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17 Nov 2003

Volume 83, Issue 20, pp. 4083-4258

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 4238 (2003); http://dx.doi.org/10.1063/1.1627935 (3 pages)

H. B. Peng, T. G. Ristroph, G. M. Schurmann, G. M. King, J. Yoon, V. Narayanamurti, and J. A. Golovchenko
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Photoluminescence study of AlGaN-based 280 nm ultraviolet light-emitting diodes

A. Yasan, R. McClintock, K. Mayes, D. H. Kim, P. Kung, and M. Razeghi

Appl. Phys. Lett. 83, 4083 (2003); http://dx.doi.org/10.1063/1.1626808 (3 pages) | Cited 19 times

Online Publication Date: 12 November 2003

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We investigated optical properties of single quantum well AlGaN-based UV 280 nm light-emitting diodes using temperature-dependent photoluminescence (PL) measurement. We found an “S-shaped” temperature dependence of the peak energy. From the Arrhenius plot of integrated PL intensity, we speculate that dislocations as well as thermal emission of carriers out of the quantum well are responsible for the PL quenching behavior. Also a second nonradiative channel with much lower activation energy was found, the origin of which we believe to be quenching of the bound excitons. © 2003 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
78.67.De Quantum wells
73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

90 W continuous-wave diode edge-pumped microchip composite Yb:Y3Al5O12 laser

T. Dascalu, N. Pavel, and T. Taira

Appl. Phys. Lett. 83, 4086 (2003); http://dx.doi.org/10.1063/1.1627960 (3 pages) | Cited 14 times

Online Publication Date: 12 November 2003

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High-power continuous-wave (cw) operation of a diode edge-pumped microchip composite Yb:Y3Al5O12 (YAG) laser is reported. Up to 90 W were obtained from a 400-μm-thick Yb:YAG/YAG structure with a 10 at. % Yb:YAG square core of 2×2 mm2 area; the slope efficiency and optical-to-optical efficiency with respect to the pump power were 40% and 28%, respectively. Measurements of the optical phase distortions induced by pumping gives a focus shift bellow 0.05 m and shows the absence of astigmatic effects, indicating the axial heat flow in this pumping configuration. © 2003 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers

Imaging of emission patterns in a T-shaped quantum wire laser

Yasushi Takahashi, Shinichi Watanabe, Masahiro Yoshita, Hirotake Itoh, Yuhei Hayamizu, Hidefumi Akiyama, Loren N. Pfeiffer, and Ken W. West

Appl. Phys. Lett. 83, 4089 (2003); http://dx.doi.org/10.1063/1.1627963 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2003

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Spatially and spectrally resolved microscopic images of spontaneous and stimulated emissions are imaged at the mirror facets of a GaAs T-shaped quantum wire laser with high uniformity. Laser emission from the one-dimensional ground state reveals a circular image located at the core of a T-shaped optical waveguide but significantly smaller in area than the low power spontaneous emission from the same waveguide. These images unambiguously allow assignment of all spontaneous and laser emissions to the wire ground state and respective intersecting wells in the structure. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Interwell intersubband electroluminescence from Si/SiGe quantum cascade emitters

R. Bates, S. A. Lynch, D. J. Paul, Z. Ikonic, R. W. Kelsall, P. Harrison, S. L. Liew, D. J. Norris, A. G. Cullis, W. R. Tribe, and D. D. Arnone

Appl. Phys. Lett. 83, 4092 (2003); http://dx.doi.org/10.1063/1.1626003 (3 pages) | Cited 43 times

Online Publication Date: 12 November 2003

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The quantum cascade laser provides one potential method for the efficient generation of light from indirect materials such as silicon. While to date electroluminescence results from THz Si/SiGe quantum cascade emitters have shown higher output powers than equivalent III–V emitters, the absence of population inversion within these structures has undermined their potential use for the creation of a laser. Electroluminescence results from Si/SiGe quantum cascade emitters are presented demonstrating intersubband emission from heavy to light holes interwell (diagonal) transitions between 1.2 THz (250 μm) and 1.9 THz (156 μm). Theoretical modeling of the transitions suggests the existence of population inversion within the system. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
78.60.Fi Electroluminescence
78.66.Db Elemental semiconductors and insulators
78.66.Li Other semiconductors
73.20.At Surface states, band structure, electron density of states

