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30 Apr 2001

Volume 78, Issue 18, pp. 2617-2804

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Investigation of the emission mechanism in InGaN/GaN-based light-emitting diodes

T. Wang, J. Bai, S. Sakai, and J. K. Ho

Appl. Phys. Lett. 78, 2617 (2001); http://dx.doi.org/10.1063/1.1368374 (3 pages) | Cited 31 times

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The exciton-localization effect and quantum-confine Stark effect (QCSE) on the performance of InGaN/GaN-based light-emitting diodes (LEDs) have been investigated with regard to indium mole fraction and well thickness by means of temperature-dependent and excitation-power-dependent photoluminescence measurements. The exciton-localization effect can be enhanced by increasing the indium mole fraction or increasing well thickness but up to 2.5 nm. The QCSE is monotonically enhanced with increasing indium concentration or well thickness. The output power of the LED can be increased by the enhanced exciton-localization effect; however, the QCSE has much stronger influence on the output power of LEDs than the exciton-localization effect, which should be taken into account for further improving the performance of InGaN/GaN-based LEDs. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
71.35.-y Excitons and related phenomena

Far-infrared surface-plasmon quantum-cascade lasers at 21.5 μm and 24 μm wavelengths

Raffaele Colombelli, Federico Capasso, Claire Gmachl, Albert L. Hutchinson, Deborah L. Sivco, Alessandro Tredicucci, Michael C. Wanke, A. Michael Sergent, and Alfred Y. Cho

Appl. Phys. Lett. 78, 2620 (2001); http://dx.doi.org/10.1063/1.1367304 (3 pages) | Cited 81 times

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Quantum-cascade lasers operating above 20 μm (at λ∼21.5 μm and λ∼24 μm) wavelength are reported. Pulsed operation was obtained up to 140 K and with a peak power of a few milliwatts at cryogenic temperatures. Laser action originates from interminiband transitions in “chirped” superlattice active regions. The waveguides are based on surface-plasmon modes confined at a metal–semiconductor interface. The wavelengths were chosen in order to avoid major phonon absorption bands, which are particularly strong at energies just above the reststrahlen band. We also report on a 21.5-μm-wavelength laser based on a two-sided interface-plasmon waveguide. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Optical parametric generation of femtosecond pulses up to 9 μm with LiInS2 pumped at 800 nm

F. Rotermund, V. Petrov, F. Noack, L. Isaenko, A. Yelisseyev, and S. Lobanov

Appl. Phys. Lett. 78, 2623 (2001); http://dx.doi.org/10.1063/1.1369386 (3 pages) | Cited 12 times

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We demonstrate direct access to the 4.8–9 μm spectral region with 800 nm, 1 kHz pumping of a femtosecond optical parametric amplifier based on the wide-gap wurtzite-type LiInS2. LiInS2 did not exhibit two-photon absorption at 800 nm and seems applicable at this pump wavelength with intensities of the order of 100 GW/cm2 for down-conversion of high energy ultrashort pulses up to its mid-IR edge at ≈12 μm. © 2001 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
78.66.Li Other semiconductors

Nonlinear coaxial photonic crystal

Louis Poirier and Alain Haché

Appl. Phys. Lett. 78, 2626 (2001); http://dx.doi.org/10.1063/1.1367296 (3 pages) | Cited 13 times

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We demonstrate that large-scale photonic crystals can be used to simulate nonlinear optical effects occurring in real photonic crystals. A crystal made of coaxial segments with periodic impedance is used to create a stop band in transmission near 10 MHz. When a semiconductor rectifying diode is added to the crystal, a nonlinear mode of propagation appears within the forbidden band gap. It originates from a breaking of symmetry and an intensity-dependent attenuation similar to that encountered in saturable absorbers. Experimental results agree well with a theory based on a simple coupled-mass model with nonlinear resistive force. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.65.-k Nonlinear optics
78.20.-e Optical properties of bulk materials and thin films

Optical mode loss and gain of multiple-layer quantum-dot lasers

P. M. Smowton, E. Herrmann, Y. Ning, H. D. Summers, P. Blood, and M. Hopkinson

Appl. Phys. Lett. 78, 2629 (2001); http://dx.doi.org/10.1063/1.1366652 (3 pages) | Cited 22 times

