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20 Apr 1998

Volume 72, Issue 16, pp. 1939-2058

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Organic light-emitting diodes using a gallium complex

Yuji Hamada, Hiroshi Kanno, Takeshi Sano, Hiroyuki Fujii, Yoshitaka Nishio, Hisakazu Takahashi, Tatsuro Usuki, and Kenichi Shibata

Appl. Phys. Lett. 72, 1939 (1998); http://dx.doi.org/10.1063/1.121448 (3 pages) | Cited 24 times

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A gallium complex (GaMq2Cl) consisting of two 2-methyl-8-hydroxyquinolines (Mq) and a chlorine was synthesized and used for the fabrication of organic light-emitting diodes (OLEDs). The photoluminescent peak of GaMq2Cl at 492 nm was as strong in intensity as that of tris(8-hydroxyquinolinato)aluminum (Alq3). The OLED using GaMq2Cl as an emitting material showed blue-green luminance of 10 490 cd/m2. When it was used as an electron transport material in a rubrene doped cell, an OLED with a high luminance of 27 700 cd/m2 was obtained. We found that GaMq2Cl also was useful as a host material. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds

Photorefractive Bragg diffraction in high- and low-molar-mass liquid crystal mixtures

Hiroshi Ono, Isao Saito, and Nobuhiro Kawatsuki

Appl. Phys. Lett. 72, 1942 (1998); http://dx.doi.org/10.1063/1.121230 (3 pages) | Cited 29 times

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Orientational photorefractive Bragg diffraction is observed in high- and low-molar-mass liquid crystal mixtures doped with fullerene (C60). These novel materials are in a nematic phase without phase separating. In the functionalized materials, we observe a high two-beam coupling gain coefficient (Γ = 75 cm−1) with a low applied field of 4 V/μm, low total losses (32 cm−1 including scattering, reflection, and absorption), a high diffraction efficiency (9%), and response time of 200 ms. © 1998 American Institute of Physics.
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61.30.-v Liquid crystals
78.20.-e Optical properties of bulk materials and thin films
78.70.Ck X-ray scattering

Electro-optic measurement of THz field pulses with a chirped optical beam

Zhiping Jiang and X.-C. Zhang

Appl. Phys. Lett. 72, 1945 (1998); http://dx.doi.org/10.1063/1.121231 (3 pages) | Cited 58 times

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Using a linearly chirped optical probe pulse in free-space electro-optic measurements, a temporal wave form of a co-propagating THz field is linearly encoded onto the frequency spectrum of the optical probe pulse, and then decoded by dispersing the probe beam from a grating to a detector array. We achieve acquisition of picosecond THz field pulses without using mechanical time-delay device. We also demonstrate a single-shot electro-optic measurement of the temporal wave form of a THz pulse. © 1998 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment

Laser purification of Ag using a time-division collection method

Hiroshi Mori

Appl. Phys. Lett. 72, 1948 (1998); http://dx.doi.org/10.1063/1.121232 (3 pages) | Cited 6 times

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In laser purification of Ag from an Ag-In alloy based on multistep photoexcitation for ionization, we demonstrated that a time-division collection method employing a high-speed rotation disk is effective in suppressing an impurity level. High purity Ag film of 0.11% In impurity concentration was obtained from a starting Ag-In alloy of 6.08% In. This impurity reduction was much higher than the case without the new method, in which only half reduction was obtained. This work also showed that the contamination is mainly due to neutral atoms that failed to be irradiated by pulsed-mode lasers. © 1998 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
81.20.Ym Purification
61.72.S- Impurities in crystals
42.62.-b Laser applications

Thermally-actuated reflection mode asymmetric Fabry–Perot modulator utilizing a thin transparent elastomeric film

John A. Rogers, Olivier J. A. Schueller, and George M. Whitesides

Appl. Phys. Lett. 72, 1951 (1998); http://dx.doi.org/10.1063/1.121233 (3 pages) | Cited 4 times