Optical gain, carrier-induced phase shift, and linewidth enhancement factor in InGaN quantum well lasers

U. T. Schwarz, E. Sturm, W. Wegscheider, V. Kümmler, A. Lell, and V. Härle

Appl. Phys. Lett. 83, 4095 (2003); http://dx.doi.org/10.1063/1.1628825 (3 pages) | Cited 39 times

Online Publication Date: 12 November 2003

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Adapting the Hakki Paoli method to group III nitrides, we measure gain, differential gain, carrier-induced change of refractive index, carrier-induced phase shift, and the antiguiding factor. Our measurements also cover the low-carrier-density regime, in which spontaneous and piezoelectric fields and Coulomb interaction are only partially screened. This regime is most interesting as a comparison with existing theoretical simulations, including many-body effects. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells

Mid-infrared external-cavity two-segment quantum-cascade laser

C. Peng, H. L. Zhang, and H. Q. Le

Appl. Phys. Lett. 83, 4098 (2003); http://dx.doi.org/10.1063/1.1627486 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2003

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An external-cavity mid-infrared quantum-cascade laser allows broad and continuous wavelength tuning and modulation when controlled with a combination of grating position and cavity phase on a two-segment optical amplifier chip. The electrically controlled phase segment allows fine wavelength tuning to complement the coarse grating tuning. The 4.8-μm laser was tested with CO gas absorption and wavelength modulation spectroscopy, showing a spectral resolution limited by the laser linewidth of ∼550 MHz, but also allowing sublinewidth modulation of ⩽200 MHz. The tuning range from 4.855 to 4.9 μm (0.57 THz) was limited by the device intrinsic gain. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Simultaneous generation of multiple pairs of transverse electric and transverse magnetic output modes from titania zirconia organically modified silicate distributed feedback waveguide lasers

Chao Ye, Lei Shi, Jun Wang, Dennis Lo, and Xiao-lei Zhu

Appl. Phys. Lett. 83, 4101 (2003); http://dx.doi.org/10.1063/1.1627468 (3 pages) | Cited 13 times

Online Publication Date: 12 November 2003

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Output polarization and output wavelength of titania zirconia organically modified silicate distributed feedback waveguide lasers were found to be dependent on the polarization of the crossing pump beams. Output waves with transverse electric polarization were obtained when the pump beams were s-polarized. Transverse electric and transverse magnetic optical waves belonging to the same propagation mode were generated by crossing two circularly polarized or p-polarized pump beams. Tuning of the polarized laser output was also achieved by varying the crossing angle. Up to sixteen output wavelengths corresponding to eight pairs of polarized output from eight propagation modes were observed simultaneously for a planar waveguide with a thickness of 6.7 μm. © 2003 American Institute of Physics.
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42.55.Mv Dye lasers

The electrical turn-on characteristics of vertical-cavity surface-emitting lasers

Yang Liu, Kent D. Choquette, and Karl Hess

Appl. Phys. Lett. 83, 4104 (2003); http://dx.doi.org/10.1063/1.1628816 (3 pages) | Cited 1 time

Online Publication Date: 12 November 2003

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We present a detailed comparison of the electrical turn-on characteristics of 980 nm vertical-cavity surface-emitting lasers (VCSELs) with simulations using a recently extended laser simulator. It is shown that the three recombination mechanisms, spontaneous emission, Shockley–Read–Hall recombination, and Auger recombination, result in distinctly different exponential current–voltage dependencies below threshold. Therefore, information can be extracted about the relative strength of the recombination rates due to those processes, and their relative contributions to the threshold current can be assessed. We show that for the VCSELs studied in this work, spontaneous emission is the dominant contribution to the threshold current. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
79.20.Fv Electron impact: Auger emission
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Threshold dependence on the spectral alignment between the quantum-well gain peak and the cavity resonance in InGaAsP photonic crystal lasers

J. R. Cao, Wan Kuang, Sang-Jun Choi, Po-Tsung Lee, John D. O’Brien, and P. Daniel Dapkus

Appl. Phys. Lett. 83, 4107 (2003); http://dx.doi.org/10.1063/1.1627466 (3 pages) | Cited 8 times

