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10 Dec 1990

Volume 57, Issue 24, pp. 2517-2616

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Meander coupler, a novel wavelength division multiplexer/demultiplexer

C. Bornholdt, F. Kappe, R. Müller, H.‐P. Nolting, F. Reier, R. Stenzel, H. Venghaus, and C. M. Weinert

Appl. Phys. Lett. 57, 2517 (1990); http://dx.doi.org/10.1063/1.103841 (3 pages) | Cited 10 times

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We have realized a novel wavelength division multiplexer/demultiplexer based on rib waveguides in GaInAsP/InP. The device is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant and has sinc2‐type characteristics. Our devices have center wavelengths around 1.3 μm, filter half‐widths 10–15 nm, and far end isolation down to −17 dB. The structure is suited for integration into optoelectronic integrated circuits for applications in bidirectional optical communication systems.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.82.-m Integrated optics

Measurement of the gain saturation spectrum in InGaAsP diode lasers

Rudolf Frankenberger and Robert Schimpe

Appl. Phys. Lett. 57, 2520 (1990); http://dx.doi.org/10.1063/1.103842 (3 pages) | Cited 11 times

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The origin of nonlinear gain suppression in InGaAsP lasers is analyzed by experiments sensitive to small gain changes. The spectral distribution of gain change is determined by measuring the intensity modulation spectra of current modulated Fabry–Perot lasers with nearly single longitudinal mode emission. The gain change spectra show a cross saturation behavior as expected for spectral hole burning with a polarization relaxation time of about 0.07 ps. They do not reveal a dominant contribution of the gain and index grating induced by the cavity standing waves.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
85.60.Jb Light-emitting devices

Mode locking and frequency tuning of a laser diode array in an extended cavity with a photorefractive phase conjugate mirror

Mordechai Segev, Yoav Ophir, Baruch Fischer, and Gadi Eisenstein

Appl. Phys. Lett. 57, 2523 (1990); http://dx.doi.org/10.1063/1.103843 (3 pages) | Cited 5 times

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We demonstrate active mode locking and a tunable narrow spectrum under cw conditions in an extended cavity laser which uses an AlGaAs/GaAs array gain medium and an external feedback from a self‐pumped photorefractive phase conjugate mirror. The mirror ensures self‐aligned, spatially matched feedback. The mode‐locked pulses are 92 ps wide. The tuning, obtained by an intracavity grating, has a range of 70 Å under cw conditions.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Reversible modification of CdTe surface composition by excimer laser irradiation

P. D. Brewer, J. J. Zinck, and G. L. Olson

Appl. Phys. Lett. 57, 2526 (1990); http://dx.doi.org/10.1063/1.103844 (3 pages) | Cited 17 times

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KrF excimer laser irradiation of CdTe at fluences below the melt threshold (≤75 mJ/cm2) removes surface layers and produces reversible changes in the surface composition that depend upon the laser fluence and number of laser pulses delivered to the surface. At fluences above ∼40 mJ/cm2 a Te‐rich layer is obtained. A stoichiometric composition can be restored by irradiation at reduced laser fluence. The primary desorption products are Cd and Te2, and the velocities of these species are well described by a Maxwellian distribution. The fluence‐dependent changes in CdTe surface composition are consistent with a photothermal mechanism based on the competition between formation and desorption of Te2 and desorption of Cd atoms from the laser‐irradiated surface.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.60.Wm Other nonelectronic physical properties

Polymer‐dispersed chiral liquid crystal color display

P. P. Crooker and D. K. Yang

Appl. Phys. Lett. 57, 2529 (1990); http://dx.doi.org/10.1063/1.103845 (3 pages) | Cited 41 times

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We describe a new type of color display consisting of polymer‐dispersed droplets of chiral liquid crystal having negative dielectric anisotropy. In the field‐off state, the droplets scatter light randomly. In the field‐on state the droplets selectively reflect a bright color. Measurements of reflectivities and switching times are presented and we discuss possible applications.
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85.60.Pg Display systems
85.60.-q Optoelectronic devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
42.70.-a Optical materials

