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13 Aug 2001

Volume 79, Issue 7, pp. 895-1063

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Intensity filtering of a two-dimensional optical image in high-performance photorefractive mesogenic composites

Hiroshi Ono, Tomomi Kawamura, Nobuhiro Kawatsuki, and Hideki Norisada

Appl. Phys. Lett. 79, 895 (2001); http://dx.doi.org/10.1063/1.1390490 (3 pages) | Cited 1 time

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Edge enhancement, a type of intensity filtering of a two-dimensional optical image, was demonstrated using a high-performance photorefractive polymer-dissolved liquid crystal. We calculated the expected images using Fourier transform holographic geometry and obtained good agreement between the observed images and the theoretical expectation. © 2001 American Institute of Physics.
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42.30.Va Image forming and processing
42.70.Df Liquid crystals
42.40.-i Holography
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Ci Filters, zone plates, and polarizers
42.30.Kq Fourier optics

Ultrabroadband photoconductive detection: Comparison with free-space electro-optic sampling

Shunsuke Kono, Masahiko Tani, and Kiyomi Sakai

Appl. Phys. Lett. 79, 898 (2001); http://dx.doi.org/10.1063/1.1394719 (3 pages) | Cited 35 times

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The spectral response of a low-temperature-grown GaAs photoconductive (PC) antenna is compared with that of the electro-optic sampling technique for the frequency region up to 40 THz. The spectral response of the PC antenna for broadband detection is found to be determined by the temporal profile of the number of photocarriers injected by ultrashort optical gate pulses. © 2001 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)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
73.50.Pz Photoconduction and photovoltaic effects

Holographic surface gratings in iron-doped lithium niobate

S. S. Sarkisov, M. J. Curley, N. V. Kukhtarev, A. Fields, G. Adamovsky, C. C. Smith, and L. E. Moore

Appl. Phys. Lett. 79, 901 (2001); http://dx.doi.org/10.1063/1.1394176 (3 pages) | Cited 5 times

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Surface gratings associated with holographic volume gratings in photorefractive crystals of iron-doped lithium niobate have been studied using diffraction of a reflected probe beam and high-resolution phase-shifted interferometric profilometry. Both techniques show that the surface gratings exist in the form of periodical corrugations of the same period as that of the volume grating. The maximum amplitude of the periodical surface relief measured by both techniques is close to 6.5 nm. We also demonstrated that the periodical electric forces on the surface were capable of assembling polystyrene microspheres along the fringes of the grating. Large amplitude of the periodic electric field (1.6×104 V/cm) is associated with the photogalvanic effect. © 2001 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.70.Gi Light-sensitive materials
42.70.Ln Holographic recording materials; optical storage media

All-epitaxial fabrication of thick, orientation-patterned GaAs films for nonlinear optical frequency conversion

L. A. Eyres, P. J. Tourreau, T. J. Pinguet, C. B. Ebert, J. S. Harris, M. M. Fejer, L. Becouarn, B. Gerard, and E. Lallier

Appl. Phys. Lett. 79, 904 (2001); http://dx.doi.org/10.1063/1.1389326 (3 pages) | Cited 73 times

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Orientation-patterned GaAs (OPGaAs) films of 200 μm thickness have been grown by hydride vapor phase epitaxy (HVPE) on an orientation-patterned template fabricated by molecular beam epitaxy (MBE). Fabrication of the templates utilized only MBE and chemical etching, taking advantage of GaAs/Ge/GaAs heteroepitaxy to control the crystal orientation of the top GaAs film relative to the substrate. Antiphase domain boundaries were observed to propagate vertically under HVPE growth conditions so that the domain duty cycle was preserved through the thick GaAs for all domain periods attempted. Quasiphase-matched frequency doubling of a CO2 laser was demonstrated with the beam confocally focused through a 4.6 mm long OPGaAs film. © 2001 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Terahertz pulse propagation through small apertures

Oleg Mitrofanov, M. Lee, J. W. P. Hsu, L. N. Pfeiffer, K. W. West, J. D. Wynn, and J. F. Federici

Appl. Phys. Lett. 79, 907 (2001); http://dx.doi.org/10.1063/1.1392303 (3 pages) | Cited 40 times

