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24 Jul 1989

Volume 55, Issue 4, pp. 325-411

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Three‐photon absorption in CaF2 at 248.5 nm

T. Tomie, I. Okuda, and M. Yano

Appl. Phys. Lett. 55, 325 (1989); http://dx.doi.org/10.1063/1.102417 (3 pages) | Cited 15 times

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Nonlinear absorption at 248.5 nm is studied with an 8 ps pulse. Two‐photon absorption in fused silica and three‐photon absorption in CaF2 are observed. Absorption coefficients are 8×10−11 cm/W and 2×10−21 cm3 /W2 for fused silica and CaF2 , respectively.
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78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Photorefractive gain and response time of Cr‐doped strontium barium niobate

Koichi Sayano, Amnon Yariv, and Ratnakar R. Neurgaonkar

Appl. Phys. Lett. 55, 328 (1989); http://dx.doi.org/10.1063/1.102418 (3 pages) | Cited 12 times

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We present experimental results on the photorefractive two‐beam coupling constant and response time of two Cr‐doped strontium barium niobate crystals with different dopant concentrations. Both showed significantly faster response times over Ce‐doped SBN:60, but with corresponding decreases in their coupling constants.
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78.66.-w Optical properties of specific thin films

Surface‐emitting two‐dimensional coherent semiconductor laser array

J. Buus, P. J. Williams, I. Goodridge, D. J. Robbins, J. Urquhart, A. P. Webb, T. Reid, R. Nicklin, P. Charles, D. C. J. Reid, and A. C. Carter

Appl. Phys. Lett. 55, 331 (1989); http://dx.doi.org/10.1063/1.101899 (3 pages) | Cited 3 times

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We describe a new surface‐emitting semiconductor structure, its fabrication, and its performance. Phase‐locked emission takes place from a region much larger than the wavelength in two dimensions; therefore we term this device a two‐dimensional coherent array. The key feature of our device is that the radiation is coupled directly from the active region using a nonresonant grating coupler, i.e., the grating is of noninteger order.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Lateral mode control of an AlGaAs laser array in a Talbot cavity

James R. Leger

Appl. Phys. Lett. 55, 334 (1989); http://dx.doi.org/10.1063/1.101900 (3 pages) | Cited 39 times

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The lateral mode thresholds of an external cavity AlGaAs laser diode array are measured as a function of cavity length. It is found that certain cavity lengths induce the array to lase in either the fundamental or highest order lateral mode. The results are explained using the theory of Talbot self‐imaging in fractional Talbot planes
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

High‐brightness terahertz beams characterized with an ultrafast detector

Martin van Exter, Ch. Fattinger, and D. Grischkowsky

Appl. Phys. Lett. 55, 337 (1989); http://dx.doi.org/10.1063/1.101901 (3 pages) | Cited 22 times

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We have significantly improved the emission and detection of electromagnetic beams of single‐cycle 0.5 THz pulses, through the use of new dipolar antenna structures. The frequency response was extended to well beyond 1 THz, and the beam power was increased by more than 15 times. The antennas were located at the foci of sapphire lenses and were photoconductively driven by ultrafast laser pulses. An additional collimation by a paraboloidal mirror produced a beam with a 25 mrad divergence, and subsequent focusing by a second identical mirror improved the coupling between the transmitting and receiving antenna by orders of magnitude.
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84.40.Ba Antennas: theory, components and accessories
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Room‐temperature electroabsorption and switching in a GaAs/AlGaAs superlattice

I. Bar‐Joseph, K. W. Goossen, J. M. Kuo, R. F. Kopf, D. A. B. Miller, and D. S. Chemla

Appl. Phys. Lett. 55, 340 (1989); http://dx.doi.org/10.1063/1.101902 (3 pages) | Cited 54 times

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We report room‐temperature observation of Wannier–Stark localization in a GaAs/AlGaAs superlattice. We show that large modulation can be obtained over a wide spectral range and demonstrate the operation of a self‐electro‐optic effect device.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.60.-q Optoelectronic devices