Optical sensitization at the phase transition in the ferroelectric vinylidene fluoride‐trifluoroethylene copolymer

K. A. Verkhovskaya, A. V. Bune, V. M. Fridkin, and J. F. Legrand

Appl. Phys. Lett. 57, 2532 (1990); http://dx.doi.org/10.1063/1.103846 (2 pages) | Cited 9 times

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At the ferroelectric phase transition in the optically sensitized ferroelectric vinylidene fluoride‐trifluoroethylene copolymers P(VDF‐TrFE) the sharp change of the dye energy level is revealed. In ferroelectric P(VDF‐TrFE) copolymer doped by indolynospiropyran the structural chromic effect is observed, which is characterized by the reversible change of the film color at the ferroelectric phase transition.
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77.80.B- Phase transitions and Curie point
78.20.-e Optical properties of bulk materials and thin films

Low‐threshold high‐efficiency high‐yield impurity‐induced layer disordering laser by self‐aligned Si‐Zn diffusion

W. X. Zou, K‐K. Law, A. C. Gossard, E. L. Hu, L. A. Coldren, and J. L. Merz

Appl. Phys. Lett. 57, 2534 (1990); http://dx.doi.org/10.1063/1.103847 (3 pages) | Cited 7 times

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Stripe geometry lasers defined by impurity‐induced layer disordering (IILD) have been fabricated utilizing a novel technology of self‐aligned Si‐Zn diffusion from which both optical and electrical confinements are obtained simultaneously. The fabrication process is considerably simpler than that for the conventional IILD lasers and the parasitic p‐n junction area in the laser structures is minimized. Typical lasers with threshold current Ith=5.2 mA and differential quantum efficiency ηd=81% at room‐temperature continuous operation as well as highly uniform yield ≳80% have been obtained.
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42.55.Px Semiconductor lasers; laser diodes
66.30.J- Diffusion of impurities
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

GaAs/AlGaAs photonic integrated circuits fabricated using chemically assisted ion beam etching

W. J. Grande, John E. Johnson, and C. L. Tang

Appl. Phys. Lett. 57, 2537 (1990); http://dx.doi.org/10.1063/1.103848 (3 pages) | Cited 14 times

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Photonic integrated circuits with a virtually complete set of active and passive devices are fabricated in the GaAs/AlGaAs system by single‐step chemically assisted ion beam etching. Using this straightforward processing technique, photonic integrated circuits consisting of etched facet ridge waveguide lasers coupled to passive waveguides, beamsplitters, etched turning mirrors, and photodetectors are demonstrated. The results presented point to the promise of this technique for the fabrication of future high‐complexity photonic integrated circuits.
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85.60.-q Optoelectronic devices
42.82.-m Integrated optics
42.55.Px Semiconductor lasers; laser diodes
42.79.Gn Optical waveguides and couplers

Mechanism for efficient blue second‐harmonic generation in periodically segmented waveguides

J. Khurgin, S. Colak, R. Stolzenberger, and R. N. Bhargava

Appl. Phys. Lett. 57, 2540 (1990); http://dx.doi.org/10.1063/1.103849 (3 pages) | Cited 11 times

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We present a theoretical investigation of the mechanisms responsible for the recently reported efficient type I blue second‐harmonic generation in periodically segmented KTiOPO4:Rb,Tl waveguides. In these guides, grating‐assisted phase matching of second‐harmonic light between 390 and 480 nm has been achieved. 5‐mm‐long guides give output powers on the order of 1 mW at around 425 nm with fundamental powers in the 50–100 mW range. We show that such high efficiencies can be expected from strongly perturbed guides through terms representing the modulation of phase mismatch and mode size in addition to the nonlinear susceptibility and refractive index modulations.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Gn Optical waveguides and couplers
42.55.Rz Doped-insulator lasers and other solid state lasers
78.20.Bh Theory, models, and numerical simulation

