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22 Sep 1997

Volume 71, Issue 12, pp. 1595-1738

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PbS quantum-dot doped glasses as saturable absorbers for mode locking of a Cr:forsterite laser

P. T. Guerreiro, S. Ten, N. F. Borrelli, J. Butty, G. E. Jabbour, and N. Peyghambarian

Appl. Phys. Lett. 71, 1595 (1997); http://dx.doi.org/10.1063/1.119843 (3 pages) | Cited 66 times

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Quantum confined nanocrystals of PbS in glass were used as intracavity saturable absorbers to obtain passive continuous-wave mode locking in a Cr:forsterite laser. We obtained near transformed-limited 4.6 ps laser pulses at 110 MHz repetition rate, and a wide tunability range of 1207–1307 nm. The absorption saturation intensity of the quantum-dot PbS doped glasses was measured to be 0.2 MW/cm2. © 1997 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Extremely broadband AlGaAs/GaAs superluminescent diodes

Ching-Fuh Lin and Bor-Lin Lee

Appl. Phys. Lett. 71, 1598 (1997); http://dx.doi.org/10.1063/1.119844 (3 pages) | Cited 23 times

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Extremely broadband AlGaAs/GaAs superluminescent diodes are fabricated on substrate with four quantum wells of different widths. By choosing 20, 33, 56, and 125 Å, respectively, for the four quantum wells, the spectrum could be broadened to several times that of the conventional superluminescent diodes. The measured spectra of the fabricated devices with such quantum-well structure show that the full-width at half-maximum spectral width could be as large as 915 Å. © 1997 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
81.05.Ea III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.45.+h Stimulated emission

Spectroscopic applications and frequency locking of THz photomixing with distributed-Bragg-reflector diode lasers in low-temperature-grown GaAs

Pin Chen, Geoffrey A. Blake, M. C. Gaidis, E. R. Brown, K. A. McIntosh, S. Y. Chou, M. I. Nathan, and F. Williamson

Appl. Phys. Lett. 71, 1601 (1997); http://dx.doi.org/10.1063/1.119845 (3 pages) | Cited 19 times

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A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth full-width at half-maximum of two optically locked DBR lasers is 50 kHz on the 20 ms time scale and 2 MHz over 10 s; free-running DBR lasers have linewidths of 40 and 90 MHz on such time scales. This instrument has been used to obtain rotational spectra of acetonitrile (CH3CN) at 313 GHz. Detection limits of 1×10−4Hz1/2 (noise/total power) have been achieved, with the noise floor dominated by the detector’s noise equivalent power. © 1997 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
42.60.Mi Dynamical laser instabilities; noisy laser behavior

Scanning thermal microscopy of a vertical-cavity surface-emitting laser

K. Luo, R. W. Herrick, A. Majumdar, and P. Petroff

Appl. Phys. Lett. 71, 1604 (1997); http://dx.doi.org/10.1063/1.119991 (3 pages) | Cited 27 times

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A scanning thermal microscope was used to measure the temperature distribution inside a vertical-cavity surface-emitting laser. The peak temperature occurred at the intersection of the optical axis and the active quantum wells, and increased with input power at a rate of 0.74 °C/mW. Comparison with model predictions showed that the n mirrors and the substrate produce higher heat generation rates, possibly due to Joule heating and/or the absorption of spontaneous emissions that are often neglected in models. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
68.35.B- Structure of clean surfaces (and surface reconstruction)

Antenna-coupled polycrystalline silicon air-bridge thermal detector for mid-infrared radiation

N. Chong and H. Ahmed

Appl. Phys. Lett. 71, 1607 (1997); http://dx.doi.org/10.1063/1.119992 (3 pages) | Cited 10 times

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Polycrystalline silicon (polysilicon) airbridges coupled to log-periodic and bow-tie planar antennas have been fabricated for mid-infrared radiation detection. The detectors in thermocouple and bolometer modes exhibit a higher electrical responsivity than previously reported metal based antenna-coupled thermal detectors. Measurements made at 10.2 μm wavelength indicate that the linearly polarized antennas have an on-axis cross-polarization ratio of about −4.5 dB and the pattern in the free-space side has a directivity of approximately 5–9 dB. The coupling efficiency is about 15%. Frequency responses for modulated optical signals agree with thermal transport models. © 1997 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.40.Ba Antennas: theory, components and accessories