Online Publication Date: 12 November 2003

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Lithographically defined multiwavelength photonic crystal laser arrays are reported. The dependence of the threshold pump power on the spectral alignment between the quantum-well gain peak and the cavity resonance wavelength is investigated. This is done at, and slightly above, room temperature. © 2003 American Institute of Physics.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Continuous-wave laser action at λ = 1064.3 nm in proton- and carbon-implanted Nd:YAG waveguides

M. Domenech, G. V. Vázquez, E. Cantelar, and G. Lifante

Appl. Phys. Lett. 83, 4110 (2003); http://dx.doi.org/10.1063/1.1628817 (3 pages) | Cited 26 times

Online Publication Date: 12 November 2003

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This work reports continuous laser oscillation at λ = 1064.3 nm at room temperature in Nd:YAG planar waveguides fabricated by two different techniques: proton implantation with a multi-implant of energies around 1 MeV and carbon implantation with a single-implant at an energy of 7 MeV. Threshold powers of 11 and 22 mW and slope efficiencies of 7% and 9% were achieved in the proton- and carbon-implanted guides, respectively. The laser outputs show a very high stability operating in cw regime at room temperature. © 2003 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
61.72.up Other materials
61.80.Jh Ion radiation effects
61.82.Ms Insulators

Terahertz pulsed imaging with 1.06 μm laser excitation

C. Baker, I. S. Gregory, W. R. Tribe, I. V. Bradley, M. J. Evans, M. Withers, P. F. Taday, V. P. Wallace, E. H. Linfield, A. G. Davies, and M. Missous

Appl. Phys. Lett. 83, 4113 (2003); http://dx.doi.org/10.1063/1.1627485 (3 pages) | Cited 35 times

Online Publication Date: 12 November 2003

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We report the operation of a pulsed terahertz (THz) imaging system that uses a 120 fs pulse-width laser operating at 1.06 μm, and photoconductive InGaAs emitters and detectors. THz images are presented of biological and nonbiological specimens. The signal-to-noise ratio and frequency range of this system are compared to those obtained from existing pulsed imaging systems based on 0.8 μm excitation. © 2003 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Jb Light-emitting devices
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Direct measurement of nanoscale sidewall roughness of optical waveguides using an atomic force microscope

J. H. Jang, W. Zhao, J. W. Bae, D. Selvanathan, S. L. Rommel, I. Adesida, A. Lepore, M. Kwakernaak, and J. H. Abeles

Appl. Phys. Lett. 83, 4116 (2003); http://dx.doi.org/10.1063/1.1627480 (3 pages) | Cited 23 times

Online Publication Date: 12 November 2003

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An atomic force microscope (AFM) with an ultrasharp tip was used to directly measure the sidewall profile of InP/InGaAsP waveguide structures etched using an inductively coupled plasma reactive ion etching (ICP-RIE) in Cl2-based plasma. A special staircase pattern was devised to allow AFM tip to access the etched sidewall of the waveguides in the normal direction. Statistical information such as correlation length and rms roughness of the sidewall profile obtained through three-dimensional imaging by AFM has been presented. rms roughness as low as 3.45 nm was measured on the sidewall of 4-μm-deep etched InP/InGaAsP heterostructures. © 2003 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)
52.77.Bn Etching and cleaning
81.05.Ea III-V semiconductors
42.87.-d Optical testing techniques

Far-infrared multilayer mirrors

Robert Schiwon, Gerhard Schwaab, Erik Bründermann, and Martina Havenith

Appl. Phys. Lett. 83, 4119 (2003); http://dx.doi.org/10.1063/1.1627479 (3 pages) | Cited 8 times

Online Publication Date: 12 November 2003

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We present a concept for highly reflecting broadband mirrors in the far-infrared. We report on the fabrication of dielectric multilayer mirrors consisting of 1–6 layers of silicon wafers with vacuum gaps in between. By comparison to gold mirrors, we can demonstrate the high reflectivity (>99%) over the frequency range between 40 and 130 cm−1. The measurements are in very good agreement with theoretical predictions. © 2003 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.86.+b Optical workshop techniques

