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9 Apr 2001

Volume 78, Issue 15, pp. 2095-2255

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Thermal annealing effect on the intersublevel transitions in InAs quantum dots

Y. Berhane, M. O. Manasreh, H. Yang, and G. J. Salamo

Appl. Phys. Lett. 78, 2196 (2001); http://dx.doi.org/10.1063/1.1363693 (3 pages) | Cited 8 times

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Isochronal thermal annealing effect on the photoluminescence (PL) spectra of intersublevel transitions in InAs self-assembled quantum dots was investigated. Several peaks due to intersublevel transitions in the quantum dots were observed in the PL spectra of two samples consisting of 10 stacks of InAs quantum dots and InP barriers. Isochronal furnace annealing in the temperature range of 500–800 °C was conducted on the two samples. The results show that the intensity of the PL peaks was dramatically reduced, and a new peak attributed to the wetting layer was observed after the samples were thermally annealed above 550 °C. A small blue shift of the PL peaks due to intermixing was observed. © 2001 American Institute of Physics.
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78.67.Hc Quantum dots
73.21.La Quantum dots
78.55.Cr III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots

Unambiguous observation of subband transitions from longitudinal valley and oblique valleys in IV–VI multiple quantum wells

H. Z. Wu, N. Dai, M. B. Johnson, P. J. McCann, and Z. S. Shi

Appl. Phys. Lett. 78, 2199 (2001); http://dx.doi.org/10.1063/1.1361104 (3 pages) | Cited 14 times

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PbSe/PbSrSe multiple-quantum-well (MQW) structures were grown on BaF2(111) substrates by molecular-beam epitaxy and characterized by Fourier transform infrared transmission spectroscopy. To reduce unwanted Fabry–Pérot interference fringes, the top surface of the MQW samples was coated with an anti-interference film, enabling clear observation of subband transitions without superposed interference fringes. Transition energies involving longitudinal and oblique valleys were unambiguously resolved and are in good agreement with calculations made using the envelope wave function approximation. © 2001 American Institute of Physics.
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78.67.De Quantum wells
81.07.St Quantum wells
78.30.Hv Other nonmetallic inorganics

Scattering (stochastic) recoupling of a coupled ten-stripe AlGaAs–GaAs–InGaAs quantum-well heterostructure laser

D. A. Kellogg and N. Holonyak

Appl. Phys. Lett. 78, 2202 (2001); http://dx.doi.org/10.1063/1.1363691 (3 pages) | Cited 1 time

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Data are presented on coupled ten-stripe AlGaAs–GaAs–InGaAs quantum well heterostructure (QWH) lasers recoupled stochastically at the cleaved end mirrors. Recoupling of neighboring elements of a ten-stripe laser is accomplished by the scattering (random feedback) afforded by applying ∼10-μm-diam Al powder or 0.3 μm α-Al2O3 polishing compound in microscopy immersion oil or in epoxy at the cleaved ends (mirrors). Data on QWH samples with the end mirrors coated with the scatterer (Al or Al2O3 powder in “liquid”) exhibit spectral and far-field broadening, as well as increased laser threshold because of the reduced cavity Q. Single mode operation is possible with the conventional evanescent wave coupling of the ten-stripe QWH and is destroyed, even the laser operation itself, with the scattering recoupling (dephasing) at the end mirrors, which is reversible (removable). The narrow ten-stripe QWH laser with strong end-mirror scattering, a long amplifier with random feedback, indicates that a photopumped III–V or II–VI powder (a random “wall” cavity) has little or no merit. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Pk Continuous operation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.79.Bh Lenses, prisms and mirrors

Fabrication of nanoperiodic surface structures by controlled etching of dislocations in bicrystals

Rikard A. Wind, Martin J. Murtagh, Fang Mei, Yu Wang, Melissa A. Hines, and Stephen L. Sass

Appl. Phys. Lett. 78, 2205 (2001); http://dx.doi.org/10.1063/1.1362330 (3 pages) | Cited 24 times