Microwave plasma generation of arsine from hydrogen and solid arsenic

Thomas R. Omstead, Ananth V. Annapragada, and Klavs F. Jensen

Appl. Phys. Lett. 57, 2543 (1990); http://dx.doi.org/10.1063/1.104182 (3 pages) | Cited 3 times

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The generation of arsine from the reactions of hydrogen and elemental arsenic in a microwave plasma reactor is described. The arsenic is evaporated from a solid source upstream and carried into the microwave plasma region by a mixture of hydrogen and argon. Stable reaction products, arsine and diarsine are observed by molecular beam sampled mass spectroscopy along with partially hydrogenated species (e.g., AsH and AsH2). The effect of composition and flow rate of the argon/hydrogen carrier gas mixture on the amount of arsine generated is investigated. The arsine production reaches a maximum for an argon‐to‐hydrogen ratio of unity indicating that metastable argon species act as energy transfer intermediates in the overall reaction. The generation of arsine and diarsine from easily handled solid arsenic by this technique makes it attractive as a possible arsenic source for the growth of compound semiconductors by low‐pressure metalorganic chemical vapor deposition.<lz> <lz> <lz> <lz> <lz>
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.50.Dg Plasma sources
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
82.30.Nr Association, addition, insertion, cluster formation

Graphitic clusters in hydrogenated amorphous carbon induced by keV‐ion irradiation

G. Compagnini, G. Foti, R. Reitano, and G. Mondio

Appl. Phys. Lett. 57, 2546 (1990); http://dx.doi.org/10.1063/1.103832 (3 pages) | Cited 13 times

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Energy gap and hydrogen concentration have been measured in hydrogenated amorphous carbon (a‐C:H) after bombardment with 100 keV He+ and 300 keV Ar+ ion beams, up to ion fluences 3×1016 ions/cm2. a‐C:H films have been obtained by ion irradiation at low ion fluences of polystyrene layers and with a subsequent low‐temperature annealing (400 °C, 10 min). Experimental values for the energy gap (2.5–0.5 eV) and hydrogen concentration (7.4×1022–1.8×1022 H atoms/cm3) have been interpreted in terms of a graphitic cluster structure with a different size (3–20 Å). We were able to determine experimentally the value of the bond integral ‖β‖ and we found it in good agreement with the calculated one for graphite.
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78.66.Qn Polymers; organic compounds
61.80.Jh Ion radiation effects
68.55.-a Thin film structure and morphology

Expansion of amorphous carbon in W/C multilayers after annealing

Xiaoming Jiang, Dingchang Xian, and Ziqin Wu

Appl. Phys. Lett. 57, 2549 (1990); http://dx.doi.org/10.1063/1.103833 (3 pages) | Cited 18 times

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Dynamical optical dispersion theory is employed to analyze the variations of the positions and intensities of x‐ray diffraction peaks from the W/C multilayer. It is confirmed that the thickness of the C layer expands with the annealing temperature and the multilayer remains undamaged until 800 °C. There is an obvious drop of interfacial root mean square (rms) roughness at 600–800 °C.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Metal reactivity effects on the surface recombination velocity at InP interfaces

Y. Rosenwaks, Yoram Shapira, and D. Huppert

Appl. Phys. Lett. 57, 2552 (1990); http://dx.doi.org/10.1063/1.103814 (3 pages) | Cited 17 times

