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22 Feb 1993

Volume 62, Issue 8, pp. 793-901

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Planar optical waveguides formed by erbium ion exchange in glass

X. H. Zheng and R. J. Mears

Appl. Phys. Lett. 62, 793 (1993); http://dx.doi.org/10.1063/1.108580 (3 pages) | Cited 5 times

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We report the use of erbium ion as the sole dopant in the formation of planar optical waveguides on glass substrates through a simple ion exchange process. Index differences of more than 0.04 have been achieved. This offers the prospect of designing active optical waveguides free from the unwanted side effects of additional index‐raising dopants currently used in the ion exchange process.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
61.72.up Other materials

Microgun‐pumped semiconductor laser

E. Molva, R. Accomo, G. Labrunie, J. Cibert, C. Bodin, Le Si Dang, and G. Feuillet

Appl. Phys. Lett. 62, 796 (1993); http://dx.doi.org/10.1063/1.108581 (3 pages) | Cited 22 times

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We demonstrate the feasibility of a novel microgun‐pumped semiconductor laser. This is the most compact (a few cm3) and the lowest threshold electron‐beam‐pumped semiconductor laser ever reported. The electron source is provided by a 104–105/mm2 array of field emissive microtip cathodes each of 1.5 μm diam. The laser operates below 10 kV and below 1 A/cm2. Laser action in a quasi‐cw mode with 5 μs pulses at 2 kHz has been obtained between 90 and 300 K with CdTe‐CdMnTe graded index separate confinement quantum‐well heterostructures, as well as with GaAs‐GaAlAs structures. Since neither doping nor ohmic contacts are needed, the microgun laser can use all direct gap semiconductors. It appears as a viable solution for making compact II‐VI lasers in the visible domain.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Influence of water vapor on the susceptibility to electric‐field damage of KTiOPO4

P. A. Morris and M. K. Crawford

Appl. Phys. Lett. 62, 799 (1993); http://dx.doi.org/10.1063/1.108582 (3 pages) | Cited 3 times

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We demonstrate that the susceptibilities of hydrothermal and flux grown KTiOPO4 (KTP) crystals to electric‐field induced darkening increase with increasing water vapor content of the atmosphere surrounding the crystals. Infrared spectroscopy shows that hydrogen ions from the atmosphere migrate into the crystals in the presence of the applied electric field and charge compensate the formation of Ti3+ defects which are responsible for damage. These observations suggest that KTP‐based electro‐optic devices should be operated in a dry environment to reduce their susceptibility to damage.
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78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
61.72.-y Defects and impurities in crystals; microstructure
66.30.J- Diffusion of impurities
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

High brightness blue and green light sources pumped with a 980 nm emitting laser diode

Yoh Mita, Y. Wang, and S. Shionoya

Appl. Phys. Lett. 62, 802 (1993); http://dx.doi.org/10.1063/1.108583 (3 pages) | Cited 12 times

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Efficient frequency upconversion from 980 nm infrared light to 480 nm wavelength blue emission has been observed in Tm3+‐activated, Yb3+‐sensitized fluoride glass. Similar upconversion to green emission has been obtained with higher efficiency in Er3+‐containing luminescent materials. The conversion efficiencies have been markedly improved when the luminescent material small in size is contained in a reflective cavity. The improvement effect is pronounced when transparent luminescent material is adopted. Processes leading to the generation of visible emission have been examined and criteria for optimizing the upconversion efficiency are presented.
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42.72.Bj Visible and ultraviolet sources
42.79.Nv Optical frequency converters

New infrared injection‐seeded optical parametric oscillator with high energy and narrow bandwidth output

F. Huisken, A. Kulcke, D. Voelkel, C. Laush, and J. M. Lisy

Appl. Phys. Lett. 62, 805 (1993); http://dx.doi.org/10.1063/1.108584 (3 pages) | Cited 23 times

