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20 Aug 2012

Volume 101, Issue 8, Articles (08xxxx)

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Appl. Phys. Lett. 101, 081102 (2012); http://dx.doi.org/10.1063/1.4745791 (3 pages)

M. K. Wu, M. Feng, and N. Holonyak, Jr.
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Universal mechanism for ion-induced nanostructure formation on III-V compound semiconductor surfaces

M. Kang, J. H. Wu, S. Huang, M. V. Warren, Y. Jiang, E. A. Robb, and R. S. Goldman

Appl. Phys. Lett. 101, 082101 (2012); http://dx.doi.org/10.1063/1.4742863 (4 pages) | Cited 1 time

Online Publication Date: 20 August 2012

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We have examined the formation of nanostructures on ion-irradiated compound semiconductor surfaces. We computed the ion doses needed to fully deplete group V elements from the surfaces. These group V depletion doses are in good agreement with the measured threshold ion doses for nucleation of group III-rich nanostructures on a wide variety of III-V compound semiconductor surfaces. Since the group V depletion doses decrease with increasing sputtering yield, these results suggest a universal nanostructure formation mechanism which depends upon the total sputtering yield of each III-V compound.
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81.16.-c Methods of micro- and nanofabrication and processing
61.80.Jh Ion radiation effects

Imaging crystal orientations in multicrystalline silicon wafers via photoluminescence

H. C. Sio, Z. Xiong, T. Trupke, and D. Macdonald

Appl. Phys. Lett. 101, 082102 (2012); http://dx.doi.org/10.1063/1.4747801 (4 pages)

Online Publication Date: 20 August 2012

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We present a method for monitoring crystal orientations in chemically polished and unpassivated multicrystalline silicon wafers based on band-to-band photoluminescence imaging. The photoluminescence intensity from such wafers is dominated by surface recombination, which is crystal orientation dependent. We demonstrate that a strong correlation exists between the surface energy of different grain orientations, which are modelled based on first principles, and their corresponding photoluminescence intensity. This method may be useful in monitoring mixes of crystal orientations in multicrystalline or so-called “cast monocrystalline” wafers.
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81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
81.65.Rv Passivation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
65.40.gp Surface energy
68.47.Fg Semiconductor surfaces
78.55.Ap Elemental semiconductors

Phase coherent transport in InSb nanowires

Huijun Yao, Hacı Yusuf Günel, Christian Blömers, Karl Weis, Junhong Chi, Jia Grace Lu, Jie Liu, Detlev Grützmacher, and Thomas Schäpers

Appl. Phys. Lett. 101, 082103 (2012); http://dx.doi.org/10.1063/1.4747200 (4 pages)

Online Publication Date: 21 August 2012

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Comprehensive electrical transport studies are performed on InSb nanowires by varying temperature, gate voltage, and magnetic field. The 3-dimensional bulk conduction is found to dominate in the nanowire channel after investigating a large number of nanowires with different diameters, which show approximately a linear relation between the conductance normalized to the length and the wire cross section. At low temperatures, universal conductance fluctuations are observed. From the amplitude and the correlation voltage of the conductance fluctuations, the phase-coherence length in InSb nanowires is determined at various temperatures.
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72.80.Ey III-V and II-VI semiconductors
73.63.Nm Quantum wires

Temperature-dependent Kelvin probe measurements of band bending in p-type GaN

M. Foussekis, J. D. McNamara, A. A. Baski, and M. A. Reshchikov

Appl. Phys. Lett. 101, 082104 (2012); http://dx.doi.org/10.1063/1.4747203 (4 pages)

Online Publication Date: 21 August 2012

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The band bending in a Mg-doped, p-type GaN film grown by hydride vapor phase epitaxy was studied at various temperatures. At 295 K, the band bending in dark was calculated to be approximately −1.5 eV. However, when the sample was heated to 600 K for 1 h in dark before performing a measurement at 295 K, the calculated value of band bending in dark became about −2.0 eV. These results are explained by the fact that increasing the sample temperature exponentially increases the rate at which the band bending restores and allows for a more accurate value of band bending to be measured.
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68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.40.Gh Other heat and thermomechanical treatments

