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9 Nov 1998

Volume 73, Issue 19, pp. 2703-2843

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1.55 μm single-mode lasers with combined gain coupling and lateral carrier confinement by focused ion-beam implantation

H. König, J. P. Reithmaier, A. Forchel, J. L. Gentner, and L. Goldstein

Appl. Phys. Lett. 73, 2703 (1998); http://dx.doi.org/10.1063/1.122564 (3 pages) | Cited 5 times

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Laterally gain-coupled distributed feedback GaInAsP/InP lasers were fabricated by focused ion-beam implantation and rapid thermal annealing of ridge waveguide structures. An absorption grating, which interacts with the evanescent light field, is formed by a periodic reduction of the band-gap absorption in the passive sections along the ridge. Room-temperature single-mode emission was observed at 1.5 μm with a 30 dB side-mode suppression ratio. Simultaneously, the increase of the band gap in the implanted section results in improved carrier confinement, which reduces the leakage current and improves the laser performance in comparison to unimplanted ridge waveguide lasers. © 1998 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Structural and optical properties of epitaxially overgrown third-order gratings for InGaN/GaN-based distributed feedback lasers

Linda T. Romano, Daniel Hofstetter, Matthew D. McCluskey, David P. Bour, and Michael Kneissl

Appl. Phys. Lett. 73, 2706 (1998); http://dx.doi.org/10.1063/1.122565 (3 pages) | Cited 4 times

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Laser-diode heterostructures of InGaAlN containing a third-order diffraction grating for distributed optical feedback have been examined with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The grating was defined holographically and etched by chemically assisted ion-beam etching into the upper GaN confinement layer of the laser structure. After the etch step, it was overgrown with an Al0.08Ga0.92N upper cladding layer. Threading dislocations were present that initiated at the sapphire substrate, but no new dislocations were observed at the grating/Al0.08Ga0.92N interface. A comparison of TEM and SEM micrographs reveals that there is a compositional gradient in the AlGaN upper cladding layer; however, calculations show that it did not reduce the optical coupling coefficient of the grating. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.40.Eq Holographic optical elements; holographic gratings
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Ea III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.65.Cf Surface cleaning, etching, patterning

Semiconducting optical properties of silver/silica mesoporous composite

Weiping Cai, Ye Zhang, Junhui Jia, and Lide Zhang

Appl. Phys. Lett. 73, 2709 (1998); http://dx.doi.org/10.1063/1.122566 (3 pages) | Cited 42 times

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The optical absorption properties were investigated for mesoporous silica loaded with different amounts (up to 5% in weight) of silver (Ag) nanoparticles (less than 4 nm in diameter) into its pores. In contrast to the previously reported glasses containing Ag particles, in this Ag particle-loaded silica no apparent surface plasmon resonance peak of Ag particle, other than an absorption edge, was observed. This composite exhibits the optical features of a semiconductor with direct band gap. The absorption edge shifts in the range from about 200 to about 700 nm with an increasing Ag loading amount up to 5% in weight, and hence, is controllable. Adsorption of oxygen in air on the surface of Ag particles within the pores, and scattering inside the porous structure were used to explain these results. © 1998 American Institute of Physics.
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78.40.Fy Semiconductors
61.46.-w Structure of nanoscale materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Modal analysis of guiding structures patterned in a metallic photonic crystal

J. Danglot, J. Carbonell, M. Fernandez, O. Vanbésien, and D. Lippens

Appl. Phys. Lett. 73, 2712 (1998); http://dx.doi.org/10.1063/1.122567 (3 pages) | Cited 17 times

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We present a modal analysis of guiding structures patterned in a two-dimensional metallic photonic crystal. Measurements are carried out on a T-stub structure with various dimensions in the 22–40 GHz frequency band. The pronounced resonances extracted from measured transmissivity spectra are interpreted in terms of multimode propagation phenomena in the T-stub region. Experimental data are assessed by the solution of a suitable form of the 2D Helmholtz equation established for metallic propagation media. © 1998 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
84.40.Az Waveguides, transmission lines, striplines
41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.50.-p Quantum optics

Pulse compression using coupled-waveguide structures as highly dispersive elements

