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26 Jul 1999

Volume 75, Issue 4, pp. 439-592

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High-efficiency oligothiopene-based light-emitting diodes

G. Gigli, G. Barbarella, L. Favaretto, F. Cacialli, and R. Cingolani

Appl. Phys. Lett. 75, 439 (1999); http://dx.doi.org/10.1063/1.124403 (3 pages) | Cited 53 times

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We report investigations of the photoluminescence (PL) and electroluminescence (EL) of a thiophene oligomer for which we have devised a variety of substitutions aimed at enhancing the solid-state efficiency. We find that the absolute PL quantum efficiency in the solid state is up 37% for both powders or spin-coated thin films of the compound. The material thus becomes competitive for applications in organic light-emitting diodes (LEDs). EL efficiencies up to 1.2 cd/A are demonstrated in LEDs prepared with indium–tin–oxide and Ca–Al electrodes. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices

Ultrafast modulation of semiconductor lasers through a terahertz field

C. Z. Ning, S. Hughes, and D. S. Citrin

Appl. Phys. Lett. 75, 442 (1999); http://dx.doi.org/10.1063/1.124402 (3 pages) | Cited 4 times

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We demonstrate, by means of numerical simulation, an interesting mechanism to modulate and switch semiconductor lasers at THz and sub-THz frequency rates. A sinusoidal terahertz field applied to a semiconductor laser heats the electron-hole plasma and consequently modifies the optical susceptibility. This allows an almost linear modulation of the output power of the semiconductor laser and leads to a faithful reproduction of the terahertz-field waveform in the emitted laser intensity. © 1999 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Temperature dependence of the relaxation time of photoconductivity and non-steady-state photocurrents in photorefractive Bi12SiO20 grown in an oxygen-free atmosphere

M. A. Bryushinin, A. A. Petrov, and I. A. Sokolov

Appl. Phys. Lett. 75, 445 (1999); http://dx.doi.org/10.1063/1.124404 (3 pages) | Cited 2 times

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We present temperature measurements of the non-steady-state photocurrent and photoconductivity relaxation time in photorefractive sillenite crystal Bi12SiO20 grown in an oxygen-free atmosphere. The obtained dependencies are explained using a conventional model of semiconductor crystal with shallow energy level. The activation energy of shallow level obtained from photocurrent measurements was found to be ET = (0.45±0.11) eV. Independent measurements of the temperature dependence of the relaxation time of photoconductivity are in reasonable agreement with this estimation and give the value for ET equal to (0.56±0.01) eV. © 1999 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
71.55.Ht Other nonmetals

Nonlinear optical characterization of a generalized Fibonacci optical superlattice

Yi-qiang Qin, Yong-yuan Zhu, Shi-ning Zhu, Gui-peng Luo, Jing Ma, and Nai-ben Ming

Appl. Phys. Lett. 75, 448 (1999); http://dx.doi.org/10.1063/1.124405 (3 pages) | Cited 16 times

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Nonlinear optical characterization in a generalized Fibonacci-type optical superlattice, which can be generated by the concurrent inflation rule A→AmB and B→A (where m = positive integer), has been studied both theoretically and experimentally. Quasi-phase-matched second-harmonicgeneration spectrum and direct third-harmonic-generation with high efficiency have been measured in a LiTaO3 superlattice structure with m = 2. Two different structures in real space have shown a similarity in reciprocal space. © 1999 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Nk Insulators
42.79.Wc Optical coatings
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Spectrum control of THz radiation from InAs in a magnetic field by duration and frequency chirp of the excitation pulses

Shinji Izumida, Shingo Ono, Zhenlin Liu, Hideyuki Ohtake, and Nobuhiko Sarukura

Appl. Phys. Lett. 75, 451 (1999); http://dx.doi.org/10.1063/1.124406 (3 pages) | Cited 18 times

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The THz radiation spectrum from InAs in a magnetic field irradiated with femtosecond pulses can be controlled by varying the excitation pulse width and chirp direction of the excitation pulse. A longer excitation pulse width produces lower-frequency THz radiation. Also, positively chirped pulse excitation will generate higher power and higher frequency THz radiation. © 1999 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.72.Ai Infrared sources
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators
85.70.Sq Magnetooptical devices

Demonstration of the high-frequency optical heterodyne technology using near-field fiber-optic probes