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A method for the fabrication of periodic arrays of surface features with controlled spacings of 2–100 nm has been developed. This process relies on the selective etching of dislocations formed at a twist–bonded interface in a bicrystal. The production of nanoscale periodic silicon surface features with a mean spacing of 38 nm is reported. The etch rate of edge and screw dislocations is compared, and the rate of dislocation etching is found to be poorly correlated to strain. This observation calls long-held theories of dislocation etching into question. © 2001 American Institute of Physics.
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81.16.Rf Micro- and nanoscale pattern formation
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
68.37.Ps Atomic force microscopy (AFM)
81.05.Cy Elemental semiconductors

High-efficiency nickel phase zone plates with 20 nm minimum outermost zone width

M. Peuker

Appl. Phys. Lett. 78, 2208 (2001); http://dx.doi.org/10.1063/1.1361285 (3 pages) | Cited 30 times

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Fresnel zone plates for high-resolution imaging in the soft x-ray regime were fabricated in nickel by a trilevel process, which makes use of electron-beam lithography, reactive-ion etching, and electrodeposition. In order to improve the zone plate’s resolution, which is determined by its outermost zone width, ZEP-7000 electron-beam resist was employed. Residues, which arose during pattern transfer by reactive-ion etching, and which hindered etching in small structures, were suppressed by a cleaning procedure. For improved electrodeposition process control, a nickel electroplating bath was optimized. Zone plates with minimum outermost zone widths of 20, 25 and 30 nm were fabricated, yielding 9.2%, 16.2% and 18.0% first-order diffraction efficiency, respectively, at λ = 2.4 nm. © 2001 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
42.79.Ci Filters, zone plates, and polarizers
81.15.Pq Electrodeposition, electroplating
81.65.Cf Surface cleaning, etching, patterning
42.86.+b Optical workshop techniques

Bright blue electroluminescence from an InGaN/GaN multiquantum-well diode on Si(111): Impact of an AlGaN/GaN multilayer

A. Dadgar, J. Christen, T. Riemann, S. Richter, J. Bläsing, A. Diez, A. Krost, A. Alam, and M. Heuken

Appl. Phys. Lett. 78, 2211 (2001); http://dx.doi.org/10.1063/1.1362327 (3 pages) | Cited 43 times

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We present an electroluminescence test structure which consists of an InGaN/GaN multiquantum well as active region on the top of an AlGaN/GaN multilayer grown by metalorganic vapor phase epitaxy on Si(111) substrate. The integral room-temperature electroluminescence spectrum reveals a peak emission wavelength of 467 nm and a significantly higher brightness than an identical reference structure on sapphire substrate. In microelectroluminescence imaging, two emission peaks at 465 and 476 nm can be separated originating from locally different areas of the diode. Cathodoluminescence measurements in cross section and high-resolution x-ray diffraction measurements show that the structure is less strained than a sample without the AlGaN/GaN multilayer. The AlGaN/GaN multiple layer sequence which has a total thickness of 1.5 μm causes lattice relaxation during growth after a thickness of around 0.9 μm as directly visualized by cathodoluminescence line scans across the diode. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.67.De Quantum wells
68.65.Fg Quantum wells
81.07.St Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence

Diameter-controlled synthesis of single-crystal silicon nanowires

Yi Cui, Lincoln J. Lauhon, Mark S. Gudiksen, Jianfang Wang, and Charles M. Lieber

Appl. Phys. Lett. 78, 2214 (2001); http://dx.doi.org/10.1063/1.1363692 (3 pages) | Cited 370 times

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Monodisperse silicon nanowires were synthesized by exploiting well-defined gold nanoclusters as catalysts for one-dimensional growth via a vapor–liquid–solid mechanism. Transmission electron microscopy studies of the materials grown from 5, 10, 20, and 30 nm nanocluster catalysts showed that the nanowires had mean diameters of 6, 12, 20, and 31 nm, respectively, and were thus well defined by the nanocluster sizes. High-resolution transmission electron microscopy demonstrated that the nanowires have single-crystal silicon cores sheathed with 1–3 nm of amorphous oxide and that the cores remain highly crystalline for diameters as small as 2 nm. © 2001 American Institute of Physics.  
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81.16.Hc Catalytic methods
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
81.05.Cy Elemental semiconductors

Conduction band offset and electron effective mass in GaInNAs/GaAs quantum-well structures with low nitrogen concentration