Yong Lee

Appl. Phys. Lett. 73, 2715 (1998); http://dx.doi.org/10.1063/1.122568 (3 pages) | Cited 8 times

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Pulse compression is experimentally demonstrated by using a coupled-waveguide structure consisting of an InGaAsP/InP semiconductor as a highly dispersive element. In this structure, waveguide dispersion associated with supermodes is significantly enhanced. The maximum temporal compression factor was 4.3 (compression from 2.2 to 0.514 ps). This result indicates that the coupled-waveguide structure has the potential for use in a simple, compact, transmissive, and sign-free dispersion compensator. © 1998 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Dynamics of gain in vertical cavity lasers and amplifiers at 1.53 μm using femtosecond photoexcitation

N. Bouché, C. Dupuy, C. Meriadec, K. Streubel, J. Landreau, L. Manin, and R. Raj

Appl. Phys. Lett. 73, 2718 (1998); http://dx.doi.org/10.1063/1.122569 (3 pages) | Cited 10 times

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Conditions for the optimization of short pulse amplification and gating times in vertical cavity laser amplifiers are elucidated using femtosecond photoexcitation. The experimental results pertaining to the temporal response are analyzed by a theoretical model taking into account the carrier heating and the Fabry–Perot nature of the cavity. A 20 dB amplification gain is obtained in a vertical cavity structure at 1.53 μm with a capacity to function at a rate >25 Gb/s. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

Fabrication of highly efficient organic electroluminescent devices

Junji Kido and Yasuhiro Iizumi

Appl. Phys. Lett. 73, 2721 (1998); http://dx.doi.org/10.1063/1.122570 (3 pages) | Cited 168 times

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Efficient organic electroluminescent (EL) devices were fabricated by using a highly fluorescent aluminum complex, tris(4-methyl-8-quinolinolato)aluminum(III) (Almq3), as an emitter layer. In addition to using this complex, a multilayer device structure, consisting of a hole-injecting layer, a hole transport layer, a dye-doped Almq3 emitting layer, and an electron transport layer, was employed in order to reduce the driving voltage as well as to maximize carrier recombination efficiency. From this device, a maximum luminance of over 140 000 cd/m2 and an external quantum efficiency of 7.1% was observed, which is the highest efficiency ever reported for organic EL devices. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices

Tapping-mode tuning fork force sensing for near-field scanning optical microscopy

Din Ping Tsai and Yuan Ying Lu

Appl. Phys. Lett. 73, 2724 (1998); http://dx.doi.org/10.1063/1.122558 (3 pages) | Cited 37 times

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A tapping-mode tuning fork force-sensing method for near-field scanning optical microscope is reported. Use of the tapping-mode tuning fork with mechanically asymmetric excitation generates better stability and sensitivity than in the shear force mode. Comparison of force curves for the two methods demonstrate that the tapping-mode tuning fork method provides a simpler and more sensitive method for near-field measurements. The method is demonstrated by imaging a sample consisting of 500 nm standard polystyrene spheres on silica in both air and water. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.10.Pz Instruments for strain, force, and torque
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Photoluminescence and electroluminescence from copper doped zinc sulphide nanocrystals/polymer composite

Wenxiu Que, Y. Zhou, Y. L. Lam, Y. C. Chan, C. H. Kam, B. Liu, L. M. Gan, C. H. Chew, G. Q. Xu, S. J. Chua, S. J. Xu, and F. V. C. Mendis

Appl. Phys. Lett. 73, 2727 (1998); http://dx.doi.org/10.1063/1.122571 (3 pages) | Cited 40 times