S. K. Han, K. Y. Kang, M. E. Ali, and H. R. Fetterman

Appl. Phys. Lett. 75, 454 (1999); http://dx.doi.org/10.1063/1.124407 (3 pages) | Cited 1 time

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We demonstrate the use of near-field fiber-optic probes in optical heterodyne characterization of high-speed devices. The submicron-size optical beam obtained from the fiber-optic probe was employed to selectively excite a small local portion of the active region of the device. Optical heterodyne measurements on heterojunction bipolar transistors were conducted at 1550 nm with a difference frequency of 100 GHz. The significant response of the device with a signal-to-noise ratio of 30 dB was observed. The dc and the ac photoresponses were also measured as a function of the distance between the fiber-optic probe and the device under test. The data showed clearly distinguishable regimes of near- and far-field operation. The high-frequency near-field optical heterodyne technique as explored in this letter provides us with capabilities that can be effectively utilized in the field of optical millimeter-wave interaction in ultrafast devices. © 1999 American Institute of Physics.
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85.30.Pq Bipolar transistors
06.60.Mr Testing and inspecting procedures
07.79.Fc Near-field scanning optical microscopes

Flashlamp pumped solid-state dye laser incorporating pyrromethene 597

A. J. Finlayson, N. Peters, P. V. Kolinsky, and M. R. W. Venner

Appl. Phys. Lett. 75, 457 (1999); http://dx.doi.org/10.1063/1.124408 (3 pages) | Cited 13 times

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Solid-state rods containing the laser dye pyrromethene 597 (Pyr 597) in a modified polymethyl methacrylate polymer host have been fabricated and shown to give significant lasing action under flashlamp excitation. The rods all displayed a favorable positive-lensing characteristic and also exhibited low bulk transmission losses. The rod with the lowest transmission loss, measured to be 0.31% cm−1 at 633 nm, gave a laser output of 880 mJ with a 0.35% energy efficiency.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
78.45.+h Stimulated emission
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The grain growth blocking effect of polycrystalline silicon film by thin native silicon oxide barrier during the excimer laser recrystallization

Kee-Chan Park, Jae-Hong Jeon, Cheol-Min Park, Min-Cheol Lee, Min-Koo Han, and Kwon-Young Choi

Appl. Phys. Lett. 75, 460 (1999); http://dx.doi.org/10.1063/1.124400 (3 pages) | Cited 3 times

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A method to control the recrystallization depth of amorphous silicon (a-Si) film during the excimer laser annealing is presented. By irradiating the XeCl excimer laser on the triple film structure of a-Si/thin native silicon oxide ( ∼ 20 Å)/thick a-Si layer, only the upper a-Si film is recrystallized, whereas the lower thick a-Si film remains amorphous. The thin native silicon oxide layer blocks the grain growth and prevents the upper grains from growing into the lower a-Si. As a result, the thin oxide film sharply defines the boundary between polycrystalline silicon (poly-Si) and the a-Si layer. The poly-Si/a-Si double layer is useful for the fabrication of high-performance poly-Si thin film transistors. © 1999 American Institute of Physics.
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61.82.Fk Semiconductors
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.43.Dq Amorphous semiconductors, metals, and alloys

Selective area metalorganic molecular-beam epitaxy of GaN and the growth of luminescent microcolumns on Si/SiO2

S. Guha, N. A. Bojarczuk, M. A. L. Johnson, and J. F. Schetzina

Appl. Phys. Lett. 75, 463 (1999); http://dx.doi.org/10.1063/1.124409 (3 pages) | Cited 28 times

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We demonstrate the selective area growth of gallium nitride on patterned Si(111)/GaN/SiO2 wafers by metalorganic molecular beam epitaxy using triethyl gallium as a Ga source. We show that such selective area deposition may be used to grow isolated microcolumns of GaN with lateral dimensions of tens of nanometers on Si/SiO2 wafers. Via high resolution cathodoluminescence imaging we show that such microcolumn structures are highly luminescent inspite of a large surface to volume ratio, indicating that nonradiative recombination at free surfaces is not a significant issue in this system. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

The equivalence of vacancy-type damage in ion-implanted Si seen by positron annihilation spectroscopy

