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25 Feb 2002

Volume 80, Issue 8, pp. 1319-1496

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Effect of chirp in diffraction of short electromagnetic pulses through subwavelength apertures

Oleg Mitrofanov, Mark Lee, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 80, 1319 (2002); http://dx.doi.org/10.1063/1.1452786 (3 pages) | Cited 5 times

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Short electromagnetic pulses experience significant spectral and temporal deformation when diffracted on subwavelength apertures. Temporal delay/advancement is one of the effects that occurs when a pulse passes through the aperture. In this study, it is demonstrated that the intrinsic negative chirp of terahertz pulses is the origin of the temporal advancement in the limit that the aperture is much smaller than the wavelength of the pulse. The advancement is shown to disappear for unchirped terahertz pulses. The chirp effect is general for any system where the diffracted or scattered field is wavelength dependent. © 2002 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation

Optical confinement in CdTe-based photonic dots

M. Obert, B. Wild, G. Bacher, A. Forchel, R. André, and Le Si Dang

Appl. Phys. Lett. 80, 1322 (2002); http://dx.doi.org/10.1063/1.1452792 (3 pages) | Cited 8 times

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We demonstrate three-dimensional optical confinement in CdTe-based microcavities. While the vertical confinement is determined by epitaxially grown CdMnTe/CdMgTe Bragg mirrors, the lateral confinement is achieved by defining pillar structures with electron beam lithography and reactive ion etching. The optical confinement is shown by a size-dependent energy splitting between the fundamental and higher photonic modes. © 2002 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
78.67.De Quantum wells
73.21.Fg Quantum wells
42.79.Bh Lenses, prisms and mirrors
81.07.St Quantum wells
78.55.Et II-VI semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Optical absorption measurements of silica containing Si nanocrystals produced by ion implantation and thermal annealing

R. G. Elliman, M. J. Lederer, and B. Luther-Davies

Appl. Phys. Lett. 80, 1325 (2002); http://dx.doi.org/10.1063/1.1454217 (3 pages) | Cited 16 times

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Optical absorption spectra from silicon-implanted silica slides are shown to contain features due to optical interference. These features, which result from the modified refractive index profile produced by the implant, can readily lead to misinterpretation of absorption spectra. To demonstrate the importance of such effects, silica samples were implanted with 80, 400, and 600 keV Si ions to fluences in the range 0.6–3.0×1017 Si.cm−2 and annealed at 1100 °C for 1 h to form Si nanocrystals. Optical absorption/transmittance spectra from these samples show considerable structure that is characteristic of the particular implant conditions. This structure is shown to correlate with the transmittance of the samples as calculated from the modified refractive index profile for each implant. The lack of such structure in absorption spectra measured by photodeflection spectrometry is used to confirm this interpretation. © 2002 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Two-photon absorption photocurrent enhancement in bulk AlGaAs semiconductor microcavities

H. Folliot, M. Lynch, A. L. Bradley, L. A. Dunbar, J. Hegarty, J. F. Donegan, L. P. Barry, J. S. Roberts, and G. Hill

Appl. Phys. Lett. 80, 1328 (2002); http://dx.doi.org/10.1063/1.1455694 (3 pages) | Cited 19 times

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We report on two-photon absorption (TPA) photocurrent in semiconductor microcavities. We experimentally show a substantial increase in the TPA photocurrent generated, at resonance, in a GaAlAs/GaAs microcavity designed for TPA operation at ∼890 nm. An enhancement factor of ∼ 12 000 of the photocurrent is obtained via the microcavity effect, which could have an important impact on the use of TPA devices for high speed switching and sampling applications. Our results also show the implications of the cavity photon lifetime on autocorrelation traces measured using TPA in semiconductor microcavities. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.50.Pz Photoconduction and photovoltaic effects
78.67.De Quantum wells
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.63.Hs Quantum wells

Simultaneous topographical and optical characterization of near-field optical aperture probes by way of imaging fluorescent nanospheres