Experimental study of guided‐wave modes in 1.3 μm InGaAsP light‐emitting diodes

P. A. Folkes, G. Henein, T. Wessel, A. Mantie, J. Hessler, and A. Ceruzzi

Appl. Phys. Lett. 55, 343 (1989); http://dx.doi.org/10.1063/1.101903 (3 pages)

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We report the results of an experimental study of the far‐field characteristics of InGaAsP edge‐emitting light‐emitting diodes. Our results show that the asymmetric structure in the transverse far‐field distribution of the device is caused by modes which are supported by the asymmetric dielectric waveguide. These modes propagate in the InP cladding layer with the higher refractive index at an angle to the fundamental mode. Their relative intensities, compared to the fundamental mode intensity, increase as the active layer thickness decreases below 0.1 μm, accounting for the observed concomitant decrease in the fiber‐coupling efficiency of these devices.
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85.60.Jb Light-emitting devices
42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics

Deep ultraviolet laser etching of vias in polyimide films

G. V. Treyz, R. Scarmozzino, and R. M. Osgood

Appl. Phys. Lett. 55, 346 (1989); http://dx.doi.org/10.1063/1.101904 (3 pages) | Cited 10 times

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A deep ultraviolet cw laser has been used to form vias in a polyimide film. The etched features have smooth sidewalls and high aspect ratios. The observations are consistent with an etching mechanism based on thermal decomposition.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
79.20.Ds Laser-beam impact phenomena

All‐silicon integrated optical modulator for 1.3 μm fiber‐optic interconnects

B. R. Hemenway, O. Solgaard, and D. M. Bloom

Appl. Phys. Lett. 55, 349 (1989); http://dx.doi.org/10.1063/1.101905 (2 pages) | Cited 12 times

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We report an all‐silicon fiber‐optic light modulator which relies on free‐carrier optical dispersion and mode filtering in single‐mode fibers. Greater than 10% peak‐to‐peak intensity modulation over a 200 MHz bandwidth for 10 mA rf current modulation at 1.3 μm wavelength is demonstrated.
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42.81.Qb Fiber waveguides, couplers, and arrays
42.79.Hp Optical processors, correlators, and modulators
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.30.Pq Bipolar transistors

Formation of crystalline diamond from amorphous diamond‐like carbon films by pulsed laser irradiation

K. Solomon Harshavardhan, R. S. Yalamanchi, and L. Kameswara Rao

Appl. Phys. Lett. 55, 351 (1989); http://dx.doi.org/10.1063/1.101906 (3 pages) | Cited 7 times

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The formation of crystalline diamond films from amorphous diamond‐like carbon films by pulsed laser irradiation with a 300 μs non‐Q‐switched Nd:YAG laser has been established by a combined study of transmission electron microscopy, x‐ray photoelectron spectroscopy, and electrical resistivity. The films have been prepared by glow discharge decomposition of a mixture of propane, n‐butane, and hydrogen in a rf plasma operating at a frequency of 13.56 MHz. Prior to laser irradiation, the films have been found to be amorphous by transmission electron microscope studies. After irradiation, the electron diffraction patterns clearly point out the formation of cubic diamond structure with a lattice spacing of 3.555 Å. However, the close similarity between diamond and graphite electron diffraction patterns could sometimes be misleading regarding the formation of a diamond structure, and hence, x‐ray photoelectron spectroscopic studies have been carried out to confirm the results. A chemical shift in the C 1s core level binding energies towards higher values, viz., from 286.5 to 287.8 eV after laser irradiation, and a high electrical resistivity >1013 Ω cm are consistent with the growth of diamond structure. This novel ‘‘low‐temperature, low‐pressure’’ synthesis of diamond films offers enormous potential in terms of device compatibility with other solid‐state devices.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Anisotropy effects on fracto‐emission from MgF2 single crystals

K. C. Yoo, R. G. Rosemeier, J. T. Dickinson, and S. C. Langford

Appl. Phys. Lett. 55, 354 (1989); http://dx.doi.org/10.1063/1.102419 (3 pages) | Cited 5 times

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An important component of fracto‐emission is the emission of electrons (EE) accompanying the fracture of materials. In this letter we present measurements of EE accompanying the fracture of MgF2 single crystals loaded in three‐point bend. In particular, we examine the effect of changing the crystal orientation relative to the loading direction on emission intensity. We find that fracture surfaces with different crystal orientations yield significantly different EE. We propose that this is due to differences in the density of defects produced by such a fracture.
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79.75.+g Exoelectron emission
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Direct measurements of Cu diffusion into a polyimide below the glass transition temperature

