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5 Apr 2004

Volume 84, Issue 14, pp. 2473-2706

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Appl. Phys. Lett. 84, 2244 (2004); http://dx.doi.org/10.1063/1.1690471 (3 pages)

David R. Smith, David Schurig, Jack J. Mock, Pavel Kolinko, and Patrick Rye
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Low-band-gap, sublimable rhenium(I) diimine complex for efficient bulk heterojunction photovoltaic devices

H. L. Wong, L. S. M. Lam, K. W. Cheng, K. Y. K. Man, W. K. Chan, C. Y. Kwong, and A. B. Djurišić

Appl. Phys. Lett. 84, 2557 (2004); http://dx.doi.org/10.1063/1.1682676 (3 pages) | Cited 21 times

Online Publication Date: 1 April 2004

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The use of chlorotricarbonyl rhenium(I) diimine complex as photosensitizing molecule in photovoltaic cells is demonstrated. Unlike other transition-metal-based sensitizers, the complex is sublimable and has low band gap. It also exhibits bipolar charge transport character with relatively high carrier mobilities on the order of 10−3 cm2 V−1 s−1. Multilayer heterojunction and bulk heterojunction devices with fullerene as the electron accepting molecule were prepared. For the bulk heterojunction devices, the fill factor and power conversion efficiency under simulated solar light illumination were 0.56 and 0.48%, respectively. Atomic force microscopic images showed that the complex dispersed evenly with fullerene molecules in solid state. © 2004 American Institute of Physics.
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85.65.+h Molecular electronic devices
85.60.Bt Optoelectronic device characterization, design, and modeling
68.37.Ps Atomic force microscopy (AFM)
73.50.Dn Low-field transport and mobility; piezoresistance

Low-resistance tunnel junctions on GaAs substrates using GaInNAs

D. E. Mars, Y.-L. Chang, M. H. Leary, S. D. Roh, and D. R. Chamberlin

Appl. Phys. Lett. 84, 2560 (2004); http://dx.doi.org/10.1063/1.1691193 (3 pages) | Cited 5 times

Online Publication Date: 1 April 2004

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Using molecular-beam epitaxy, we have fabricated p-n tunnel junctions lattice matched to GaAs substrates that consist of highly C-doped Ga0.93In0.07As on the p side, and highly Si-doped Ga0.93In0.07N0.02As0.98 on the n side. The introduction of N on the n side of the tunnel junction: (1) lowers the conduction band edge while leaving the valence band edge unchanged, (2) allows the introduction of In to further lower the band gap while remaining lattice matched to GaAs, and (3) increases the maximum Si donor activation that can be achieved. All three of these effects increase the tunneling probability for carriers across the junction and decrease the specific resistance. We estimate the active C acceptors on the p side to be 1.5×1020 cm−3 and the active Si donors on the n side to be 1.8×1019 cm−3. Because of the mutual passivation effect between N and Si atoms, the Si doping level was increased to 1.0×1020 cm−3 to achieve this active net donor concentration. The specific resistance of test tunnel junctions has been measured to be <1×10−5 Ω cm2 corresponding to <0.1 V drop at a current density of 10 kA/cm2. These results are a substantial improvement over corresponding test structures without N on the n side of the junction. The experimental results are in good agreement with model calculations. © 2004 American Institute of Physics.
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71.20.Nr Semiconductor compounds
73.40.Gk Tunneling
61.72.uj III-V and II-VI semiconductors
61.72.uf Ge and Si
71.15.-m Methods of electronic structure calculations
81.65.Rv Passivation

High-quality single-crystal Ge on insulator by liquid-phase epitaxy on Si substrates

Yaocheng Liu, Michael D. Deal, and James D. Plummer

Appl. Phys. Lett. 84, 2563 (2004); http://dx.doi.org/10.1063/1.1691175 (3 pages) | Cited 60 times