C. Höppener, D. Molenda, H. Fuchs, and A. Naber

Appl. Phys. Lett. 80, 1331 (2002); http://dx.doi.org/10.1063/1.1454220 (3 pages) | Cited 10 times

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We introduce a method for a simultaneous topographical and optical characterization of aperture probes for scanning near-field optical microscopy which is based on imaging of small sized fluorescent nanospheres (∼20 nm). The near-field optical fluorescence image of a nanosphere maps the intensity distribution of light at the end face of the probe whereas the simultaneously taken height image contains information about the aperture–sample distance. We used this method to control a mechanical modification of a near-field probe. By squeezing a probe repeatedly against a smooth glass substrate and thereby removing obstructing protrusions the aperture was brought as close as possible to the sample surface which resulted in a strongly improved optical resolution. © 2002 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
33.50.Dq Fluorescence and phosphorescence spectra
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.30.Va Image forming and processing
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Production of nitrogen acceptors in ZnO by thermal annealing

N. Y. Garces, N. C. Giles, L. E. Halliburton, G. Cantwell, D. B. Eason, D. C. Reynolds, and D. C. Look

Appl. Phys. Lett. 80, 1334 (2002); http://dx.doi.org/10.1063/1.1450041 (3 pages) | Cited 97 times

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Nitrogen acceptors are formed when undoped single crystals of zinc oxide (ZnO) grown by the chemical-vapor transport method are annealed in air or nitrogen atmosphere at temperatures between 600 and 900 °C. After an anneal, an induced near-edge absorption band causes the crystals to appear yellow. Also, the concentration of neutral shallow donors, as monitored by electron paramagnetic resonance (EPR), is significantly reduced. A photoinduced EPR signal due to neutral nitrogen acceptors is observed when the annealed crystals are exposed to laser light (e.g., 364, 442, 458, or 514 nm) at low temperature. The nitrogens are initially in the nonparamagnetic singly ionized state (N−) in an annealed crystal, because of the large number of shallow donors, and the light converts a portion of them to the paramagnetic neutral acceptor state (N0). © 2002 American Institute of Physics.
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71.55.Gs II-VI semiconductors
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
81.05.Dz II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
76.30.Lh Other ions and impurities

Growth of epitaxial NdNiO3 and integration with Si(100)

Ashutosh Tiwari, J. Narayan, C. Jin, and A. Kvit

Appl. Phys. Lett. 80, 1337 (2002); http://dx.doi.org/10.1063/1.1451984 (3 pages) | Cited 2 times

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We have grown epitaxial NdNiO3 films on Si(100) substrate under ambient oxygen pressure using a pulsed-laser deposition method. The integration of NdNiO3 with Si(100) was accomplished by lattice-matching epitaxy of MgO and SrTiO3 and domain matching epitaxy of TiN on Si(100). During domain matching epitaxy, four lattice constants of TiN match with three of silicon across the TiN/Si(100) interface. High-quality epitaxial NdNiO3 film on SrTiO3/MgO/TiN/Si(100) showed a very sharp metal–insulator (MI) phase transition at 200 K. Observed MI transition in epitaxial NdNiO3 is much sharper than that usually observed in bulk and polycrystalline films with more than four orders of magnitude change in resistivity. This MI transition is understood to arise because of the opening of charge transfer gap between Ni3+(3d) and O2−(2p) band. © 2002 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
72.60.+g Mixed conductivity and conductivity transitions
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Electrical characterization of vapor-phase-grown single-crystal ZnO

F. D. Auret, S. A. Goodman, M. J. Legodi, W. E. Meyer, and D. C. Look

Appl. Phys. Lett. 80, 1340 (2002); http://dx.doi.org/10.1063/1.1452781 (3 pages) | Cited 87 times

