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28 Jan 2002

Volume 80, Issue 4, pp. 535-701

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InAs/GaAs quantum dot lasers with InGaP cladding layer grown by solid-source molecular-beam epitaxy

Nien-Tze Yeh, Wei-Sheng Liu, Shu-Han Chen, Pe-Chin Chiu, and Jen-Inn Chyi

Appl. Phys. Lett. 80, 535 (2002); http://dx.doi.org/10.1063/1.1445269 (3 pages) | Cited 7 times

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This letter presents the lasing properties of InAs/GaAs quantum dot lasers with InGaP cladding layers grown by solid-source molecular-beam epitaxy. These Al-free lasers exhibit a threshold current density of 138 A/cm2, an internal loss of 1.35 cm−1, and an internal quantum efficiency of 31% at room temperature. At a low temperature, a very high characteristic temperature of 425 K and very low threshold current density of 30 A/cm2 are measured. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Towards a voltage tunable two-color quantum-well infrared photodetector

Amlan Majumdar, K. K. Choi, L. P. Rokhinson, and D. C. Tsui

Appl. Phys. Lett. 80, 538 (2002); http://dx.doi.org/10.1063/1.1436529 (3 pages) | Cited 5 times

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Two-color quantum-well infrared photodetectors (QWIPs), based on electron transfer between coupled QWs, suffer from the presence of the shorter wavelength peak at all bias voltages Vb. We investigate this problem by studying the bias dependence of absorption coefficient α and photoconductive gain g as a function of wavelength at 10 K. We fabricate such a detector with a peak wavelength of 8 μm for both bias polarities but a voltage tunable cutoff wavelength (9 μm for Vb>0 and 11 μm for Vb<0). We use corrugated QWIPs with different corrugation periods to extract α and g for different values of Vb. We find α ≈ 0.1 μm−1 in the 6–12 μm range with small peaks at 8 and 9.8 μm for Vb>0 and 10 μm for Vb<0. g has a pronounced peak at 7.8 μm for both bias polarities and determines the line shape of the QWIP spectral responsivity. These results are attributed to insufficient electron transfer between the coupled QWs and to low tunneling probability of the longer wavelength photoelectrons. A modified QWIP structure has been proposed for complete switching of spectral responsivity peak when the bias voltage polarity is reversed. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Coherent x-ray pulse generation in the sub-Ångström regime

C. H. Keitel and S. X. Hu

Appl. Phys. Lett. 80, 541 (2002); http://dx.doi.org/10.1063/1.1436277 (3 pages) | Cited 17 times

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A mechanism is proposed to generate femtosecond coherent light pulses with a wavelength shorter than the dimension of a single atom. X rays of such short wavelength and high energy are shown to arise from the relativistic interaction of multiply charged ions with short and intense near-optical laser pulses. The generated x-ray pulses have thus potential to be useful in investigating the dynamics of chemical and biological systems with a subatomic resolution. © 2002 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
32.80.-t Photoionization and excitation

Emission gain narrowing from single crystals of a thiophene/phenylene co-oligomer

Michifumi Nagawa, Ryota Hibino, Shu Hotta, Hisao Yanagi, Musubu Ichikawa, Toshiki Koyama, and Yoshio Taniguchi

Appl. Phys. Lett. 80, 544 (2002); http://dx.doi.org/10.1063/1.1435797 (3 pages) | Cited 54 times

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Emission gain narrowing has been observed for single crystals of a thiophene/phenylene co-oligomer. The hexagon flake crystals were placed on a quartz substrate with the crystals’ face in close contact with the substrate plane. These crystals were irradiated with a N2 laser with a 337.1 nm wavelength at a repetition rate 10 Hz that tuned its intensity to 100–1150 μJ/cm2. The emission gain narrowing takes place at 21490 (465.4 nm) and 20220 cm−1 (494.5 nm) with increased intensities, with their half width at half maxima reaching ∼ 50 cm−1. On the basis of the nonlinear relationship between the emission peak intensities and the laser light intensity, the gain narrowing has been attributed to the amplified spontaneous emission. © 2002 American Institute of Physics.
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78.55.Kz Solid organic materials
78.45.+h Stimulated emission

Photonic-crystal ultrashort bends with improved transmission and low reflection at 1.55 μm