Focusing of millimeter-wave radiation beyond the Abbe barrier

A. Pimenov and A. Loidl

Appl. Phys. Lett. 83, 4122 (2003); http://dx.doi.org/10.1063/1.1627474 (3 pages) | Cited 1 time

Online Publication Date: 12 November 2003

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A hemispherical focusing system for millimeter waves is presented. Focusing of the beam to a spot of ∼ 0.3λ was obtained in the frequency range from 100 to 200 GHz. Compared to the scanning near-field optical spectroscopy, the system allows simultaneous imaging of extensive subwavelength objects. As an example, a double slit of size d = 1 mm was clearly resolved using a radiation with a wavelength λ = 2 mm. Using future optically dense lenses, a resolution of the order λ/100 seems to become possible. © 2003 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
42.79.Bh Lenses, prisms and mirrors

Optical parametric chirped-pulse amplification in periodically poled KTiOPO4 at 1053 nm

Igor Jovanovic, Jason R. Schmidt, and Christopher A. Ebbers

Appl. Phys. Lett. 83, 4125 (2003); http://dx.doi.org/10.1063/1.1627467 (3 pages) | Cited 19 times

Online Publication Date: 12 November 2003

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We have demonstrated a high-gain preamplifier for Nd:glass-based chirped-pulse amplification systems using optical parametric chirped-pulse amplification (OPCPA) in periodically poled potassium titanyl phosphate (PPKTP) in a collinear quasi-phase-matched configuration. The absence of birefringent walk-off enables high conversion efficiency and high beam quality using <1 mJ of pump energy. PPKTP has a potential to replace traditional angularly sensitive beta-barium borate preamplifiers for nearly degenerate OPCPA at wavelengths near 1 μm. © 2003 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Point defects as result of surface deformation on a GaAs wafer

C. Zamponi, U. Männig, T. E. M. Staab, K. Maier, S. Eichler, and R. Hammer

Appl. Phys. Lett. 83, 4128 (2003); http://dx.doi.org/10.1063/1.1625786 (3 pages) | Cited 2 times

Online Publication Date: 12 November 2003

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Scratches on the surface of an undoped semi-insulating GaAs wafer have been produced by a wedge-shaped single diamond grain. The subsurface damage has been analyzed by a positron microprobe. This instrument provides laterally resolved positron annihilation measurements, which are sensitive to lattice defects like vacancies and dislocations. We can clearly identify different regions of damage which have been characterized both by conventional scanning electron microscopy and the positron microbeam. The latter reveals indications of plastic deformation due to the trace of created defects observed. We discuss the possible implications of the observed ductile behavior of GaAs usually known to be brittle at room temperature and under atmospheric pressure. © 2003 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
68.35.Dv Composition, segregation; defects and impurities
68.47.Fg Semiconductor surfaces
61.72.J- Point defects and defect clusters
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
78.70.Bj Positron annihilation
62.20.F- Deformation and plasticity

Digital alloy interface grading of an InAlAs/InGaAs quantum cascade laser structure studied by cross-sectional scanning tunneling microscopy

P. Offermans, P. M. Koenraad, J. H. Wolter, M. Beck, T. Aellen, and J. Faist

Appl. Phys. Lett. 83, 4131 (2003); http://dx.doi.org/10.1063/1.1627942 (3 pages) | Cited 13 times

Online Publication Date: 12 November 2003

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We have studied an InGaAs/InAlAs quantum cascade laser structure with cross-sectional scanning tunneling microscopy. In the quantum cascade laser structure digital alloy grading was used to soften the barriers of the active region. We show that due to alloy fluctuations, softening of the barriers occurs even without the digital grading. © 2003 American Institute of Physics.
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68.35.Ct Interface structure and roughness
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Reduction of boron thermal diffusion in silicon by high energy fluorine implantation

H. A. W. El Mubarek and P. Ashburn

Appl. Phys. Lett. 83, 4134 (2003); http://dx.doi.org/10.1063/1.1622434 (3 pages) | Cited 14 times