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Gold Schottky-barrier diodes (SBDs) were fabricated on vapor-phase-grown single-crystal ZnO. Deep-level transient spectroscopy, using these SBDs, revealed the presence of four electron traps, the major two having levels at 0.12 eV and 0.57 below the conduction band. Comparison with temperature-dependent Hall measurements suggests that the 0.12 eV level has a temperature activated capture cross section with a capture barrier of about 0.06 eV and that it may significantly contribute to the free-carrier density. Based on the concentrations of defects other than this shallow donor, we conclude that the quality of the vapor-phase-grown ZnO studied here supercedes that of other single-crystal ZnO reported up to now. © 2002 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Gs II-VI semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
72.20.My Galvanomagnetic and other magnetotransport effects

Thermochromic effect in YH3−δ and Mg0.1Y0.9H2.9−δ

I. A. M. E. Giebels, S. J. van der Molen, R. Griessen, and M. Di Vece

Appl. Phys. Lett. 80, 1343 (2002); http://dx.doi.org/10.1063/1.1446993 (3 pages) | Cited 3 times

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Pure YH3−δ and Mg0.1Y0.9H2.9−δ exhibit large differences in their thermochromic properties. Whereas the transmittance of YH3−δ decreases by 9% to 36%, in Mg0.1Y0.9H2.9−δ it decreases by 64% to 83% between 30 °C and 160 °C. This thermochromic effect is caused by hydrogen desorption upon temperature increase. The main difference between the two systems is that the face-centered-cubic to hexagonal-close-packed phase transition between YH2+δ and YH3−δ is absent in Mg0.1Y0.9Hx, i.e., the YHx stays cubic for all 2 ⩽ x ⩽ 3. Because of this, there are no plateaus in the pressure–composition isotherms of Mg0.1Y0.9Hx and the steepness of the optical transition upon hydrogen desorption increases drastically compared to pure YHx. © 2002 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
68.43.Mn Adsorption kinetics
64.70.K- Solid-solid transitions

Interface of directly bonded InP wafers for vertical couplers

N. Y. Jin-Phillipp, B. Liu, J. E. Bowers, E. L. Hu, M. Kelsch, J. Thomas, and M. Rühle

Appl. Phys. Lett. 80, 1346 (2002); http://dx.doi.org/10.1063/1.1454216 (3 pages) | Cited 2 times

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Vertical directional couplers fabricated using direct wafer bonding have demonstrated a very short coupling length and a small excess optical loss introduced by the bonded interface layer. The structure of the interface of directly bonded InP wafers is investigated. Dislocations at the interface are found to accommodate the tilt misorientation between the two wafers without introducing extra misfit. Body-centered-tetragonal In inclusions of a size of few nanometers are identified at the interface. The excess optical loss of the coupler based on directly bonded InP wafers due to the formation of these inclusions may be eliminated by using lower temperature and a phosphor atmosphere for direct bonding. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
78.66.Fd III-V semiconductors
61.72.Mm Grain and twin boundaries
81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness

Mixed metal films with switchable optical properties

T. J. Richardson, J. L. Slack, B. Farangis, and M. D. Rubin

Appl. Phys. Lett. 80, 1349 (2002); http://dx.doi.org/10.1063/1.1454218 (3 pages) | Cited 37 times

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Thin, Pd-capped metallic films containing magnesium and first-row transition metals (Mn, Fe, Co) switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen or following cathodic polarization in an alkaline electrolyte. Reversion to the reflecting state is achieved by exposure to air or by anodic polarization. The films were prepared by cosputtering from one magnesium target and one manganese, iron, or cobalt target. Both the dynamic optical switching range and the speed of the transition depend on the magnesium-transition metal ratio. Infrared spectra of films in the transparent, hydrided (deuterided) states support the presence of the intermetallic hydride phases Mg3MnH7, Mg2FeH6, and Mg2CoH5. © 2002 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
42.70.Km Infrared transmitting materials
78.30.Er Solid metals and alloys
82.45.Mp Thin layers, films, monolayers, membranes
78.20.Jq Electro-optical effects
78.40.Kc Metals, semimetals, and alloys

