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14 Feb 2011

Volume 98, Issue 7, Articles (07xxxx)

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Appl. Phys. Lett. 98, 073101 (2011); http://dx.doi.org/10.1063/1.3554360 (3 pages)

Wei Xu, Rajesh Leeladhar, Yao-Tsan Tsai, Eui-Hyeok Yang, and Chang-Hwan Choi
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Structural and electronic interaction at CuO-hexa-peri-hexabenzocoronene hybrid interface

Bharti Singh, B. R. Mehta, M. Singh, Govind Gupta, L. Dössel, X. Feng, and K. Müllen

Appl. Phys. Lett. 98, 072101 (2011); http://dx.doi.org/10.1063/1.3544937 (3 pages) | Cited 2 times

Online Publication Date: 14 February 2011

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Interfacial interaction at hybrid interfaces results in structural and electronic properties different from organic and inorganic components. In this study, x-ray photoelectron spectroscopy analysis carried out on CuO-hexa-peri-hexabenzocoronene (HBC) bilayers shows the appearance of an additional C 1s peak at lower energy due to Cu–C interaction. Spectroscopic ellipsometry investigation shows that interfacial layer ( ∼ 4 nm) has absorption features related to Cu–C bonding, modified HBC valence states, and Cu2+-π electron interaction. The observed resistive switching property of the CuO-HBC layers is considerably different from junction properties of HBC and CuO layers and is directly related to the hybrid interfacial layer.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.63.Bd Nanocrystalline materials
78.67.Sc Nanoaggregates; nanocomposites
79.60.Jv Interfaces; heterostructures; nanostructures

Electron band alignment at the interface of (100)GaSb with molecular-beam deposited Al2O3

V. V. Afanas’ev, H.-Y. Chou, A. Stesmans, C. Merckling, and X. Sun

Appl. Phys. Lett. 98, 072102 (2011); http://dx.doi.org/10.1063/1.3549878 (3 pages) | Cited 3 times

Online Publication Date: 14 February 2011

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From internal photoemission and photoconductivity measurements at the (100)GaSb/Al2O3 interface, the semiconductor valence band is found to be 3.05±0.10 eV below the oxide conduction band. This band alignment corresponds to conduction and valence band offsets of 2.3±0.10 and 3.05±0.15 eV, respectively. These results indicate that the valence band in GaSb lies energetically well above the valence band in InxGa1−xAs (0 ≤ x ≤ 0.53) or InP, suggesting the possibility of fabrication of hole quantum-well channel structures.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Jv Interfaces; heterostructures; nanostructures
72.40.+w Photoconduction and photovoltaic effects

Effect of edge threading dislocations on the electronic structure of InN

E. Kalesaki, J. Kioseoglou, L. Lymperakis, Ph. Komninou, and Th. Karakostas

Appl. Phys. Lett. 98, 072103 (2011); http://dx.doi.org/10.1063/1.3553772 (3 pages) | Cited 6 times

Online Publication Date: 15 February 2011

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The open issue of the n-type conductivity and its correlation to threading dislocations (TDs) in InN is addressed through first principles calculations on the electronic properties of a-edge TDs. All possible dislocation core models are considered (4-, 5/7-, and 8-atom cores) and are found to modify the band structure of InN in a distinct manner. In particular, nitrogen and indium low coordinated atoms in the eight-atom core induce states near the valence band maximum and above the conduction band minimum, respectively. The formation of a nitrogen–nitrogen “wrong” bond is observed at the 5/7-atom core resulting in a state inside the band gap. The 4- and 5/7-atom cores induce occupied states resonant in the conduction band due to In–In strain induced interactions and wrong bonds, respectively. These occupied states designate TDs as a source of higher electron concentrations in InN and provide direct evidence that TDs contribute to its inherent n-type conductivity.
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71.55.Eq III-V semiconductors
61.72.Lk Linear defects: dislocations, disclinations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
71.20.Nr Semiconductor compounds

Role of nonradiative recombination centers and extended defects in nonpolar GaN on light emission efficiency

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, H. Amano, S. J. Pearton, I.-H. Lee, Q. Sun, J. Han, and S. Yu. Karpov

Appl. Phys. Lett. 98, 072104 (2011); http://dx.doi.org/10.1063/1.3555470 (3 pages) | Cited 7 times

