3 will show little bandgap degradation and maintain the same band offset as silica at the Si interface, and can serve as promising candidates for an alternative gate oxide. © 2003 American Institute of Physics.
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71.20.Ps Other inorganic compounds
71.55.Ht Other nonmetals
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.70.Dm X-ray absorption spectra
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Time-resolved carrier tunneling in nanocrystalline silicon/amorphous silicon dioxide superlattices

V. Duzhko and L. Tsybeskov

Appl. Phys. Lett. 83, 5229 (2003); http://dx.doi.org/10.1063/1.1630151 (3 pages) | Cited 2 times

Online Publication Date: 17 December 2003

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Eight period nanocrystalline Si/amorphous SiO2 superlattices with Si nanocrystals of ∼5 nm diameter and tunnel-transparent (1.6–1.8-nm-thick) layers of SiO2 reveal a sharp resonance in conductivity at a low (∼0.8 V) applied bias. The performed measurements of time-resolved photocurrent decay show two distinctly different components. A fast, temperature-independent decay dominates at the applied bias close to the resonant conditions. Slower, temperature-dependent photocurrent decay becomes dominant at higher (>1.5 V) voltages. The observed fast photocurrent transient is associated with resonant hole tunneling throughout nanocrystalline Si superlattices. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
78.47.-p Spectroscopy of solid state dynamics
73.61.Cw Elemental semiconductors

Low-frequency noise and radiation response of metal-oxide-semiconductor transistors with Al2O3/SiOxNy/Si(100) gate stacks

H. D. Xiong, D. M. Fleetwood, J. A. Felix, E. P. Gusev, and C. D’Emic

Appl. Phys. Lett. 83, 5232 (2003); http://dx.doi.org/10.1063/1.1635071 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2003

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Low-frequency noise and irradiation response are studied for n-channel metal-oxide-semiconductor field-effect transistors with Al2O3/SiOxNy/Si(100) gate stacks. Radiation-induced threshold-voltage shifts and low-frequency noise increase with dose and decrease with postirradiation annealing. The border trap density in the gate dielectric inferred from the noise measurements is significantly higher than that typically observed in thermal SiO2. Similarly, the effective radiation-induced-hole trapping efficiency in Al2O3 gate dielectrics is significantly higher than for SiO2 gate dielectrics of comparable thickness. The low-frequency noise in these high-κ devices can be described well by a number fluctuation model. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.55.Ht Other nonmetals
61.82.-d Radiation effects on specific materials
73.50.Td Noise processes and phenomena

Low-temperature, in situ tunable, uniaxial stress measurements in semiconductors using a piezoelectric actuator

M. Shayegan, K. Karrai, Y. P. Shkolnikov, K. Vakili, E. P. De Poortere, and S. Manus

Appl. Phys. Lett. 83, 5235 (2003); http://dx.doi.org/10.1063/1.1635963 (3 pages) | Cited 34 times

Online Publication Date: 17 December 2003

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We demonstrate the use of a piezoelectric actuator to apply, at low temperatures, uniaxial stress in the plane of a two-dimensional electron system confined to a modulation-doped AlAs quantum well. Via the application of stress, which can be tuned in situ and continuously, we control the energies and occupations of the conduction-band minima and the electronic properties of the electron system. We also report measurements of the longitudinal and transverse strain versus bias for the actuator at 300, 77, and 4.2 K. A pronounced hysteresis is observed at 300 and 77 K, while at 4.2 K, strain is nearly linear and shows very little hysteresis with the applied bias. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.65.Fg Quantum wells
81.05.Ea III-V semiconductors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.07.St Quantum wells

High frequency capacitance–voltage characterization of Al2O3/ZrO2/Al2O3 in fully depleted silicon-on-insulator metal–oxide–semiconductor capacitors

N. L. Zhang, Z. T. Song, Q. W. Shen, Y. J. Wu, Q. B. Liu, C. L. Lin, X. Z. Duo, L. R. Zheng, Y. F. Ding, and Z. Q. Zhu

Appl. Phys. Lett. 83, 5238 (2003); http://dx.doi.org/10.1063/1.1579865 (3 pages) | Cited 2 times

Online Publication Date: 17 December 2003

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Al2O3/ZrO2/Al2O3 gate stacks were prepared on ultrathin silicon-on-insulator (SOI) by ultrahigh vacuum electron-beam evaporation and postannealed in N2 at 450 °C for 30 min. A three clear nanolaminate layered structure of Al2O3 (2.1 nm)/ZrO2 (3.5 nm)/Al2O3 (2.3 nm) was observed with high-resolution cross-sectional transmission electron microscopy. High frequency capacitance voltage (C–V) characteristics of the fully depleted (FD) SOI metal–oxide–semiconductor (MOS) capacitor at 1 and 5 MHz were studied. It is the minority carriers that determine the high frequency C–V properties, which are opposite to the case of bulk MOS capacitors. And the series resistance of the SOI is the determinant factor of the high frequency characteristics of the FD SOI MOS capacitors. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
85.30.Tv Field effect devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.72.Cc Kinetics of defect formation and annealing

Doped red organic electroluminescent devices based on a cohost emitter system

Tswen-Hsin Liu, Chung-Yeh Iou, and Chin H. Chen

Appl. Phys. Lett. 83, 5241 (2003); http://dx.doi.org/10.1063/1.1635986 (3 pages) | Cited 52 times

Online Publication Date: 17 December 2003

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We have developed an efficient red emitter in organic light-emitting diodes based on the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran doped in a cohost emitter system of 5,6,11,12-tetraphenylnathacene/tris(8-hydroxyquinolinato)aluminum which achieved an electroluminescence (EL) efficiency of 4.4 cd/A and 2.1 lm/W at 20 mA/cm2 and 6.8 V, with a near saturated Commission Internationale d’Eclairage coordinates (x = 0.65, y = 0.35). This cohost emitter system has the advantage of alleviating the current-induced fluorescence quenching often encountered in red organic EL devices and greatly improves the EL efficiency over a wide range of drive current conditions. From accelerated degradation tests, a device half-life of about 33 800 h can be projected in this system at an initial device luminance of 100 cd/m2. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
78.60.Fi Electroluminescence
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