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20 Jul 2009

Volume 95, Issue 3, Articles (03xxxx)

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Appl. Phys. Lett. 95, 033502 (2009); http://dx.doi.org/10.1063/1.3178556 (3 pages)

Akihito Ikedo, Takahiro Kawashima, Takeshi Kawano, and Makoto Ishida
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On the 1/f noise of triple-gate field-effect transistors with high-k gate dielectric

N. Lukyanchikova, N. Garbar, V Kudina, A. Smolanka, S. Put, C. Claeys, and E. Simoen

Appl. Phys. Lett. 95, 032101 (2009); http://dx.doi.org/10.1063/1.3180703 (3 pages) | Cited 7 times

Online Publication Date: 20 July 2009

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The low-frequency noise of triple-gate fin field-effect transistors (finFETs) fabricated on silicon-on-insulator (SOI) substrates, with HfO2 or HfSiON gate stacks has been studied. In most cases, 1/fγ noise has been observed with γ<1 for low frequencies f. It is shown that this type of noise can be ascribed to number fluctuations and scales with the effective device area. Based on a simple tunneling model, the noise spectral density has been converted to an oxide trap density profile, exhibiting a decay in Not for larger distances from the Si–SiO2 interface. This stands in contrast with planar bulk devices with a similar high-k gate stack and seems to be typical for the fin processing used, irrespective of further process details, like the use of selective epitaxial growth, strained SOI or strain-inducing cap layers.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.70.+m Noise processes and phenomena
73.40.Gk Tunneling

Hole diffusion profile in a p-p+ silicon homojunction determined by terahertz and midinfrared spectroscopic ellipsometry

T. Hofmann, C. M. Herzinger, T. E. Tiwald, J. A. Woollam, and M. Schubert

Appl. Phys. Lett. 95, 032102 (2009); http://dx.doi.org/10.1063/1.3184567 (3 pages) | Cited 7 times

Online Publication Date: 20 July 2009

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Noninvasive optical measurement of hole diffusion profiles in p-p+ silicon homojunction is reported by ellipsometry in the terahertz (0.2–1.5 THz) and midinfrared (9–50 THz) spectral regions. In the terahertz region a surface-guided wave resonance with transverse-electrical polarization is observed at the boundary of the p-p+ homojunction, and which is found to be extremely sensitive to the low-doped p-type carrier concentration as well as to the hole diffusion profile within the p-p+ homojunction. Effective mass approximations allow determination of homojunction hole concentrations as p = 2.9×1015 cm−3, p+ = 5.6×1018 cm−3, and diffusion time constant Dt = 7.7×10−3 μm2, in agreement with previous electrical investigations.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
66.30.H- Self-diffusion and ionic conduction in nonmetals
72.80.Cw Elemental semiconductors

Probing microwave capacitance of self-assembled quantum dots

Guanglei Cheng, Jeremy Levy, and Gilberto Medeiros-Ribeiro

Appl. Phys. Lett. 95, 032103 (2009); http://dx.doi.org/10.1063/1.3184572 (3 pages)

Online Publication Date: 20 July 2009

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Self-assembled quantum dots have remarkable optical, electronic, and spintronic properties that make them leading candidates for quantum information technologies. Their characterization requires rapid and local determination of both charge and spin degrees of freedom. We present a way to probe the capacitance of small ensembles of quantum dots at microwave frequencies. The technique employs a capacitance sensor based on a microwave microstrip resonator with sensitivity ∼ 10−19 F/math, high enough to probe single electrons. The integration of this design in a scanning microscope will provide an important tool for investigating single charge and spin dynamics in self-assembled quantum dot systems.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.07.Mp Transducers
81.07.Ta Quantum dots
81.16.Dn Self-assembly
84.40.-x Radiowave and microwave (including millimeter wave) technology
84.40.Az Waveguides, transmission lines, striplines

Atomic migration in molten and crystalline Ge2Sb2Te5 under high electric field

Tae-Youl Yang, Il-Mok Park, Byoung-Joon Kim, and Young-Chang Joo

Appl. Phys. Lett. 95, 032104 (2009); http://dx.doi.org/10.1063/1.3184584 (3 pages) | Cited 18 times