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Cu-doped ZnS nanocrystals were prepared in an inverse microemulsion at room temperature as well as under a hydrothermal condition. X-ray diffraction analysis showed that the diameter of the Cu-doped ZnS nanocrystals particles was about 9 nm. These particles showed a strong photoluminescence intensity and a broad emission band from 490 to 530 nm. The half-width of emission was about 60 nm. Cu-doped ZnS nanocrystals/polymethylmethacrylate composite as a light-emitting layer was used to fabricate a single layer structure electroluminescent device which had low turn on voltage (less than 5 V). The green light of electroluminescence was observed at room temperature. The electroluminescence and photoluminescence spectra were nearly identical at room temperature. © 1998 American Institute of Physics.
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78.60.Fi Electroluminescence
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.55.Et II-VI semiconductors
81.05.Qk Reinforced polymers and polymer-based composites
42.70.Jk Polymers and organics
82.70.Kj Emulsions and suspensions
85.60.Jb Light-emitting devices
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Diagnostic technique for measuring plasma parameters near surfaces in radio frequency discharges

Shahid Rauf and Mark J. Kushner

Appl. Phys. Lett. 73, 2730 (1998); http://dx.doi.org/10.1063/1.122572 (3 pages) | Cited 6 times

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A plasma diagnostic technique for measuring the electron density, electron temperature, and ion current near a surface in radio frequency (rf) discharges is proposed. The sensor uses a small wire probe to determine the plasma potential and a small metal electrode to measure the current and voltage profiles. The values of current, sheath voltage, and time derivative of sheath voltage at three distinct points during the rf cycle are used in conjunction with an analytical sheath model to determine the plasma parameters. The technique is demonstrated by implementing the diagnostic in a computer model of an inductively coupled plasma reactor which has an rf biased substrate. Although any three disjoint sets of measurements can ideally be used, a sensitivity analysis is used to show that certain sets may be more suitable in experimental systems where noise is present. © 1998 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges
52.25.Fi Transport properties
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Two different domains in a cubic boron nitride (111) surface observed by friction force microscopy

Tomohide Takami, Isao Kusunoki, Katsunori Suzuki, Kian Ping Loh, Mikka Nishitani-Gamo, Isao Sakaguchi, Takashi Taniguchi, and Toshihiro Ando

Appl. Phys. Lett. 73, 2733 (1998); http://dx.doi.org/10.1063/1.122573 (3 pages) | Cited 2 times

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A single-crystalline cubic boron nitride (c-BN) (111) surface has been studied by atomic force microscopy with simultaneous measurements of normal atomic force (constant height mode and constant force mode) and lateral (friction) force in air. On the friction force mode the different two domains observed can be attributed to the termination of the surface; boron (A side) or nitrogen (B side). 2.6 Å periodicity corresponding to the 1×1 surface unit cell as of c-BN (111) (as = a0/√ = 2.56 Å, where a0 is the lattice constant, 3.62 Å) has been observed also on the friction force mode, which is in agreement with our low-energy electron diffraction measurement. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

In situ monitoring of ion sputtering and thermal annealing of crystalline surfaces using an oblique-incidence optical reflectance difference method

X. D. Zhu and E. Nabighian

Appl. Phys. Lett. 73, 2736 (1998); http://dx.doi.org/10.1063/1.122574 (3 pages) | Cited 8 times

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We demonstrate that the morphology of crystalline surfaces during ion sputtering and thermal annealing can be monitored in situ with an oblique-incidence polarization-modulated optical reflectance difference technique. Such a technique is effective under high ambient pressures as well as ultrahigh vacuum. We studied the Ne ion sputtering and thermal annealing of Ni(111) from 623 to 823 K. We found that the rate-limiting step (with an activation energy of 1.1 eV/atom) during annealing is most likely to be direct evaporation of Ni atoms from step edges. © 1998 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.Cc Kinetics of defect formation and annealing
81.05.Bx Metals, semimetals, and alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning

Effect of twinning on the grain shape of crystallized amorphous Si0.7Ge0.3 thin films on SiO2

Hong Seung Kim and Jeong Yong Lee

Appl. Phys. Lett. 73, 2739 (1998); http://dx.doi.org/10.1063/1.122575 (3 pages)

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The grain morphology of Si0.7Ge0.3 depends on the number of the primary noncoplanar twin variants formed at the early stage of solid-phase crystallization. The grain with major twin bands of a single twin variant parallel to a {111} plane develops an elongated shape, owing to the preferential growth in a 〈112〉 direction along twins. When the grain has major twin bands of two or more noncoplanar twin variants, the growth front between noncoplanar twin bands develops as fast as the 〈112〉 direction along twins propagates, because such a growth front is formed from a {111} ledge. As results, the grain becomes more or less equiaxed due to the increasing number of primary, noncoplanar twin variants. © 1998 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
68.55.-a Thin film structure and morphology

