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27 Jun 2005

Volume 86, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 86, 263107 (2005); http://dx.doi.org/10.1063/1.1952585 (3 pages)

B. Yang, M. S. Marcus, D. G. Keppel, P. P. Zhang, Z. W. Li, B. J. Larson, D. E. Savage, J. M. Simmons, O. M. Castellini, M. A. Eriksson, and M. G. Lagally
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Microwave modulation of electron heating and Shubnikov–de Haas oscillation in two-dimensional electron systems

X. L. Lei and S. Y. Liu

Appl. Phys. Lett. 86, 262101 (2005); http://dx.doi.org/10.1063/1.1949287 (3 pages) | Cited 9 times

Online Publication Date: 20 June 2005

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Recently discovered modulations of Shubnikov–de Haas oscillations in microwave-irradiated two-dimensional electron systems are shown to arise from electron heating induced by the radiation. The electron temperature, obtained by balancing the energy absorption from the microwave field and the energy dissipation to the lattice through realistic electron-phonon couplings, exhibits resonance. The modulation of the Shubnikov–de Haas oscillation and the suppression of magnetoresistance are demonstrated together with microwave-induced resistance oscillation, in agreement with experimental findings.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Ht High-field and nonlinear effects
73.63.-b Electronic transport in nanoscale materials and structures
71.38.-k Polarons and electron-phonon interactions

Interfacial and electrical characteristics of Al2O3 gate dielectric on fully depleted SiGe on insulator

Zengfeng Di, Miao Zhang, Weili Liu, Qinwo Shen, Suhua Luo, Zhitang Song, Chenglu Lin, Anping Huang, and Paul K. Chu

Appl. Phys. Lett. 86, 262102 (2005); http://dx.doi.org/10.1063/1.1957109 (3 pages) | Cited 4 times

Online Publication Date: 21 June 2005

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The interfacial and electrical characteristics of as-deposited or annealed A2O3 gate dielectric films grown on fully depleted SiGe-on-insulator are investigated. An interfacial layer composed of SiOx and GeOx is observed in the as-grown film. The interfacial silicate formation is effectively suppressed by GeOx formation. However, GeOx is reduced to Ge and extensive silicate formation occurs after annealing. The formation of silicate and disappearance of GeOx after annealing leads to a decrease in the density of the interfacial states.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness

Effect of duty cycle on plasma parameters in the pulsed dc magnetron argon discharge

Sang-Hun Seo, Jung-Hwan In, Hong-Young Chang, and Jeon-Geon Han

Appl. Phys. Lett. 86, 262103 (2005); http://dx.doi.org/10.1063/1.1946900 (3 pages) | Cited 12 times

Online Publication Date: 21 June 2005

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The time-resolved probe measurements of the plasma parameters and the electron energy distribution function are carried out in a unipolar pulsed dc magnetron argon discharge. The cathode target is driven by the 20 kHz midfrequency unipolar dc pulses at three operating modes, such as constant voltage, constant power, and constant current with the duty cycles ranging from 10% to 90%. It is observed that as the duty cycle is reduced, the electron temperature averaged during the pulse-on period rapidly increases irrespective of the operating mode although the average electron density strongly depends on the operating mode. The comparison of the measured electron energy distribution functions shows that the electron heating during the pulse-on period becomes efficient in the pulse operation with short duty cycle, which is closely related to the deep penetration of the high-voltage sheath into the bulk during the pulse-on period.
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52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties
52.50.Gj Plasma heating by particle beams
52.40.Kh Plasma sheaths

Molecular-beam epitaxy of p-type m-plane GaN

M. McLaurin, T. E. Mates, and J. S. Speck

Appl. Phys. Lett. 86, 262104 (2005); http://dx.doi.org/10.1063/1.1977204 (3 pages) | Cited 28 times

Online Publication Date: 22 June 2005

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We report on the plasma-assisted molecular-beam epitaxy of Mg-doped (10math0) GaN on (10math0) 6H–SiC. Secondary ion mass spectroscopy measurements show the incorporation of Mg into the GaN films with an enhanced Mg incorporation under N-rich conditions relative to Ga-rich growth. Transport measurements of Mg-doped layers grown under Ga-rich conditions show hole concentrations in the range of p = 1×1018 to p = 7×1018 cm−3 and a dependence between hole concentration and Mg beam equivalent pressure. An anisotropy in in-plane hole mobilities was observed, with the hole mobility parallel to [11math0] being higher than that parallel to [0001] for the same hole concentration. Mobilities parallel to [11math0] were as high as ∼ 11.5 cm2/Vs (at p ∼ 1.8×1018 cm−3).
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Resonant localized donor state above the conduction band minimum in InN

L. H. Dmowski, J. A. Plesiewicz, T. Suski, Hai Lu, W. Schaff, M. Kurouchi, Y. Nanishi, L. Konczewicz, V. Cimalla, and O. Ambacher

Appl. Phys. Lett. 86, 262105 (2005); http://dx.doi.org/10.1063/1.1977212 (3 pages) | Cited 12 times