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Transmission of single-cycle terahertz pulses through subwavelength apertures is experimentally studied in the near-field zone. Measurements of throughput for aperture sizes d as small as λ/300 show that the theoretical d3 law requires a correction term which takes into account the physical thickness of the aperture screen. Frequency dependent transmission of the broad band pulses explains changes in their spectral and temporal characteristics. Practical application of small apertures in near-field microscope probes allows achievement of spatial resolution of 7 μm for pulses with a broad spectral content of λ = 120–1500 μm. © 2001 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
41.20.Jb Electromagnetic wave propagation; radiowave propagation
07.79.Fc Near-field scanning optical microscopes

Visualization of mode transformation in a planar waveguide splitter by near-field optical phase imaging

M. L. M. Balistreri, J. P. Korterik, L. Kuipers, and N. F. van Hulst

Appl. Phys. Lett. 79, 910 (2001); http://dx.doi.org/10.1063/1.1394175 (3 pages) | Cited 10 times

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The gradual transformation of a guided TM00 mode into an “intermediate” double mode by a splitting junction has been investigated with a phase-sensitive photon scanning tunneling microscope. Field profiles and wave vectors of the modes have been directly determined from the phase information. Via a Fourier analysis of the measured phase and amplitude maps the decay of the TM00 mode and buildup of the intermediate mode have been directly visualized. Phase singularities and phase jumps in the transition region underline the mode transformation process. Finally, a partial polarization conversion of the TM modes to TE-polarized modes has been observed. © 2001 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
07.79.Fc Near-field scanning optical microscopes
42.30.Kq Fourier optics
42.79.Fm Reflectors, beam splitters, and deflectors
07.60.Ly Interferometers
42.79.Gn Optical waveguides and couplers
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Forward current propagation beyond the virtual cathode formed by a high injection current

Han S. Uhm, Eun H. Choi, and Myung C. Choi

Appl. Phys. Lett. 79, 913 (2001); http://dx.doi.org/10.1063/1.1391408 (3 pages) | Cited 8 times

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A virtual cathode is formed in a cavity, if the injection current from the diode exceeds the critical current. The propagation properties of the forward current beyond the virtual cathode are investigated. It is shown that the forward current increases significantly as the diode gap distance LCA increases, although the injection current from the diode decreases drastically. Experimental data agree well with theoretical results obtained analytically. © 2001 American Institute of Physics.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources

Reactive ion etching of silicon carbide in SF6 gas: Detection of CF, CF2, and SiF2 etch products

P. Chabert, G. Cunge, J.-P. Booth, and J. Perrin

Appl. Phys. Lett. 79, 916 (2001); http://dx.doi.org/10.1063/1.1395520 (3 pages) | Cited 12 times

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We have detected by laser-induced fluorescence the radicals SiF2, CF, and CF2 produced during the reactive ion etching of SiC substrates in a pure SF6 plasma. Spatially and temporally resolved measurements were used to distinguish between gas phase and etched surface radical production. Whereas CF and CF2 are produced directly at the etched surface, the SiF2 radicals are produced in the gas phase (probably by electron-impact dissociation of SiF4). We attribute this difference to the formation of a carbon-rich layer on the SiC substrate surface, the removal of which produces CFx (x = 1,2,3) radicals. The CF2 radical represents up to 20% of the total carbon etch products under our conditions. © 2001 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.80.Dx Analytical methods involving electronic spectroscopy

Electron-beam enhancement of ion charge state fractions in the metal-vapor vacuum-arc ion source

Alexey Bugaev, Vasily Gushenets, George Yushkov, Efim Oks, Timur Kulevoy, Ady Hershcovitch, and Brant M. Johnson

Appl. Phys. Lett. 79, 919 (2001); http://dx.doi.org/10.1063/1.1392969 (3 pages) | Cited 9 times

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We report demonstrations of ion charge-state enhancement for an electron-beam metal-vapor vacuum-arc (E-MEVVA) ion source. Results with a lead cathode yielded a maximum ion charge state of Pb7+, which implies an ionization potential of at least 130 eV. Electron current densities j = 70 A/cm2 and ionization times τ ≅ 100 μs produced jτ = 9.2×10−3 C/cm2 (5.8×1016 electrons/cm2). Standard analysis for these conditions indicates—somewhat surprisingly—that successive single (stepwise) ionization accounts for the present observations, even though the charge states are substantially higher than most previous results with MEVVA-based ion sources. © 2001 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum

Plasma wave instability in gated collisionless two-dimensional electron gas

A. P. Dmitriev, V. Yu. Kachorovskii, and M. S. Shur

Appl. Phys. Lett. 79, 922 (2001); http://dx.doi.org/10.1063/1.1391395 (3 pages) | Cited 3 times

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We present the solution of the Boltzmann equation for relatively low density gated two-dimensional electron gas where electron–electron collisions are not significant. This solution describes the plasma waves with the same dispersion law as for a high electron sheet density. In both cases, the plasma waves become instable in a short channel field effect transistor with asymmetric boundary conditions at small channel currents (provided that the scattering by phonons and impurity is sufficiently small). Our analysis also shows that for realistic values of the device parameters, the Landau damping is small. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Mx High-frequency effects; plasma effects
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Pulsed atomic layer epitaxy of quaternary AlInGaN layers

J. Zhang, E. Kuokstis, Q.  Fareed, H. Wang, J.  Yang, G. Simin, M. Asif Khan, R. Gaska, and M. Shur

Appl. Phys. Lett. 79, 925 (2001); http://dx.doi.org/10.1063/1.1392301 (3 pages) | Cited 31 times

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In this letter, we report on a material deposition scheme for quaternary AlxInyGa1−x–yN layers using a pulsed atomic layer epitaxy (PALE) technique. The PALE approach allows accurate control of the quaternary layer composition and thickness by simply changing the number of aluminum, indium, and gallium pulses in a unit cell and the number of unit cell repeats. Using PALE, AlInGaN layers with Al mole fractions in excess of 40% and strong room-temperature photoluminescence peaks at 280 nm can easily be grown even at temperatures lower than 800 °C. © 2001 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Observations of Al segregation around dislocations in AlGaN

L. Chang, S. K. Lai, F. R. Chen, and J. J. Kai

Appl. Phys. Lett. 79, 928 (2001); http://dx.doi.org/10.1063/1.1391409 (3 pages) | Cited 8 times

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Transmission electron microscopy has been used to observe Al segregation around the threading dislocations in Al0.1Ga0.9N and Al0.3Ga0.7N grown by metalorganic chemical vapor deposition on 6H–SiC. Dislocation lines were found to have up to 70% more Al concentration than those regions free of dislocations in the matrix. The Al-depleted regions around the dislocations are shown to be within a few nanometers from the dislocation lines. The results also show that more Al segregate to edge dislocations than to screw ones. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
64.75.-g Phase equilibria
68.37.Lp Transmission electron microscopy (TEM)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Lk Linear defects: dislocations, disclinations
81.05.Ea III-V semiconductors

Influence of microstructure on electrical properties of diluted GaNxAs1−x formed by nitrogen implantation

J. Jasinski, K. M. Yu, W. Walukiewicz, J. Washburn, and Z. Liliental-Weber

Appl. Phys. Lett. 79, 931 (2001); http://dx.doi.org/10.1063/1.1390487 (3 pages) | Cited 10 times

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Structural studies of GaAs implanted with N or coimplanted with other elements showed that, in addition to typical postimplant defects, small voids were present in the implanted region in such materials. Comparison of the microstructure found in these layers with electrical results indicates that these voids are responsible for the low activation efficiency of N implanted into GaAs. The results show that the N-induced enhancement of the donor activation efficiency can be achieved only in a void-free region of the implanted sample. © 2001 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.72.uj III-V and II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
71.55.Eq III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Theoretical prediction of local distortion in an ErO6 cluster: Stabilization of a C4v structure by a rack and pinion effect

Masashi Ishii and Yasuo Komukai

Appl. Phys. Lett. 79, 934 (2001); http://dx.doi.org/10.1063/1.1392305 (3 pages) | Cited 10 times