Ion-beam nanotexturing of buffer layers for near-single-crystal thin-film deposition: Application to YBa2Cu3O7-δ superconducting films

R. P. Reade, P. Berdahl, and R. E. Russo

Appl. Phys. Lett. 80, 1352 (2002); http://dx.doi.org/10.1063/1.1450059 (3 pages) | Cited 8 times

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A method of producing biaxially textured template layers for near-single-crystal-quality film growth on substrates that do not provide a template for oriented crystalline growth is described and compared to existing methods. This technique, ion-beam nanotexturing (ITEX), produces a biaxially textured layer by oblique ion irradiation of an amorphous film surface. Using in situ reflection high-energy electron diffraction and ex situ x-ray diffraction, an yttria-stabilized zirconia (YSZ) template layer fabricated by ITEX is shown to have the appropriate surface texture for YBa2Cu3O7-δ coated conductor fabrication. A YBa2Cu3O7-δ thin film deposited on an ITEX YSZ layer has a critical current of 2.5×105 A/cm2 (77 K, 1 μV/cm). ITEX produces texture rapidly and should be ideally suited for future low-cost manufacturing. © 2002 American Institute of Physics.
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81.65.-b Surface treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents

Correlations between spatially resolved Raman shifts and dislocation density in GaN films

G. Nootz, A. Schulte, L. Chernyak, A. Osinsky, J. Jasinski, M. Benamara, and Z. Liliental-Weber

Appl. Phys. Lett. 80, 1355 (2002); http://dx.doi.org/10.1063/1.1449523 (3 pages) | Cited 16 times

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Spatially resolved Raman spectra were measured on thick GaN samples with known dislocation density grown by hydride vapor phase epitaxy. The frequencies of the E2 (high) and E1 (transverse optical) phonons shift to lower wave number over a distance of 30 μm from the sapphire substrate/GaN interface. The shifts are linearly correlated with the dislocation density suggesting that the strain due to the lattice mismatch at the interface determines both quantities. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Ja Surface and interface dynamics and vibrations
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Morphology evolution of ZnO(000 math) surface during plasma-assisted molecular-beam epitaxy

Yefan Chen, Hang-Ju Ko, Soon-Ku Hong, Takafumi Yao, and Yusaburo Segawa

Appl. Phys. Lett. 80, 1358 (2002); http://dx.doi.org/10.1063/1.1454229 (3 pages) | Cited 22 times

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Morphology evolution of ZnO(000 math) surface during plasma-assisted molecular-beam epitaxy was studied. In a step-flow growth mode, terraces bounded by anisotropic steps along 〈11 math0〉 characterize the surface of ZnO epilayers. Adatoms favorably incorporate at upsteps, which translates hexagonal islands to regular terraces with equalized width. Surface morphology is sensitive to the Zn/O ratio. Oxygen stabilizes mobile Zn adatoms hence oxygen rich conditions result in rough step edges and irregular hexagonal terraces. Steps become smoother with increasing Zn/O ratio until the stoichiometric condition is achieved. As the Zn flux exceeds the stoichiometry, faceted hexagonal pits form on the ZnO(000 math) surface. Rather than the lack of surface mobility, the lack of stabilization of adatoms is responsible to the formation of pit. © 2002 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.47.Gh Oxide surfaces
81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.37.Ps Atomic force microscopy (AFM)

Real-time x-ray scattering study on the thermal evolution of interface roughness in CoSi2 formation

Tae Soo Kang and Jung Ho Je

Appl. Phys. Lett. 80, 1361 (2002); http://dx.doi.org/10.1063/1.1455149 (3 pages) | Cited 8 times