Online Publication Date: 1 April 2004

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Ge on insulator (GOI) is desired to obtain metal-oxide-semiconductor transistors with high performance and low leakage current. We have developed a method to make GOI based on liquid-phase epitaxial (LPE) growth on Si substrates and a defect necking technique in which defects are confined to a very short distance. Self-aligned microcrucibles were used to hold the Ge liquid. High-quality single-crystal (100) as well as (111) oriented GOI structures were obtained with a process compatible with Si-based fabrication. No dislocations or stacking faults were found in the LPE Ge films on insulator. The orientation of the Ge crystals was controlled by the seeding Si substrate. This method opens up the possibility of integrating Ge device structures in a baseline Si integrated circuit process. © 2004 American Institute of Physics.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Fabrication of GaN cantilevers on silicon substrates for microelectromechanical devices

S. Davies, T. S. Huang, M. H. Gass, A. J. Papworth, T. B. Joyce, and P. R. Chalker

Appl. Phys. Lett. 84, 2566 (2004); http://dx.doi.org/10.1063/1.1695196 (3 pages) | Cited 18 times

Online Publication Date: 1 April 2004

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The fabrication of free-standing GaN cantilevers on Si(111) is demonstrated, and the growth of III-nitride epilayers on silicon (111) using an AlN buffer layer is characterized. Mechanically releasing GaN structures from Si(111) required a combination of two dry inductively coupled plasma etch processes using Cl2/Ar and CF4/Ar/O2 chemistries, and a potassium hydroxide (KOH) aqueous etch. Scanning transmission electron microscopy reveals a columnar growth habit for the nitrides. Electron energy loss spectroscopy imaging of an AlGaN/GaN interface indicates columnar growth may strongly influence the potential piezoelectric properties of III-nitride cantilever microelectromechanical devices. © 2004 American Institute of Physics.
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52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.05.Ea III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)
79.20.Uv Electron energy loss spectroscopy
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Acoustic manipulation of electron–hole pairs in GaAs at room temperature

M. M. de Lima, R. Hey, J. A. H. Stotz, and P. V. Santos

Appl. Phys. Lett. 84, 2569 (2004); http://dx.doi.org/10.1063/1.1695636 (3 pages) | Cited 7 times

Online Publication Date: 1 April 2004

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We demonstrate the optically detected long-range (>100 μm) ambipolar transport of photogenerated electrons and holes at room temperature by surface acoustic waves (SAWs) in (In,Ga)As-based quantum well structures coupled to an optical microcavity. We also show the control of the propagation direction of the carriers by a switch composed of orthogonal SAW beams, which can be used as a basic control gate for information processing based on ambipolar transport. © 2004 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Fr Low-field transport and mobility; piezoresistance
68.35.Iv Acoustical properties
72.50.+b Acoustoelectric effects
73.63.Hs Quantum wells

Fabrication and characteristics of C84 fullerene field-effect transistors

Kana Shibata, Yoshihiro Kubozono, Takayoshi Kanbara, Tomoko Hosokawa, Akihiko Fujiwara, Yasuhiro Ito, and Hisanori Shinohara

Appl. Phys. Lett. 84, 2572 (2004); http://dx.doi.org/10.1063/1.1695193 (3 pages) | Cited 22 times

Online Publication Date: 1 April 2004

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Fullerene field-effect transistors (FETs) were fabricated with thin films of C84, which showed n-channel normally-on depletion-type FET characteristics. The C84 FET device exhibited the highest mobility, μ, of 2.1×10−3 cm2 V−1 s−1 among normally-on fullerene FETs. The carrier transport of this FET device can be interpreted as thermally activated hopping transport. Carrier type (n-channel) and transport mechanism (hopping) reflect the electronic properties of the C84 molecule. © 2004 American Institute of Physics.
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85.65.+h Molecular electronic devices
72.20.Ee Mobility edges; hopping transport
85.30.Tv Field effect devices

Influence of Al doping on lattice strain and electrical properties of epitaxial GaN films grown by metalorganic chemical vapor deposition on Al2O3 substrate

Jae Kyeong Jeong, Jung-Hae Choi, Cheol Seong Hwang, Hyeong Joon Kim, Jae-Hoon Lee, Jung-Hee Lee, and Chang-Soo Kim

Appl. Phys. Lett. 84, 2575 (2004); http://dx.doi.org/10.1063/1.1702135 (3 pages) | Cited 1 time