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Using an electrically pumped multisection technique, we have directly measured the internal optical mode loss of semiconductor-laser structures containing 1, 3, 5, and 7 layers of uncoupled InGaAs quantum dots. The optical loss does not increase with the number of dot layers so higher net modal gain can be achieved by using multiple layers. The maximum modal gain obtained from the ground state increases with dot layer number from 10±4 cm−1 for a single layer to 49±4 cm−1 for the 7 layer sample, which is typical of the threshold gain requirement of a 350 μm long device with uncoated facets. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.La Quantum dots

Wafer bonded 1.55 μm vertical-cavity lasers with continuous-wave operation up to 105 °C

Adil Karim, Patrick Abraham, Daniel Lofgreen, Yi-Jen Chiu, Joachim Piprek, and John Bowers

Appl. Phys. Lett. 78, 2632 (2001); http://dx.doi.org/10.1063/1.1368377 (2 pages) | Cited 15 times

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We report 105 °C continuous-wave, electrically pumped operation of a 1526 nm vertical-cavity surface-emitting laser. An InP/InGaAsP active region was wafer bonded to GaAs/AlGaAs mirrors, with a superlattice barrier to reduce the number of nonradiative recombination centers in the bonded active region. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Fd III-V semiconductors

Observation of sub-100-fs optical response from spin-coated films of squarylium dye J aggregates

Makoto Furuki, Minquan Tian, Yasuhiro Sato, Lyong Sun Pu, Hitoshi Kawashima, Satoshi Tatsuura, and Osamu Wada

Appl. Phys. Lett. 78, 2634 (2001); http://dx.doi.org/10.1063/1.1369621 (3 pages) | Cited 15 times

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For spin-coated films of squarylium dye J aggregates, ultrafast nonlinear optical responses were investigated by pump–probe measurements. By using a broadband mode-locked titanium:sapphire laser, we succeeded in observing the optical response with a time resolution of better than 60 fs. Time-resolved transmission data are shown for different excitation wavelengths, resonant to the excitonic absorption band and off-resonant. Relaxation times of the absorption saturation were evaluated to be 140 fs (fast component) and 950 fs (slow component) in the case of resonant excitation and 98 fs in the case of off-resonant excitation. © 2001 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
42.79.Wc Optical coatings
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.47.-p Spectroscopy of solid state dynamics
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Wavelength tuning in InGaAs/InGaAsP quantum well lasers using pulsed-photoabsorption-induced disordering

T. K. Ong, Y. C. Chan, Y. L. Lam, and B. S. Ooi

Appl. Phys. Lett. 78, 2637 (2001); http://dx.doi.org/10.1063/1.1362329 (3 pages) | Cited 10 times

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Pulsed-laser irradiation followed by rapid thermal annealing was used to induce layer disordering of an InGaAs/InGaAsP laser structure. A band gap shift larger than 160 nm was achieved using energy densities of about 3.9 mJ mm−2 with 4800 pulses of laser irradiation. Transmission electron microscopy and photoluminescence were used to understand the possible effect of the laser irradiation on the material structure. Band gap-tuned lasers exhibiting blueshift up to 82 nm were obtained. This approach offers the prospect of a powerful and relatively simple postgrowth process for integrating multiple-wavelength lasers for wavelength-division-multiplexing applications. © 2001 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
81.05.Ea III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
42.60.By Design of specific laser systems
73.21.Fg Quantum wells
78.67.De Quantum wells
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
71.20.Nr Semiconductor compounds

Theoretical performance and structure optimization of 3.5–4.5 μm InGaSb/InGaAlSb multiple-quantum-well lasers

A. D. Andreev, E. P. O’Reilly, A. R. Adams, and T. Ashley

Appl. Phys. Lett. 78, 2640 (2001); http://dx.doi.org/10.1063/1.1369146 (3 pages) | Cited 16 times