A. Talneau, L. Le Gouezigou, N. Bouadma, M. Kafesaki, C. M. Soukoulis, and M. Agio

Appl. Phys. Lett. 80, 547 (2002); http://dx.doi.org/10.1063/1.1445270 (3 pages) | Cited 60 times

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We propose and demonstrate improved designs in order to increase the transmission level through double 60°-bend photonic-crystal-based waveguides. These bends are defined in a two-dimensional photonic crystal (PC) patterned into a GaInAsP slab on InP substrate. Transmission spectra calculated using a two-dimensional finite difference time domain method that accounts for radiation losses, as well as measurements, demonstrate enhancement of the transmission when moving holes in the corner. As expected a drop in reflection is obtained. The sensitivity to the PC guide width is also evidenced. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
78.66.Fd III-V semiconductors
42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
02.70.Bf Finite-difference methods

Low Stokes shift in thick and homogeneous InGaN epilayers

S. Srinivasan, F. Bertram, A. Bell, F. A. Ponce, S. Tanaka, H. Omiya, and Y. Nakagawa

Appl. Phys. Lett. 80, 550 (2002); http://dx.doi.org/10.1063/1.1436531 (3 pages) | Cited 27 times

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The optical properties of thick InxGa1−xN layers have been studied using optical absorption and cathodoluminescence techniques. The indium composition x of the layers ranged from 0.03 to 0.17 as determined by Rutherford backscattering measurements. The difference between the band gap and the peak emission energy (Stokes shift) was found to be considerably smaller than reported in the past for these alloys. Monochromatic images show that light emission from most of the film is homogeneous and is associated with a low Stokes shift. A second emission band at longer wavelengths is observed for x ≥ 0.08. This band originates from indium-rich regions in the vicinity of extended defects, and exhibits a larger Stokes shift. Our observations indicate that it is possible to grow InGaN epilayers with high indium composition, high homogeneity, and lower Stokes shift. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
78.60.Hk Cathodoluminescence, ionoluminescence
78.40.Fy Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ultraviolet photoresponse of porous ZnO thin films prepared by unbalanced magnetron sputtering

Parmanand Sharma, Abhai Mansingh, and K. Sreenivas

Appl. Phys. Lett. 80, 553 (2002); http://dx.doi.org/10.1063/1.1445480 (3 pages) | Cited 35 times

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Fast ultraviolet photoresponse is observed in ZnO thin films prepared by unbalanced magnetron sputtering. Films with a porous microstructure and a mixed (100), (002) and (101) crystallographic orientation exhibit photoresponse with good linearity and minimal aging effects. A fast rise time of 792 ms and a fall time of 805 ms are observed under low intensity (9.5 mW/cm2, λ = 365 nm) ultraviolet light. © 2002 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Ga II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Cd Deposition by sputtering
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.66.Hf II-VI semiconductors
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Investigation of direct and indirect band gaps of [100]-oriented nearly strain-free β-FeSi2 films grown by molecular-beam epitaxy

Ken-ichiro Takakura, Noriyoshi Hiroi, Takashi Suemasu, Shigefusa F. Chichibu, and Fumio Hasegawa

Appl. Phys. Lett. 80, 556 (2002); http://dx.doi.org/10.1063/1.1432755 (3 pages) | Cited 14 times

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Optical absorption (OA) spectra of [100]-oriented, nearly strain-free β-FeSi2 continuous films grown by molecular-beam epitaxy were investigated. Although the film is a multidomain epilayer, the OA spectra of the annealed film were fitted well by the sum of the contributions from both direct and indirect absorption transitions for a wide range of temperatures from 77 to 300 K. The indirect absorption edge of 0.78 eV obtained at 77 K agreed with the effective band gap energy obtained from temperature dependence of the carrier density. © 2002 American Institute of Physics.
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78.66.Li Other semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Thermal decomposition of ZrO2/SiO2 bilayer on Si(001) caused by void nucleation and its lateral growth

Heiji Watanabe and Nobuyuki Ikarashi

Appl. Phys. Lett. 80, 559 (2002); http://dx.doi.org/10.1063/1.1435810 (3 pages) | Cited 34 times