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Direct measurements of the surface recombination velocity (SRV) on etched InP(110) and at its interfaces with various metals deposited by thermal evaporation have been performed using ultrafast time‐resolved photoluminescence. The results show that the original InP low SRV is retained when these surfaces are coverd with metals which tend to react with the semiconductor’s anion, such as Al, Cr, and Zn. On the other hand, the SRV increases sharply as a function of unreactive metal coverage, such as Cu, Au, and Ag. The SRV results are explained in terms of metal‐induced interface states, whose position in the band gap and thus their cross section for recombination depends on the metal reactivity. The similarity of the SRV and the reported Schottky barrier height dependence on the metal‐phosphorus heat of reaction is noted.
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78.55.Cr III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.20.At Surface states, band structure, electron density of states
71.55.Eq III-V semiconductors

Orientation independence of heterojunction‐band offsets at GaAs‐AlAs heterointerfaces characterized by x‐ray photoemission spectroscopy

K. Hirakawa, Y. Hashimoto, and T. Ikoma

Appl. Phys. Lett. 57, 2555 (1990); http://dx.doi.org/10.1063/1.103815 (3 pages) | Cited 14 times

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We systematically studied the orientation and the growth sequence dependence of the valence‐band offset ΔEv at the lattice‐matched common anion GaAs‐AlAs interfaces. High quality GaAs‐AlAs heterojunctions were carefully grown on GaAs substrates with three major orientations, namely, (100), (110), and (111)B. The core level energy distance ΔECL between Ga 3d and Al 2p levels was measured by in situ x‐ray photoemission spectroscopy. ΔECL is found to be independent of the substrate orientation and the growth sequence, which clearly indicates the face independence of ΔEv. This result suggests that the band lineup at lattice‐matched isovalent semiconductor heterojunctions is determined </m1;&6p>by the bulk properties of the constituent materials. ΔEv is determined to be 0.44 ± 0.05 eV.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b Surface treatments

High transconductance and large peak‐to‐valley ratio of negative differential conductance in three‐terminal InGaAs/InAlAs real‐space transfer devices

Piotr M. Mensz, Paul A. Garbinski, Alfred Y. Cho, Deborah L. Sivco, and Serge Luryi

Appl. Phys. Lett. 57, 2558 (1990); http://dx.doi.org/10.1063/1.103816 (3 pages) | Cited 25 times

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Three‐terminal real‐space transfer devices with improved room‐temperature characteristics have been implemented in InGaAs/InAlAs/InGaAs heterostructures lattice matched to InP. The devices exhibit extremely sharp charge injection, characterized by a transconductance exceeding 23 S/mm and a negative differential conductance with a peak‐to‐peak ratio of over 7000. Our experiments suggest that both of these characteristics are limited only by the dielectric strength of the InAlAs barrier layer.
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72.20.Ht High-field and nonlinear effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Pa Thermoelectric and thermomagnetic effects
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Hydrogen in carbon‐doped GaAs grown by metalorganic molecular beam epitaxy

D. M. Kozuch, Michael Stavola, S. J. Pearton, C. R. Abernathy, and J. Lopata

Appl. Phys. Lett. 57, 2561 (1990); http://dx.doi.org/10.1063/1.103817 (3 pages) | Cited 53 times

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Atomic profiles show that hydrogen is incorporated in GaAs:C that has been grown by metalorganic molecular beam epitaxy. The hydrogen concentration has been found to be about 5% of the carbon concentration for our growth conditions. An infrared absorption study shows that this hydrogen is involved in stable C‐H complexes. At the lower C concentrations (<1019 cm−3) the CAs‐H complex is the dominant species involving C and H. At higher C concentrations new complexes involving C and H appear.
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61.72.Bb Theories and models of crystal defects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
85.40.Ls Metallization, contacts, interconnects; device isolation

Influence of temperature on defect creation during plasma exposure of SiO2 films

R. A. B. Devine

Appl. Phys. Lett. 57, 2564 (1990); http://dx.doi.org/10.1063/1.104183 (3 pages) | Cited 3 times