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The thermal evolution of interface roughness during cobalt silicide formation in the Co/Ti/Si(001) and Co/Si(001) systems was investigated using real-time synchrotron x-ray scattering measurement. We find that the enhancement of the CoSi2/Si(001) interface roughness is caused by the retardation of silicide phase formation almost up to the CoSi2 nucleation temperature. In the Co(120 Å)/Ti(50 Å)/Si(001), the interface roughness increases only to 6 Å during silicidation, by suppressing the reaction between the Co overlayer and Si substrate with a Ti diffusion barrier nearly up to the CoSi2 nucleation temperature of 660 °C. In the Co(120 Å)/Si(001), however, the reaction already starts at a low temperature of 300 °C, resulting in a significant rise of the interface roughness up to 13 Å, which is mainly attributed to the formation of Si{111} facets that act as the nucleation sites of misoriented CoSi2 grains. © 2002 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
66.30.Ny Chemical interdiffusion; diffusion barriers
61.05.cf X-ray scattering (including small-angle scattering)

Periodic oxide breakdown during oxidation of AlN/Sapphire(0001) films

H. C. Kang, S. H. Seo, J. W. Kim, and D. Y. Noh

Appl. Phys. Lett. 80, 1364 (2002); http://dx.doi.org/10.1063/1.1453486 (3 pages) | Cited 6 times

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We present an in situ synchrotron x-ray scattering study on the thermal oxidation of epitaxial AlN/Sapphire(0001) films. During annealing to 700 °C, an epitaxial AlN film transforms progressively into a planar epitaxial γ-Al2O3 layer. The oxidation proceeds through the γ-Al2O3/AlN interfacial motion that is observed directly from the intensity fringes near the AlN(0002) Bragg reflection. The oxidation rate, deduced from the interfacial motion, exhibits repeating transitions from a linear to a parabolic oxidation behavior. This suggests that the oxide break down periodically. During the oxidation the strain in the remaining AlN reverts to the value measured at the same thickness during the growth of the AlN film. © 2002 American Institute of Physics.
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81.65.Mq Oxidation
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology
78.70.Ck X-ray scattering

Effects of the matrix on self-organization of InAs quantum nanostructures grown on InP substrates

Hanxuan Li, Theda Daniels-Race, and Mohamed-Ali Hasan

Appl. Phys. Lett. 80, 1367 (2002); http://dx.doi.org/10.1063/1.1452784 (3 pages) | Cited 27 times

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We have studied the influence of matrix materials on the self-organization of InAs nanostructures grown on InP substrates by molecular-beam epitaxy. Our results show that InAs quantum dots are formed on InAlGaAs, whereas quantum-wire-like structures are produced on InAlAs and InGaAs. Tuning from vertical anticorrelation in InAs/InAlAs superlattices to vertical correlation in InAs/InGaAs and InAs/InAlGaAs superlattices is observed, which is explained by the size effects in the nanostructure–nanostructure interaction. © 2002 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.07.Bc Nanocrystalline materials
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.16.Dn Self-assembly
68.65.La Quantum wires (patterned in quantum wells)

Characterization of pit formation in III-nitrides grown by metalorganic chemical vapor deposition

H. K. Cho, J. Y. Lee, and G. M. Yang

Appl. Phys. Lett. 80, 1370 (2002); http://dx.doi.org/10.1063/1.1454215 (3 pages) | Cited 13 times

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Pit formation in III-nitride heterostructures such as InGaN/GaN and AlGaN/GaN grown by metalorganic chemical vapor deposition was characterized by transmission electron microscopy. The pit formation related with V defects has been reported in the InGaN/GaN multiple quantum well with high In composition [Appl. Phys. Lett. 79, 215 (2001)]. In this letter, we found that the mechanism of pit formation strongly depends on the indium and aluminum compositions in InxGa1-xN and AlxGa1-xN layers, respectively. By increasing the indium composition, the origin of pits is changed from the vertex of threading dislocations to the stacking mismatch boundaries induced by stacking faults and the three-dimensional island growth at the initial stage due to the large lattice mismatch. By increasing the aluminum composition, the origin of the pits also varied from the surface undulation due to the elastic misfit strain to the vertex of threading dislocations. In addition, several inversion domains observed in III nitrides result in pit formation in the surface of films. © 2002 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.37.Lp Transmission electron microscopy (TEM)
68.35.Ct Interface structure and roughness
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Nn Stacking faults and other planar or extended defects
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Effect of n-type modulation doping on the photoluminescence of GaN/Al0.07Ga0.93N multiple quantum wells