Online Publication Date: 20 July 2009

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Atomic migration under an electric field, electromigration, in molten and crystalline Ge2Sb2Te5 was studied using a pulsed dc stress to an isolated line structure. Under a single pulse ( ∼ 10−3 s), Ge2Sb2Te5 was melted by Joule heating, and an electrostatic force-induced drift of Ge and Sb toward the cathode and Te toward the anode was observed. Effective charge numbers were calculated to be 0.28, 0.38, and −0.29 for Ge, Sb, and Te, respectively. Electromigration in the crystalline state was studied by applying a 10 MHz pulsed dc; constituent elements migrated toward the cathode, which suggests a hole wind-force operating in this phase.
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81.05.Bx Metals, semimetals, and alloys
82.45.Fk Electrodes
66.30.Qa Electromigration

Sn12Sb88 material for phase change memory

Feng Rao, Zhitang Song, Kun Ren, Xuelai Li, Liangcai Wu, Wei Xi, and Bo Liu

Appl. Phys. Lett. 95, 032105 (2009); http://dx.doi.org/10.1063/1.3184787 (3 pages) | Cited 18 times

Online Publication Date: 21 July 2009

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Phase change memory cell based on Sn12Sb88 film shows reversible phase change abilities between high and low resistance states. We calculate the resonance character of crystalline SnSb material, which proves that SnSb is a potential phase change candidate. Sn12Sb88 is the suitable composition that has faster crystallization speed, higher crystallization temperature, and larger crystallization activation energy but lower melting point than those of Ge2Sb2Te5 material. Hence, phase change memory cell using this composition is able to show quicker set operation speed, better data retention ability, and lower reset power consumption than those of the Ge2Sb2Te5 based cell.
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64.70.K- Solid-solid transitions
64.70.dj Melting of specific substances
68.55.A- Nucleation and growth

Analysis of point defects in AlN epilayers by cathodoluminescence spectroscopy

Barbara Bastek, Frank Bertram, Juergen Christen, Thomas Hempel, Armin Dadgar, and Alois Krost

Appl. Phys. Lett. 95, 032106 (2009); http://dx.doi.org/10.1063/1.3154518 (3 pages) | Cited 4 times

Online Publication Date: 21 July 2009

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We present a systematic cathodoluminescence study yielding a clear correlation between the different growth conditions and the appearance and strength of the characteristic luminescence fingerprints of the individual point defects in AlN. In particular, the incorporation of oxygen and the formation of oxygen-related and probably silicon-related DX centers as well as the native Al and N vacancies are still a problem. The thermal activation of the deep defect centers is investigated by temperature dependent cathodoluminescence spectroscopy.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.jd Vacancies

Band structure design and photocatalytic activity of In2O3/N–InNbO4 composite

Jun Lv, Tetsuya Kako, Zhigang Zou, and Jinhua Ye

Appl. Phys. Lett. 95, 032107 (2009); http://dx.doi.org/10.1063/1.3183507 (3 pages) | Cited 7 times

Online Publication Date: 21 July 2009

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In this study, the band structure of In2O3/N–InNbO4 composite was considered to be advantageous for the transportation and separation of photoexcited electron/hole pairs. This composite was synthesized and characterized by powder x-ray diffraction, UV-visible diffuse reflectance spectroscopy, transmission electron microscope, and x-ray photoelectrons spectroscopy. The photocatalytic experiments indicated the H2 evolution rate of In2O3/N–InNbO4 composite was 27.3 μmol h−1 g−1 under visible light irradiation (λ>420 nm), which was 18.6 times the rate of In2O3 and 2.3 times the rate of N–InNbO4.
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81.20.-n Methods of materials synthesis and materials processing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.40.-q Absorption and reflection spectra: visible and ultraviolet
79.60.-i Photoemission and photoelectron spectra
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.05.cp X-ray diffraction
82.50.-m Photochemistry
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Relationship between 4H-SiC/SiO2 transition layer thickness and mobility

T. L. Biggerstaff, C. L. Reynolds, Jr., T. Zheleva, A. Lelis, D. Habersat, S. Haney, S.-H. Ryu, A. Agarwal, and G. Duscher

Appl. Phys. Lett. 95, 032108 (2009); http://dx.doi.org/10.1063/1.3144272 (3 pages) | Cited 14 times