High-speed all-semiconductor optically addressed spatial light modulator

Parviz Tayebati, Ergun Canoglu, Christos Hantzis, and Robert N. Sacks

Appl. Phys. Lett. 71, 1610 (1997); http://dx.doi.org/10.1063/1.119993 (3 pages) | Cited 4 times

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We report a monolithically grown optically addressed multiple-quantum-well spatial light modulator with high-frame rate operation (>44 kHz) and large sensitivity (<1 μJ/cm2). The separated-detector-modulator device operates in the reflection mode and can provide a modulation gain of 35 with 60% modulation depth. We also show that higher modulation gains (>50) can be achieved at the expense of modulation depth. In addition, by using a voltage pulse, we reduce the recovery time of the device from 90 ms to 1 μs such that high-frame rate operation can be achieved. We demonstrate 60% modulation of the reflected readout beam at 44 kHz by only using 43 mW/cm2 cw writing illumination. © 1997 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Pulse propagation of accumulated photon echoes in Nd3+ ion-doped silicate glass fiber

Ryuzi Yano and Naoshi Uesugi

Appl. Phys. Lett. 71, 1613 (1997); http://dx.doi.org/10.1063/1.119994 (3 pages) | Cited 1 time

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Pulse-propagation phenomena of accumulated photon echo signals was investigated for the 4F3/2(1)–4I9/2 transition of the Nd3+ ion doped with 20 ppm concentration in silicate glass fiber (core diameter of 6 μm) at 4.2 K using an 82 MHz mode-locked dye laser. The intensity of the transmitted probe pulses from the Nd3+ fiber was measured as a function of the Nd3+ fiber length. The fiber length for the maximum probe-pulse intensity induced by the pump pulses was determined to be 4 m when the pump pulses of 0.50 mW average power and the probe pulses of 0.25 mW average power were used. We derived the pulse area equations which take into account the coherent interaction between the pulses and the Nd3+ fiber. The fiber-length dependence of the signal intensity was explained well by the pulse area equations. © 1997 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)

Enhancement of optical gain of semiconductors embedded in three-dimensional photonic crystals

Yu. A. Vlasov, K. Luterova, I. Pelant, B. Hönerlage, and V. N. Astratov

Appl. Phys. Lett. 71, 1616 (1997); http://dx.doi.org/10.1063/1.119995 (3 pages) | Cited 95 times

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The three-dimensional photonic crystals used in this study were synthetic opals, composed of submicron silica spheres, close-packed in a face-centered cubic structure with a period of 200 nm, that exhibit photonic stopbands around 600 nm. We present measurements of the optical gain of CdS quantum dots (QDs) embedded inside the interstitials between the silica spheres. Unlike the usual gain spectra of CdS QDs in glass matrices, which display maximum gain at energies of the first quantum-confined transitions, for QDs embedded in photonic crystals the gain maximum is shifted toward the high-frequency edge of the photonic stopband (2.2 eV) far below the absorption edge of the semiconductor (2.5 eV). Studies of temperature, intensity, and orientation dependencies of the gain spectra allow one to ascribe the observed effect to gain enhancement caused by multiple coherent Bragg scattering of light in the periodic photonic crystal. © 1997 American Institute of Physics.
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78.66.Hf II-VI semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.70.Qs Photonic bandgap materials
42.70.Ce Glasses, quartz
61.72.J- Point defects and defect clusters

Two-photon pumped partially cross-linked polymer laser

Guang S. He, Kie-Soo Kim, Lixiang Yuan, Ning Cheng, and Paras N. Prasad

Appl. Phys. Lett. 71, 1619 (1997); http://dx.doi.org/10.1063/1.119996 (3 pages) | Cited 18 times

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Two-photon pumped (TPP) frequency-upconverted lasing properties of a partially cross-linked fluorescent polymer are reported. This lasing medium is a cross-linked homogeneous copolymer with two major compounds: the chromophore, 4-[bis(2-hydroxyethyl)amino]-N-methylstilbazolium iodide, and the monomer, 2-hydroxyethyl methacrylate. The spectral, temporal, and spatial structures as well as the output/input characteristics of the TPP cavity lasing were measured using a 13 mm long polymer rod. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the ∼ 606 nm upconverted cavity lasing energy was found to be ∼ 4%. © 1997 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
33.80.Be Level crossing and optical pumping
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)