Influence of GaAs capping on the optical properties of InGaAs/GaAs surface quantum dots with 1.5 μm emission

Hideaki Saito, Kenichi Nishi, and Shigeo Sugou

Appl. Phys. Lett. 73, 2742 (1998); http://dx.doi.org/10.1063/1.122576 (3 pages) | Cited 87 times

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Uncapped InGaAs quantum dots (surface quantum dots) on a GaAs substrate emit photoluminescence at a long wavelength of 1.53 μm at room temperature. When the surface dots are covered by a GaAs cap layer, the emission energy of the dots increases by 287 meV. This large energy shift is mainly caused by inducing compressive stress from the cap layer. In segregation on the surface led to greater photoluminescence intensity in the surface quantum dots even at room temperature due to the suppression of nonradiative surface recombination.© 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Fx Diffusion; interface formation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena

Incongruent transfer related to surface segregation in pulsed-laser-deposited La–Ca–Mn–O films

Wei Zhang, Xiaoru Wang, and Ian W. Boyd

Appl. Phys. Lett. 73, 2745 (1998); http://dx.doi.org/10.1063/1.122577 (3 pages) | Cited 10 times

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A range of La–Ca–Mn–O films have been grown using pulsed-laser deposition on hot Si substrates. The composition of the films is found to be strongly dependent on substrate temperature (Ts) with the calcium and oxygen content being significantly reduced at high Ts (>700 °C). The kinetic energies of the various ions in the laser generated plume are found to be distributed in the 10–100 eV range, high enough to induce resputtering from deposited films. Surface segregation was also observed in the films grown at high Ts (>700 °C), resulting in a Ca-rich surface. Preferential resputtering of these surface Ca-rich segregated samples, driven by a mixture of high energy ion irradiation and thermally activated processes, is proposed to explain the observed phenomena. © 1998 American Institute of Physics.
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68.55.Nq Composition and phase identification
64.75.-g Phase equilibria
81.15.Fg Pulsed laser ablation deposition
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.35.Fx Diffusion; interface formation
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.66.Bi Elemental solids
61.66.Dk Alloys

Electromigration threshold in damascene versus plasma-etched interconnects

Joris Proost, Karen Maex, and Luc Delaey

Appl. Phys. Lett. 73, 2748 (1998); http://dx.doi.org/10.1063/1.122578 (3 pages) | Cited 9 times

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Electromigration threshold has been measured for unpassivated damascene Al(Cu) interconnects by drift experiments on Blech-type test structures, and results are compared to equivalent plasma-etched lines. When using a damascene implementation, the critical product of current density and stripe length increases significantly. As a result, the incubation period, needed for Cu depletion beyond a critical length, is increased over a wide temperature range (155–230 °C). This is shown to be an intrinsic effect, directly controlling the relative electromigration performance of both metallization schemes. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
73.61.At Metal and metallic alloys

The effect of doping and growth stoichiometry on the core structure of a threading edge dislocation in GaN

A. F. Wright and Ulrike Grossner

Appl. Phys. Lett. 73, 2751 (1998); http://dx.doi.org/10.1063/1.122579 (3 pages) | Cited 111 times

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Density-functional-theory calculations have been performed to study the effect of doping and growth stoichiometry on the core structure of a threading edge dislocation in GaN. Four candidate structures were examined and their formation energies were found to depend strongly on Fermi level and growth stoichiometry. A structure having gallium vacancies at the dislocation core is predicted to be most stable in n-type material grown under nitrogen-rich conditions, while a structure without vacancies is most stable in p-type material grown under these conditions. In material grown under gallium-rich conditions, a structure having nitrogen vacancies at the dislocation core is predicted to be most stable in p-type material, whereas a variety of core structures should be present in n-type material. Edge dislocations are predicted to behave as electron traps in n-type material and may act as hole traps in p-type material depending on the growth conditions. © 1998 American Institute of Physics.
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61.72.Lk Linear defects: dislocations, disclinations
71.55.Eq III-V semiconductors
61.72.Bb Theories and models of crystal defects
61.66.Bi Elemental solids
61.66.Dk Alloys
71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect

Deposition of transition metal carbide superlattices using C60 as a carbon source

Lars Norin, Hans Högberg, Jun Lu, Ulf Jansson, and Jan-Olle Malm

Appl. Phys. Lett. 73, 2754 (1998); http://dx.doi.org/10.1063/1.122580 (3 pages) | Cited 5 times

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Epitaxial films of TiC and VC can be deposited at low temperatures on Mg(001) substrates by coevaporation of the metals with C60 in a ultrahigh vacuum system. This process was used to deposit TiC/VC (001) superlattices on MgO(001) at 400 °C. The superlattice structure was characterized with low electron energy diffraction, x-ray diffraction, and transmission electron microscopy (TEM). Cross-sectional high-resolution TEM showed good registry between the different carbide layers. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
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Thermal effects in widely tunable germanium terahertz lasers

E. Bründermann, D. R. Chamberlin, and E. E. Haller

Appl. Phys. Lett. 73, 2757 (1998); http://dx.doi.org/10.1063/1.122581 (3 pages) | Cited 14 times

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We report laser emission from Be-doped Ge lasers at high repetition rates of up to 45 kHz which is one order of magnitude higher than previously reported. Laser radiation was detected from Ge:Be crystals with volumes as small as 0.5 mm3 and with intercontact distances down to 1 mm. We present a thermal analysis and derive the design parameters for continuous wave Ge lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.60.Pk Continuous operation

Metamorphic InGaAs/InAlAs quantum well structures grown on GaAs substrates for high electron mobility transistor applications

M. Behet, K. van der Zanden, G. Borghs, and A. Behres

Appl. Phys. Lett. 73, 2760 (1998); http://dx.doi.org/10.1063/1.122582 (3 pages) | Cited 18 times

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Modulation-doped In0.5Ga0.5As/In0.5Al0.5As quantum well structures grown by molecular beam epitaxy on GaAs substrates using a relaxed AlGaAsSb buffer showed carrier mobilities of 8500 cm2/V s for a sheet concentration of 3.5×1012 cm−2 at room temperature. The crystallinity of the quaternary buffer layer was verified by x-ray diffractometry. Transistors with 0.25×100 μm2 gates demonstrated transconductance values as high as 800 mS/mm. S-parameter measurements revealed a cutoff frequency fT of 87 GHz and a maximum oscillation frequency fMAX of 140 GHz (both extrinsic values). © 1998 American Institute of Physics.  
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.Tv Field effect devices
84.40.-x Radiowave and microwave (including millimeter wave) technology
73.61.Ey III-V semiconductors

Electronic structure of 8-hydroxyquinoline aluminum/LiF/Al interface for organic electroluminescent device studied by ultraviolet photoelectron spectroscopy

T. Mori, H. Fujikawa, S. Tokito, and Y. Taga

Appl. Phys. Lett. 73, 2763 (1998); http://dx.doi.org/10.1063/1.122583 (3 pages) | Cited 108 times

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Electronic structures of the 8-hydroxyquinoline aluminum (Alq3)/LiF/Al and Alq3/Al interfaces were measured by ultraviolet photoelectron spectroscopy. Shifts of the highest occupied molecular orbital level and the vacuum level of the Alq3 layer due to insertion of a thin LiF layer were observed. This result indicates that the thin LiF layer at the Alq3/Al interface reduces barrier height for electron injection from the Al to Alq3. We, therefore, conclude that lowering of the driving voltage in an organic electroluminescent device with a thin LiF layer is attributable to the reduction of the barrier height. © 1998 American Institute of Physics.  
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence

Optical characterization of porous silicon embedded with CdSe nanoparticles

A. I. Belogorokhov, L. I. Belogorokhova, A. Pérez-Rodríguez, J. R. Morante, and S. Gavrilov

Appl. Phys. Lett. 73, 2766 (1998); http://dx.doi.org/10.1063/1.122584 (3 pages) | Cited 12 times