Online Publication Date: 22 July 2009

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The interfacial region between silicon carbide (SiC) and its native oxide contains a high density of interfacial traps, which is considered a major problem leading to a lower mobility that has hindered SiC metal oxide semiconductor field effect transistors from reaching their theoretical expectations. We investigate the microstructure and chemistry of the 4H-SiC/SiO2 interface due to variations in nitric oxide annealing and aluminum implantation using Z-contrast imaging and electron energy loss spectroscopy. A transition layer with a carbon to silicon ratio greater than 1 is consistently observed on the SiC side of the interface in each of these samples, and the width of this transition layer is found to be inversely related to the effective channel mobility measured on fabricated devices.
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73.20.-r Electron states at surfaces and interfaces
85.30.Tv Field effect devices
81.40.Gh Other heat and thermomechanical treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.55.ag Semiconductors
79.20.Uv Electron energy loss spectroscopy

Optical and magnetic properties of CuMnO2 epitaxial thin films with a delafossite-derivative structure

H. Hiraga, T. Fukumura, A. Ohtomo, T. Makino, A. Ohkubo, H. Kimura, and M. Kawasaki

Appl. Phys. Lett. 95, 032109 (2009); http://dx.doi.org/10.1063/1.3186790 (3 pages) | Cited 3 times

Online Publication Date: 22 July 2009

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A distorted delafossite CuMnO2, called crednerite, was formed into epitaxial thin films on MgAl2O4 (111) substrates by pulsed laser deposition method. X-ray diffraction revealed that the films had high crystalline quality with epitaxial relationship of CuMnO2 (001)//MgAl2O4 (111) and CuMnO2 [100]//MgAl2O4 〈11-2〉. The ultraviolet-visible optical response revealed a distinct absorption peak at 4.5 eV presumably with excitonic nature and broad peaks at 3.0 and 3.7 eV assignable to O 2p–Mn 3d charge transfer excitation. Small magnetic hysteresis with remanent magnetization of 0.04μB/Mn was observed below 20 K, representing canted antiferromagnetic spin ordering.
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78.66.-w Optical properties of specific thin films
75.50.Ee Antiferromagnetics
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.40.Ha Other nonmetallic inorganics
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Aharonov–Bohm oscillations in a nanoscale dopant ring in silicon

T. C. G. Reusch, A. Fuhrer, M. Füchsle, B. Weber, and M. Y. Simmons

Appl. Phys. Lett. 95, 032110 (2009); http://dx.doi.org/10.1063/1.3186031 (3 pages) | Cited 1 time

Online Publication Date: 23 July 2009

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We have fabricated a nanoscale ring of phosphorus dopants in silicon using a scanning tunneling microscope to pattern a hydrogen resist layer. Low-temperature magnetotransport measurements reveal both aperiodic universal conductance fluctuations and periodic Aharonov–Bohm oscillations. From the ratio of the h/e and h/2e components of the Aharonov–Bohm oscillations, we estimate a phase coherence length of ≃ 100 nm at a temperature T = 100 mK. This is in agreement with previous results from weak localization measurements on low-dimensional dopant devices in silicon.
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61.72.uf Ge and Si
73.63.-b Electronic transport in nanoscale materials and structures
72.20.My Galvanomagnetic and other magnetotransport effects

Electroconductance in single-wall carbon nanotubes

Manu Jaiswal, C. S. Suchand Sangeeth, and Reghu Menon

Appl. Phys. Lett. 95, 032111 (2009); http://dx.doi.org/10.1063/1.3186082 (3 pages) | Cited 2 times

Online Publication Date: 24 July 2009

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A comparative study of the electric-field induced hopping transport probes the effective dimensionality (D) in bulk and ultrathin films of single-wall carbon nanotubes (SWNTs). The values of the scaling function exponents for the electroconductance are found to be consistent with that in three-dimensional and two-dimensional systems. The significant difference in threshold voltage in these two types of SWNTs is a consequence of the variation in the number of energetically favorable sites available for charge carriers to hop by using the energy from the field. Furthermore, a modification to the magnetotransport is observed under high electric-fields.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance
73.63.Fg Nanotubes
73.61.Wp Fullerenes and related materials
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