Importance of the correct Fermi energy on the calculation of defect formation energies in semiconductors

D. West, Y. Y. Sun, and S. B. Zhang

Appl. Phys. Lett. 101, 082105 (2012); http://dx.doi.org/10.1063/1.4745779 (4 pages) | Cited 1 time

Online Publication Date: 22 August 2012

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Density functional theory (DFT) is a major theoretical tool for the study of defects in semiconductors. However, the results suffer from the often too-small DFT band gap. The calculation of defect formation energy (ΔH) using more sophisticated DFT+GW and hybrid functional methods, however, suggest qualitatively different conclusions about the nature of the DFT error. Here we show that these discrepancies originate from large differences in the representation of the Fermi energy of bulk for the different methods and that they can be largely brought into agreement by correcting the DFT ionization energy.
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71.20.Nr Semiconductor compounds
73.20.At Surface states, band structure, electron density of states
81.05.Hd Other semiconductors
61.72.-y Defects and impurities in crystals; microstructure
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Negligible carrier freeze-out facilitated by impurity band conduction in highly p-type GaN

Brendan Gunning, Jonathan Lowder, Michael Moseley, and W. Alan Doolittle

Appl. Phys. Lett. 101, 082106 (2012); http://dx.doi.org/10.1063/1.4747466 (5 pages) | Cited 1 time

Online Publication Date: 22 August 2012

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Highly p-type GaN films with hole concentrations exceeding 6 × 1019 cm−3 grown by metal-modulated epitaxy are electrically characterized. Temperature-dependent Hall effect measurements at cryogenic temperatures reveal minimal carrier freeze-out in highly doped samples, while less heavily doped samples exhibited high resistivity and donor-compensated conductivity as is traditionally observed. Effective activation energies as low as 43 meV were extracted, and a maximum Mg activation efficiency of 52% was found. In addition, the effective activation energy was found to be negatively correlated to the hole concentration. These results indicate the onset of the Mott-Insulator transition leading to impurity band conduction.
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68.55.A- Nucleation and growth
71.30.+h Metal-insulator transitions and other electronic transitions
72.20.My Galvanomagnetic and other magnetotransport effects
72.60.+g Mixed conductivity and conductivity transitions
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Optomechanical photoabsorption spectroscopy of exciton states in GaAs

Takayuki Watanabe, Hajime Okamoto, Koji Onomitsu, Hideki Gotoh, Tetsuomi Sogawa, and Hiroshi Yamaguchi

Appl. Phys. Lett. 101, 082107 (2012); http://dx.doi.org/10.1063/1.4747328 (3 pages) | Cited 2 times

Online Publication Date: 23 August 2012

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We demonstrate a scheme for the photoabsorption spectroscopy of semiconductors via mechanical vibration characteristics. The thermal vibration of an AlGaAs/GaAs heterostructure-based cantilever sensitively reflects the photoabsorption properties of GaAs because of the optically induced piezoelectric effect. The Q factor and the peak amplitude of mechanical vibration are strongly enhanced near the exciton-related absorption peaks of GaAs at 10 K, showing good agreement with reported photoluminescence spectra.
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78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
77.65.Bn Piezoelectric and electrostrictive constants

Millimeter-wave hybrid un-cooled narrow-gap hot-carrier and Schottky diodes direct detectors

F. Sizov, V. Petriakov, V. Zabudsky, D. Krasilnikov, M. Smoliy, and S. Dvoretski

Appl. Phys. Lett. 101, 082108 (2012); http://dx.doi.org/10.1063/1.4747334 (5 pages)