A. P. Knights, F. Malik, and P. G. Coleman

Appl. Phys. Lett. 75, 466 (1999); http://dx.doi.org/10.1063/1.124410 (3 pages) | Cited 20 times

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The response of the Doppler-broadened annihilation linewidth parameter S to ion dose has been measured using a controllable-energy positron beam for n-type Fz–Si(100) implanted with 120 keV Ge+, 400 keV O+, 200 keV He+, and 450 keV H+ ions. For all ions S increases with dose, indicating the presence of vacancy-type defects. It is found that the maximum S values for the Ge+, O+, and H+ implants can be normalized to one well-defined distribution using values of predicted vacancy concentration from the Monte Carlo code TRIM. This result implies that vacancy-type defects from these three implantations are similar in both structure and interstitial recombination rate. The He+ data do not lie perfectly on the universal distribution; it is suggested that this is a result of defect passivation by the implanted He. © 1999 American Institute of Physics.
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78.70.Bj Positron annihilation
61.72.uf Ge and Si
61.72.J- Point defects and defect clusters
81.05.Cy Elemental semiconductors
02.50.Ng Distribution theory and Monte Carlo studies
02.70.Rr General statistical methods
61.72.Yx Interaction between different crystal defects; gettering effect

Dynamics of photoexcited carriers in ZnO epitaxial thin films

Aishi Yamamoto, Takeo Kido, Takenari Goto, Yefan Chen, Takafumi Yao, and Atsuo Kasuya

Appl. Phys. Lett. 75, 469 (1999); http://dx.doi.org/10.1063/1.124411 (3 pages) | Cited 44 times

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Optical gain spectra of ZnO epitaxial thin films have been measured by using a pump–probe technique. The optical gain is thought to be due to electron–hole plasma. In the differential absorption spectra, we observed saturation of the exciton absorption, band-gap renormalization, as well as the optical gain. From the temporal changes of these structures, the dynamical properties of the photoexcited carriers are discussed. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.47.-p Spectroscopy of solid state dynamics

Recrystallization of carbon–aluminum ion coimplanted epitaxial silicon carbide—evidenced by room temperature optical measurements

Z. C. Feng, S. J. Chua, K. Tone, and J. H. Zhao

Appl. Phys. Lett. 75, 472 (1999); http://dx.doi.org/10.1063/1.124412 (3 pages) | Cited 8 times

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Effects of carbon (C)-aluminum (Al) coimplantation and annealing of epitaxial n-type 6H polytype silicon carbide (6H–SiC) have been studied by Raman scattering, photoluminescence (PL), and optical transmission (OT), measured at room temperature. The amorphization and damage of 6H–SiC due to ion implantation are observed. The recovery of the 6H–SiC crystallinity by a high temperature annealing at 1550 °C for 30 min after C–Al implantation has been confirmed from the Raman, PL, and OT measurements. Evidences of the recrystallization of C–Al coimplanted epitaxial 6H–SiC are obtained nondestructively by these three optical techniques. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Hd Other semiconductors
61.72.up Other materials
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.Cc Kinetics of defect formation and annealing
78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Observation of a large third-order nonlinear response of exciton polaritons in GaAs thin film

Koich Akiyama, Nobuyuki Tomita, Yoshinori Nomura, and Toshiro Isu

Appl. Phys. Lett. 75, 475 (1999); http://dx.doi.org/10.1063/1.124413 (3 pages) | Cited 31 times

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We investigated the third-order nonlinear response of excitons in GaAs thin films grown by molecular beam exitaxy. Degenerate four-wave mixing (DFWM) measurements were made using picosecond pulses of 3.2 ps auto correlation width at T = 5 K. The DFWM signal of a 110-nm-thick GaAs film at exciton resonance energy is 25 times larger than that of a 1-μm-thick GaAs film. This enhancement is explained by the confinement effect of exciton polaritons, which is due to the nonlocal response of the center-of-mass quantized states of excitons in a radiation field. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.-y Excitons and related phenomena

Synthesis, structure, and optical properties of colloidal GaN quantum dots

O. I. Mićić, S. P. Ahrenkiel, D. Bertram, and A. J. Nozik

Appl. Phys. Lett. 75, 478 (1999); http://dx.doi.org/10.1063/1.124414 (3 pages) | Cited 46 times