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We present a comprehensive theoretical investigation to optimize 3.5–4.5 μm InGaSb/InGaAlSb quantum-well (QW) lasers grown on ternary InGaSb substrates. We use an eight-band k⋅P Hamiltonian to calculate the Auger recombination and optical absorption coefficients in the active region, as well as the gain and threshold characteristics. The dominant Auger process involves hole excitation from the QW to unbound valence states. For structure optimization we varied the Ga content in the substrate and QW barrier layers. The optimized structure was obtained by maximizing the strain in the QWs, despite the Auger coefficient also increasing with strain. It is, therefore, demonstrated that the main aim for midinfrared laser optimization can be minimization of the threshold carrier density rather than reduction of the Auger coefficient. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness

Switching dynamics of suspended mesogenic polymer microspheres

Darran R. Cairns, Merwin Sibulkin, and Gregory P. Crawford

Appl. Phys. Lett. 78, 2643 (2001); http://dx.doi.org/10.1063/1.1367292 (3 pages) | Cited 16 times

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Ordered polymer microspheres were produced by photo-polymerizing reactive nematic liquid crystal droplets suspended in glycerol, thus capturing the mesogenic order indefinitely. The electro-optic switching of these structures suspended in a fluid is investigated and described by a simple phenomenological model. © 2001 American Institute of Physics.
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61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems
42.70.Df Liquid crystals
78.20.Jq Electro-optical effects
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Voltage–current characteristics of high-current glow discharges

K. Takaki, D. Taguchi, and T. Fujiwara

Appl. Phys. Lett. 78, 2646 (2001); http://dx.doi.org/10.1063/1.1369612 (3 pages) | Cited 14 times

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The voltage–current characteristics of glow discharges in gas mixture (N2:O2 = 8:2) at a pressure of 10 Torr were obtained with the discharge current up to 150 A. Parallel-plane electrodes with a diameter of 10.7 cm and a discharge chamber with co-axial geometry were used to produce glow discharge with high current. The glow discharge voltage was almost constant until the whole surface of the cathode was covered with glow, i.e., until the discharge current became 3.7 A in our experimental condition (a normal glow discharge mode). The voltage, however, increased with the current when the glow covered over the cathode (an abnormal glow discharge mode). The electron density in positive column of the high-current glow discharge was obtained to be 3×1011 cm−3 from Langmuir probe measurements. © 2001 American Institute of Physics.
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52.80.Hc Glow; corona
52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements

Radio-frequency plasma jet generator of singlet delta oxygen with high yield

Josef Schmiedberger and Hiroo Fujii

Appl. Phys. Lett. 78, 2649 (2001); http://dx.doi.org/10.1063/1.1367899 (3 pages) | Cited 26 times

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O2(a 1Δg) was generated in a flowing discharge of a radio-frequency (rf) hollow electrode. The radio frequency was 99.9 MHz and the rf power was 200 W. The discharge was done in the gas mixture O2:N2:NO = 200:20:10 sccm and then it was chilled reactively by the mixture Ar:NO2=200:10 sccm. The O2(a 1Δg) relative yield of 32% was achieved at the pressure of 0.43 Torr. Usage of the mixtures O2:NO = 200:100 sccm and Ar:NO2 = 100:100 sccm resulted in the O2(a 1Δg) yield of 25% at the pressure of 0.6–0.9 Torr. The effluent was mixed with molecular iodine in a far afterglow region and it was tested in an oxygen–iodine laser. The iodine flow rate was 0.3 mmol/min. A strong enhancement of atomic iodine spontaneous emission at the wavelength of 1315 nm was observed in the optical resonator. © 2001 American Institute of Physics.
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52.75.-d Plasma devices
42.55.Lt Gas lasers including excimer and metal-vapor lasers
52.80.Pi High-frequency and RF discharges
52.30.-q Plasma dynamics and flow
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Direct observation of a critical length effect in dual-damascene Cu/oxide interconnects

Ennis T. Ogawa, Alexander J. Bierwag, Ki-Don Lee, Hideki Matsuhashi, Patrick R. Justison, Anup N. Ramamurthi, Paul S. Ho, Volker A. Blaschke, David Griffiths, Anne Nelsen, Mark Breen, and Robert H. Havemann

Appl. Phys. Lett. 78, 2652 (2001); http://dx.doi.org/10.1063/1.1365414 (3 pages) | Cited 18 times