Online Publication Date: 23 June 2005

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We have studied the pressure dependence of Hall electron concentration and mobility in degenerated, not intentionally doped InN samples. The results obtained for a whole set of samples with electron concentrations from 5.4×1017 cm−3 to 3.3×1018 cm−3 consistently reveal the existence of a localized donor type state, resonant with the conduction band. Its energy position is estimated to be about 80–90 meV above the bottom of the conduction band. This donor state is not the only source of electrons in these not intentionally doped samples and can be entirely populated and hidden in samples with very high electron concentrations.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.61.Ey III-V semiconductors
73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena
72.20.My Galvanomagnetic and other magnetotransport effects
71.55.Eq III-V semiconductors

Study of low-temperature crystallization of amorphous Si films obtained using ferritin with Ni nanoparticles

Hiroya Kirimura, Yukiharu Uraoka, Takashi Fuyuki, Mitsuhiro Okuda, and Ichiro Yamashita

Appl. Phys. Lett. 86, 262106 (2005); http://dx.doi.org/10.1063/1.1954872 (3 pages) | Cited 29 times

Online Publication Date: 23 June 2005

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A polycrystalline silicon thin film with a high crystallinity was obtained using ferritin with a Ni core (7 nm), which enabled us to precisely control the density and position of the nucleus for crystal growth. The core density of ferritin adsorbed on the amorphous silicon surface was controlled in the range from 109 cm−2 to 1011 cm−2. Crystal growth was performed at 550 °C in N2. Crystallinity or grain size strongly depended on Ni core density. Polycrystalline silicon film with the average grain size of 3 μm and a high crystallinity was obtained at a low Ni atom density of 1012 cm−2.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
68.47.Fg Semiconductor surfaces
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Strongly temperature-dependent free-energy barriers measured in a polycrystalline semiconductor

David L. Young and Richard S. Crandall

Appl. Phys. Lett. 86, 262107 (2005); http://dx.doi.org/10.1063/1.1977211 (3 pages) | Cited 8 times

Online Publication Date: 24 June 2005

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We measured temperature-dependent changes in free-energy barriers for emission of holes and electrons from metastable defects in polycrystalline CuIn1−xGaxSe2 using transient capacitance techniques. The free-energy barrier for holes increases by 17 meV, while the barrier for electrons decreases by 30 meV as the temperature increases from 380 to 400 K. The usual relation between thermal emission time and activation energy is reversed in this temperature range (we find a shorter emission time for the larger activation energy). Large entropy changes of +15 kB and −21 kB for the electron and hole emission, respectively, are calculated using transition-rate theory. These entropy terms in the free energy barrier account for the temperature dependences and the emission time inversion.
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65.40.G- Other thermodynamical quantities
71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Photographic surveying of minority carrier diffusion length in polycrystalline silicon solar cells by electroluminescence

Takashi Fuyuki, Hayato Kondo, Tsutomu Yamazaki, Yu Takahashi, and Yukiharu Uraoka

Appl. Phys. Lett. 86, 262108 (2005); http://dx.doi.org/10.1063/1.1978979 (3 pages) | Cited 78 times

Online Publication Date: 24 June 2005

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Photographic surveying of the minority carrier diffusion length distribution in polycrystalline silicon solar cells was proposed. Light emission from the cell under the forward bias was captured by a charge coupled device camera. We have found that the intensity distribution of light emission clearly agreed with the mapping of minority carrier diffusion length in polycrystalline silicon active layers. The emission intensity had a one-to-one relationship with the minority carrier diffusion length, which yielded a semiquantitative analysis method of the diffusion length mapping and the detection of the deteriorated areas.
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84.60.Jt Photoelectric conversion
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.60.Fi Electroluminescence

Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors

R. W. I. de Boer, A. F. Stassen, M. F. Craciun, C. L. Mulder, A. Molinari, S. Rogge, and A. F. Morpurgo

Appl. Phys. Lett. 86, 262109 (2005); http://dx.doi.org/10.1063/1.1984093 (3 pages) | Cited 58 times

Online Publication Date: 24 June 2005

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We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches 0.3 cm2/V s in both materials. The highest mobility for electrons is observed for iron-phthalocyanines and is approximately one order of magnitude lower. Our measurements indicate that these values are limited by extrinsic contact effects due to the transistor fabrication and suggest that considerably higher values for the electron and hole mobility can be achieved in these materials.
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85.30.Tv Field effect devices

Monte Carlo study of vertical electron transport in GaN/AlGaN heterostructures

A. Reklaitis

Appl. Phys. Lett. 86, 262110 (2005); http://dx.doi.org/10.1063/1.1968434 (3 pages) | Cited 5 times

Online Publication Date: 24 June 2005

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The dc and large-signal ac vertical electron transport in the double-barrier GaN/AlGaN heterostructures are studied by Monte Carlo simulations. It is found that the current-voltage characteristic of the GaN/AlGaN diode is asymmetric due to polarization charges at GaN/AlGaN interfaces. On the contrary, the calculated capacitance-voltage characteristic is nearly symmetric in respect to the shifted bias voltage. The capacitance-voltage characteristic shows that GaN/AlGaN heterostructures are promising candidates for the design of efficient varactor diodes. Study of the large-signal ac electron transport predicts that GaN/AlGaN varactors are capable to operate as frequency triplers in the near-terahertz frequency range.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes
84.32.Tt Capacitors
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