F. Faupel, D. Gupta, B. D. Silverman, and P. S. Ho

Appl. Phys. Lett. 55, 357 (1989); http://dx.doi.org/10.1063/1.101907 (3 pages) | Cited 26 times

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Diffusion of a metal (Cu) into a fully cured polymer (polyimide) below the glass transition has been systematically investigated for the first time by means of low‐energy ion sputtering in combination with a radiotracer technique. The penetration profiles exhibit a steep non‐Fickian decay of the tracer concentration over several orders of magnitude followed by a relatively flat Fickian tail. The initial decay is attributed to the formation of Cu clusters and is discussed in terms of a Monte Carlo simulation. The Fickian tail is related to the diffusion of single Cu atoms. Diffusion measured at the lowest temperature deviates from linearity on the Arrhenius plot and seems to be controlled by a free‐volume mechanism of diffusion below the glass transition temperature.
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66.30.J- Diffusion of impurities
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
68.35.Fx Diffusion; interface formation
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Heteroepitaxial growth of Y2O3 films on silicon

Hirofumi Fukumoto, Takeshi Imura, and Yukio Osaka

Appl. Phys. Lett. 55, 360 (1989); http://dx.doi.org/10.1063/1.102420 (2 pages) | Cited 57 times

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Yttria (Y2 O3 ) films have been grown on Si (100) and Si (111) substrates heated at 800 °C by vacuum evaporation. X‐ray diffraction and reflection high‐energy electron diffraction observations reveal the heteroepitaxial growth of Y2 O3 films on Si (100) and Si (111) substrates. The (111) oriented Y2 O3 films are grown directly on Si (111) substrates. The (100) oriented Y2 O3 films are grown on the thin (Y2 O3 )0.09 (ZrO2 )0.91 layer predeposited on Si (100) substrates instead of direct growth on Si (100) substrates.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Growth temperature dependent radiative relaxation in AlGaAs/GaAs multiple quantum wells

Hideaki Matsueda and Kiyoaki Hara

Appl. Phys. Lett. 55, 362 (1989); http://dx.doi.org/10.1063/1.101893 (3 pages) | Cited 8 times

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Decay times of photoexcited electrons in AlGaAs/GaAs multiple quantum wells are evaluated using a time‐correlated photon counting method. The decay time was observed to increase with crystal growth temperature between 600 and 730 °C for metalorganic chemical vapor deposition. It also increased with the photoluminescence sample temperature, in agreement with theoretical considerations based on Fermi’s golden rule.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Optical characterization of stress in narrow GaAs stripes on patterned Si substrates

J. De Boeck, K. Deneffe, J. Christen, D. J. Arent, and G. Borghs

Appl. Phys. Lett. 55, 365 (1989); http://dx.doi.org/10.1063/1.101894 (3 pages) | Cited 14 times

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Photoluminescence (PL) and spatially resolved cathodoluminescence (CL) techniques are used to characterize the stress in narrow GaAs stripes grown on Si platforms. Since no overgrowth occurs over the recess edges, the GaAs stripes are grown unconstrained along one dimension. A duplication of the optical transitions is found in the PL spectrum from a region containing embedded GaAs and stripes. The peaks in the high‐energy shoulders of the PL spectrum are identified by CL measurements with high spatial resolution as the luminescence contribution of the GaAs stripes. They are submitted to lower internal stress values. A study on the geometrical dependence of the strain regime shows that a nonuniform biaxial strain field with a dominant longitudinal component is present in the stripes. The uniform biaxial strain, found in GaAs on Si (001), is present at stripe intersections.
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68.60.Bs Mechanical and acoustical properties
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Wave function sweeping in AlxGa1−xAs‐GaAs quantum wells

K. Ensslin, D. Heitmann, and K. Ploog

Appl. Phys. Lett. 55, 368 (1989); http://dx.doi.org/10.1063/1.101873 (3 pages) | Cited 3 times