Online Publication Date: 12 November 2003

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This letter investigates the effect of a deep F+ implant on the diffusion of boron in silicon. The effects on boron thermal diffusion and transient enhanced diffusion are separately studied by characterizing the diffusion of a buried boron marker layer in wafers with and without a 185 keV, 2.3 ×1015 cm−2 F+ implant, and with and without a 288 keV, 6 ×1013 cm−2 P+ implant. In samples given both P+ and F+ implants, the fluorine completely eliminates the transient, enhanced boron diffusion caused by the P+ implant, and in samples implanted with F+ only, the fluorine suppresses the boron thermal diffusion by 65%. These results are explained by the effect of the fluorine on the vacancy concentration in the vicinity of the boron profile. © 2003 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.uf Ge and Si

Mega-electron-volt ion beam induced anisotropic plasmon resonance of silver nanocrystals in glass

J. J. Penninkhof, A. Polman, Luke A. Sweatlock, Stefan A. Maier, Harry A. Atwater, A. M. Vredenberg, and B. J. Kooi

Appl. Phys. Lett. 83, 4137 (2003); http://dx.doi.org/10.1063/1.1627936 (3 pages) | Cited 29 times

Online Publication Date: 12 November 2003

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30 MeV Si ion beam irradiation of silica glass containing Ag nanocrystals causes alignment of Ag nanocrystals in arrays along the ion tracks. Optical transmission measurements show a large splitting of the surface plasmon resonance bands for polarizations longitudinal and transversal to the arrays. The splitting is in qualitative agreement with a model for near-field electromagnetic plasmon coupling within the arrays. Resonance shifts as large as 1.5 eV are observed, well into the near-infrared. © 2003 American Institute of Physics.
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73.22.Lp Collective excitations
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials

Reduction of threading dislocations in crack-free AlGaN by using multiple thin SixAl1−xN interlayers

T. Akasaka, T. Nishida, Y. Taniyasu, M. Kasu, T. Makimoto, and N. Kobayashi

Appl. Phys. Lett. 83, 4140 (2003); http://dx.doi.org/10.1063/1.1628397 (3 pages) | Cited 10 times

Online Publication Date: 12 November 2003

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Crack-free AlGaN thin films were directly grown on SiC substrates by metalorganic vapor phase epitaxy, and their threading dislocation density was reduced by one order of magnitude using 1–2 nm thick, heavily Si-doped AlN multiple interlayers. The interlayers form SixAl1−xN ternary alloys, where the Si molar fraction ranges typically from 0.07 to 0.17. This technique enables us to grow crack-free AlGaN films, since the film thickness of about 1 μm is much smaller than that required in conventional epitaxial lateral overgrowth techniques. Both termination and looping of threading dislocations were observed near the interlayers using cross-sectional transmission electron microscopy. Light emitting devices with the SixAl1−xN multiple interlayers showed a remarkable improvement in the intensity and spectral width of electroluminescence and the series resistance. © 2003 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
61.72.Lk Linear defects: dislocations, disclinations
68.37.Lp Transmission electron microscopy (TEM)
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Band gap tailoring of Nd3+-doped TiO2 nanoparticles

W. Li, Y. Wang, H. Lin, S. Ismat Shah, C. P. Huang, D. J. Doren, Sergey A. Rykov, J. G. Chen, and M. A. Barteau

Appl. Phys. Lett. 83, 4143 (2003); http://dx.doi.org/10.1063/1.1627962 (3 pages) | Cited 49 times

Online Publication Date: 12 November 2003

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Undoped and Nd3+-doped TiO2 nanoparticles were synthesized by chemical vapor deposition in order to tailor the band gap of TiO2. The doping reduced the band gap. The band gap was measured by ultraviolet-visible light absorption experiments and by near-edge x-ray absorption fine structure. The maximum band gap reduction was 0.55 eV for 1.5 at. % Nd-doped TiO2 nanoparticles. Density functional theory calculations using the generalized gradient approximation with the linearized augmented plane wave method were used to interpret the band gap narrowing. The band gap narrowing was primarily attributed to the substitutional Nd3+ ions which introduced electron states into the band gap of TiO2 to form the new lowest unoccupied molecular orbital. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra
78.40.Ha Other nonmetallic inorganics
61.72.up Other materials
73.22.-f Electronic structure of nanoscale materials and related systems
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Highly sensitive optical monitoring of molecular film growth by organic molecular beam deposition