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We report on a new infrared injection‐seeded optical parametric oscillator with narrow bandwidth (Γ≤0.2 cm−1) and high energy (E≥4 mJ/pulse) output between 2.5 and 4 μm which has been developed for cluster spectroscopy in molecular beams. The oscillator contains a LiNbO3 crystal pumped by the 1.064 μm fundamental of a Q‐switched Nd:YAG laser. In order to reduce the linewidth and to increase the output energy, it is seeded with narrow bandwidth IR‐radiation obtained by difference frequency mixing the output of a tunable dye laser with the second harmonic of the same Nd:YAG laser in a LiIO3 crystal.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.72.Ai Infrared sources

Aspheric waveguide lenses for photonic integrated circuits

J.‐M. Verdiell, M. A. Newkirk, T. L. Koch, R. P. Gnall, U. Koren, B. I. Miller, and L. L. Buhl

Appl. Phys. Lett. 62, 808 (1993); http://dx.doi.org/10.1063/1.108585 (3 pages) | Cited 8 times

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We report the fabrication of aspheric waveguide lenses on the InP/InGaAsP material system. A wide aperture (f/5) lens working at 1.5 times the diffraction limit is reported. Insertion loss below 1 dB is also measured. The lens is fabricated by a selective chemical etch of a planar waveguide and has potential applications in InP‐based photonic integrated circuits.  
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Gw Other integrated-optical elements and systems

Simple in‐line method to measure the dispersion of an optical system

X. Steve Yao and Jack Feinberg

Appl. Phys. Lett. 62, 811 (1993); http://dx.doi.org/10.1063/1.108586 (3 pages) | Cited 1 time

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We describe a simple in‐line method to measure the dispersion of an optical system. The light beam passing through the optical system interferes with a reference beam in a spectrometer, and the resulting spectrum yields the quadratic and cubic dispersion terms of the system. We demonstrate this technique on an optical system made of grating pairs.
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42.87.-d Optical testing techniques
42.62.Fi Laser spectroscopy
07.60.Ly Interferometers

Source of sidelobe asymmetry in integrated acousto‐optic filters

D. A. Smith, A. d’Alessandro, J. E. Baran, and H. Herrmann

Appl. Phys. Lett. 62, 814 (1993); http://dx.doi.org/10.1063/1.108587 (3 pages) | Cited 20 times

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The often‐observed extreme asymmetry in the sidelobe spectra of integrated acousto‐optic filters exacerbates cross talk between wavelength‐multiplexed optical channels. We explain the source of this asymmetry in terms of a systematic even‐order variation of the effective waveguide birefringence as a function of distance from the device center. Calculations show what degree of nonuniformity in Ti‐stripe thickness, width, or diffusion temperature are required to account for typical asymmetries. We describe two experiments in which temperature gradients were applied to low‐power acousto‐optic filters in order to induce sidelobe suppression on either side of the optical transmission function, while greatly enhancing sidelobes on the opposite side.  
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.79.Ci Filters, zone plates, and polarizers
42.25.Lc Birefringence

Cross-sectional transmission electron microscopy parallel to the active stripe of degraded buried heterostructure distributed feedback laser devices

S. N. G. Chu and S. Nakahara

Appl. Phys. Lett. 62, 817 (1993); http://dx.doi.org/10.1063/1.108588 (3 pages) | Cited 5 times