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Electromigration results have provided clear evidence of a short or “Blech” length effect in dual- damascene, Cu/oxide, multilinked interconnects. The test structure incorporates a repeated chain of Blech-type line elements and is amenable to failure analysis tools such as focused ion beam imaging. This large interconnect ensemble provides a statistical representation of electromigrationinduced damage in the regime where steady-state interconnect stress is manifest. Statistical analysis yields a critical length of 90 μm for interconnects with line width 0.5 μm at j = 1.0×106 A/cm2 and T = 325 °C. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
66.30.Qa Electromigration
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.40.Ls Metallization, contacts, interconnects; device isolation

Photon energy dependence of the sign of the current-induced absorption polarization sensitivity in degenerate semiconductors

B. S. Ryvkin, E. A. Avrutin, and A. C. Walker

Appl. Phys. Lett. 78, 2655 (2001); http://dx.doi.org/10.1063/1.1367290 (3 pages) | Cited 2 times

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We theoretically analyze the effect of current-induced polarization dependence of absorption (fundamental and intersubband) and gain in degenerate semiconductors. The sign of the currentinduced polarization selectivity of absorption is shown to depend on the energy of the initial (or final) state of the transition with respect to the Fermi level and, therefore, on the photon energy. The effect is predicted to be important for understanding and, potentially, engineering polarization properties of devices such as vertical-cavity surface-emitting lasers. © 2001 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
42.55.Px Semiconductor lasers; laser diodes

Characterization of the surface irregularities of cubic GaN using micro-Raman spectroscopy

Ming S. Liu, Steven Prawer, Les A. Bursill, D. J. As, and R. Brenn

Appl. Phys. Lett. 78, 2658 (2001); http://dx.doi.org/10.1063/1.1367303 (3 pages) | Cited 2 times

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The surface irregularities of molecular-beam-epitaxy-grown cubic GaN on GaAs substrates were characterized by micro-Raman spectroscopy. Some surface irregularities are found to be the result of the mixed phases of cubic (zinc-blende) and hexagonal (wurtzite) GaN, while others originate from the alloying of GaN with the GaAs substrate. The polarization scattering of the surface irregularities suggests that misoriented wurtzite GaN clusters sit on or are imbedded in the cubic GaN layer. It is revealed that the crystalline defects created during the growth of cubic GaN induce a growth of hexagonal GaN and, therefore, the surface irregularities consist of a phase mixture of cubic and hexagonal GaN polytypes. © 2001 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Observation of current crowding near fabricated voids in gold lines

R. Yongsunthon, A. Stanishevsky, J. McCoy, and E. D. Williams

Appl. Phys. Lett. 78, 2661 (2001); http://dx.doi.org/10.1063/1.1368190 (3 pages) | Cited 13 times

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The spatial variation of current density in lines with model void defects fabricated using focused-ion beam milling has been imaged using magnetic force microscopy (MFM). At current densities of 3–4×106 A/cm2, an asymmetry in the MFM signal is clearly visible at (1×1) μm2 and (0.5×0.5) μm2 notches at the edge of a 10 μm wide line. Comparison to a simple model calculation suggests that the asymmetry is due to current crowding, with the displaced current 70% localized to within 1μm of the notch. © 2001 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Qa Electromigration

Anatase TiO2 thin films grown on lattice-matched LaAlO3 substrate by laser molecular-beam epitaxy

M. Murakami, Y. Matsumoto, K. Nakajima, T. Makino, Y. Segawa, T. Chikyow, P. Ahmet, M. Kawasaki, and H. Koinuma

Appl. Phys. Lett. 78, 2664 (2001); http://dx.doi.org/10.1063/1.1365412 (3 pages) | Cited 58 times

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Epitaxial anatase thin films were fabricated on lattice-matched (−0.2%) LaAlO3 (001) substrates in the layer-by-layer fashion by laser molecular-beam epitaxy. X-ray diffraction and transmission electron microscope show the films to exhibit high crystallinity and atomically defined interfaces. By virtue of the adoption of LaAlO3 substrate, which is transparent to photoexcitation of TiO2, optical band gaps could be determined to be 3.3 eV at room temperature. A photoluminescence band due to recombination of self-trapped excitons was observed at 5 K to give the peak maximum at 2.2 eV. As a result of the high degree of orientation of the epitaxial films, anisotropic optical absorption was clearly observed. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.55.Hx Other solid inorganic materials
78.66.Nk Insulators
68.55.-a Thin film structure and morphology
71.35.Aa Frenkel excitons and self-trapped excitons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Depth profiling of ZnO thin films by cathodoluminescence