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This letter describes a thermally-actuated reflection mode asymmetric Fabry–Perot modulator that consists of a thin transparent elastomeric film bounded by partially and highly reflecting metallic mirrors. The thickness of the transparent layer determines the intensity of light reflected from the modulator; changes in its thickness modulate the reflectivity. Electrical current flowing through the highly reflecting mirror provides a source of heat for controlling, by thermal expansion, the thickness of the elastomeric film. Modulators with this design show contrast ratios >15 dB and insertion losses <0.3 dB. © 1998 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
65.40.De Thermal expansion; thermomechanical effects

Electrical wavelength tunable and multiwavelength actively mode-locked fiber ring laser

Shenping Li and K. T. Chan

Appl. Phys. Lett. 72, 1954 (1998); http://dx.doi.org/10.1063/1.121263 (3 pages) | Cited 28 times

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Electrical single- and dual-wavelength tuning and three-wavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses were demonstrated by using a cavity with large dispersion. A continuous tuning range up to ∼37 nm of single-wavelength picosecond pulses at ∼1 GHz was achieved by only changing the modulation frequency. Continuous wavelength tuning of dual-wavelength (18.5 nm spacing) 3 GHz picosecond pulses was also demonstrated with a tuning range up to ∼17 nm. The tuning ranges were mainly limited by the gain bandwidth of the Er-doped fiber. Simultaneous generation of three-wavelength picosecond pulses at ∼2 GHz was also demonstrated by further increasing the cavity dispersion. © 1998 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Spontaneous emission from fluorescent molecules embedded in photonic crystals consisting of polystyrene microspheres

Takashi Yamasaki and Tetsuo Tsutsui

Appl. Phys. Lett. 72, 1957 (1998); http://dx.doi.org/10.1063/1.121234 (3 pages) | Cited 82 times

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Spontaneous emission from dye molecules embedded in periodic dielectric structures was investigated. The structures consist of close-packed arrays of dye-doped polystyrene microspheres. Periodic arrays of polystyrene spheres with a submicrometer diameter were shown to provide a nonoverlapping gap or pseudogap in the visible spectral region. The modification of the spontaneous emission from inside the pseudogap structure was observed as a deep dip in the photoluminescence spectra. The alteration in the emission spectra is explained in terms of the partial suppression of radiation modes due to the periodic dielectric structures. © 1998 American Institute of Physics.
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78.55.Kz Solid organic materials
42.70.Qs Photonic bandgap materials

All-optical beam deflection and switching in strontium–barium–niobate waveguides

D. Kip, M. Wesner, E. Krätzig, V. Shandarov, and P. Moretti

Appl. Phys. Lett. 72, 1960 (1998); http://dx.doi.org/10.1063/1.121317 (3 pages) | Cited 11 times

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Self-focusing by thermal heating because of absorption of a guided light beam in a planar strontium–barium–niobate waveguide is of interest for all-optical data processing. When a guided probe beam intersects the pump beam under a small angle inside the waveguide, the self-focusing effect in conjunction with self-bending because of the photorefractive effect can be used for large angle deflection of the probe beam and for switching with time constants of fractions of milliseconds. Deflection angles of the outcoupled probe light up to 0.23 rad in air and frequencies up to 3 kHz for optical switching are reached in the experiment. © 1998 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Wi Nonlinear waveguides
42.79.Fm Reflectors, beam splitters, and deflectors
42.82.Et Waveguides, couplers, and arrays

Frequency control in laser ultrasound with computer generated holography

M. Clark, F. Linnane, S. D. Sharples, and M. G. Somekh

Appl. Phys. Lett. 72, 1963 (1998); http://dx.doi.org/10.1063/1.121235 (3 pages) | Cited 8 times

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In laser ultrasonics a laser is used to excite ultrasonic waves. The intensity profile of the laser on the sample can be used to control the frequency of the ultrasound generated. In this letter we show how the frequency content of Rayleigh (surface acoustic) waves generated with an 82 MHz mode-locked laser can be controlled using computer generated holograms (CGHs). To demonstrate the effectiveness of the frequency control the CGHs used were defocused to generate new illumination profiles. The agreement between the actual and predicted amplitudes for these profiles is striking. Using this technique, the intensity output from the CGHs may be considered as a tunable Rayleigh wave source. © 1998 American Institute of Physics.  
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43.38.Zp Acoustooptic and photoacoustic transducers
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
62.65.+k Acoustical properties of solids
43.38.Rh Surface acoustic wave transducers
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
68.35.Gy Mechanical properties; surface strains
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Synthesis of boron nitride nanotubes by means of excimer laser ablation at high temperature