Magnetic-field-enhanced rf argon plasma for ionized sputtering of copper

W. Wang, J. Foster, A. E. Wendt, J. H. Booske, T. Onuoha, P. W. Sandstrom, H. Liu, S. S. Gearhart, and N. Hershkowitz

Appl. Phys. Lett. 71, 1622 (1997); http://dx.doi.org/10.1063/1.119997 (3 pages) | Cited 7 times

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A multipole magnetic field was used to increase the ion density of an inductively coupled rf (13.5 MHZ) argon plasma for ionized magnetron sputtering of copper (Cu). Langmuir probe measurements showed an increase of plasma density over a factor of 2 with the application of the magnetic field. At an argon pressure of 15 mTorr and a rf power of 600 W, an ion density of 1.2×1012 ions/cm3 was achieved. When this plasma was applied to ionize the magnetron sputtered Cu vapor, a high emission intensity ratio from the Cu+ ion line to the Cu neutral line was observed from the optical emission spectroscopy, suggesting a high ionization fraction for the sputtered Cu vapor. © 1997 American Institute of Physics.
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52.50.Dg Plasma sources
52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Temperature derivatives of the fundamental elastic constants of isotropic materials

S. Ballandras, E. Gavignet, E. Bigler, and E. Henry

Appl. Phys. Lett. 71, 1625 (1997); http://dx.doi.org/10.1063/1.119998 (3 pages) | Cited 3 times

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The calculation of the first temperature derivatives of the fundamental elastic constants proposed by Sinha and Tiersten [J. Appl. Phys. 50, 2732 (1979)] for quartz is applied to isotropic materials. Numerical applications are provided for metals used in acoustic wave devices and which may affect the thermal properties of the latter. © 1997 American Institute of Physics.
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62.20.D- Elasticity
65.20.-w Thermal properties of liquids
65.40.gd Entropy
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Temperature dependence of MeV heavy ion irradiation-induced viscous flow in SiO2

M. L. Brongersma, E. Snoeks, and A. Polman

Appl. Phys. Lett. 71, 1628 (1997); http://dx.doi.org/10.1063/1.119999 (3 pages) | Cited 32 times

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In-situ wafer curvature measurements were performed to determine the mechanical stress in thermally grown SiO2 films on Si during 4 MeV Xe ion irradiation at various temperatures in the range from 90 to 575 K. Radiation induced viscous flow is observed and the radiation induced viscosity is determined at various temperatures. It ranges from 2.9×1023 at Pa ion/cm2 90–300 K to 1.6×1023 Pa ion/cm2 at 500 K. Both its magnitude and temperature dependence can be explained in terms of a phenomenological model in which stress relaxation takes place in locally heated, mesoscopic regions of low viscosity, centered around individual ion tracks. According to this model, stress relaxation occurs in ∼ 10 ps and within ∼ 3 nm of the ion track. © 1997 American Institute of Physics.
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61.82.Ms Insulators
61.80.Jh Ion radiation effects
68.60.Bs Mechanical and acoustical properties
83.10.Gr Constitutive relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations

In-situ observations of classical grain growth mechanisms during sintering of copper nanoparticles on (001) copper

M. Yeadon, J. C. Yang, R. S. Averback, J. W. Bullard, D. L. Olynick, and J. M. Gibson

Appl. Phys. Lett. 71, 1631 (1997); http://dx.doi.org/10.1063/1.120000 (3 pages) | Cited 21 times

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The sintering of randomly oriented copper nanoparticles in the size range 4–20 nm with a single crystal (001) copper substrate has been studied in real time using a novel in situ ultrahigh vacuum (UHV) transmission electron microscope. The particles were generated in situ using an UHV DC sputtering attachment and deposited directly onto an electron transparent copper foil inside the microscope. We demonstrate that these particles reorient upon heating to assume the same orientation as the substrate by a classical mechanism involving neck growth and grain boundary motion. © 1997 American Institute of Physics.  
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.46.-w Structure of nanoscale materials
61.72.Mm Grain and twin boundaries
81.40.Gh Other heat and thermomechanical treatments
66.30.Lw Diffusion of other defects

Crystalline-to-amorphous transition in chemical vapor deposition of pseudomorphic Si1−x−yGexCy films