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Chemical vapor deposited silicon dioxide films have been exposed to ultraviolet radiation from a microwave excited Kr/F plasma. Sample temperatures during exposure were in the range 82–300 K. The creation of oxygen‐vacancy like defects was measured as a function of exposure time and temperature. Two possible defect creation mechanisms are suggested which would account for reduced creation efficiency at low temperatures, one involving hole injection from the substrate and the other, interaction of H with Si—H bonds. Both processes are diffusion limited.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
61.72.Bb Theories and models of crystal defects

Effect of interface quality on the electrical properties of p‐Si/SiGe two‐dimensional hole gas systems

T. Mishima, C. W. Fredriksz, G. F. A. van de Walle, D. J. Gravesteijn, R. A. van den Heuvel, and A. A. van Gorkum

Appl. Phys. Lett. 57, 2567 (1990); http://dx.doi.org/10.1063/1.103818 (3 pages) | Cited 20 times

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Electrical properties have been examined for single Si/Si0.8Ge0.2 p‐type modulation‐doped heterostructures which have been grown by molecular beam epitaxy. It is shown that the two‐dimensional hole gas in a normal modulation‐doped heterostructure (doped layer on the surface side) has a higher mobility than in an inverted structure (doped layer on the substrate side). Secondary‐ion mass spectrometry analysis indicates that the lower mobility in the inverted structure is due to surface segregation of boron. Hole mobilities as high as 6000 cm2/V s at 2 K and 3800 cm2/V s at 6 K have been obtained which are the highest values reported so far for Si/SiGe heterostructures.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Md Surface thermodynamics, surface energies
73.50.Dn Low-field transport and mobility; piezoresistance

Unpinning of GaAs surface Fermi level by 200 °C molecular beam epitaxial layer

D. C. Look, C. E. Stutz, and K. R. Evans

Appl. Phys. Lett. 57, 2570 (1990); http://dx.doi.org/10.1063/1.104110 (3 pages) | Cited 11 times

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Previous attempts to passivate the n‐type (100)GaAs surface have significantly reduced only the surface recombination centers, but not the surface acceptors which pin the Fermi level. Here we show that a 100 Å molecular beam epitaxial layer grown at 200 °C reduces the effective surface potential energy − eϕs from 0.70 to 0.17 eV, nearly eliminates light sensitivity, and permits nonalloyed ohmic contacts. After a 10 min, 450 °C anneal, − eϕs increases only to 0.22 eV.
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73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Cg Contact resistance, contact potential

Anomalous capacitance‐voltage characteristics of BF2‐implanted and rapid thermal annealed p+‐polycrystalline silicon gate metal‐oxide‐semiconductor structures

G. Q. Lo, D. L. Kwong, and S. Lee

Appl. Phys. Lett. 57, 2573 (1990); http://dx.doi.org/10.1063/1.103819 (3 pages) | Cited 5 times

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Anomalous capacitance‐voltage (C‐V) characteristics of BF2‐implanted p+‐polycrystalline silicon (polysilicon) gate metal‐oxide‐semiconductor (MOS) structures annealed by rapid thermal annealing (RTA) are reported for the first time. It is found that both high‐frequency and quasi‐static C‐V curves exhibit an increased capacitance at the depletion and weak inversion regions, which increases with p+‐polysilicon RTA drive‐in durations. The quasi‐static C‐V curves show a gate bias dependence of the inversion capacitance which shows a distorted ‘‘plateau’’ (i.e., reduced inversion capacitance for a very narrow gate voltage range) in the strong inversion regions. These anomalous C‐V characteristics are believed to be due to the penetrated B‐F complexes which act as interface state and deep level defect centers.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Dielectric‐assisted liftoff technique for the formation and monolithic integration of electronic and optical devices

G. M. Metze, A. B. Cornfeld, P. E. Laux, T. C. Ho, and K. P. Pande

Appl. Phys. Lett. 57, 2576 (1990); http://dx.doi.org/10.1063/1.103820 (3 pages) | Cited 2 times