D. P. Yu, X. S. Sun, C. S. Lee, I. Bello, S. T. Lee, H. D. Gu, K. M. Leung, G. W. Zhou, Z. F. Dong, and Z. Zhang

Appl. Phys. Lett. 72, 1966 (1998); http://dx.doi.org/10.1063/1.121236 (3 pages) | Cited 95 times

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Boron nitride nanotubes (BN-NTs) were synthesized by using excimer laser ablation at 1200 °C in different carrier gases. The main characteristic of the BN-NTs produced by this method is that nanotubes are of only one to three atomic layers thick, which could be attributed to the dominance of the axial growth rate over the radial growth rate. The diameter of the BN-NTs ranged from 1.5 to 8 nm. The tips of the BN-NTs are either a flat cap or of polygonal termination, in contrast to the conical ends of carbon nanotubes. The atomic ratio of boron to nitrogen as measured by means of parallel electron energy loss spectroscopy is 0.8, which is within the experimental error of the stoichiometry of hexagonal BN structure. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
79.20.Kz Other electron-impact emission phenomena
61.66.Bi Elemental solids
61.66.Dk Alloys

Multimillion-atom molecular dynamics simulation of atomic level stresses in Si(111)/Si3N4(0001) nanopixels

Martina E. Bachlechner, Andrey Omeltchenko, Aiichiro Nakano, Rajiv K. Kalia, Priya Vashishta, Ingvar Ebbsjö, Anupam Madhukar, and Paul Messina

Appl. Phys. Lett. 72, 1969 (1998); http://dx.doi.org/10.1063/1.121237 (3 pages) | Cited 26 times

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Ten million atom multiresolution molecular-dynamics simulations are performed on parallel computers to determine atomic-level stress distributions in a 54 nm nanopixel on a 0.1 μm silicon substrate. Effects of surfaces, edges, and lattice mismatch at the Si(111)/Si3N4(0001) interface on the stress distributions are investigated. Stresses are found to be highly inhomogeneous in the nanopixel. The top surface of silicon nitride has a compressive stress of +3 GPa and the stress is tensile, −1 GPa, in silicon below the interface. © 1998 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
81.05.Cy Elemental semiconductors
68.60.Bs Mechanical and acoustical properties
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

The effect of composition on the thermal stability of Si1−x−yGexCy/Si heterostructures

L. V. Kulik, D. A. Hits, M. W. Dashiell, and J. Kolodzey

Appl. Phys. Lett. 72, 1972 (1998); http://dx.doi.org/10.1063/1.121238 (3 pages) | Cited 15 times

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The thermal stability of molecular beam epitaxy grown Si1−x−yGexCy/Si heterostructures (0 ⩽ x<0.30, y ∼ 0.008) was studied using infrared absorption spectroscopy. The local vibrational mode of C in Si and Si1−x−yGex was used to quantify the loss of C atoms from substitutional sites with high temperature annealing. The activation energy (Ea = 4.9 eV) for the loss of substitutional C achieved a maximum for the strain compensated alloy (x ∼ 0.1). An additional increase of Ge content resulted in a rapid decrease in Ea, which was found to be 3.4 eV for x ∼ 0.27. The nonmonotonic behavior of Ea on Ge content is explained by the effect of the interface strain between the epitaxial layer and Si substrate. © 1998 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.Am Elemental semiconductors and insulators
78.30.Hv Other nonmetallic inorganics
61.72.Cc Kinetics of defect formation and annealing
63.20.Pw Localized modes
78.66.Li Other semiconductors
78.66.Db Elemental semiconductors and insulators

Optical unwinding and reentrance phenomena in chiral smectic-C liquid crystals

Shu-Hsia Chen and Ching-Yih Chen

Appl. Phys. Lett. 72, 1975 (1998); http://dx.doi.org/10.1063/1.121264 (3 pages)