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We demonstrate for the first time that cross-sectional transmission electron microscopy can be applied parallel to the active stripe of a distributed feedback buried heterostructure laser diode to identify the cause for degradation during reliability qualification. A dominant defect mechanism is found to be the generation of dislocation loops at or near the grating/waveguide-layer interface which subsequently propagate up through the multilayer structure. The vertical segments of the loops tend to be trapped onto the {111} planes to form a V-shaped configuration as revealed in the (011) cross section. A dislocation reaction mechanism is proposed to explain the observed dislocation configuration. Furthermore, complicated dislocation loops are grown out of the segments of dislocation threading through the active region forming <100≳ dark line defects revealed by the electroluminescence. The defect growth mechanism is believed to be a condensation of point defects induced by the nonradiative recombination assisted point defect migration process similar to that previously observed in degraded channeled substrate buried heterostructure lasers. The nucleation of dislocations at or near the grating/waveguide layer interface is consistent with a high interfacial strain observed in the degraded devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Mi Dynamical laser instabilities; noisy laser behavior
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Distributed feedback strained layer quantum well heterostructure 980 nm laser fabricated by two‐step metalorganic chemical vapor deposition

T. M. Cockerill, J. Honig, D. V. Forbes, and J. J. Coleman

Appl. Phys. Lett. 62, 820 (1993); http://dx.doi.org/10.1063/1.108589 (3 pages) | Cited 6 times

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Data are presented for single longitudinal mode, strained‐layer AlGaAs‐GaAs‐InGaAs quantum well heterostructure distributed feedback lasers emitting near 980 nm. Device fabrication consists of conventional holographic photolithography and two‐step metalorganic chemical vapor deposition growth. Regrowth over a GaAs grating layer and GaAs solid phase mass transport are discussed. The lasers are single mode up to twice Ith, have differential quantum efficiencies of 50%, and have threshold current densities of 600 A/cm2.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Stimulated Raman scattering from a laser‐produced Pb vapor

Yasuhiro Akiyama, Yuuki Matsunawa, Katsumi Midorikawa, Minoru Obara, and Hideo Tashiro

Appl. Phys. Lett. 62, 823 (1993); http://dx.doi.org/10.1063/1.108590 (3 pages)

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We have demonstrated that the Pb metal vapor produced by moderate laser irradiation is an effective medium for stimulated electronic Raman scattering. The maximum density of 1016 cm−3 of Pb atoms in the ground state was produced by focusing a Nd:YAG laser pulse onto a solid Pb target at the focused intensity of 40 MW/cm2. A 277‐nm pump pulse of 50‐mJ energy and of 5‐ns width (FWHM) was converted to the Stokes pulse (393 nm) of 0.1 mJ.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
79.20.Ds Laser-beam impact phenomena

Polarization insensitive multiple quantum well laser amplifiers for the 1300 nm window

L. F. Tiemeijer, P. J. A. Thijs, T. van Dongen, R. W. M. Slootweg, J. M. M. van der Heijden, J. J. M. Binsma, and M. P. C. M. Krijn

Appl. Phys. Lett. 62, 826 (1993); http://dx.doi.org/10.1063/1.108591 (3 pages) | Cited 36 times

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A polarization insensitive (less than 1 dB gain difference over the 3 dB gain bandwidth) multiple quantum well laser amplifier for the 1300 nm window is reported for the first time. The amplifiers employ a single active layer containing three tensile strained and four compressively strained quantum wells and show a fiber to fiber gain of 16 dB at 1310 nm and 200 mA driving current. Furthermore at the same wavelength these devices have a record low fiber coupled noise figure of 6.5 dB and a conveniently high fiber coupled saturation output power of 13 dBm for both polarizations.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes

Scanning microdeformation microscopy

B. Cretin and F. Sthal

Appl. Phys. Lett. 62, 829 (1993); http://dx.doi.org/10.1063/1.108592 (3 pages) | Cited 38 times

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We have developed a new scanning microscope based on a vibrating contact tip and piezoelectric detection. Scanning the sample reveals surface topography and mainly, subsurface elastic properties. The preliminary images presented show surface and subsurface inhomogeneities in metallic samples. Lateral resolution is essentially related to the tip diameter as in near‐field microscopes.
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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
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

Measurement of frequency spectrum of submillimeter‐wave gyrotron output using Michelson interferometer