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The stability of a ZrO2/SiO2 bilayer on a Si(001) substrate was investigated in terms of thermal decomposition during ultrahigh-vacuum annealing. In spite of the intrinsic thermal stability of the ZrO2/SiO2 system, void nucleation initiated by local defects and the following lateral growth of the voids proceed at temperatures over 900 °C. The remaining Zr atoms accumulate and react with the Si substrate to form silicide (ZrSi2) islands within the voids. It was found that the decomposition temperature of the ZrO2/SiO2 bilayer is lower than that of a SiO2 single layer, which suggests defect generation in the SiO2 underlayer by ZrO2 deposition. © 2002 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
68.35.Dv Composition, segregation; defects and impurities
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.35.Ct Interface structure and roughness
68.60.Dv Thermal stability; thermal effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators

Polymorphism in CuInS2 epilayers: Origin of additional Raman modes

J. Alvarez-García, A. Pérez-Rodríguez, B. Barcones, A. Romano-Rodríguez, J. R. Morante, A. Janotti, Su-Huai Wei, and R. Scheer

Appl. Phys. Lett. 80, 562 (2002); http://dx.doi.org/10.1063/1.1435800 (3 pages) | Cited 32 times

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CuInS2 epitaxial films grown on Si(111) substrates at different conditions have been investigated. Transmission electron diffraction shows the coexistence of domains having the Cu–Au and chalcopyrite structure. X-ray diffraction analysis allows the estimation of the relative amount of the phase domains, which is dependent on the growth conditions of the films. The films also present additional modes in the Raman spectra, together with the ones that are chalcopyrite related. The relative intensity of the additional modes directly correlates with the estimated amount of Cu–Au ordered phase. This supports the interpretation that the additional Raman modes are related to Cu–Au ordered domains. Group theory analysis is in agreement with the symmetry of the observed modes. The phonon frequency of the Cu–Au assigned Raman mode is also in excellent agreement with the first-principles frozen-phonon calculations. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Temperature-gradient epitaxy under in situ growth mode diagnostics by scanning reflection high-energy electron diffraction

T. Koida, D. Komiyama, H. Koinuma, M. Ohtani, M. Lippmaa, and M. Kawasaki

Appl. Phys. Lett. 80, 565 (2002); http://dx.doi.org/10.1063/1.1445483 (3 pages) | Cited 18 times

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We have developed a parallel film growth method on a temperature-gradient substrate to quickly control and optimize the film growth mode. A continuous-wave neodymium-doped yttrium–aluminum–garnet laser heating was used to achieve a stable temperature gradient covering a 300 °C range of temperatures over a distance of 11 mm. The growth mode was determined by time-resolved scanning reflection high-energy electron diffraction. Transition from layer-by-layer to step-flow growth by the deposition temperature was observed during La0.5Sr0.5MnO3 film growth on a single SrTiO3 substrate, proving a powerful tool not only for investigating the growth dynamics but also for seeking the optimized deposition conditions in one run of experiment. © 2002 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)

Glass-forming ability of Pd42.5Cu30Ni7.5P20 alloy with a low critical cooling rate of 0.067 K/s

N. Nishiyama and A. Inoue

Appl. Phys. Lett. 80, 568 (2002); http://dx.doi.org/10.1063/1.1445475 (3 pages) | Cited 55 times

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We investigated the glass-forming ability of three Pd–Cu–Ni–P alloys with different compositions (Pd40Cu30Ni10P20, Pd42.5Cu27.5Ni10P20 and Pd42.5Cu30Ni7.5P20) under a continuous cooling condition. The lowest critical cooling rate for glass formation was determined to be 0.067 K/s for the Pd42.5Cu30Ni7.5P20 alloy. The melting behavior indicates that the 7.5% Ni alloy has the nearest eutectic composition of the three alloys. The exceptionally low critical cooling rate of below 0.1 K/s is attributed to the elimination of the primary crystallization that occurs due to off-eutectic composition. © 2002 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Pressure sensor based on freely suspended ferroelectric liquid crystal film

S. V. Yablonskii, K. Nakano, A. S. Mikhailov, M. Ozaki, and K. Yoshino

Appl. Phys. Lett. 80, 571 (2002); http://dx.doi.org/10.1063/1.1430270 (3 pages) | Cited 5 times

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We report on a pressure gauge based on a vibrating, freely suspended ferroelectric liquid crystal film, which shows some promise of being sensitive to the pressures in the range from 50 to 105 Pa. The gauge indicates changes in resonant frequency of the film caused by changes of air pressure. Pressure measurements using such sensor have been carried out. © 2002 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Kr Display devices, liquid-crystal devices
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Orientation-controlled epitaxy and anisotropic properties of La2−xSrxNiO4 with 0.5 ⩽ x ⩽ 1.5 covering the insulator–metal transition