H. Haratizadeh, P. P. Paskov, G. Pozina, P. O. Holtz, B. Monemar, S. Kamiyama, M. Iwaya, H. Amano, and I. Akasaki

Appl. Phys. Lett. 80, 1373 (2002); http://dx.doi.org/10.1063/1.1448144 (3 pages) | Cited 7 times

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The influence of Si doping on exciton localization in modulation-doped GaN/Al0.07Ga0.93N multiple-quantum-well structures has been studied by means of photoluminescence (PL) and time-resolved PL measurements. Surprisingly, the PL decay time is constant in the range 320–420 ps for all doping levels at 2 K in these samples, due to a strong localization of the holes. The temperature dependence of radiative as well as nonradiative lifetime has also been evaluated between 2 K and room temperature for different Si doping. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.De Quantum wells
78.47.-p Spectroscopy of solid state dynamics
73.61.Ey III-V semiconductors

Self-doping of cadmium stannate in the inverse spinel structure

S. B. Zhang and Su-Huai Wei

Appl. Phys. Lett. 80, 1376 (2002); http://dx.doi.org/10.1063/1.1452789 (3 pages) | Cited 17 times

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Using first-principles total energy calculations, we have studied self-doping in the ternary transparent conducting oxide, Cd2SnO4. Formation of the CdO and SnO2 binaries limits the inverse spinel Cd2SnO4 phase into a narrow region in the atomic chemical potential (μ) space. This suggests that μSn is not independent of μCd, so a Cd-rich growth or annealing condition also implies Sn-rich, and vice versa. We found that the widely accepted intrinsic donors such as oxygen vacancy and cadmium interstitial are not responsible for the observed conductivity in Cd2SnO4: both require too much energy to form. In addition, the oxygen vacancy is rather deep. We show instead that the Sn-on-Cd antisite defect is the most probable donor responsible for the n typeness under Cd-rich conditions. © 2002 American Institute of Physics.
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71.55.Ht Other nonmetals
71.15.Nc Total energy and cohesive energy calculations
65.40.G- Other thermodynamical quantities
72.80.Jc Other crystalline inorganic semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
72.20.Fr Low-field transport and mobility; piezoresistance

Minority carrier diffusion and defects in InGaAsN grown by molecular beam epitaxy

Steven R. Kurtz, J. F. Klem, A. A. Allerman, R. M. Sieg, C. H. Seager, and E. D. Jones

Appl. Phys. Lett. 80, 1379 (2002); http://dx.doi.org/10.1063/1.1453480 (3 pages) | Cited 48 times

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To gain insight into the nitrogen-related defects of InGaAsN, nitrogen vibrational mode spectra, Hall mobilities, and minority carrier diffusion lengths are examined for InGaAsN (1.1 eV band gap) grown by molecular beam epitaxy (MBE). Annealing promotes the formation of In–N bonding, and lateral carrier transport is limited by large scale (≫mean free path) material inhomogeneities. Comparing solar cell quantum efficiencies with our earlier results for devices grown by metalorganic chemical vapor deposition (MOCVD), we find significant electron diffusion in the MBE material (reversed from the hole diffusion in MOCVD material), and minority carrier diffusion in InGaAsN cannot be explained by a “universal,” nitrogen-related defect. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.55.Eq III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
72.20.My Galvanomagnetic and other magnetotransport effects
63.20.-e Phonons in crystal lattices

Temperature-dependent Hall measurements of molecular beam epitaxial grown Si-doped AlxGa1−xN for Al mole fraction up to 0.5