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As a possible atomic coordination of erbium dopants surrounded by oxygen, a molecular orbital calculation of an ErO6 cluster can predict a C4v pseudo-octahedral structure with Er distortion of ∼0.1 Å from the octahedral center. It was found that bond alternation by a “rack and pinion effect” can minimize the electron transfer from O2− to Er3+ at this distortion range, resulting in stable ionic bonding; the rotation of an O 2p orbital due to Er 5d translation, similar to rack and pinion motion, forms a new O 2p–Er 5d bond, while a dipole moment induced by symmetrical degradation makes an O 2p–Er 6s bond unstable. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
36.40.-c Atomic and molecular clusters

Advantage of anti-Stokes Raman scattering for high-temperature measurements

Hirotaka Fujimori, Masato Kakihana, Koji Ioku, Seishi Goto, and Masahiro Yoshimura

Appl. Phys. Lett. 79, 937 (2001); http://dx.doi.org/10.1063/1.1394174 (3 pages) | Cited 7 times

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We present the results of experiments that assess the viability of anti-Stokes scattering to investigate in situ materials at high temperatures. Both anti-Stokes and Stokes Raman measurements have been performed at various high temperatures using hafnia as a test material. As compared with Stokes Raman spectra, anti-Stokes spectra were observed with lower thermal emission backgrounds in accordance with Planck’s equation. The intensity ratio of anti-Stokes to Stokes scattering approaches 1 as the temperature increases at high temperatures satisfying the Boltzmann distribution law. These results clearly demonstrate the advantage and feasibility of anti-Stokes Raman scattering for the elimination of the thermal emission in comparison with Stokes scattering. © 2001 American Institute of Physics.
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07.20.Ka High-temperature instrumentation; pyrometers
07.20.Dt Thermometers
07.60.Rd Visible and ultraviolet spectrometers
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
78.30.Hv Other nonmetallic inorganics

Surface molecular alignment by in-plane anchoring in the cell showing the V-shaped switching

S. S. Seomun, J. K. Vij, N. Hayashi, T. Kato, and A. Fukuda

Appl. Phys. Lett. 79, 940 (2001); http://dx.doi.org/10.1063/1.1389770 (3 pages) | Cited 6 times

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The surface molecular alignment in a sandwich cell showing V-shaped switching has been investigated using a photocontrolling method. The results indicate that the molecules on the rubbed surface are aligned parallel to the rubbing direction as in an open cell with an air–liquid crystal boundary. This alignment is due to strong in-plane anchoring, due to which the small twisted state appears along the cell thickness through intralayer molecular interaction. © 2001 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions

Green luminescent center in undoped zinc oxide films deposited on silicon substrates

Bixia Lin, Zhuxi Fu, and Yunbo Jia

Appl. Phys. Lett. 79, 943 (2001); http://dx.doi.org/10.1063/1.1394173 (3 pages) | Cited 585 times

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The photoluminescence (PL) spectra of the undoped ZnO films deposited on Si substrates by dc reactive sputtering have been studied. There are two emission peaks, centered at 3.18 eV (UV) and 2.38 eV (green). The variation of these peak intensities and that of the I–V properties of the ZnO/Si heterojunctions were investigated at different annealing temperatures and atmospheres. The defect levels in ZnO films were also calculated using the method of full-potential linear muffin-tin orbital. It is concluded that the green emission corresponds to the local level composed by oxide antisite defect OZn rather than oxygen vacancy VO, zinc vacancy VZn, interstitial zinc Zni, and interstitial oxygen Oi. © 2001 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
71.55.Gs II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Dz II-VI semiconductors
81.15.Cd Deposition by sputtering
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
61.72.Cc Kinetics of defect formation and annealing

Internal self-ordering in In(Sb,As), (In,Ga)Sb, and (Cd,Zn,Mn)Se nano-agglomerates/quantum dots

P. Möck, T. Topuria, N. D. Browning, G. R. Booker, N. J. Mason, R. J. Nicholas, M. Dobrowolska, S. Lee, and J. K. Furdyna

Appl. Phys. Lett. 79, 946 (2001); http://dx.doi.org/10.1063/1.1394161 (3 pages) | Cited 8 times