S. Shinomori, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 80, 574 (2002); http://dx.doi.org/10.1063/1.1436523 (3 pages) | Cited 10 times

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The a- and c-axis-oriented epitaxial thin films of layered nickelate La2−xSrxNiO4 (0.5 ⩽ x ⩽ 1.5), of which bulk single crystals are not available, were grown on LaSrAlO4 (100) and (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (001) substrates, respectively. Due to the in-plane anisotropy of the lattice mismatch, the lattice parameters of the a-axis-oriented films vary with x in a different manner from those of the ceramics. In the a-axis-oriented films, resistivity, and optical spectra show large anisotropy between the b and c axes, indicating the quasi-two-dimensional nature of the electronic structure in La2−xSrxNiO4. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Fg Pulsed laser ablation deposition
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
78.66.-w Optical properties of specific thin films

Hydrogen desorption properties of multiwall carbon nanotubes with closed and open structures

Ho Lee, Youn-Seon Kang, Seoung-Hoe Kim, and Jai-Young Lee

Appl. Phys. Lett. 80, 577 (2002); http://dx.doi.org/10.1063/1.1446208 (3 pages) | Cited 19 times

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The multiwall carbon nanotubes (MWNTs) synthesized by microwave plasma enhanced chemical vapor deposition in 0.1% CH4 (H2 dilution) reaction gas were shaped in curly structures with the blocked nanoholes and closed caps. On the contrary, the carbon nanotubes with different structures could be obtained in oxygen loaded reaction gas, showing aligned structures with connected holes and open caps. The hydrogen desorption properties of the carbon nanotubes (CNTs) with these closed and open structures were compared by thermal desorption technique. The MWNTs with closed structure desorbed hydrogen at two different temperature ranges such as 290–330 and ∼420 K, where the evolved hydrogen amount were ∼0.64 and ∼0.03 wt %, respectively. In case of aligned and open MWNTs, hydrogen as high as ∼1.97 wt % was released at ambient temperature. The hydrogen desorption of MWNTs with open and closed structure at ambient temperature showed the hydrogen desorption activation energies of −16.5 kJ/mol H2 and −18.5 kJ/mol H2, respectively. The high temperature hydrogen desorption observed only in CNTs with closed and highly defective structure was high desorption activation energy of −124.4 kJ/mol. © 2002 American Institute of Physics.
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68.43.Vx Thermal desorption
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth

Current-crowding-induced electromigration failure in flip chip solder joints

Everett C. C. Yeh, W. J. Choi, K. N. Tu, Peter Elenius, and Haluk Balkan

Appl. Phys. Lett. 80, 580 (2002); http://dx.doi.org/10.1063/1.1432443 (3 pages) | Cited 115 times

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In a flip chip solder joint, the cross-section of the solder bump is one to two orders of magnitude bigger than that of an interconnect wire. At the contact interface between the bump and the wire, a very large current crowding occurs and it causes a unique and fast electromigration failure in the bump. Simulation of the current crowding phenomenon in a flip chip solder bump is reported here. Experimental results of real flip chip solder bumps show that void formation begins near the current crowding region of the contact, and after it is nucleated, it spreads quickly across the contact area. By designing the solder bump to achieve a uniform current distribution, we can improve its electromigration resistance and increase its current carrying capacity. © 2002 American Institute of Physics.
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85.40.Qx Microcircuit quality, noise, performance, and failure analysis
61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Qa Electromigration

Metal–insulator transition of VO2 thin films grown on TiO2 (001) and (110) substrates

Y. Muraoka and Z. Hiroi

Appl. Phys. Lett. 80, 583 (2002); http://dx.doi.org/10.1063/1.1446215 (3 pages) | Cited 91 times

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The effect of uniaxial stress along the c axis on the metal–insulator transition of VO2 has been studied in the form of epitaxial thin films grown on TiO2 (001) and (110) substrates. A large reduction in the transition temperature TMI from 341 K for a single crystal to 300 K has been observed in the film on TiO2 (001) where the c-axis length is compressed owing to an epitaxial stress, while the TMI has been increased to 369 K in the film on TiO2 (110) where the c-axis length is expanded. The correlation between the c-axis length and TMI is suggested: the shorter c-axis length results in the lower TMI. © 2002 American Institute of Physics.
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71.30.+h Metal-insulator transitions and other electronic transitions
64.70.K- Solid-solid transitions
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties

Computational designing of graphitic silicon carbide and its tubular forms

Yoshiyuki Miyamoto and Byung Deok Yu

Appl. Phys. Lett. 80, 586 (2002); http://dx.doi.org/10.1063/1.1445474 (3 pages) | Cited 51 times

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By employing density-functional theory calculations we predict graphitic and tubular forms of silicon carbide (SiC) and proposes their synthesis. The present calculations suggest that the metastable SiC tubes can be synthesized by using a technique of extreme hole injection [J. M. Schön, Ch. Kloc, and B. Batlogg, Nature (London) 406, 702 (2000); 408, 549 (2000)]. This method is in contrast to the idea to synthesize new-tubular forms with a usage of a carbon nanotube as nucleation seed. Furthermore, the strain energies of SiC nanotubes are lower than those of the carbon nanotubes. The calculated band gaps of the investigated SiC tubes are either direct or indirect depending on the helicities. We expect that the SiC tubes with direct band gaps can be applied as nanoscale optoelectronics devices with strong oscillator strengths. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Microstructure-size dependence of the 1.520 μm Er3+ luminescence lifetime in Al2O3–ZrO2 eutectic melt growth composites

R. I. Merino, J. A. Pardo, J. I. Peña, and V. M. Orera

Appl. Phys. Lett. 80, 589 (2002); http://dx.doi.org/10.1063/1.1445469 (3 pages) | Cited 2 times

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The radiative lifetime of the 4I13/2 level of Er3+ was modified up to 15% by changing the microstructure in laser-floating-zone-grown Er3+-doped Al2O3–ZrO2 eutectic melt growth composites. Erbium enters only the higher-refractive-index ZrO2 phase, which occupies 30% of the volume of the sample. The lifetimes of 4S3/2 (545 nm) and 4I13/2 (1520 nm) Er3+ levels were measured at 10 K and room temperature in different microstructures. The variation in the lifetime of this last level with interphase spacing is due to the change of the available electromagnetic modes at 1520 nm due to the change in the optical environment of the luminescent ion. © 2002 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.10.Fq Growth from melts; zone melting and refining

Sputtering of Si with decaborane cluster ions

Marek Sosnowski, Maria A. Albano, Cheng Li, Hans-Joachim L. Gossmann, and Dale C. Jacobson

Appl. Phys. Lett. 80, 592 (2002); http://dx.doi.org/10.1063/1.1446211 (3 pages) | Cited 1 time

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Decaborane cluster ions (B10Hx+) may play an important role in the manufacturing of future semiconductor devices, as they facilitate a very shallow implantation of B with a relatively high beam energy, due to its partition among the constituent atoms. While the formation of B-doped shallow junctions in Si has been demonstrated, little is known about other effects of these complex ions on a solid. We have measured the sputtering yield of Si with decaborane cluster ions at 12 keV and demonstrated that their impacts smooth rather than roughen the surface, similarly to much larger Ar cluster ions. The results have implications for the understanding of low-energy atomic impacts in terms of collective motion of many surface atoms and of the behavior of solids far from equilibrium. © 2002 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.65.-b Surface treatments
81.05.Cy Elemental semiconductors
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
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Thermal stability study of Ni/Ta n-GaN Schottky contacts

G. L. Chen, F. C. Chang, K. C. Shen, J. Ou, W. H. Chen, M. C. Lee, W. K. Chen, M. J. Jou, and C. N. Huang

Appl. Phys. Lett. 80, 595 (2002); http://dx.doi.org/10.1063/1.1425455 (3 pages) | Cited 11 times

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The Schottky behavior of Ni/Ta and Ni contacts on n-GaN was investigated under various annealing conditions by current–voltage measurements. It is found that with the addition of Ta between the Ni layer and the GaN substrate the thermal stability properties of devices can be significantly improved. Experimental results indicate that a high quality Ni/Ta n-GaN Schottky diode with an ideality factor and barrier height of 1.16 and 1.24 eV, respectively, can be obtained under 1 h annealing, at 700 °C. © 2002 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
68.60.Dv Thermal stability; thermal effects
73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
85.30.Hi Surface barrier, boundary, and point contact devices