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Arrays of a few nanometer-size clusters have been realized using a porous silicon (PS) matrix by filling its pores with CdSe. The photoluminescence (PL) peak from the embedded area of the PS samples with different luminescence stabilizes at 1.79 eV. This has been interpreted as due to emission from the CdSe clusters with an average size of about 3–5 nm. Likewise, the PL and Raman scattering spectra of the pure PS area of the samples have been compared with those obtained from the embedded areas. PL spectra were examined as a function of laser irradiation. Finally, to analyze the possibility of the formation of metal/porous semiconductor contacts, cross-section structures have been observed by scanning electron microscopy in the electron-beam-induced current mode. © 1998 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.55.Mb Porous materials
78.55.Ap Elemental semiconductors
78.66.Hf II-VI semiconductors
61.46.-w Structure of nanoscale materials
78.30.Na Fullerenes and related materials

Tunneling characteristics of nonuniform ultrathin oxides

D. Z.-Y. Ting

Appl. Phys. Lett. 73, 2769 (1998); http://dx.doi.org/10.1063/1.122585 (3 pages) | Cited 5 times

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The reverse-bias current–voltage characteristics of metal–oxide–silicon tunnel structures containing nonuniform ultrathin oxide layers are analyzed using a numerical three-dimensional quantum mechanical scattering calculation. We find that, in general, roughness at the Si/SiO2 interface renders the oxide layer more permeable, but does not qualitatively alter I–V characteristics. In the direct tunneling regime interface roughness induces lateral localization of wave functions which leads to preferential current paths, and is characterized by current densities which increase with island size. In the Fowler–Nordheim tunneling regime, however, interface roughness affects transport primarily through scattering, which increases with island size, and results in current densities which decrease with island size. We have also shown that appropriate one-dimensional models may be used to estimate the effect of interface roughness in limiting cases. © 1998 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
68.35.Ct Interface structure and roughness
73.25.+i Surface conductivity and carrier phenomena
73.20.-r Electron states at surfaces and interfaces

Transfer of patterned ion-cut silicon layers

C. H. Yun, A. B. Wengrow, N. W. Cheung, Y. Zheng, R. J. Welty, Z. F. Guan, K. V. Smith, P. M. Asbeck, E. T. Yu, and S. S. Lau

Appl. Phys. Lett. 73, 2772 (1998); http://dx.doi.org/10.1063/1.122586 (3 pages) | Cited 9 times

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The technique of transferring patterned ion-cut layers from one Si wafer to another was demonstrated. The starting silicon wafer was masked with checkerboard and line patterns with a 3 μm thick polymethylmethacrylate/photoresist and was implanted with 5×1016 H+ ions/cm2 at 150 keV. After stripping off the mask, the wafer was bonded to an oxide-coated receptor wafer through low-temperature direct wafer bonding. Heat treatment of this bonded pair showed that the hydrogen-induced silicon surface layer cleavage (ion cut) could propagate throughout about 16 μm×16 μm of nonimplanted material with implanted regions only 4 μm wide. Mask width, spacing, and implantation profiles through the mask shape were shown to have effects on the internal microfracturing mechanisms. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer
85.40.Ry Impurity doping, diffusion and ion implantation technology

Interwell inhomogeneity of carrier injection in InGaN/GaN/AlGaN multiquantum well lasers

K. Domen, R. Soejima, A. Kuramata, K. Horino, S. Kubota, and T. Tanahashi

Appl. Phys. Lett. 73, 2775 (1998); http://dx.doi.org/10.1063/1.122587 (3 pages) | Cited 10 times

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A simulation of current flow for an InGaN/GaN/AlGaN multiquantum well (MQW) laser showed that generation of the optical gain is inhomogeneous across the MQW due to inhomogeneous carrier injection. Laser diodes with three and five wells in MQW were compared to experimentally investigate inhomogeneous carrier injection. We found that external quantum efficiency was significantly improved by a reduction in the number of wells from five to three. The result was explained quantitatively by the fact that the five-well laser had a larger internal loss and a poorer internal quantum efficiency due to the inhomogeneous carrier injection. © 1998 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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