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13 May 2002

Volume 80, Issue 19, pp. 3467-3650

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Crack-free thick AlGaN grown on sapphire using AlN/AlGaN superlattices for strain management

J. P. Zhang, H. M. Wang, M. E. Gaevski, C. Q. Chen, Q. Fareed, J. W. Yang, G. Simin, and M. Asif Khan

Appl. Phys. Lett. 80, 3542 (2002); http://dx.doi.org/10.1063/1.1477620 (3 pages) | Cited 57 times

Online Publication Date: 7 May 2002

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We report on an AlN/AlGaN superlattice approach to grow high-Al-content thick n+-AlGaN layers over c-plane sapphire substrates. Insertion of a set of AlN/AlGaN superlattices is shown to significantly reduce the biaxial tensile strain, thereby resulting in 3-μm-thick, crack-free Al0.2Ga0.8N layers. These high-quality, low-sheet-resistive layers are of key importance to avoid current crowding in quaternary AlInGaN multiple-quantum-well deep-ultraviolet light-emitting diodes over sapphire substrates. © 2002 American Institute of Physics.
Show PACS
81.07.St Quantum wells
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.60.Bs Mechanical and acoustical properties
73.61.Ey III-V semiconductors
68.55.-a Thin film structure and morphology
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
72.20.Ee Mobility edges; hopping transport
72.20.My Galvanomagnetic and other magnetotransport effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

In-doped SrTiO3 ceramic thin films

Shouyu Dai, Huibin Lu, Fan Chen, Zhenghao Chen, Z. Y. Ren, and D. H. L. Ng

Appl. Phys. Lett. 80, 3545 (2002); http://dx.doi.org/10.1063/1.1478148 (3 pages) | Cited 15 times

Online Publication Date: 7 May 2002

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We report the characterization of the ceramic SrIn0.1Ti0.9O3 thin film grown by laser molecular-beam epitaxy. The lattice constant is determined to be 0.3948 nm, slightly larger than that of the SrTiO3 substrate. Hall measurement confirms that this film is a p-type semiconductor either below 92 K or above 158 K. X-ray photoemission spectroscopy study shows that the width of the valence band of the p-type SrIn0.1Ti0.9O3 film is narrower than that of the n-type SrNb0.1Ti0.9O3 film. There is a 0.35 eV difference in the Fermi energy level of the two films. The electronic state of the surface layer of the SrIn0.1Ti0.9O3 film is found to be different from that of its interior. © 2002 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.Fg Pulsed laser ablation deposition
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.-a Thin film structure and morphology

Electrical transport properties of individual gallium nitride nanowires synthesized by chemical-vapor-deposition

Jae-Ryoung Kim, Hye Mi So, Jong Wan Park, Ju-Jin Kim, Jinhee Kim, Cheol Jin Lee, and Seung Chul Lyu

Appl. Phys. Lett. 80, 3548 (2002); http://dx.doi.org/10.1063/1.1478158 (3 pages) | Cited 71 times

Online Publication Date: 7 May 2002

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We have synthesized high-quality gallium nitride (GaN) nanowires by a chemical-vapor-deposition method and studied the electrical transport properties. The electrical measurements on individual GaN nanowires show a pronounced n-type field effect due to nitrogen vacancies in the whole measured temperature ranges. The n-type gate response and the temperature dependence of the current–voltage characteristics could be understood by the band bending at the interface of the metal electrode and GaN wire. The estimated electron mobility from the gate modulation characteristics is about 2.15 cm2/V s at room temperature, suggesting the diffusive nature of electron transport in the nanowires. © 2002 American Institute of Physics.
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73.63.Bd Nanocrystalline materials
81.05.Ea III-V semiconductors
81.07.Bc Nanocrystalline materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.J- Point defects and defect clusters
61.46.-w Structure of nanoscale materials

Direct measurement of the polarization charge in AlGaN/GaN heterostructures using capacitance–voltage carrier profiling

E. J. Miller, E. T. Yu, C. Poblenz, C. Elsass, and J. S. Speck

Appl. Phys. Lett. 80, 3551 (2002); http://dx.doi.org/10.1063/1.1477275 (3 pages) | Cited 22 times