Online Publication Date: 15 February 2011

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The correlation of integrated microcathodoluminescence efficiency with crystalline quality and deep trap density of nonpolar GaN films grown by metal organic chemical vapor deposition on semi-insulating 6H-m-SiC or r-sapphire is analyzed. The results suggest a strong influence of nonradiative recombination centers whose concentration decreases with decreased density of extended defects. Electron traps with energy levels at Ec−0.6 eV and which pin the Fermi level in films with high defect density are the most likely candidates for the decrease in light emission efficiency in nonpolar GaN.
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78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.jn Color centers
71.55.Eq III-V semiconductors
68.55.ag Semiconductors

Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSb2−xTex

P. Sun, M. Søndergaard, Y. Sun, S. Johnsen, B. B. Iversen, and F. Steglich

Appl. Phys. Lett. 98, 072105 (2011); http://dx.doi.org/10.1063/1.3556645 (3 pages) | Cited 10 times

Online Publication Date: 16 February 2011

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Substitution of Sb in FeSb2 by less than 0.5% of Te induces a transition from a correlated semiconductor to an unconventional metal with large effective charge carrier mass m∗. Spanning the entire range of the semiconductor-metal crossover, we observed an almost constant enhancement of the measured thermopower compared to that estimated by the classical theory of electron diffusion. Using the latter for a quantitative description one has to employ an enhancement factor of 10–30. Our observations point to the importance of electron-electron correlations in the thermal transport of FeSb2, and suggest a route to design thermoelectric materials for cryogenic applications.
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81.05.Hd Other semiconductors
72.80.Jc Other crystalline inorganic semiconductors
72.60.+g Mixed conductivity and conductivity transitions
72.20.Pa Thermoelectric and thermomagnetic effects

Photoconductivity in inverse silicon opals enhanced by slow photon effect: Yet another step towards optically amplified silicon photonic crystal solar cells

Takashi Suezaki, Hiroshi Yano, Tomoaki Hatayama, Geoffrey A. Ozin, and Takashi Fuyuki

Appl. Phys. Lett. 98, 072106 (2011); http://dx.doi.org/10.1063/1.3555338 (3 pages) | Cited 3 times

Online Publication Date: 16 February 2011

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While silicon photonic crystals have promised revolutionary advances in the field of optical telecommunications and optical computing, it has only recently been realized that their prowess to trap and slow photons could potentially improve the efficiency of silicon solar cells. In this work, spectral responses for the electrical properties of inverse silicon opals are evaluated and show a correlation with photonic bandgaps. In particular, a sign of the enhanced photoelectric generation by the slow photon effect is observed at the edges of photonic bandgaps.
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72.40.+w Photoconduction and photovoltaic effects
78.56.-a Photoconduction and photovoltaic effects
72.80.Cw Elemental semiconductors
42.70.Qs Photonic bandgap materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Roles of silver oxide in the bipolar resistance switching devices with silver electrode

C. Y. Dong, D. S. Shang, L. Shi, J. R. Sun, B. G. Shen, F. Zhuge, R. W. Li, and W. Chen

Appl. Phys. Lett. 98, 072107 (2011); http://dx.doi.org/10.1063/1.3556618 (3 pages) | Cited 6 times

Online Publication Date: 17 February 2011

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Three devices, Ag/WO3−x/Pt, Ag/AgOx/Pt, and Ag/AgOx/WO3−x/Pt, were investigated to elucidate the influence of the silver oxide on the bipolar resistive switching behavior. The silver oxide films were obtained by depositing silver at oxygen atmosphere. We find that the resistive switching behavior was determined by the silver oxide layer. Bulk and interface resistive switching were observed in the Ag/AgOx/Pt and Ag/AgOx/WO3−x/Pt devices, respectively. By the micro-x-ray photoemission spectroscopy analysis, it was demonstrated that the electrochemical redox reaction occurred in the AgOx layer is responsible for the resistive switching behavior at silver/oxide interface.
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73.40.Rw Metal-insulator-metal structures
73.50.-h Electronic transport phenomena in thin films
72.20.-i Conductivity phenomena in semiconductors and insulators
82.45.Fk Electrodes

Enhancement-mode AlGaN/GaN heterostructure field effect transistors fabricated by selective area growth technique