Z. Pan, L. H. Li, Y. W. Lin, B. Q. Sun, D. S. Jiang, and W. K. Ge

Appl. Phys. Lett. 78, 2217 (2001); http://dx.doi.org/10.1063/1.1362335 (3 pages) | Cited 66 times

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We have investigated the optical transitions in Ga1−yInyNxAs1−x/GaAs single and multiple quantum wells using photovoltaic measurements at room temperature. From a theoretical fit to the experimental data, the conduction band offset Qc, electron effective mass me∗, and band gap energy Eg were estimated. It was found that the Qc is dependent on the indium concentration, but independent on the nitrogen concentration over the range x = (0–1)%. The me∗ of GaInNAs is much greater than that of InGaAs with the same concentration of indium, and increases as the nitrogen concentration increases up to 1%. Our experimental results for the me∗ and Eg of GaInNAs are quantitatively explained by the two-band model based on the strong interaction of the conduction band minimum with the localized N states. © 2001 American Institute of Physics.
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73.21.Fg Quantum wells
81.05.Ea III-V semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Nr Semiconductor compounds
78.66.Fd III-V semiconductors
78.67.De Quantum wells
72.40.+w Photoconduction and photovoltaic effects
73.63.Hs Quantum wells

Effect of phosphorus on Ge/Si(001) island formation

T. I. Kamins, D. A. A. Ohlberg, and R. Stanley Williams

Appl. Phys. Lett. 78, 2220 (2001); http://dx.doi.org/10.1063/1.1361096 (3 pages) | Cited 5 times

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Adding PH3 during chemical vapor deposition of Ge on Si(001) partially suppresses island formation and changes the shape of the islands that do form. A shape not previously seen in undoped layers grown by chemical vapor deposition is a large pyramid, with base edges aligned along the 〈110〉 directions and sides bounded by {111} planes near the base and {113} planes near the top. This suggests that phosphorus changes the thermodynamics of island formation. During annealing in H2, the shape of the large pyramids changes toward a multifaceted structure. The presence of PH3 during annealing of undoped islands retards coarsening, probably by decreasing surface diffusion. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Evolution of nanoscale texture in ultrathin TiN films

M. J. Williamson, D. N. Dunn, R. Hull, S. Kodambaka, I. Petrov, and J. E. Greene

Appl. Phys. Lett. 78, 2223 (2001); http://dx.doi.org/10.1063/1.1360235 (3 pages) | Cited 10 times

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We investigate the evolution of texture and grain morphology in fine-grained TiN thin films using cross correlation of dark-field images obtained using annular objective apertures with radii that correspond to different low index TiN reflections. This technique enables parallel analyses of the orientations of thousands of grains, with a spatial resolution of order 10 nm. Preferred grain orientations were determined for 40 and 100 nm thick TiN layers grown on SiO2 by magnetically unbalanced reactive magnetron sputter deposition. We find that no single orientation is dominant in the 40 nm films but that a 〈100〉 texture has developed by the time these films reach 100 nm in thickness. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
85.40.Ls Metallization, contacts, interconnects; device isolation
68.37.Lp Transmission electron microscopy (TEM)
61.46.-w Structure of nanoscale materials

Electron field emission from carbon nanoparticles prepared by microwave-plasma chemical-vapor deposition

J. Yu, E. G. Wang, and X. D. Bai

Appl. Phys. Lett. 78, 2226 (2001); http://dx.doi.org/10.1063/1.1361286 (3 pages) | Cited 22 times

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Carbon nanoparticles were prepared from H2 and CH4 at various temperatures. The carbon nanoparticles were well graphitized, and the degree of graphitization increased with increasing growth temperature. Field-emission measurements showed that the carbon nanoparticles were excellent electron field emitters, comparable to carbon nanotubes. The field-emission properties became better with increasing growth temperature, and the threshold fields of the carbon nanoparticles deposited at 400, 500, 670 °C were 3.2, 3, and 1 V/μm, respectively. The low-threshold field of the carbon nanoparticles is attributed to the field-enhancement effect and the higher degree of graphitization. © 2001 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.U- Carbon/carbon-based materials
52.77.Dq Plasma-based ion implantation and deposition
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