T. Laursen, D. Chandrasekhar, David J. Smith, J. W. Mayer, J. Huffman, R. Westhoff, and McD. Robinson

Appl. Phys. Lett. 71, 1634 (1997); http://dx.doi.org/10.1063/1.120001 (3 pages) | Cited 4 times

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Pseudomorphic SiGeC films have been grown on (100) Si by atmospheric pressure chemical vapor deposition at 600 and 700 °C using SiH2Cl2, GeH4, and C2H4 precursors. Films with C concentrations of up to 2.5 at. % were entirely pseudomorphic and a 120-nm-thick Si66.5Ge31C2.5 film had 90% substitutional carbon. With increasing C incorporation due to increased ethylene flow, a layered structure was formed consisting of an amorphous film overlaying a buried pseudomorphic film. The crystalline-to-amorphous transition was initiated by the accumulation of C on the epitaxial growth surface. This deteriorated surface resulted in the formation of stacking faults along {111} planes and subsequent amorphization. Defect formation and amorphization could be prevented by periodically growing a thin Si epilayer. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
61.72.Nn Stacking faults and other planar or extended defects

Scanning probe nanolithography of conducting metal oxides

Chen-Jen Hung, Jianian Gui, and Jay A. Switzer

Appl. Phys. Lett. 71, 1637 (1997); http://dx.doi.org/10.1063/1.120002 (3 pages) | Cited 4 times

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The scanning tunneling microscope (STM) was used to form nanometer-size holes in thin conducting films of thallium (III) oxide. Hole formation was only observed when the process was performed in humid ambient conditions. The hole formation was attributed to localized electrochemical etching reactions beneath the STM tip. Etching reactions consistent with the observed hole formation are a direct electrochemical reduction of thallium (III) oxide to soluble Tl (I) at negative sample bias, and local reduction of pH at positive sample bias. The fastest etching was observed at negative sample bias. Holes as small as 10 nm or as large as 1 μm in diameter could be etched in the films. © 1997 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.65.Cf Surface cleaning, etching, patterning
82.45.-h Electrochemistry and electrophoresis
07.79.Cz Scanning tunneling microscopes

Ce-substituted yttrium iron garnet films prepared on Gd3Sc2Ga3O12 garnet substrates by sputter epitaxy

Toshihiro Shintaku, Akiyuki Tate, and Shinji Mino

Appl. Phys. Lett. 71, 1640 (1997); http://dx.doi.org/10.1063/1.120003 (3 pages) | Cited 19 times

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Ce-substituted yttrium iron garnet films are epitaxially grown in situ on (111)-oriented substrates of Gd3Sc2Ga3O12 garnet by conventional rf diode sputtering for application to magneto-optic waveguide devices in optical communication systems. The lattice constant of the substrates is larger than that of the previously used (Gd,Ca)3(Ga,Mg,Zr)5O12 garnet substrates whose lattice constant is smaller than that of the films. The lowest ever reported propagation losses of 9.7 dB/cm in the TE mode and 5.8 dB/cm in the TM mode are obtained for a film thickness of 0.5 μm at λ = 1.55 μm. © 1997 American Institute of Physics.
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81.15.Cd Deposition by sputtering
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.50.Gg Ferrimagnetics
85.70.Sq Magnetooptical devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.Gn Optical waveguides and couplers

Submicron-sized spherical yttrium oxide based phosphors prepared by supercritical CO2-assisted aerosolization and pyrolysis

Chongying Xu, Barbara A. Watkins, Robert E. Sievers, Xiping Jing, Philip Trowga, Carol S. Gibbons, and Aron Vecht

Appl. Phys. Lett. 71, 1643 (1997); http://dx.doi.org/10.1063/1.120004 (3 pages) | Cited 23 times

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The synthesis of Eu(III)- and Tb(III)-doped yttrium oxide phosphor powders by supercritical CO2-assisted aerosolization and pyrolysis (at 1010 °C) from aqueous solutions of Y(NO3)3, Eu(NO3)3, and Tb(NO3)3 is presented. Dense, submicron aerosols are formed by contacting aqueous solutions of the precursor metal nitrates with supercritical CO2 at 1500 psi, and decompressing the mixture through a restrictor nozzle into a heated tube. X-ray diffraction data indicate that the powders are crystalline, and consist of a single phase. Scanning electron microscope shows that they are spherical in morphology and less than 1 μm in size with average diameters of ∼ 0.2 μm. The cathodoluminescence intensity of the Y1.91Eu0.09O3 powders, annealed at 1200 °C for 1 h, is more than twice greater than that of the industrial standard (P56, 3–10 μm in diameter) phosphor. The phosphors synthesized by this method are promising candidates for use in high-resolution low-voltage flat panel displays. © 1997 American Institute of Physics.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.Rg Aerosols in materials synthesis and processing
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
78.60.Hk Cathodoluminescence, ionoluminescence
42.79.Kr Display devices, liquid-crystal devices