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Nano-agglomerates of In(Sb,As) in InAs, (In,Ga)Sb in GaSb, and (Cd,Zn,Mn)Se in (Zn,Mn)Se are classified by transmission electron microscopy. In scanning transmission electron microscopy, atomic resolution Z-contrast images reveal different modes of internal compositional modulation on the atomic length scale, resulting for all three material systems in nano-agglomerates of an appropriate size that may constitute a new type of quantum dot. For other nano-agglomerates of In(Sb,As) in InAs and (In,Ga)Sb in GaSb, we observed a second type of nanoscale ordering that results in nano-agglomerates with an internal compositional modulation on a length scale of a few nm. Both types of compositional modulation are discussed as having arisen from a rather long-term structural response to a combination of internal and external strains. © 2001 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.46.-w Structure of nanoscale materials
68.37.Lp Transmission electron microscopy (TEM)

Surface photovoltage spectroscopy characterization of a GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor structure

Y. T. Cheng, Y. S. Huang, D. Y. Lin, K. K. Tiong, Fred H. Pollak, and K. R. Evans

Appl. Phys. Lett. 79, 949 (2001); http://dx.doi.org/10.1063/1.1392974 (3 pages) | Cited 4 times

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Using room-temperature surface photovoltage spectroscopy (SPS), we have characterized a GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) structure. Signals have been observed from every region of the sample. From a line shape fit to the normalized first derivative of the surface photovoltage signal with respect to photon energy, the two-dimensional electron gas density (Ns) was obtained and found to be in good agreement with Hall measurement. The Al composition and the properties of the GaAs/GaAlAs superlattice buffer layer also were obtained from the SPS spectrum. The results demonstrate the considerable potential of SPS for the contactless and nondestructive characterization of pHEMT structures at room temperature. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
73.25.+i Surface conductivity and carrier phenomena
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Spatially resolved photoluminescence of inversion domain boundaries in GaN-based lateral polarity heterostructures

P. J. Schuck, M. D. Mason, R. D. Grober, O. Ambacher, A. P. Lima, C. Miskys, R. Dimitrov, and M. Stutzmann

Appl. Phys. Lett. 79, 952 (2001); http://dx.doi.org/10.1063/1.1390486 (3 pages) | Cited 28 times

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Intentionally grown GaN inversion domain boundaries (IDBs) of lateral polarity heterostructures have been spectroscopically imaged at low temperature using high spatial resolution photoluminescence. It is shown that the IDBs are not only optically active, but are more than an order of magnitude brighter than the GaN bulk material. Our findings are in agreement with calculations predicting that IDBs should not adversely affect near-band-gap photoluminescence due to the absence of midgap electronic states. Typical linewidths are on the order of 10–20 meV, however, features less than 0.6 meV are observed. The boundary emission is found to be neither spectrally nor spatially uniform. Also, a strong polarization dependence of the IDB photoluminescence is measured and determined to be oriented parallel to the boundary between GaN of N- or Ga-face polarity. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology

Structural characterization of GaN laterally overgrown on a (111)Si substrate

Shigeyasu Tanaka, Yoshio Honda, Nobuhiko Sawaki, and Michio Hibino

Appl. Phys. Lett. 79, 955 (2001); http://dx.doi.org/10.1063/1.1394716 (3 pages) | Cited 10 times

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Using transmission electron microscopy, we have characterized defect structures in laterally overgrown GaN crystals, grown directly on SiO2 stripe-patterned (111)Si substrates by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer. The width and the period of the stripe windows were nominally 1 and 2 μm, respectively. The average threading dislocation density for a completely coalesced 2-μm-thick GaN crystal obtained on the [112]-oriented stripe-patterned substrate was ∼ 2×109 cm−2. The reduction in threading dislocation density is a consequence of the lateral growth and dislocation reactions at the coalesced front of the mask. On the other hand, valleys and pits tend to remain on the mask during the growth on the [110]-oriented stripe-patterned substrate. Cracks were present in both crystals. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
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Photoluminescence properties of a GaN0.015As0.985/GaAs single quantum well under short pulse excitation

X. D. Luo, Z. Y. Xu, W. K. Ge, Z. Pan, L. H. Li, and Y. W. Lin

Appl. Phys. Lett. 79, 958 (2001); http://dx.doi.org/10.1063/1.1390484 (3 pages) | Cited 34 times