H. C. Ong, A. S. K. Li, and G. T. Du

Appl. Phys. Lett. 78, 2667 (2001); http://dx.doi.org/10.1063/1.1368187 (3 pages) | Cited 30 times

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The depth-resolved luminescence of the ZnO epilayer has been studied by using cathodoluminescence (CL) at room temperature. Other than the usual excitonic and deep level emissions, two peaks at 3.13 and 2.57 eV have been observed and are attributed to the defects. The variation of all the emission peaks has been examined as a function of accelerating voltage. The decrease of near-band edge emissions with depth is due to the internal absorption caused by the pronounced band tail. The deep level emission, however, is shown to increase with increasing depth. We have modeled the CL spectra with the consideration of internal absorption and determine the profile of the Urbach parameter, EUrbach, to study the structural imperfection at different depths. A strong dependence between the intensity ratios of the defect emissions to the excitonic emission and the imperfection of material has been found. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Dz II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
71.55.Gs II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.-y Defects and impurities in crystals; microstructure
71.35.-y Excitons and related phenomena

Robustness of ultrathin aluminum oxide dielectrics on Si(001)

M. Copel, E. Cartier, E. P. Gusev, S. Guha, N. Bojarczuk, and M. Poppeller

Appl. Phys. Lett. 78, 2670 (2001); http://dx.doi.org/10.1063/1.1367902 (3 pages) | Cited 63 times

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The stability of Al2O3 films during thermal processing will help determine their usefulness as an alternative gate dielectric for advanced complementary metal-oxide-semiconductor devices. We used medium energy ion scattering and atomic force microscopy to examine the degradation of ultrathin Al2O3 layers under ultrahigh vacuum annealing and the effects of low-temperature oxidation. No degradation is observed at 900 °C, but voids appear at higher temperatures. Growth of interfacial SiO2 takes place during low-pressure oxidation at 600 °C, which may limit the capacitance of extremely thin structures. © 2001 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
81.65.Mq Oxidation
68.60.Dv Thermal stability; thermal effects
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Young’s modulus measurements and grain boundary sliding in free-standing thin metal films

A. J. Kalkman, A. H. Verbruggen, and G. C. A. M. Janssen

Appl. Phys. Lett. 78, 2673 (2001); http://dx.doi.org/10.1063/1.1367896 (3 pages) | Cited 39 times

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Young’s modulus of free-standing polycrystalline Al, Au, and W films with submicron thickness has been studied using a dynamic bulge-testing technique. For Au and Al films a clear frequency dependence of the modulus is observed at room temperature in the range 1×10−4–0.5 rad/s. The values of the moduli are considerably smaller than the corresponding values of bulk material. The modulus of W films measured under the same conditions does not depend on frequency and is equal to the bulk value. The origin of the behavior found in the Al and Au films is anelastic grain boundary sliding. As a consequence of the relatively small grain size of thin polycrystalline films this phenomenon is observable at room temperature in films with a relatively low melting point. © 2001 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
68.60.Bs Mechanical and acoustical properties

Local environment of rare-earth dopants in silica–titania–alumina glasses: An extended x-ray absorption fine structure study at the K edges of Er and Yb

F. d’Acapito, S. Mobilio, L. Santos, and Rui M. Almeida

Appl. Phys. Lett. 78, 2676 (2001); http://dx.doi.org/10.1063/1.1369417 (3 pages) | Cited 15 times

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We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to the K edge of rare earths (RE) in a study of the local environments of diluted Er and Yb dopants in silicate glasses, prepared by sol-gel processing. Silica–titania–alumina glasses, doped with RE ions at and above the luminescence quenching concentration were investigated and EXAFS spectra were recorded in a wide k range up to 160 nm−1 not obtainable when working at the LIII edge. No direct RE–RE correlations were found, providing a strong support for previous studies. A model of RE aggregation derived from these observations is also discussed. © 2001 American Institute of Physics.
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61.43.Fs Glasses
78.70.Dm X-ray absorption spectra
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.05.Kf Glasses (including metallic glasses)