Yuhua Wen, Zhiyuan He, Jialin Li, Ruihong Luo, Peng Xiang, Qingyu Deng, Guangning Xu, Zhen Shen, Zhisheng Wu, Baijun Zhang, Hao Jiang, Gang Wang, and Yang Liu

Appl. Phys. Lett. 98, 072108 (2011); http://dx.doi.org/10.1063/1.3553229 (3 pages)

Online Publication Date: 17 February 2011

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In this letter, a method of using selective area growth (SAG) technique was proposed to fabricate the enhancement-mode (E-mode) AlGaN/GaN heterostructure field effect transistors (HFETs), which can effectively avoid the plasma treatment damage to the active region of HFETs in comparison with the conventional methods. The SAG-HFETs exhibited a good performance of the maximum drain current of 300 mA/mm and peak transconductance of 135 mS/mm with a larger positive threshold voltage of 0.4 V. The results indicate that the SAG technique is a promising method to realize the high performance E-mode GaN based HFETs.
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85.30.Tv Field effect devices

Great thermoelectric power factor enhancement of CoSb3 through the lightest metal element filling

Jianjun Zhang, Bo Xu, Li-Min Wang, Dongli Yu, Zhongyuan Liu, Julong He, and Yongjun Tian

Appl. Phys. Lett. 98, 072109 (2011); http://dx.doi.org/10.1063/1.3557068 (3 pages) | Cited 4 times

Online Publication Date: 17 February 2011

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Lithium, the lightest metal element with a small ionic radius, is successfully filled into the voids of CoSb3 by utilizing the high pressure synthesis technique. The synthesized Li0.4Co4Sb12 shows the largest thermoelectric power factor of 6000 μW m−1 K−2 among all elemental filled CoSb3 materials. This significantly enhanced thermoelectric power factor is attributed to the large carrier mobility of Li0.4Co4Sb12, 61 cm2 V−1 s−1, featuring a good electron crystal property for the Li-filled CoSb3 samples.
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81.05.Bx Metals, semimetals, and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
62.50.-p High-pressure effects in solids and liquids
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Numerical simulations of space charge waves in InP films and microwave frequency conversion under negative differential conductivity

Abel Garcia-Barrientos and Vassil Palankovski

Appl. Phys. Lett. 98, 072110 (2011); http://dx.doi.org/10.1063/1.3555467 (3 pages)

Online Publication Date: 17 February 2011

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Numerical simulations of amplification and propagation of space charge waves in InP films is investigated theoretically. A microwave frequency conversion using the negative differential conductivity phenomenon is carried out when the harmonics of the input signal are generated. An increment in the amplification is observed in n-InP films at essentially higher frequencies f<70 GHz, when compared with n-GaAs films f<44 GHz. This work provides a way to achieve a frequency conversion and amplification of micrometer and millimeter waves.
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73.61.Ey III-V semiconductors
78.70.Gq Microwave and radio-frequency interactions

Multifunctional Ti1−xTaxO2: Ta doping or alloying?

A. Roy Barman, M. Motapothula, A. Annadi, K. Gopinadhan, Y. L. Zhao, Z. Yong, I. Santoso, Ariando, M. Breese, A. Rusydi, S. Dhar, and T. Venkatesan

Appl. Phys. Lett. 98, 072111 (2011); http://dx.doi.org/10.1063/1.3553773 (3 pages) | Cited 5 times

Online Publication Date: 18 February 2011

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Useful electronic, magnetic, and optical properties have been proposed and observed in thin films of Ti1−xMxO2 (M = Ta,Nb,V). In this work, we have studied phase formation for films of Ti1−xTaxO2 prepared by pulsed laser deposition. We show that substitutional Ta in TiO2 results in a different material system in terms of its electronic properties. Moss–Burstein shift is ruled out by comparing the electrical transport data of anatase and rutile TiO2. Vegard’s law fit to the blueshift data and the high energy optical reflectivity studies confirm the formation of an alloy with a distinct band structure.
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81.15.Fg Pulsed laser ablation deposition
78.40.Fy Semiconductors
81.30.Dz Phase diagrams of other materials
78.66.Li Other semiconductors
61.72.up Other materials
71.20.Nr Semiconductor compounds
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