T. Idehara, T. Tatsukawa, I. Ogawa, Y. Yamagishi, and T. Kanemaki

Appl. Phys. Lett. 62, 832 (1993); http://dx.doi.org/10.1063/1.109601 (2 pages) | Cited 1 time

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Measurements of frequency spectra of millimeter to submillimeter wave range and its application to gyrotron output are described. The results demonstrate that mode competition in the gyrotron between cyclotron fundamental (n=f/fc=1) and its harmonics (n=2,3,4,...) operations occurs in almost all cases, however, auxiliary operations can be suppressed about 30 dB lower than main operation by controlling an electron beam current and applied magnetic field.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers

Atomic resolution with an atomic force microscope using piezoresistive detection

M. Tortonese, R. C. Barrett, and C. F. Quate

Appl. Phys. Lett. 62, 834 (1993); http://dx.doi.org/10.1063/1.108593 (3 pages) | Cited 224 times

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A new detection scheme for atomic force microscopy (AFM) is shown to yield atomic resolution images of conducting and nonconducting layered materials. This detection scheme uses a piezoresistive strain sensor embedded in the AFM cantilever. The cantilever is batch fabricated using standard silicon micromachining techniques. The deflection of the cantilever is measured directly from the resistance of the piezoresistive strain sensor without the need for external deflection sensing elements. Using this cantilever we achieved 0.1 Årms vertical resolution in a 10 Hz–1 kHz bandwidth.
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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
68.35.B- Structure of clean surfaces (and surface reconstruction)

Photon‐assisted quantum transport in quantum point contacts

Qing Hu

Appl. Phys. Lett. 62, 837 (1993); http://dx.doi.org/10.1063/1.108567 (3 pages) | Cited 35 times

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We have studied the feasibility of photon‐assisted quantum transport in semiconductor quantum point contacts or electron waveguides. Due to photon‐induced intersubband transitions, it is expected that the drain/source conductance of the quantum point contacts can be modulated by far‐infrared (f≥300 GHz) radiation, which is similar to the photon‐assisted tunneling in superconducting tunnel junctions. An antenna/gate electrodes structure will be used to couple far‐infrared photons into quantum point contacts of submicron dimensions. A calculation of the photon‐induced drain/source current as a function of the far‐infrared radiation power is also presented.
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73.40.Gk Tunneling
73.50.Pz Photoconduction and photovoltaic effects
85.60.Gz Photodetectors (including infrared and CCD detectors)

Heavy p‐doping of ZnTe by molecular beam epitaxy using a nitrogen plasma source

J. Han, T. S. Stavrinides, M. Kobayashi, R. L. Gunshor, M. M. Hagerott, and A. V. Nurmikko

Appl. Phys. Lett. 62, 840 (1993); http://dx.doi.org/10.1063/1.108568 (3 pages) | Cited 36 times

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The successful p‐doping of ZnSe and Zn(S,Se) using a nitrogen plasma source during growth by molecular beam epitaxy has been an important factor leading to the recent realization of blue‐green diode lasers and light‐emitting diodes. This letter reports the results of the nitrogen doping of ZnTe using similar techniques. Doping levels approaching the 1019 cm−3 range are reported along with electrical, optical, and microstructural characterization. Highly doped ZnTe provides an opportunity for forming an ohmic contact to p‐ZnSe.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Interface roughness in quantum wells prepared with growth interruptions

Benno Orschel, Gerhard Oelgart, and Romuald Houdré

Appl. Phys. Lett. 62, 843 (1993); http://dx.doi.org/10.1063/1.108542 (3 pages) | Cited 16 times