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A technique for the selective growth and patterning of device quality materials has been developed. This technology uses a dielectric‐assisted liftoff (DAL) process to pattern molecular beam epitaxy (MBE) grown GaAs into isolated device regions. We have successfully demonstrated the applicability of this dielectric‐assisted liftoff process by fabricating power metal‐semiconductor field‐effect transistor (MESFET) devices with 1, 1.5, and 3 mm gate width geometries. Material and device performance of these DAL patterned MESFETs has been found to be comparable to our standard MBE‐grown and mesa isolated MESFET structures.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.80.Ey III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
85.40.Hp Lithography, masks and pattern transfer

Contactless optical evaluation of processing effects on carrier lifetime in silicon

P. F. Baude, T. Tamagawa, and D. L. Polla

Appl. Phys. Lett. 57, 2579 (1990); http://dx.doi.org/10.1063/1.103821 (3 pages) | Cited 8 times

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Contactless, optical modulation of free‐carrier absorption has been used to identify minority‐carrier lifetime degradation associated with both novel and common very large scale integrated circuit processing steps in p‐type silicon wafers. Carrier lifetime degradation and a corresponding increase in surface recombination velocity was found to be associated with the silicon etchants ethylenediamine‐pyrocatechol‐water (EDP) and potassium hydroxide (KOH), prolonged exposure to hydrofluoric acid (HF and BHF), and ion bombardment associated with a variety of plasma etching steps. Knowledge of process‐induced lifetime degradation obtained by this technique may offer significant input into the development of high‐yield very large scale integrated circuit processes.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
72.80.Jc Other crystalline inorganic semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Excitonic electroabsorption in extremely shallow quantum wells

K. W. Goossen, J. E. Cunningham, and W. Y. Jan

Appl. Phys. Lett. 57, 2582 (1990); http://dx.doi.org/10.1063/1.103822 (3 pages) | Cited 50 times

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We report the remarkable observation of strong room‐temperature excitonic features in the absorption spectra of GaAs‐AlxGa1−xAs quantum wells (QWs) for values of x as low as 0.02. This has important implications for high‐power modulators, since saturation intensities have been shown to be higher in QW modulators with low barriers. In addition, very shallow QWs have enhanced electroabsorption at small biases because of ease of ionization. In our p‐i(multi‐QW)‐n device with x=0.02, we obtain a transmission change from 29% to 47% for a voltage change from +1 to −3 V.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
71.35.-y Excitons and related phenomena
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.79.Hp Optical processors, correlators, and modulators

Intersubband absorption in Si1−xGex/Si multiple quantum wells

R. P. G. Karunasiri, J. S. Park, Y. J. Mii, and K. L. Wang

Appl. Phys. Lett. 57, 2585 (1990); http://dx.doi.org/10.1063/1.103823 (3 pages) | Cited 39 times

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The intersubband infrared absorption of holes in Si1−xGex/Si multiple quantum wells is observed. The quantum well structure consists of 10 periods of 40−Å−thick Si0.6Ge0.4 wells and 300−Å−thick Si barriers. The samples are prepared using molecular beam epitaxy. In the experiment, the infrared absorption as a function of wavelength is measured using a waveguide geometry. An absorption peak near 8.1 μm has been observed, which is due to the transition between first two heavy hole bound states. The polarization dependence spectra are in good agreement with the selection rules for the intersubband transition.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Ls Scanners, image intensifiers, and image converters

Superconducting YBa2Cu3O7−δ thin films on GaAs with conducting indium‐tin‐oxide buffer layers

B. J. Kellett, A. Gauzzi, J. H. James, B. Dwir, D. Pavuna, and F. K. Reinhart

Appl. Phys. Lett. 57, 2588 (1990); http://dx.doi.org/10.1063/1.104184 (3 pages) | Cited 14 times

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Superconducting YBa2Cu3O7−δ (YBCO) thin films have been grown in situ on GaAs with conducting indium‐tin‐oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky‐like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room‐temperature resistivity of about 1 mΩ cm.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
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