C. Goletti, G. Bussetti, P. Chiaradia, A. Sassella, and A. Borghesi

Appl. Phys. Lett. 83, 4146 (2003); http://dx.doi.org/10.1063/1.1626810 (3 pages) | Cited 20 times

Online Publication Date: 12 November 2003

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Reflectance anisotropy spectroscopy (RAS) has been employed to study in situ the growth of thin α-sexithiophene films by organic molecular beam deposition onto an organic substrate. A large anisotropy can be detected by following the line shape evolution of the RAS spectrum; in addition, the signal variation at a fixed wavelength is used to monitor the film growth. The signal intensity scales with the deposited thickness, demonstrating a very high sensitivity of RAS to less than 1/50 of a monolayer. Evidence of the advantages of RAS to monitor in real time the growth of molecular films and to probe in situ their properties is therefore obtained. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Qn Polymers; organic compounds

Structural and optical properties of strain-compensated GaAsSb/GaAs quantum wells with high Sb composition

X. H. Zheng, D. S. Jiang, S. Johnson, and Y. H. Zhang

Appl. Phys. Lett. 83, 4149 (2003); http://dx.doi.org/10.1063/1.1628395 (3 pages) | Cited 6 times

Online Publication Date: 12 November 2003

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The structural and optical properties of GaAsSb/GaAs quantum wells (QWs) and strain-compensated GaAsP/GaAs/GaAsSb/GaAs/GaAsP QWs grown on a GaAs substrate by molecular beam epitaxy are investigated using high-resolution x-ray diffraction and photoluminescence (PL) measurements. We demonstrated that the insertion of tensile GaAsP layers into the active region of GaAsSb/GaAs QWs effectively improves the structural and optical quality. Even the Sb composition is as high as 0.39. The PL spectra at 11 K and room temperature indicate that the PL peak of strain-compensated QWs has a narrower linewidth and higher intensity in comparison to the sample without strain compensation. The results of PL peak blueshift with increasing excitation show the strain-compensated GaAsSb/GaAs interface characteristic of type-I band alignment. © 2003 American Institute of Physics.
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68.65.Fg Quantum wells
78.67.De Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors

Long-wavelength emission from nitridized InAs quantum dots

Takashi Kita, Yoshitaka Masuda, Takayoshi Mori, and Osamu Wada

Appl. Phys. Lett. 83, 4152 (2003); http://dx.doi.org/10.1063/1.1627943 (2 pages) | Cited 7 times

Online Publication Date: 12 November 2003

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A technique to grow InAs quantum dots (QDs) to extend the emission wavelength into 1.3 μm range has been developed. We performed nitridation after growing InAs QDs by molecular-beam epitaxy. During nitridation, the reflection high-energy electron diffraction keeps chevron patterns, as well as streak rods, coming from the wetting layer. A longer-wavelength emission line with a narrower spectral linewidth compared with those of InAs QDs has been observed. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.30.Fs III-V and II-VI semiconductors
73.21.La Quantum dots
42.55.Px Semiconductor lasers; laser diodes
73.20.Hb Impurity and defect levels; energy states of adsorbed species
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots

Localization of intrinsic defects in CaF2–BaF2 superlattices

Ricardo Kagimura, H. Chacham, T. M. Schmidt, and R. H. Miwa

Appl. Phys. Lett. 83, 4154 (2003); http://dx.doi.org/10.1063/1.1627473 (3 pages)

Online Publication Date: 12 November 2003

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We perform first-principles calculations for the formation energies of fluorine self-interstitials (Fi−) and fluorine vacancies (VF+) in CaF2–BaF2 superlattices and in the corresponding bulk compounds. In dislocation-free (strained-layer) superlattices, the calculations show that both the Fi− and the VF+ defects are energetically more stable in the CaF2 layers than in the BaF2 layers. If the misfit stress in the superlattices is released (by dislocations, for instance), our results indicate that charge transfer between layers becomes energetically favorable with Fi− in the CaF2 layers and VF+ in the BaF2 layers. This is consistent with recent experiments. © 2003 American Institute of Physics.
Show PACS
68.65.Cd Superlattices
61.72.J- Point defects and defect clusters
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