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We use photoluminescence to examine GaAs/(AlGa)As single quantum wells of different thickness grown by molecular beam epitaxy with and without growth interruptions. We observed distinctive peaks arising from the heavy‐hole exciton splitting associated with heterointerface growth ‘‘islands.’’ Comparison of the exciton peak energies with the predictions of the theory proposed by L. C. Andreani and A. Pasquarello [Phys. Rev. B 42, 8928 (1990)] (which was supported by independent experiments) yields a constant value of 0.85 monolayers for the apparent thickness fluctuations given rise to the different exciton peaks observed from each well. This behavior strongly supports the bimodal roughness model of the heterointerface in quantum wells prepared with growth interruptions as it was recently suggested by C. A. Warwick and R. F. Kopf [Appl. Phys. Lett. 60, 386 (1992)].
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors

Si‐acceptor passivation on n‐type (AlGa)As post‐growth hydrogenation

M. Proctor, G. Oelgart, G. Lippold, and F.‐K. Reinhart

Appl. Phys. Lett. 62, 846 (1993); http://dx.doi.org/10.1063/1.108543 (3 pages) | Cited 3 times

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We have studied AlGaAs:Si grown by molecular beam epitaxy before and after post‐growth hydrogen plasma treatment by low temperature photoluminescence (PL) capacitance‐voltage, and Hall effect. The PL strength increases after hydrogen plasma treatment. We observe, for the first time, that in n‐type AlGaAs:Si not only the shallow donors but also the Si acceptor can be passivated by a long time (3 h) hydrogen diffusion, at 570 K. The change of the relative PL intensities associated with the Si and C acceptors demonstrates the dependence of the passivation effect on the chemical species.
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71.55.Eq III-V semiconductors
61.72.uj III-V and II-VI semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
78.55.Cr III-V semiconductors

Time‐dependent formalism for interband tunneling application to the InxGa1−xAs system

V. Sankaran and J. Singh

Appl. Phys. Lett. 62, 849 (1993); http://dx.doi.org/10.1063/1.108544 (3 pages)

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A formalism is presented to study interband tunneling which involves a direct, numerical solution of the time‐dependent Schrödinger equation, employing the tight‐binding representation for electronic states with an eight‐element (sp3) basis. Using this explicitly time‐dependent formalism, one can study the dynamics of interband tunneling in the presence of complicated space‐ and time‐dependent electric field profiles encountered in many devices. This technique is well suited to study interband tunneling in heterostructures since the tight‐binding method describes their band structure adequately. In conjunction with deformation potential theory, it can be applied to strained systems as well. The technique is applied to the important semiconductor system of InxGa1−xAs.
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73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Calcium fluoride thin films on GaAs(100) for possible metal‐insulator‐semiconductor applicationsa)

G. N. Chaudhari and V. J. Rao

Appl. Phys. Lett. 62, 852 (1993); http://dx.doi.org/10.1063/1.108545 (3 pages) | Cited 3 times

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Calcium fluoride thin films were deposited onto low‐temperature GaAs substrates by thermal evaporation followed by an in situ or ex situ annealing process. The influence of the deposition and annealing conditions on the structure and electronic properties of the films were investigated. It is shown that it was possible to obtain smooth epitaxial layers through in situ annealing. In addition, the substantial improvements in the electrical properties of the interfaces between GaAs and CaF2 have been obtained by in situ substrate annealing of CaF2 on GaAs(100) at 590 °C for 10 s which produced a dramatic reduction of capacitance frequency dispersion.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Correlation of optical and structural properties of light emitting porous silicon

H.‐J. Lee, Y. H. Seo, D.‐H. Oh, K. S. Nahm, E.‐K. Suh, Y. H. Lee, H. J. Lee, Y. G. Hwang, K.‐H. Park, S. H. Chang, and E. H. Lee

Appl. Phys. Lett. 62, 855 (1993); http://dx.doi.org/10.1063/1.109605 (3 pages) | Cited 11 times