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Under short pulse laser excitation, we have observed an extra high-energy photoluminescence (PL) emission from GaNAs/GaAs single quantum wells (QWs). It dominates the PL spectra under high excitation and/or at high temperature. By measuring the PL dependence on both temperature and excitation power and by analyzing the time-resolved PL results, we have attributed the PL peak to the recombination of delocalized excitons in QWs. Furthermore, a competition process between localized and delocalized excitons is observed in the temperature-dependent PL spectra under the short pulse excitation. This competition is believed to be responsible for the temperature-induced S-shaped PL shift often observed in the disordered alloy semiconductor system under continuous-wave excitation. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.67.De Quantum wells
78.47.-p Spectroscopy of solid state dynamics
73.21.Fg Quantum wells
71.35.-y Excitons and related phenomena

Radiotracer investigation of a deep Be-related band gap state in 4H-SiC

F. Albrecht, J. Grillenberger, G. Pasold, W. Witthuhn, and N. Achtziger

Appl. Phys. Lett. 79, 961 (2001); http://dx.doi.org/10.1063/1.1394724 (3 pages) | Cited 2 times

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One Be-related deep level in the band gap of 4H-SiC was identified by radiotracer deep level transient spectroscopy (DLTS). The radioactive isotope 7Be was recoil implanted into p-type as well as n-type 4H-SiC for these radiotracer experiments. DLTS spectra were taken repeatedly during the elemental transmutation of 7Be to 7Li. In the case of p-type 4H-SiC, they exhibit one peak of time-dependent height. Its concentration decreases with the halflife of the nuclear decay of 7Be (T1/2 = 53.3 d). Thus, this level at 1.06 eV above the valence band edge is identified as Be-related. In n-type 4H-SiC, neither Be- nor Li-correlated deep levels have been found in the investigated part of the band gap within the measurement accuracy. © 2001 American Institute of Physics.
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71.55.Ht Other nonmetals

Measurement of the Auger lifetime in GaInAsSb/GaSb heterostructures using the photoacoustic technique

I. Riech, M. L. Gomez-Herrera, P. Díaz, J. G. Mendoza-Alvarez, J. L. Herrera-Pérez, and E. Marín

Appl. Phys. Lett. 79, 964 (2001); http://dx.doi.org/10.1063/1.1383281 (3 pages) | Cited 7 times

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We have studied GaxIn1−xAsySb1−y/GaSb heterostructures for x = 0.84 and y = 0.14 using the photoacoustic technique with the heat transmission configuration. A theoretical model, which includes all the possible nonradiative recombination mechanisms that contribute to heat generation, was developed to calculate the photoacoustic signal for this type of heterostructure. The Auger recombination lifetime τAuger was determined by fitting our experimental results to the calculated frequency dependence of the theoretical photoacoustic signal. The obtained value for τAuger is compatible with those reported in the literature for semiconductors with band-gap energies below and above 0.5 eV, the energy region where there is a lack of experimental τAuger values. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.20.Fv Electron impact: Auger emission
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.66.Fd III-V semiconductors
73.20.At Surface states, band structure, electron density of states

Improved n+-GaAs/p+-In0.49Ga0.51P/n-GaAs camel-like gate structure for high-breakdown, low-leakage, and high-temperature applications

Wen-Chau Liu, Kuo-Hui Yu, Rong-Chau Liu, Kun-Wei Lin, Chin-Chuan Cheng, Kuan-Po Lin, Chih-Hung Yen, and Cheng-Zu Wu

Appl. Phys. Lett. 79, 967 (2001); http://dx.doi.org/10.1063/1.1394720 (3 pages) | Cited 4 times

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A n+-GaAs/p+-In0.49Ga0.51P/n-GaAs camel-like gate structure has been applied to fabricate high-performance transistors. The studied heterostructure field-effect transistor exhibits a large barrier height, high breakdown voltage, low leakage current, and good temperature-dependent characteristics. Experimentally, for a 1×100 μm2 device, the gate-drain breakdown voltage and gate leakage current are 52 (31.5) V, and 37 μ A/mm (3.5 mA/mm) at the gate-drain voltage of 40 V, respectively, at the temperature of 300 (480) K. In addition, the high drain-source operation voltage over 20 V with low leakage current is obtained. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
84.40.-x Radiowave and microwave (including millimeter wave) technology
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