Online Publication Date: 23 August 2012

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Un-cooled narrow-gap mercury-cadmium-telluride (MCT) semiconductor thin layers grown on GaAs substrates that are hybridized with antennas on low permittivity dielectric substrates were considered as 128–144 GHz direct detection 6-element bolometers. Noise equivalent power (NEP) of such detectors in observed frequency range ν ≈ 128–144 GHz reaches NEP300K ≈ 2.6 × 10−10 W/Hz1/2 (with calculated gain G ≈ 9 dBi). To compare the results obtained, the measurements of GaAs conventional Schottky barrier diode detectors were fulfilled in the same conditions and similar to MCT bolometers NEP was observed.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
84.40.Ba Antennas: theory, components and accessories
85.30.Kk Junction diodes
85.60.Gz Photodetectors (including infrared and CCD detectors)

Correlations between the band structure, activation energies of electron traps, and photoluminescence in n-type GaNAs layers

R. Kudrawiec, M. Latkowska, M. Welna, J. Misiewicz, M. Shafi, R. H. Mari, M. Henini, and W. Walukiewicz

Appl. Phys. Lett. 101, 082109 (2012); http://dx.doi.org/10.1063/1.4747504 (4 pages)

Online Publication Date: 23 August 2012

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It has been observed that activation energies of electron traps in GaNAs layers of various nitrogen concentrations vary consistently if the N-related changes in the band structure of GaNAs and energy positions of donor levels are plotted relative to the valence band edge on the same diagram. Within this diagram, it is expected that the activation energy of electron traps of the same microscopic nature should decrease with the increase of nitrogen concentration. The identification of electron traps in GaNAs within the proposed diagram allows to interpret the broad emission at ∼0.9 eV as the donor trap–valence band and the donor acceptor pair recombination involving of these traps.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.20.Nr Semiconductor compounds

AlGaN/GaN two-dimensional-electron gas heterostructures on 200 mm diameter Si(111)

S. Tripathy, Vivian K. X. Lin, S. B. Dolmanan, Joyce P. Y. Tan, R. S. Kajen, L. K. Bera, S. L. Teo, M. Krishna Kumar, S. Arulkumaran, G. I. Ng, S. Vicknesh, Shane Todd, W. Z. Wang, G. Q. Lo, H. Li, et al.

Appl. Phys. Lett. 101, 082110 (2012); http://dx.doi.org/10.1063/1.4746751 (5 pages) | Cited 1 time

Online Publication Date: 23 August 2012

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This Letter reports on the epitaxial growth, characterization, and device characteristics of crack-free AlGaN/GaN heterostructures on a 200 mm diameter Si(111) substrate. The total nitride stack thickness of the sample grown by the metal-organic chemical vapor deposition technique is about 3.3 ± 0.1 μm. The structural and optical properties of these layers are studied by cross-sectional scanning transmission electron microscopy, high-resolution x-ray diffraction, photoluminescence, and micro-Raman spectroscopy techniques. The top AlGaN/GaN heterointerfaces reveal the formation of a two-dimensional electron gas with average Hall mobility values in the range of 1800 to 1900 cm2/Vs across such 200 mm diameter GaN on Si(111) samples. The fabricated 1.5 μm-gate AlGaN/GaN high-electron-mobility transistors exhibited the drain current density of 660 mA/mm and extrinsic transconductance of 210 mS/mm. These experimental results show immense potential of 200-mm diameter GaN-on-silicon technology for electronic device applications.
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85.30.Tv Field effect devices

A method to increase sheet electron density and mobility by vacuum annealing for Ti/Al deposited AlGaN/GaN heterostructures

Hirokuni Tokuda, Toshikazu Kojima, and Masaaki Kuzuhara

Appl. Phys. Lett. 101, 082111 (2012); http://dx.doi.org/10.1063/1.4748169 (4 pages) | Cited 1 time