Online Publication Date: 7 May 2002

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The polarization charge at AlxGa1−xN/GaN heterostructure interfaces arising from differences in spontaneous polarization between AlxGa1−xN and GaN and the presence of piezoelectric polarization in strained layers has been directly measured using capacitance–voltage carrier profiling in GaN/AlxGa1−xN/GaN heterostructures with varying Al composition grown by molecular-beam epitaxy. The measured polarization charge densities (2.36±0.30×1012 e/cm2, 6.79±0.48×1012 e/cm2, and 6.92±0.74×1012 e/cm2 for 5%, 12%, and 16% AlxGa1−xN/GaN interfaces, respectively) reveal substantial bowing in the polarization charge as a function of Al composition, and are in reasonable agreement with those calculated using a model that accounts for the nonlinearity of the spontaneous and piezoelectric polarizations as functions of Al composition. Our results yield an explicit expression for polarization charge as a function of Al composition at an AlxGa1−xN/GaN interface. © 2002 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ej Polarization and depolarization
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Abnormal dependence of contact resistivity on hole concentration in nonalloyed ohmic contacts to p-GaN

Joon Seop Kwak, Ok-Hyun Nam, and Yongjo Park

Appl. Phys. Lett. 80, 3554 (2002); http://dx.doi.org/10.1063/1.1478154 (3 pages) | Cited 30 times

Online Publication Date: 7 May 2002

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The dependence of contact resistivity on hole concentration has been investigated for nonalloyed Pd contacts to p-GaN. The hole concentration was varied by changing the Mg concentration, [Mg], in p-GaN. The p-GaN having the [Mg] of 4.5×1019 cm−3 showed the hole concentration of 2.2×1017 cm−3, where contact resistivity was measured as 8.9×10−2 Ω cm2. When the [Mg] increased to 1.0×1020 cm−3, the hole concentration was significantly reduced to 2.0×1016 cm−3. Nevertheless, the Pd contacts on the p-GaN displayed contact resistivity as low as 5.5×10−4 Ω cm2. The abnormal dependence of contact resistivity on hole concentration may be explained by predominant current flow at the Pd/p-GaN interface through a deep level defect band, rather than the valence band. © 2002 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors
73.61.At Metal and metallic alloys

Hall mobility enhancement caused by annealing of Si0.2Ge0.8/Si0.7Ge0.3/Si(001) p-type modulation-doped heterostructures

M. Myronov, P. J. Phillips, T. E. Whall, and E. H. C. Parker

Appl. Phys. Lett. 80, 3557 (2002); http://dx.doi.org/10.1063/1.1478779 (3 pages) | Cited 6 times

Online Publication Date: 7 May 2002

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The effect of post-growth furnace thermal annealing (FTA) on the Hall mobility and sheet carrier density measured at 9–300 K in the Si0.2Ge0.8/Si0.7Ge0.3/Si(001) p-type modulation-doped heterostructures was studied. FTA treatments in the temperature range of 600–900 °C for 30 min were performed on similar heterostructures but with two Si0.2Ge0.8 channel thicknesses. The annealing at 600 °C is seen to have a negligible effect on the Hall mobility as well as on the sheet carrier density. Increases in the annealing temperature resulted in pronounced successive increases of the mobility. For both samples the maximum Hall mobility was observed after FTA at 750 °C. Further increases of the annealing temperature resulted in a decrease in mobility. The sheet carrier density showed the opposite behavior with an increase in annealing temperature. The mechanism causing this behavior is discussed. Structural characterization of as-grown and annealed samples was done by cross-sectional transmission electron microscopy. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Hd Other semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Fr Low-field transport and mobility; piezoresistance
81.05.Cy Elemental semiconductors
72.20.Ee Mobility edges; hopping transport
61.72.Cc Kinetics of defect formation and annealing
68.37.Lp Transmission electron microscopy (TEM)

Dislocation-free formation of relaxed SiGe-on-insulator layers

T. Tezuka, N. Sugiyama, S. Takagi, and T. Kawakubo

Appl. Phys. Lett. 80, 3560 (2002); http://dx.doi.org/10.1063/1.1479457 (3 pages) | Cited 15 times

Online Publication Date: 7 May 2002

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We demonstrate the fabrication of dislocation-free strain-relaxed SiGe-on-insulator (SGOI) layers as virtual substrates for strained Si-on-insulator (SOI) metal–oxide–semiconductor field-effect transistors (MOSFETs) by forming SiGe-mesa structures and successive oxidation. A pseudomorphic Si0.9Ge0.1 layer on a SOI layer was etched to form mesa structures. After the oxidation of the mesas, thin (<100 nm) Si0.85Ge0.15 mesa structures were formed on the buried oxide layer. It was found that the mesas with a diameter smaller than 3 μm were almost completely relaxed after oxidation at 1200 °C, without generating any threading dislocations and crosshatch patterns, which generally exist in the relaxed SiGe layers on bulk Si substrates. The formation of SGOI mesas before oxidation has the potential to provide ideal SGOI virtual substrates for strained SOI MOSFETs. © 2002 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
85.30.Tv Field effect devices
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