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Specially tailored gated AlxGa1−xAs‐GaAs quantum well (QW) structures have been prepared, where it is possible to sweep the maximum of the electron wave function and, thus, the electron density via the gate voltage very effectively from the substrate side of the QW to the front side. In our structure this sweeping is so pronounced that it leads to a unique influence on the actual band structure and cyclotron resonance mass.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
76.40.+b Diamagnetic and cyclotron resonances
76.30.Pk Conduction electrons
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Observation of intrinsic bistability in resonant tunneling diode modeling

R. K. Mains, J. P. Sun, and G. I. Haddad

Appl. Phys. Lett. 55, 371 (1989); http://dx.doi.org/10.1063/1.101874 (3 pages) | Cited 31 times

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Intrinsic bistability has been observed experimentally and attributed to the effect on the potential profile from stored charge in the quantum well through Poisson’s equation. This effect leads to two possible current states corresponding to a single voltage within the negative resistance region. In this letter a simulation method is presented which clearly shows bistability in the current‐voltage curve of a resonant tunneling diode. This method self‐consistently combines a Thomas–Fermi equilibrium model for the electron concentrations outside the double‐barrier structure with a quantum calculation for the concentration inside the structure.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling

Photon emission from avalanche breakdown in the collector junction of GaAs/AlGaAs heterojunction bipolar transistors

J. Chen, G. B. Gao, D. Huang, J. I. Chyi, M. S. Ünlü, and H. Morkoç

Appl. Phys. Lett. 55, 374 (1989); http://dx.doi.org/10.1063/1.101875 (3 pages) | Cited 8 times

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The base‐collector junction of GaAs/AlGaAs single heterojunction bipolar transistors has been observed to emit light at avalanche breakdown. The spectral distribution curve exhibits broad peaks at 2.03 and 1.43 eV, with the intensities dependent upon the reverse current. These observations suggest that electrons, excited to the upper conduction band by the field, lose their energy by impact ionizing electron‐hole pairs and producing the 2.03 eV light, which corresponds to the threshold energy for electron impact ionization. The band‐edge emission is the result of direct‐gap free‐carrier recombination and self‐absorption of the high‐energy transition.
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85.30.Pq Bipolar transistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b Surface treatments

Quantum device microfabrication: Resolution limits of ion beam patterning

A. Scherer and M. L. Roukes

Appl. Phys. Lett. 55, 377 (1989); http://dx.doi.org/10.1063/1.101876 (3 pages) | Cited 18 times

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We have achieved precise control of the lateral electrical damage accompanying ion beam patterning of submicron electron devices from semiconductor materials. In situ transport measurements, made in the etching chamber during the definition process, provide an exact and reproducible means of end‐point detection, irrespective of material structure and ion beam parameters. We apply this to routinely fabricate conducting channels having widths below 100 nm from high‐mobility GaAs/AlGaAs heterojunctions. Subsequent low‐temperature magnetotransport measurements and successive optimization of processing conditions enable us to systematically obtain the minimum conducting width. Through these studies we explore the ultimate resolution limits of the ion beam patterning process.
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61.80.Jh Ion radiation effects
81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Far‐infrared magneto‐optical study of Hg1−xCdxTe superlattices with graded composition

Z. Yang, M. Dobrowolska, H. Luo, J. K. Furdyna, J. T. Cheung, and N. Otsuka

Appl. Phys. Lett. 55, 380 (1989); http://dx.doi.org/10.1063/1.101877 (3 pages) | Cited 2 times

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Far‐infrared magnetotransmission experiments were carried out on two Hg1−xCdxTe superlattices with graded composition grown by laser molecular beam epitaxy. A superlattice k⋅p model was used to calculate the subband structures of the superlattices. Good agreement is found between the experimental results and the theory if the valence‐band offset is assumed to be small.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Electroabsorption and electrorefraction in GaAs/AlGaAs waveguides containing asymmetric coupled quantum wells

K. W. Steijn, R. P. Leavitt, and J. W. Little

Appl. Phys. Lett. 55, 383 (1989); http://dx.doi.org/10.1063/1.101878 (3 pages) | Cited 6 times