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We optically measure the molecular reorientation induced by an argon laser in homeotropically aligned chiral smectic-C films. Optical unwinding of the helix is observed and the critical unwinding intensity is determined. We have also developed a theory which not only explains the observed effect but also predicts a novel reentrance phenomenon of the unwinding state. © 1998 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
68.15.+e Liquid thin films
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.-e Ferroelectricity and antiferroelectricity
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Reflective mode of a nematic liquid crystal with chirality in a hybrid aligned configuration

Young Jin Kim and Sin-Doo Lee

Appl. Phys. Lett. 72, 1978 (1998); http://dx.doi.org/10.1063/1.121239 (3 pages) | Cited 5 times

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A reflective type of a liquid crystal (LC) display is proposed in a twisted hybrid aligned configuration with a reflective electrode and a single polarizer. A chiral dopant was introduced into a nematic LC to produce a proper amount of twist in a hybrid aligned geometry. Numerical simulations were performed to optimize the cell parameters so that the electro-optical switching between the black and white states could be easily achieved. It was experimentally demonstrated that this reflective mode gives wide viewing and fast response characteristics. The effect of an optical retardation film on the device performance is also discussed. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
78.20.Jq Electro-optical effects
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

The role of nonstoichiometry in 180° domain switching of LiNbO3 crystals

Venkatraman Gopalan, Terence E. Mitchell, Y. Furukawa, and K. Kitamura

Appl. Phys. Lett. 72, 1981 (1998); http://dx.doi.org/10.1063/1.121491 (3 pages) | Cited 113 times

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We show here conclusively that the internal field originates from nonstoichiometric point defects in LiNbO3 crystals. The switching fields required for 180° domain reversal in congruent crystals [C=Li2O/(Li2O+Nb2O5) = 0.484] are ∼4–5 times larger than the switching fields for nearstoichiometric crystals (C = 0.498). An internal field of ∼2.5 kV/mm observed in congruent crystals disappears in stoichiometric crystals. The concentration of hydrogen incorporated during crystal growth has no effect on the switching or internal fields. The measured spontaneous polarization, Ps = 80±5 μC/cm2 is relatively insensitive to the crystal nonstoichiometry and the hydrogen content. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
61.72.J- Point defects and defect clusters
61.66.Bi Elemental solids
61.66.Dk Alloys
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Two-dimensional arsenic precipitation in superlattice structures of alternately undoped and heavily Be-doped GaAs grown by low-temperature molecular beam epitaxy

Z. A. Su, J. H. Huang, L. Z. Hsieh, and W.-I. Lee

Appl. Phys. Lett. 72, 1984 (1998); http://dx.doi.org/10.1063/1.121240 (3 pages) | Cited 4 times

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The precipitation of arsenic in superlattice structures of alternately undoped and [Be] = 2.4×1019 cm−3 doped GaAs grown at low temperatures has been studied using transmission electron microscopy. Novel precipitate microstructures were observed in annealed samples, including preferential accumulation of precipitates toward each interface of Be-doped GaAs and the following grown undoped GaAs. Specifically, after 800 °C annealing, the precipitates are totally confined in Be-doped regions, forming two-dimensional dot arrays near the aforementioned interfaces. Data are also presented to show that the heavily Be-doped GaAs has a smaller lattice constant than the undoped GaAs. A strain-induced mechanism was proposed to account for the segregation of As clusters. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
61.72.Cc Kinetics of defect formation and annealing

Observation and creation of current leakage sites in ultrathin silicon dioxide films using scanning tunneling microscopy

Heiji Watanabe, Ken Fujita, and Masakazu Ichikawa

Appl. Phys. Lett. 72, 1987 (1998); http://dx.doi.org/10.1063/1.121241 (3 pages) | Cited 32 times

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We used scanning tunneling microscopy (STM) to investigate the local leakage current through ultrathin silicon dioxide (SiO2) films grown on Si substrates. Individual leakage sites, which were created by hot-electron injection from the STM tip under a high sample bias of +10 V, were identified from the local change in surface conductivity due to defect creation in the oxide films. When we reversed the stressing polarity (using a negative sample bias) no leakage sites were created in the oxide film. © 1998 American Institute of Physics.
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77.22.Jp Dielectric breakdown and space-charge effects
73.25.+i Surface conductivity and carrier phenomena
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films