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Microscopic structures of light emitting porous silicon layers have been studied. The samples prepared in an aqueous HF solution by anodizing p‐type silicon substrates show a strong positional dependence of photoluminescence and Raman spectra. The photoluminescence peaks are broad around 1.8 eV, where the photoluminescence intensities are comparable to that of GaAs at 5 K. We have found from Raman studies showing two characteristic peaks at 500 and 520 cm−1 that microscopic structures reveal gradual changes from porous silicon to a mixture of polycrystalline and hydrogenated amorphous phases as the probing spot is moved to the edge of the sample. This is explained by the redeposition of silicon atoms on top of the porous silicon layers near the edge of the sample as a result of liquid flow caused by bubbles of hydrogen gas which was produced near the surface of the sample during the anodization process.
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78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
82.45.-h Electrochemistry and electrophoresis

Virtual‐surfactant epitaxy of strained InAs/Al0.48In0.52As quantum wells

Eric Tournié and Klaus H. Ploog

Appl. Phys. Lett. 62, 858 (1993); http://dx.doi.org/10.1063/1.108546 (3 pages) | Cited 9 times

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The solid‐source molecular beam epitaxy growth of strained InAs films embedded in an Al0.48In0.52As matrix on InP substrates is studied by in situ reflection high‐energy electron diffraction. Under standard As stable conditions, the highly (3.2%) strained InAs film grows on Al0.48In0.52As in the Stranski–Krastanov mode. Islanding starts at a thickness of 8 monolayers. On the contrary, when growing InAs under In stable conditions, islanding is inhibited. The highly reactive In stable surface imposes kinetic limitations to the sticking atoms and forces two‐dimensional nucleation, thus acting as a virtual surfactant. This growth technique produces samples of superior quality and opens a new route for the preparation of strained heterostructures.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Minority electron mobility and lifetime in the p+GaAs base of AlGaAs/GaAs heterojunction bipolar transistors

D. M. Kim, S. Lee, M. I. Nathan, A. Gopinath, F. Williamson, K. Beyzavi, and A. Ghiasi

Appl. Phys. Lett. 62, 861 (1993); http://dx.doi.org/10.1063/1.108547 (3 pages) | Cited 15 times

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AlGaAs/GaAs heterojunction bipolar transistors with different base doping concentrations grown by gas source molecular beam epitaxy were fabricated and characterized at dc and high frequency. Three different base doping concentrations; 5×1018, 1×1019, and 5×1019 cm−3 doped with Be were used for the characterization with the same structural and process parameters, including 0.2 μm base width. Minority electron mobilities in heavily doped p type were measured as 1.1×103, 1.3×103, and 3×103 cm2 V/s for 5×1018, 1×1019, and 5×1019 cm−3, respectively, by using the current gain cutoff frequency (fT) which agrees well with theoretical predictions in heavily doped p‐type GaAs. Combining dc and high frequency measurements, electron lifetimes of 1.2×10−9, 5.5×10−10, and 2×10−11 s have been obtained for these three dopings, respectively.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
85.30.Pq Bipolar transistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

In situ oxidation of a thin layer of Ge on Si(001): Observation of GeO to SiO2 transition

K. Prabhakaran, T. Nishioka, K. Sumitomo, Y. Kobayashi, and T. Ogino

Appl. Phys. Lett. 62, 864 (1993); http://dx.doi.org/10.1063/1.108548 (3 pages) | Cited 13 times

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A thin layer of Ge grown on Si(001) surface is oxidized in situ and investigated using XPS, AES, RHEED, and MEIS. The samples used are, Ge layer formed by deposition at room temperature and SiGe mixed layer formed by deposition at 550 °C. Oxidation at 250 °C of the RT grown layer leads to the formation of GeO and on heating the surface to 360 °C, oxygen bonds with Si forming SiO2, thereby reducing GeO to elemental Ge. In the epitaxially grown layer (grown at 550 °C), after oxidation, SiO2 and a small amount of GeO are formed. Similar reaction takes place on this surface also, forming SiO2 as the final product on the surface. In the RT grown layer, after oxidation, MEIS shows evidence for the diffusion of Si through the Ge layer towards the surface.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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