Online Publication Date: 1 April 2004

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The effects of the isoelectronic Al doping of epitaxial GaN films grown by metalorganic chemical vapor deposition on a (0001) Al2O3 single crystal substrate were investigated. It was found that the threading screw and edge dislocation densities of the GaN film decreased to less than half of that of the undoped GaN film up to Al doping concentration of 0.45%. The in-plane and out-of-plane strains were simultaneously reduced with the decrease in dislocation density as a result of the solution hardening effect. Accordingly, the electron mobility of the 0.45% Al-doped GaN film (524 cm2/Vs) was greatly improved compared to that of the undoped GaN film (178 cm2/Vs). However, the threading dislocation densities and strains were increased at a 0.64% Al concentration, and the electron mobility decreased accordingly. Therefore, the improvement in the electron mobility by Al doping up to 0.45% is the result of a decrease in the threading dislocation density and not a decrease in the number of point defects (Ga-site vacancy) as suggested earlier [Lee et al., Appl. Phys. Lett. 83, 917 (2003)]. © 2004 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors
61.72.J- Point defects and defect clusters

Effect of nucleation layer on the magnetic properties of GaMnN

G. Thaler, R. Frazier, B. Gila, J. Stapleton, M. Davidson, C. R. Abernathy, S. J. Pearton, and Carlos Segre

Appl. Phys. Lett. 84, 2578 (2004); http://dx.doi.org/10.1063/1.1695207 (3 pages) | Cited 19 times

Online Publication Date: 1 April 2004

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The effects of nucleation layer and growth temperature on the magnetic properties of GaMnN have been investigated. It was found that the largest magnetic moment was measured in films prepared on metalorganic chemical vapor deposition (MOCVD) GaN buffers at a growth temperature of 700 °C. Extended x ray absorption fine structure measurements indicate that the improved magnetic quality of the films grown on MOCVD layers versus gas source molecular beam epitaxy nucleation layers is not due to a change in the lattice position of the Mn and is more likely due to a reduction in defect density. Growth temperature was also found to have a significant impact on the magnetic properties, with the optimal growth temperature found to be 700 °C. © 2004 American Institute of Physics.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
68.55.A- Nucleation and growth
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Dm X-ray absorption spectra
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.50.Dd Nonmetallic ferromagnetic materials

A distributed charge storage with GeO2 nanodots

T. C. Chang, S. T. Yan, C. H. Hsu, M. T. Tang, J. F. Lee, Y. H. Tai, P. T. Liu, and S. M. Sze

Appl. Phys. Lett. 84, 2581 (2004); http://dx.doi.org/10.1063/1.1697627 (3 pages) | Cited 27 times

Online Publication Date: 1 April 2004

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In this study, a distributed charge storage with GeO2 nanodots is demonstrated. The mean size and aerial density of the nanodots embedded in SiO2 are estimated to be about 5.5 nm and 4.3×1011 cm−2, respectively. The composition of the dots is also confirmed to be GeO2 by x-ray absorption near-edge structure analyses. A significant memory effect is observed through the electrical measurements. Under the low voltage operation of 5 V, the memory window is estimated to ∼ 0.45 V. Also, a physical model is proposed to demonstrate the charge storage effect through the interfacial traps of GeO2 nanodots. © 2004 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Modified transmission line model and its application to aluminum ohmic contacts with n-type GaN

N. C. Chen, P. H. Chang, A. P. Chiu, M. C. Wang, W. S. Feng, G. M. Wu, C. F. Shih, and K. S. Liu

Appl. Phys. Lett. 84, 2584 (2004); http://dx.doi.org/10.1063/1.1704855 (3 pages) | Cited 4 times

Online Publication Date: 1 April 2004

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A modified transmission line model (MTLM) of ohmic contact measurement is presented. This model preserves the simplicity of the circular transmission line model but eliminates the shortcoming of the possibility of obtaining misleading results. This model was applied to n-type GaN ohmic contacts and results similar to those obtained by Hall measurement were obtained. The ohmic contact pattern used in MTLM method occasionally exists during the fabrication of several devices. In such cases, the method can be used to determine the device processing quality without the need for any other test pattern. © 2004 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
73.40.Ns Metal-nonmetal contacts
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