High figure of merit in Eu-filled CoSb3-based skutterudites

G. A. Lamberton, S. Bhattacharya, R. T. Littleton, M. A. Kaeser, R. H. Tedstrom, T. M. Tritt, J. Yang, and G. S. Nolas

Appl. Phys. Lett. 80, 598 (2002); http://dx.doi.org/10.1063/1.1433911 (3 pages) | Cited 95 times

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We report measurements of electrical resistivity, thermopower, thermal conductivity, and Hall coefficient of polycrystalline Eu-doped CoSb3-based skutterudites with compositions Eu0.20Co4Sb12, Eu0.43Co4Sb11.59Ge0.31, and Eu0.42Co4Sb11.37Ge0.50. The relatively high mobility of these compounds, as compared to that of La- and Ce-filled skutterudites, may play a role in the large thermoelectric figure of merit (ZT>1 at 700 K) of Eu0.42Co4Sb11.37Ge0.50. We discuss the significant potential of these compounds for thermoelectric applications. © 2002 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
72.20.My Galvanomagnetic and other magnetotransport effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Relaxed SiGe-on-insulator substrates without thick SiGe buffer layers

Tomohisa Mizuno, Naoharu Sugiyama, Tsutomu Tezuka, and Shin-ichi Takagi

Appl. Phys. Lett. 80, 601 (2002); http://dx.doi.org/10.1063/1.1435799 (3 pages) | Cited 17 times

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We have developed a technology for relaxing top SiGe layers with low dislocation density on Si substrates, without using thick SiGe buffer structures. By introducing a thin strained SiGe layer and the internal-oxidation (ITOX) process following the separation-by-implanted-oxygen (SIMOX) process, we have experimentally demonstrated relaxed SiGe-on-insulator (SGOI) substrates with the Ge content of 20%, and it has been realized that their dislocation density is a factor of 20 lower than that of SGOI with SiGe buffer layer. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
61.72.uf Ge and Si
68.55.Nq Composition and phase identification
81.65.Mq Oxidation

Influence of 60Co γ-rays on dc performance of AlGaN/GaN high electron mobility transistors

B. Luo, J. W. Johnson, F. Ren, K. K. Allums, C. R. Abernathy, S. J. Pearton, A. M. Dabiran, A. M. Wowchack, C. J. Polley, P. P. Chow, D. Schoenfeld, and A. G. Baca

Appl. Phys. Lett. 80, 604 (2002); http://dx.doi.org/10.1063/1.1445809 (3 pages) | Cited 20 times

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AlGaN/GaN high electron mobility transistors (HEMTs) with different gate length and widths were irradiated with 60Co γ-rays to doses up to 600 Mrad. Little measurable change in dc performance of the devices was observed for doses lower than 300 Mrad. At the maximum dose employed, the forward gate current was significantly decreased, with an accompanying increase in reverse breakdown voltage. This is consistent with a decrease in effective carrier density in the channel as a result of the introduction of deep electron trapping states. The threshold voltage shifted to more negative voltages as a result of the irradiation, while the magnitude of the drain–source current was relatively unaffected. This is consistent with a strong increase of trap density in the material. The magnitude of the decrease in transconductance of the AlGaN/GaN HEMTs is roughly comparable to the decrease in dc current gain observed in InGaP/GaAs heterojunction bipolar transistors irradiated under similar conditions. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
61.80.Ed γ-ray effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Eq III-V semiconductors
61.82.Fk Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Transient model for terminal current noise

M. Nedjalkov, T. Grasser, H. Kosina, and S. Selberherr

Appl. Phys. Lett. 80, 607 (2002); http://dx.doi.org/10.1063/1.1447002 (3 pages)

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The condition of a stationary transport process is a common origin for the approaches for terminal current noise. Based on a recently-proposed stationary model and the integral form of the Boltzmann equation, we derive a transient stochastic process whose autocovariance function characterizes the terminal current noise. The properties and the domain of application of this transient model and its stationary counterpart are investigated. Numerical experiments are presented which support the conclusions drawn for the two models. © 2002 American Institute of Physics.
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72.70.+m Noise processes and phenomena
85.30.De Semiconductor-device characterization, design, and modeling
02.50.Ey Stochastic processes
05.60.-k Transport processes
02.30.Rz Integral equations
02.60.Nm Integral and integrodifferential equations
05.40.Ca Noise
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