Amplified spontaneous emission from a soluble thiophene-based oligomer

M. Anni, G. Gigli, R. Cingolani, M. Zavelani-Rossi, C. Gadermaier, G. Lanzani, G. Barbarella, and L. Favaretto

Appl. Phys. Lett. 78, 2679 (2001); http://dx.doi.org/10.1063/1.1369392 (3 pages) | Cited 15 times

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Optical gain is demonstrated, through pump-probe measurement, in a spin-coated film of a quinquethiophene-S,S-dioxide. The temporal evolution of the gain as a function of the pump intensity shows a progressive shortening of the lifetime as the pump intensity increases. The photoluminescence spectra show line narrowing for excitation intensity higher than 960 μJ cm−2. From these measurements, we conclude that oligothiophene-S,S-dioxides are valuable candidates for thin-film organic light amplifier and lasers. © 2001 American Institute of Physics.
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42.55.Mv Dye lasers
78.45.+h Stimulated emission
78.55.Kz Solid organic materials

Selectivity of nanocavities and dislocations for gettering of Cu and Fe in silicon

B. Stritzker, M. Petravic, J. Wong-Leung, and J. S. Williams

Appl. Phys. Lett. 78, 2682 (2001); http://dx.doi.org/10.1063/1.1363689 (3 pages) | Cited 5 times

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The selectivity of interstitial-based extended defects (loops) and nanocavities for the gettering of Cu and Fe in Si has been studied. Controlled amounts of Cu and Fe were introduced by ion implantation into wafers containing pre-existing nanocavities and/or dislocations. Results show that Cu has a strong preference for gettering to open volume defects, even when high concentrations of interstitial-based loops are present in close proximity. However, the gettering of Fe in samples containing both vacancy- and interstitial-type defects is more complex, with Fe accumulation at all regions in the sample which contain defects, whether they are vacancy- or interstitial-like in character. © 2001 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.82.Fk Semiconductors
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
85.40.Ry Impurity doping, diffusion and ion implantation technology
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Evolution of structure, morphology, and reactivity of hydrogenated amorphous silicon film surfaces grown by molecular-dynamics simulation

Shyam Ramalingam, Saravanapriyan Sriraman, Eray S. Aydil, and Dimitrios Maroudas

Appl. Phys. Lett. 78, 2685 (2001); http://dx.doi.org/10.1063/1.1367298 (3 pages) | Cited 27 times

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The relationship between the structure, H coverage, morphology, and reactivity of plasma deposited hydrogenated amorphous silicon (a-Si:H) film surfaces was investigated using molecular-dynamics simulations. Surfaces of a-Si:H films grown with SiH3 as the sole deposition precursor are found to be remarkably smooth due to a valley-filling mechanism where mobile precursors, such as SiH3 and Si2H6, diffuse and react with dangling bonds in the valleys on the surface. Surface valleys are reactive due to the increased concentration of dangling bonds and decreased H coverage in these regions. The previously speculated physisorbed configuration, where SiH3 is weakly bound to the surface through a H atom, is highly unlikely to be the mobile precursor state. © 2001 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Inversion domains in GaN layers grown on (111) silicon by molecular-beam epitaxy

A. M. Sánchez, F. J. Pacheco, S. I. Molina, R. Garcia, P. Ruterana, M. A. Sánchez-García, and E. Calleja

Appl. Phys. Lett. 78, 2688 (2001); http://dx.doi.org/10.1063/1.1368373 (3 pages) | Cited 8 times

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Transmission electron microscopy is used to investigate GaN layers grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy. These layers were grown on top of different AlN buffer layers. Multiple-beam dark-field techniques applied to both cross-sectional and planar-view samples show the presence of inversion domains. These domains grow directly from the interface with the Si(111) substrate. Such observations are related, as in the case of growth on sapphire, to the symmetry difference between wurtzite and diamond. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
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