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Changes in the optical phase and transmission with applied electric fields were measured in GaAs/AlGaAs waveguides containing asymmetric coupled quantum wells. At sufficiently high applied bias, the lowest energy optical transition supported by this system is that between the lowest energy hole subband of the wide well and the lowest energy electron subband of the narrow well. We show that this interwell transition produces significant contributions to both the electroabsorption and the electrorefraction in the coupled quantum well system.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.-q Optoelectronic devices
42.79.Gn Optical waveguides and couplers

One step method to produce hydrogen by a triple stack amorphous silicon solar cell

G. H. Lin, M. Kapur, R. C. Kainthla, and J. O’M. Bockris

Appl. Phys. Lett. 55, 386 (1989); http://dx.doi.org/10.1063/1.101879 (2 pages) | Cited 8 times

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A new direct one step method to split the water into hydrogen and oxygen by using a triple stack amorphous silicon solar cell with an n‐i‐p‐n‐i‐p‐n‐i‐p structure is reported. The ruthenium oxide layer, which is directly painted on the back surface of the solar cell, catalytically aids the evolution of the oxygen. The isolated islands of platinum deposited on the top side of the cell materially help the production of hydrogen. The conversion efficiency of 5% of solar to chemical energy in steady state is achieved under simulated AM1, 100 mW/cm2 solar radiation.
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82.47.-a Applied electrochemistry
84.60.Jt Photoelectric conversion
82.45.-h Electrochemistry and electrophoresis

Nature of Pb in superconducting cuprates containing lead: A Pb L3 x‐ray absorption near‐edge spectroscopy study

G. U. Kulkarni, G. Sankar, and C. N. R. Rao

Appl. Phys. Lett. 55, 388 (1989); http://dx.doi.org/10.1063/1.102421 (2 pages) | Cited 3 times

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X‐ray absorption near‐edge spectroscopy studies show that Pb in superconducting Tl0.5Pb0.5CaSr2Cu2O7+δ is essentially in the 4+ state while it is in the 2+ state in Pb2Sr2Ca1−xLnxCu3O8+δ.
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74.70.-b Superconducting materials other than cuprates
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
78.70.Dm X-ray absorption spectra
71.23.An Theories and models; localized states

Superconducting Bi‐Sr‐Ca‐Cu‐O crystalline fibers prepared by the micro‐Czochralski method

Akihito Kurosaka, Mamoru Aoyagi, Haruo Tominaga, Osamu Fukuda, and Hiroshi Osanai

Appl. Phys. Lett. 55, 390 (1989); http://dx.doi.org/10.1063/1.101880 (3 pages) | Cited 7 times

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Superconducting Bi‐Sr‐Ca‐Cu‐O crystalline fibers were successfully prepared by the micro‐Czochralski method from Bi2Sr2 CaCu2 Ox source ceramic rods. The maximum length of the fibers obtained was 55 mm (0.3 mm diameter). The fiber crystal grains were oriented with the current carrying a‐b basal planes parallel to the fiber axis. The values of Tc (zero) and Jc (77 K and zero magnetic field) for these fibers were ∼84 K and ∼3170 A/cm2 , respectively.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.10.Fq Growth from melts; zone melting and refining
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Evidence for local composition variations within YBa2Cu3O7−δ grain boundaries

S. E. Babcock and D. C. Larbalestier

Appl. Phys. Lett. 55, 393 (1989); http://dx.doi.org/10.1063/1.102422 (3 pages) | Cited 40 times

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The composition variations associated with grain boundaries in bulk sintered YBa2Cu3O7−δ have been investigated by means of energy‐dispersive x‐ray microanalysis in a high spatial resolution scanning transmission electron microscope. A series of composition profiles indicates that considerable variations in composition occur on a very local scale both parallel and perpendicular to these grain boundaries. The regular, oscillatory (period ∼25 nm) nature of the composition variations observed along a grain boundary suggests that these heterogeneities may be an intrinsic feature of the boundary. Some possible implications of these observations for percolative conduction mechanisms are discussed briefly.
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74.70.-b Superconducting materials other than cuprates
68.35.Dv Composition, segregation; defects and impurities
61.72.Mm Grain and twin boundaries
61.50.Nw Crystal stoichiometry
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