Crystal stress dynamics by means of nanosecond time-resolved x-ray diffraction

P. Chen, I. V. Tomov, and P. M. Rentzepis

Appl. Phys. Lett. 71, 1646 (1997); http://dx.doi.org/10.1063/1.120005 (3 pages) | Cited 2 times

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Time-resolved transient lattice deformation in Pt (111) crystal has been directly observed from the shift of a nanosecond x-ray diffraction rocking curve. The development of a tabletop nanosecond x-ray system, which consists of an excimer laser, x-ray diode, and charge coupled device detector is described. With this system, we observed the time-dependent strain distribution during the laser heating process in the bulk of a Pt (111) crystal. This method provides a means of relative low cost for the study of fast transient properties and structures of materials. © 1997 American Institute of Physics.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Bg Metals and alloys

Polarization responses in lead magnesium niobate based relaxor ferroelectrics

Q. M. Zhang and J. Zhao

Appl. Phys. Lett. 71, 1649 (1997); http://dx.doi.org/10.1063/1.119784 (3 pages) | Cited 24 times

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Changes in the electrostrictive coefficients Qij, especially the volumetric coefficient, with temperature and bias field provides important information regarding the nature of the polarization in lead magnesium niobate based relaxor ferroelectrics. We show that the polarization response at temperatures near the dielectric constant maximum is mainly through the polar-vector reorientation of the nanopolar regions, as suggested by the polar glass model. As the temperature is lowered through the freezing transition, the polarization response is governed by the phase switching and intrinsic contributions rather than by the domain wall motions found in normal ferroelectrics. © 1997 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ch Permittivity (dielectric function)

Plastic behavior of nanophase Ni: A molecular dynamics computer simulation

H. Van Swygenhoven and A. Caro

Appl. Phys. Lett. 71, 1652 (1997); http://dx.doi.org/10.1063/1.119785 (3 pages) | Cited 89 times

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We report molecular dynamics computer simulations of low temperature-high load plastic deformation of Ni nanophase samples with several mean grain sizes in the range of 3–5 nm. The samples are polycrystals nucleated from different seeds, with random location and orientation. Among the mechanisms responsible for the deformation, grain boundary sliding and motion, as well as grain rotation are identified. No dislocation activity is detected, in contrast to the behavior of coarse grain metals. Interpreting the results in terms of grain boundary viscosity, a linear dependence of strain rate with the inverse of the grain size is obtained. © 1997 American Institute of Physics.
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62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.72.Mm Grain and twin boundaries
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.30.Bx Phase diagrams of metals, alloys, and oxides
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.05.Bx Metals, semimetals, and alloys

Perfect spatial ordering of self-organized InGaAs/AlGaAs box-like structure array on GaAs (311)B substrate with silicon nitride dot array

Eiichi Kuramochi, Jiro Temmyo, Toshiaki Tamamura, and Hidehiko Kamada

Appl. Phys. Lett. 71, 1655 (1997); http://dx.doi.org/10.1063/1.120075 (3 pages) | Cited 21 times

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The metalorganic vapor phase epitaxial growth of strained InGaAs/AlGaAs box-like structure self-organized on GaAs (311)B substrate was investigated using fine silicon nitride (SiN) dot arrays for improving the controllability of self-organization phenomena. AlGaAs barrier layer grown at 750 °C buries SiN dots, forming novel pentagonally shaped hollows on(311)B substrate due to the (−100) facet growth and lateral growth. TheIn0.3Ga0.7As layer is preferentially grown in these hollows, then box-like structure is formed in these hollows during the growth interruption. Successive growth ofAlGaAs/In0.3Ga0.7As epilayers induces the stacking of box-like structures just on top of the bottom boxes. The pairing probability of bottom and upper boxes is strongly dependent on the SiN dot array pitch, and the perfect spatial ordering of upper box arrays is achieved when the SiN dot pitch is in a range of 250–300 nm. This approach allows the exact positioning of self-formed box structure. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.-a Thin film structure and morphology
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Study of contact formation in AlGaN/GaN heterostructures