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Colloidal chemistry was used to synthesize GaN quantum dots. A GaN precursor, polymeric gallium imide, {Ga(NH)3/2}n, which was prepared by the reaction of dimeric amidogallium with ammonia at room temperature, was heated in trioctylamine at 360 °C for one day to produce GaN nanocrystals. The GaN particles were separated, purified, and partially dispersed in a nonpolar solvent to yield transparent colloidal solutions that consisted of individual GaN particles. The GaN nanocrystals have a spherical shape and mean diameter of about 30±12 Å. The spectroscopic behavior of colloidal transparent dispersion has been investigated and shows that the band gap of the GaN nanocrystals shifts to slightly higher energy due to quantum confinement. The photoluminescence spectrum at 10 K (excited at 310 nm) shows band edge emission with several emission peaks in the range between 3.2 and 3.8 eV, while the photoluminescence excitation spectrum shows two excited-state transitions at higher energies. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
82.70.Dd Colloids
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.55.Cr III-V semiconductors
78.66.Fd 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
71.20.Nr Semiconductor compounds
73.22.-f Electronic structure of nanoscale materials and related systems

Controlling growth and field emission property of aligned carbon nanotubes on porous silicon substrates

Dongsheng Xu, Guolin Guo, Linlin Gui, Youqi Tang, Zujin Shi, Zhaoxia Jin, Zhennan Gu, Weimin Liu, Xiulan Li, and Guanghua Zhang

Appl. Phys. Lett. 75, 481 (1999); http://dx.doi.org/10.1063/1.124415 (3 pages) | Cited 52 times

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An aligned and well-distributed carbon nanotubes array was produced by pyrolysis of hydrocarbons catalyzed by nickel nanoparticles embedded in porous silicon (PS) substrates. Scanning electron microscope images show that the nanotubes form an aligned array approximately perpendicular to the surface of the PS substrate and the diameters of most of the tubes within the array are 10–30 nm. High-magnification transmission electron microscopy images confirmed that the nanotubes are well graphitized and typically consist of about 15 concentric shells of carbon sheets. Furthermore, the strong field emission from the aligned carbon nanotubes emitter by pyrolysis of hydrocarbons was observed. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
79.70.+q Field emission, ionization, evaporation, and desorption
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

High-quality AlN grown on Si(111) by gas-source molecular-beam epitaxy with ammonia

S. A. Nikishin, V. G. Antipov, S. Francoeur, N. N. Faleev, G. A. Seryogin, V. A. Elyukhin, H. Temkin, T. I. Prokofyeva, M. Holtz, A. Konkar, and S. Zollner

Appl. Phys. Lett. 75, 484 (1999); http://dx.doi.org/10.1063/1.124423 (3 pages) | Cited 33 times

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Hexagonal AlN layers were grown on Si(111) by gas-source molecular-beam epitaxy with ammonia. The transition between the (7×7) and (1×1) silicon surface reconstructions, at 1100 K, was used for in situ calibration of the substrate temperature. The initial deposition of Al, at 1130–1190 K, produced an effective nucleation layer for the growth of AlN. The Al layer also reduced islands of SiNx that might be formed due to background NH3 on the silicon surface prior to the onset of epitaxial growth. The transition to two-dimensional growth mode, under optimum conditions, was obtained after the initial AlN thickness of ∼7 nm. © 1999 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Elasticity and mechanical instabilities of diamond at megabar stresses: Implications for diamond-anvil-cell research

Ji-Jun Zhao, S. Scandolo, J. Kohanoff, G. L. Chiarotti, and E. Tosatti

Appl. Phys. Lett. 75, 487 (1999); http://dx.doi.org/10.1063/1.124424 (2 pages) | Cited 15 times

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We present first-principles calculations of the stress–strain curves for diamond under nonhydrostatic tetragonal compression, in the regime of operation of diamond-anvil cells (DACs). We provide a parametrization of the stress components as a function of strain, which is potentially useful for the controlled design of DACs. A stability analysis shows that a tetragonal-shear mechanical instability sets in in diamond when σz−σr = 200 GPa, where σz and σr are the axial and radial components of the stress, respectively. © 1999 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.05.ub Fullerenes and related materials
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Blue photoluminescence from thermally grown SiO2 on micromachined arrays of silicon planes