M. Ahoujja, Y. K. Yeo, R. L. Hengehold, and J. E. Van Nostrand

Appl. Phys. Lett. 80, 1382 (2002); http://dx.doi.org/10.1063/1.1452795 (3 pages) | Cited 2 times

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Electrical properties of Si-doped AlxGa1−xN films grown on sapphire substrates with AlN buffer layers by gas source molecular beam epitaxy (MBE) have been investigated using temperature dependent Hall-effect measurements. These measurements show that the AlxGa1−xN sapphire interfacial layer significantly affect the electrical properties of the AlxGa1−xN layer doped with Si at a nominal value of 1×1018 cm−3. This study indicates that good quality AlxGa1−xN films can be grown for x⩽0.3 by gas source MBE, but lesser quality films are obtained for x>0.3. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.uj III-V and II-VI semiconductors

Carbon cage-like materials as potential low work function metallic compounds: Case of clathrates

V. Timoshevskii, D. Connétable, and X. Blase

Appl. Phys. Lett. 80, 1385 (2002); http://dx.doi.org/10.1063/1.1453481 (3 pages) | Cited 13 times

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We present an ab initio calculation of the electronic affinity of the hypothetical C-46 clathrate by studying its bare and hydrogenated (100) surfaces. We show that such a system shares with the diamond phase a small electronic affinity. Furthermore, contrary to the diamond phase, the possibility of endohedrally doping these cage-like systems allows to significantly raise the position of the Fermi level, resulting in a true metal with a small work function. This is illustrated in the case of the Li8C-46 doped compound. Such a class of materials might be of much interest for the design of electron-emitting devices. © 2002 American Institute of Physics.
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71.20.Tx Fullerenes and related materials; intercalation compounds
73.30.+y Surface double layers, Schottky barriers, and work functions
79.70.+q Field emission, ionization, evaporation, and desorption

Electronic passivation of Si(111) by Ga–Se half-sheet termination

R. Fritsche, E. Wisotzki, A. B. M. O. Islam, A. Thissen, A. Klein, W. Jaegermann, R. Rudolph, D. Tonti, and C. Pettenkofer

Appl. Phys. Lett. 80, 1388 (2002); http://dx.doi.org/10.1063/1.1454228 (3 pages) | Cited 5 times

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A Si(111):GaSe van der Waals surface is prepared using sequential deposition of Ga and Se at elevated temperature on a Si(111)-7×7 surface. Surface properties were investigated by soft x-ray photoelectron spectroscopy and low-energy electron diffraction. The Si(111)-1×1:GaSe surface remains with electronic surface potentials near flatband condition. © 2002 American Institute of Physics.
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81.65.Rv Passivation
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
79.60.Dp Adsorbed layers and thin films
73.30.+y Surface double layers, Schottky barriers, and work functions

Hot exciton transport in ZnSe quantum wells

Hui Zhao, Sebastian Moehl, Sven Wachter, and Heinz Kalt

Appl. Phys. Lett. 80, 1391 (2002); http://dx.doi.org/10.1063/1.1452793 (3 pages) | Cited 23 times

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The in-plane transport of excitons in ZnSe quantum wells is investigated directly by microphotoluminescence in combination with a solid immersion lens. Due to the strong Fröhlich coupling, the initial kinetic energy of the excitons is well controlled by choosing the excess energy of the excitation laser. When increasing the laser excess energy, we find a general trend of increasing transport length and more importantly a pronounced periodic quenching of the transport length when the excess energy corresponds to multiples of the LO-phonon energy. Such features show the dominant role of the kinetic energy of excitons in the transport process. Together with the excitation intensity dependence of the transport length, we distinguish the phonon wind driven transport of cold excitons and defect-limited hot exciton transport. © 2002 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
78.55.Et II-VI semiconductors
63.20.kk Phonon interactions with other quasiparticles
71.35.Gg Exciton-mediated interactions
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