The incorporation of arsenic in GaN by metalorganic chemical vapor deposition

X. Li, S. Kim, E. E. Reuter, S. G. Bishop, and J. J. Coleman

Appl. Phys. Lett. 72, 1990 (1998); http://dx.doi.org/10.1063/1.121242 (3 pages) | Cited 39 times

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We report on the successful incorporation of arsenic (As) in GaN during metalorganic chemical vapor deposition (MOCVD). A characteristic room-temperature luminescence band centered around 2.6 eV (480 nm), similar to the peak position of the As ion-implanted GaN, is found to be related to the As impurity in the MOCVD grown GaN:As films. The arsenic incorporation efficiency as a function of experimental conditions and structure is presented. Temperature- and power-dependent cathodoluminescence measurements have been performed to help establish the nature of the As-related peak. © 1998 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence
71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors

Doping-density dependence of scanning tunneling spectroscopy on lightly doped silicon

H.-A. Lin, R. Jaccodine, and M. S. Freund

Appl. Phys. Lett. 72, 1993 (1998); http://dx.doi.org/10.1063/1.121243 (3 pages) | Cited 11 times

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The doping-density dependence of scanning tunneling spectroscopy on lightly doped hydrogen-terminated Si(100) (resistivities in the range of 0.2–12 Ω cm) was investigated in air with and without illumination. The observed doping-density dependence is consistent with a generation model in which the changes in the three-dimensional depletion region, induced by a scanning tunneling microscopy tip, contributes to changes in the concentration of thermally and/or photogenerated carriers in lightly doped samples. These results suggest that scanning tunneling spectroscopy can be used to image variations in dopant density in lightly doped samples. © 1998 American Institute of Physics.
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61.72.uf Ge and Si
61.72.S- Impurities in crystals
81.70.Jb Chemical composition analysis, chemical depth and dopant profiling
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
72.80.Cw Elemental semiconductors

Truly ohmic contacts in engineered Al/Si/InGaAs(001) diodes

Silvano De Franceschi, Fabio Beltram, Claudio Marinelli, Lucia Sorba, Marco Lazzarino, Bernhard H. Müller, and Alfonso Franciosi

Appl. Phys. Lett. 72, 1996 (1998); http://dx.doi.org/10.1063/1.121244 (3 pages) | Cited 7 times

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We report the fabrication of nonalloyed ohmic contacts on n-InxGa1−xAs (0.25 ⩽ x ⩽ 0.38) grown by molecular beam epitaxy (MBE) on GaAs(001). This result is obtained by suppression of the native Al/InGaAs Schottky barrier by means of the MBE growth of Si bilayers at the metal-semiconductor interface. Truly ohmic contacts are demonstrated by x-ray photoemission spectroscopy and current-voltage techniques. © 1998 American Institute of Physics.
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85.30.Kk Junction diodes
73.40.Ns Metal-nonmetal contacts
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Metalorganic molecular beam epitaxy of GaAsN with dimethylhydrazine

Y. Qiu, C. Jin, S. Francoeur, S. A. Nikishin, and H. Temkin

Appl. Phys. Lett. 72, 1999 (1998); http://dx.doi.org/10.1063/1.121245 (3 pages) | Cited 12 times

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Epitaxial layers and superlattices of GaAsN/GaAs were grown by metalorganic molecular beam epitaxy using dimethylhydrazine, triethylgallium, and conventional arsenic sources. The incorporation of nitrogen into the solid was investigated as a function of the substrate temperature and the flux of dimethylhydrazine and modeled assuming formation of an adduct. Growth of GaAsN is characterized by an activation energy of 0.97 eV arising from a difference between activation energies of the adduct sticking coefficient, EB ∼ 1.27 eV, and the adduct formation, EA ∼ 0.3 eV. Nitrogen incorporation of 3% is obtained at a growth temperature of 400 °C. High-resolution x-ray diffraction and photoluminescence data demonstrate excellent quality of epitaxial layers and superlattices grown with dimethylhydrazine. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors

Device quality submicron arrays of stacked sidewall quantum wires on patterned GaAs (311)A substrates

Richard Nötzel, Uwe Jahn, Zhichuan Niu, Achim Trampert, Jörg Fricke, Hans-Peter Schönherr, Thomas Kurth, Detlef Heitmann, Lutz Däweritz, and Klaus H. Ploog

Appl. Phys. Lett. 72, 2002 (1998); http://dx.doi.org/10.1063/1.121246 (3 pages) | Cited 17 times

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Three-dimensional arrays of vertically stacked sidewall quantum wires are fabricated by molecular beam epitaxy on GaAs (311)A substrates patterned with 500-nm-pitch gratings. The cathodoluminescence spectra at low temperature are dominated by the emission from the quantum wires with narrow linewidth accompanied by a very weak emission from the connecting thin quantum wells due to localization of excitons at random interface fluctuations. When the carriers in the quantum well become delocalized at elevated temperature, only the strong emission from the quantum-wire array is observed revealing perfect carrier capture into the quantum wires without detectable thermal repopulation of the quantum well up to room temperature. Thus, unpreceded device quality of this quantum-wire structure is demonstrated. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Ea III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
73.20.Fz Weak or Anderson localization
78.66.Fd III-V semiconductors

Electronic properties of arsenic-doped gallium nitride

L. J. Guido, P. Mitev, M. Gherasimova, and B. Gaffey

Appl. Phys. Lett. 72, 2005 (1998); http://dx.doi.org/10.1063/1.121247 (3 pages) | Cited 13 times

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Arsenic-doped GaN films were grown via metalorganic chemical vapor deposition using trimethylgallium, ammonia, and arsine precursors. The arsenic concentration increases from 3×1016 to 5×1017 cm−3 in response to a change in arsine mole fraction from 3.3×102 to 3.2×104 ppm. The electron mobility increases with arsenic content reaching a maximum value of 374 cm2/V s at 300 K. In addition, the integrated photoluminescence intensity exhibits a 35-fold increase in magnitude at 300 K. To explain these findings, a simple physical model is proposed in which arsenic “impurities” occupy otherwise vacant sites on both the gallium and nitrogen sublattices. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
72.80.Ey III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance

Carrier capture into InGaAs/GaAs quantum wells via impurity mediated resonant tunneling

L. V. Dao, M. Gal, H. Tan, and C. Jagadish

Appl. Phys. Lett. 72, 2008 (1998); http://dx.doi.org/10.1063/1.121248 (3 pages) | Cited 2 times

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We have investigated the photoexcited carrier dynamics in In1−xGaxAs/GaAs quantum wells using the photoluminescence up-conversion technique. We found a unique capture process which was exceptional both in terms of the capture time and its temperature dependence. In the case of a specific quantum well with wide barriers, the photoluminescence rise time, a parameter which includes the overall capture time and the exciton formation time, was less than 600 fs instead of the expected few hundred picoseconds. We show in this work that this unusually rapid process is the result of the capture of the photoexcited carriers (or excitons) by impurities in the GaAs barriers, from where they resonantly tunnel into the quantum well. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
71.35.-y Excitons and related phenomena
78.47.-p Spectroscopy of solid state dynamics

Calculated natural band offsets of all II–VI and III–V semiconductors: Chemical trends and the role of cation d orbitals

Su-Huai Wei and Alex Zunger

Appl. Phys. Lett. 72, 2011 (1998); http://dx.doi.org/10.1063/1.121249 (3 pages) | Cited 248 times

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Using first-principles all-electron band structure method, we have systematically calculated the natural band offsets ΔEv between all II–VI and separately between III–V semiconductor compounds. Fundamental regularities are uncovered: for common-cation systems ΔEv decreases when the cation atomic number increases, while for common-anion systems ΔEv decreases when the anion atomic number increases. We find that coupling between anion p and cation d states plays a decisive role in determining the absolute position of the valence band maximum and thus the observed chemical trends. © 1998 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.15.-m Methods of electronic structure calculations
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