A. Diligenti, F. Pieri, M. Piotto, F. Fuso, and M. Allegrini

Appl. Phys. Lett. 75, 489 (1999); http://dx.doi.org/10.1063/1.124425 (3 pages) | Cited 1 time

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SiO2 was thermally grown on arrays of silicon planes obtained from 〈110〉 substrates by means of micromachining. Blue photoluminescence was observed under pulsed-laser excitation from SiO2 grown on these planes. Experiments revealed that this emission was not affected by the Si/SiO2 interface properties or the silicon thickness, whereas its intensity and spectral features depended on the oxide thickness. Moreover, no detectable luminescence was observed from the oxide grown on unpatterned regions, where a smaller amount of oxide was excited by the laser beam. The photoluminescence disappeared when the oxide was removed. © 1999 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials

Photoluminescence and Raman studies in thin-film materials: Transition from amorphous to microcrystalline silicon

Guozhen Yue, J. D. Lorentzen, Jing Lin, Daxing Han, and Qi Wang

Appl. Phys. Lett. 75, 492 (1999); http://dx.doi.org/10.1063/1.124426 (3 pages) | Cited 75 times

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We measured photoluminescence (PL) and Raman spectra for films deposited by hot-wire chemical vapor deposition using various hydrogen to silane ratios. We observed: (a) a PL peak energy increase from 1.25 to 1.4 eV as the material approaches the a- to μc-Si transition region; (b) a dual-PL peak at 1.3 and 1.0 eV for the film with a H dilution ratio of 3; and (c) as the H ratio increases, the 1.3 eV PL fades away and the low energy PL dominates. Meanwhile, a redshift of the peak position, a decrease of the intensity, and a narrower bandwidth for the low energy PL are also observed. The low energy PL is explained by band-tail radiative transitions from two types of grain boundaries. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
64.70.K- Solid-solid transitions
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Photoluminescence of indium–oxide nanoparticles dispersed within pores of mesoporous silica

Huijuan Zhou, Weiping Cai, and Lide Zhang

Appl. Phys. Lett. 75, 495 (1999); http://dx.doi.org/10.1063/1.124427 (3 pages) | Cited 86 times

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Photoluminescence study was performed on indium–oxide (INO) nanoparticles dispersed within pores of mesoporous silica, annealed at different temperatures (from 500 to 850 °C). It was found that, for the dispersed INO nanoparticles, there exists a broad luminescence band, consisting of three peaks at about 430, 480, and 520 nm, spanning the whole visible region, in contrast to the aggregates of INO nanoparticles which exhibit no luminescence. This band increases with rise of annealing temperature up to 650 °C, at which the band reaches maximum. When annealing temperature is 700 °C, the whole band redshifts and peaks at about 545 nm. Annealing at higher temperatures leads to additional redshift and decrease of the luminescence band. It has been shown that the luminescence in this study is associated with the size and the structure of the INO particles within pores of porous silica. The peaks at 430, 480, and 520 nm originate from amorphous INO particles about 2, 4, and 6 nm in diameter. The 545 nm peak is attributed to crystallized INO particles with larger size. © 1999 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
78.55.Mb Porous materials
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Dynamics of the excimer laser annealing of hydrogenated amorphous silicon thin films

G. Ivlev, E. Gatskevich, V. Cháb, J. Stuchlík, V. Vorlíček, and J. Kočka

Appl. Phys. Lett. 75, 498 (1999); http://dx.doi.org/10.1063/1.124428 (3 pages) | Cited 12 times

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Time-resolved reflectivity and time-resolved conductivity spectroscopies have been used to monitor phase changes as a function of pulse-energy density during the recrystallization of amorphous hydrogenated Si by an ArF excimer laser. The simultaneous application of both spectroscopies allowed clear identification of the melting threshold and time of melting. The dc conductivity of irradiated Si was measured as a function of pulse energy and number of pulses. These results, together with Raman spectroscopy, revealed that single-pulse annealing gives a conductive, but still amorphous and rather defective layer. At least two consecutive pulses are necessary for obtaining of the substantial crystalline fraction. © 1999 American Institute of Physics.
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73.61.Jc Amorphous semiconductors; glasses
78.66.Jg Amorphous semiconductors; glasses
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.47.-p Spectroscopy of solid state dynamics
73.61.Cw Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
61.82.Fk Semiconductors
64.70.D- Solid-liquid transitions
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Mechanism for low-temperature photoluminescence in GaNAs/GaAs structures grown by molecular-beam epitaxy