Online Publication Date: 24 August 2012

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Temperature dependence of sheet electron density (ns) and mobility (μ) for Ti/Al deposited AlGaN/GaN heterostructures annealed in vacuum has been investigated using Hall effect measurements. The vacuum annealing at 1020 K caused the increase in both ns and μ at room temperature, with the amount of one order of magnitude and 65%, respectively, as compared to without annealed sample. The amount of increase was much less for only Ti or Al deposited or totally thin Ti/Al deposited sample. The origin of the increase is attributed to tensile strain induced by vacuum annealing. The method is useful for reducing the ohmic contact resistivity and/or the access resistance between source and gate in AlGaN/GaN HEMTs.
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71.20.Nr Semiconductor compounds
72.20.My Galvanomagnetic and other magnetotransport effects
85.30.Tv Field effect devices
73.40.Ns Metal-nonmetal contacts

Growth of high Bi concentration GaAs1−xBix by molecular beam epitaxy

R. B. Lewis, M. Masnadi-Shirazi, and T. Tiedje

Appl. Phys. Lett. 101, 082112 (2012); http://dx.doi.org/10.1063/1.4748172 (4 pages) | Cited 3 times

Online Publication Date: 24 August 2012

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The incorporation of Bi is investigated in the molecular beam epitaxy growth of GaAs1−xBix. Bi content increases rapidly as the As2:Ga flux ratio is lowered to 0.5 and then saturates for lower flux ratios. Growth under Ga and Bi rich conditions shows that Bi content increases strongly with decreasing temperature. A model is proposed where Bi from a wetting layer incorporates through attachment to Ga-terminated surface sites. The weak Ga-Bi bond can be broken thermally, ejecting Bi back into the wetting layer. Highly crystalline films with up to 22% Bi were grown at temperatures as low as 200 °C.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
61.72.uj III-V and II-VI semiconductors

Mg doping for p-type AlInN lattice-matched to GaN

Yoshitaka Taniyasu, Jean-François Carlin, Antonino Castiglia, Raphaël Butté, and Nicolas Grandjean

Appl. Phys. Lett. 101, 082113 (2012); http://dx.doi.org/10.1063/1.4747524 (5 pages) | Cited 4 times

Online Publication Date: 24 August 2012

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P-type AlInN layers lattice-matched to GaN are achieved by Mg doping. The net acceptor concentration NA – ND is 5 × 1018 cm−3 at a Mg concentration [Mg] of ∼2 × 1019 cm−3. Mg acceptors are partly compensated and one of the compensating defects is related to the occurrence of surface pits. At [Mg] < 2 × 1019 cm−3, the pit density is independent of [Mg] and NA – ND increases together with increasing [Mg]. At [Mg] > 2 × 1019 cm−3, as [Mg] increases, the pit density increases and the NA – ND decreases. By decreasing the pit density, a higher NA – ND value is obtained and light-emitting diodes with p-type AlInN layer show improved emission intensity.
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61.72.uj III-V and II-VI semiconductors
68.35.bg Semiconductors
73.63.Hs Quantum wells
81.05.Ea III-V semiconductors
85.60.Jb Light-emitting devices

Electron band alignment at the interface of (100)InSb with atomic-layer deposited Al2O3

H.-Y. Chou, V. V. Afanas’ev, M. Houssa, A. Stesmans, Lin Dong, and P. D. Ye

Appl. Phys. Lett. 101, 082114 (2012); http://dx.doi.org/10.1063/1.4747797 (4 pages) | Cited 2 times

Online Publication Date: 24 August 2012

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From experiments on internal photoemission of electrons at the (100)InSb/Al2O3 interface, the top of the InSb valence band is found to be 3.05 ± 0.10 eV below the oxide conduction band and corresponds to a conduction band offset of 2.9 ± 0.1 eV. These results indicate that the top of valence band in InSb lies energetically at the same level as in GaSb and above the valence bands in InxGa1−xAs (0 ≤ x ≤ 0.53) or InP, suggesting that variation of the group III cation has no significant impact on the energy of the semiconductor valence band top and, therefore, it mostly affects the conduction band bottom edge.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.20.Nr Semiconductor compounds
73.20.At Surface states, band structure, electron density of states
79.60.-i Photoemission and photoelectron spectra
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