Q. Z. Liu, L. S. Yu, F. Deng, S. S. Lau, Q. Chen, J. W. Yang, and M. A. Khan

Appl. Phys. Lett. 71, 1658 (1997); http://dx.doi.org/10.1063/1.119786 (3 pages) | Cited 30 times

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The contact formation of Ti/Al and Ti metallization on AlGaN/GaN heterojunction field effect transistors (HFET) was investigated. It was found that ohmic contact formation is related to the low work function of the Ti contacting layer and the formation of a TiN phase at the Ti/nitride interface. Contact resistance as low as 1 Ω mm or less can be obtained on HFET samples with a nsμ product of ∼ 0.8×1016/V s and on n-GaN with a carrier concentration of 1.5×1018/cm3. Ti/Al bilayer contact scheme is superior to Ti-only contact due to a surface Al3Ti layer in the bilayer contact, which may reduce the oxidation problem when annealed in N2 at high temperatures. Preannealing the HFET samples at 850 °C for 1 h in N2 appears to improve the ohmic contact in general, but not always observed. Our results indicate that Ti/Al contact scheme yields sufficiently low contact resistance on HFET structures for microwave applications. © 1997 American Institute of Physics.
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85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
72.80.Ey III-V and II-VI semiconductors
81.65.Mq Oxidation

Effects of O2 on the {113} defect formation in Si observed by in situ ultrahigh vacuum transmission electron microscopy

K. Koto, S. Takeda, T. Ichihashi, and S. Iijima

Appl. Phys. Lett. 71, 1661 (1997); http://dx.doi.org/10.1063/1.119787 (3 pages) | Cited 3 times

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The nucleation and growth of the {113} defects in floating zone Si have been observed in situ in a ultrahigh vacuum (UHV) transmission electron microscopy. After the surfaces of a Si foil are controlled, intense irradiation of 200 keV electrons proceeds at 400 or 500 °C in the base pressure of 1.0×10−7 Pa. We have found that the defect development changes prominently after O2 is injected in a specimen chamber. While O2 flows, the pressure is kept at about 5.0×10−5 Pa. This result has brought direct evidence for the effect of O2 on formation of the defects, since no other impurities are involved in the UHV environment. © 1997 American Institute of Physics.
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81.05.Cy Elemental semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

The persistent photoconductivity effect in modulation Si δ-doped pseudomorphic In0.2Ga0.8As/GaAs quantum well structure

Adam Babinski, G. Li, and C. Jagadish

Appl. Phys. Lett. 71, 1664 (1997); http://dx.doi.org/10.1063/1.119788 (3 pages) | Cited 10 times

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Persistent conductivity effect in modulation Si δ-doped In0.2Ga0.8As/GaAs quantum well (QW) structure grown by metal organic vapor phase epitaxy was examined using Hall effect and magnetotransport measurements in magnetic fields up to 12 T at T = 1.7 K. No measurable electron density was found in the QW after cooling down the sample in the dark and the electron density in the V-shaped δ-doped potential well (V-QW) of the modulation Si δ-doped layer was two times lower than the electron density of the same Si δ-doped layer in GaAs. The illumination resulted in the increase of electron density in the V-QW at the beginning and consequently in the population of the ground subband in the InGaAs QW. Due to parallel conduction, a nonmonotonic dependence of Hall density as a function of illumination time was observed. The total electron density in the modulation doped InGaAs/GaAs heterostructure after the illumination became approximately equal to the electron density in the Si δ-doped layer in GaAs. © 1997 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Noise in single quantum well infrared photodetectors

M. Ershov and A. N. Korotkov

Appl. Phys. Lett. 71, 1667 (1997); http://dx.doi.org/10.1063/1.119789 (3 pages) | Cited 8 times

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The spectral density of current fluctuations in single quantum well infrared photodetectors is calculated using the Langevin approach. The noise gain and photocurrent gain are expressed in terms of basic transport parameters. Fluctuations of the incident photon flux are taken into account. © 1997 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.De Semiconductor-device characterization, design, and modeling
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