I. A. Buyanova, W. M. Chen, G. Pozina, J. P. Bergman, B. Monemar, H. P. Xin, and C. W. Tu

Appl. Phys. Lett. 75, 501 (1999); http://dx.doi.org/10.1063/1.124429 (3 pages) | Cited 138 times

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The mechanism for low-temperature photoluminescence (PL) emissions in GaNAs epilayers and GaAs/GaNxAs1−x quantum well (QW) structures grown by molecular-beam epitaxy is studied in detail, employing PL, PL excitation, and time-resolved PL spectroscopies. It is shown that even though quantum confinement causes a strong blueshift of the GaNAs PL emission, its major characteristic properties are identical in both QW structures and epilayers. Based on the analysis of the PL line shape, its dependence on the excitation power and measurement temperature, as well as transient data, the PL emission is concluded to be caused by a recombination of excitons trapped by potential fluctuations in GaNAs. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Influence of (001) vicinal GaAs substrates on the optical properties of defects in low-temperature grown GaAs/AlGaAs multiple quantum wells

M. H. Zhang, Q. Li, Y. F. Zhang, Q. Huang, J. M. Zhou, and Z. Y. Xu

Appl. Phys. Lett. 75, 504 (1999); http://dx.doi.org/10.1063/1.124430 (3 pages) | Cited 3 times

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Photoluminescence (PL) spectroscopy and carrier lifetime measurement has been used to characterize optical properties of defects in the low-temperature (LT) grown GaAs/AlGaAs multiple quantum well structures. Two sets of samples were grown at 400 °C by molecular beam epitaxy on nominal (001) and miscut [4° off (001) towards (111) A] GaAs substrates, respectively. After growth, samples were subjected to 30 s rapid thermal annealing at 600–800 °C. It is found that after annealing, two defect-related PL features appear in the samples grown on nominal (001) GaAs substrates, but not in those grown on miscut (001) GaAs substrates. The carrier lifetimes are about 31 and 5 ps in as-grown samples grown on nominal and miscut (001) GaAs substrates, respectively. The different PL spectra and carrier lifetimes in two sets of samples are attributed to different structures of the AsGa-like defects formed during LT growth. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
61.72.Cc Kinetics of defect formation and annealing
81.05.Ea III-V semiconductors

Growth of SiC nanorods at low temperature

Qingyi Lu, Junqing Hu, Kaibin Tang, Yitai Qian, Guien Zhou, Xianming Liu, and Jingsheng Zhu

Appl. Phys. Lett. 75, 507 (1999); http://dx.doi.org/10.1063/1.124431 (3 pages) | Cited 67 times

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Cubic-phase SiC (β-SiC) nanorods were synthesized through a one-step reaction under pressure at 400 °C by which the crystalline product can be obtained directly without annealing at high temperature. The reaction was carried out in an autoclave by using SiCl4 and CCl4 as reactants and metal Na as coreductant. The x-ray diffraction pattern indicates the formation of β-SiC and x-ray photoelectron spectra display the stoichiometric relation between Si and C. Transmission electron microscopy images reveal that the product consists of nanorods with diameters from 10 to 40 nm and lengths up to several micrometers. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
79.60.Jv Interfaces; heterostructures; nanostructures

Electrostatic force characterization on InAs dot-covered n-type (001) GaAs surfaces by contact-mode atomic force microscopy with a conductive tip

T. Takahashi, T. Kawamukai, and I. Kamiya

Appl. Phys. Lett. 75, 510 (1999); http://dx.doi.org/10.1063/1.124432 (3 pages) | Cited 4 times

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We performed atomic force microscopy in contact mode while applying an ac bias voltage between a conductive tip and a sample to characterize near surface band structures of InAs-covered n-type (001) GaAs, where self-assembled dot structures were formed. Electrostatic force of less than 10 pN was detectable, and clear electrostatic force images and topographic images were simultaneously obtained with lateral resolution higher than 20 nm. The electrostatic force images from single and double frequency components reveal that the gap width between the tip and the conductive region under the dot-covered area of the sample is smaller and is less modulated by the bias voltage than under the wetting layer. The results indicate that surface depletion is more suppressed beneath the dots. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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
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