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28 Apr 1997

Volume 70, Issue 17, pp. 2215-2323

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Midinfrared molecular gas lasers optically pumped by a continuously tunable infrared optical parametric oscillator

H. Charles Tapalian, Chris A. Michaels, and George W. Flynn

Appl. Phys. Lett. 70, 2215 (1997); http://dx.doi.org/10.1063/1.118818 (3 pages) | Cited 1 time

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We report the observation of midinfrared super radiant pulses emitted from molecular gases pumped by a narrow-band, continuously tunable infrared optical parametric oscillator. Molecules pumped either into a vibrational combination band or a vibrational overtone state decay by means of super radiant emission to a lower vibrationally excited state. Emission was observed in N2O at 4.5 and 8 μm, and in C2H2 at 13.6 μm and 15.7 μm. Pulse energies as high as 0.5 mJ and pulse widths as short as 7 ns make this an excellent technique for the production of intense midinfrared light. © 1997 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
42.65.Yj Optical parametric oscillators and amplifiers

Widely tunable efficient intracavity quasiphase-matched midinfrared generation

Gary Y. Wang, Jing Zhao, Qiushui Chen, and Mark Conin-Golomb

Appl. Phys. Lett. 70, 2218 (1997); http://dx.doi.org/10.1063/1.118820 (3 pages) | Cited 2 times

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We describe in this letter a novel approach to obtain a tunable midinfrared (mid-IR) laser output. By applying quasiphase-matched difference frequency generation in a periodically domain inverted LiNbO3 crystal placed inside a Cr3+:LiSAF laser cavity, more than 50 mW of mid-IR output was generated using only 1.8 watts of red diode or dye laser pumping. Wavelength tuning of the mid-IR signals from 3.3 to 4.2 μm was demonstrated by tuning only the wavelength of the Cr3+:LiSAF emission, without the need to reorient the LiNbO3 crystal for domain period adjustment. © 1997 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

The consistent application of Maxwell–Garnett effective medium theory to anisotropic composites

I. L. Skryabin, A. V. Radchik, P. Moses, and G. B. Smith

Appl. Phys. Lett. 70, 2221 (1997); http://dx.doi.org/10.1063/1.118821 (3 pages) | Cited 16 times

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The Maxwell–Garnett class of effective medium model applies if a representative cell can be found whose polarization vanishes upon insertion in the effective medium. For an anisotropic composite with randomly distributed ellipsoidal particles aligned along the principal axis, this leads to electrostatic restraints on the shape of such cells. It is shown that the cell boundary must have different depolarization factors to the inclusion within the cell. Practice is to equate them. A new physically correct ellipsometric modeling routine still with only two fitting parameters is demonstrated. © 1997 American Institute of Physics.
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78.20.Bh Theory, models, and numerical simulation
78.66.Sq Composite materials
77.55.-g Dielectric thin films

Synthetic wide bandpass x-ray polarizers

J. O. Cross, B. R. Bennett, M. I. Bell, and K. J. Kuhn

Appl. Phys. Lett. 70, 2224 (1997); http://dx.doi.org/10.1063/1.118822 (3 pages)

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A wide bandpass x-ray polarizer for photon energies near 8358 eV (LIII absorption edge of erbium) has been grown using molecular beam epitaxy. The results illustrate a general approach to preparing graded-lattice diffracting optical components. The active optical element is an 8-μm-thick single crystal film of In0.51Ga0.49Sb grown on a GaAs (001) substrate. The alloy was chosen to ensure maximum linear polarization for the (006) Bragg reflection at the target energy. The polarizer reflectivity has a full width at half-maximum of 27 eV in a fixed geometry with an angle of 90° between the incident and diffracted beams. © 1997 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Transverse-electric/transverse-magnetic polarization converter using twisted optic–axis waveguides in poled polymers

Min-Cheol Oh, Wol-Yon Hwang, and Kwangjoon Kim

Appl. Phys. Lett. 70, 2227 (1997); http://dx.doi.org/10.1063/1.118823 (3 pages) | Cited 6 times

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Polymeric passive TE/TM polarization converters are fabricated based on an adiabatic following in twisted optic–axis waveguides. Waveguides are formed by a reactive ion etching, and the optic axis of the waveguide is twisted by 90° with specially designed poling electrodes. Both TE and TM modes confined in the waveguides are converted to their counterparts by following the twisted ordinary and extraordinary axes, respectively. Conversion efficiency better than 20 dB and polarization-dependent loss less than 0.5 dB are obtained. The device provides wavelength insensitive operations and has large fabrication tolerances. © 1997 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers
42.70.Jk Polymers and organics
42.82.Et Waveguides, couplers, and arrays
42.86.+b Optical workshop techniques

Optically pumped lasing of ZnO at room temperature

D. M. Bagnall, Y. F. Chen, Z. Zhu, T. Yao, S. Koyama, M. Y. Shen, and T. Goto

Appl. Phys. Lett. 70, 2230 (1997); http://dx.doi.org/10.1063/1.118824 (3 pages) | Cited 914 times

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We report the observation of optically pumped lasing in ZnO at room temperature. Thin films of ZnO were grown by plasma-enhanced molecular beam epitaxy on (0001) sapphire substrates. Laser cavities formed by cleaving were found to lase at a threshold excitation intensity of 240 kW cm−2. We believe these results demonstrate the high quality of ZnO epilayers grown by molecular beam epitaxy while clearly demonstrating the viability of ZnO based light emitting devices. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Low-dispersion thin-film microstrip lines with cyclotene (benzocyclobutene) as dielectric medium

H.-M. Heiliger, M. Nagel, H. G. Roskos, H. Kurz, F. Schnieder, W. Heinrich, R. Hey, and K. Ploog

Appl. Phys. Lett. 70, 2233 (1997); http://dx.doi.org/10.1063/1.118849 (3 pages) | Cited 27 times

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We report on thin-film microstrip lines (TFMSLs) fabricated on low-resistivity Si with polymerized cyclotene as the dielectric between signal and ground conductor, all on top of the wafer. Electro-optic high-frequency characterization of the TFMSLs reveals negligible modal dispersion up to the highest frequencies of 1.0 THz. In spite of the high substrate conductivity, the attenuation is low ( ⩽ 1 dB/mm at 100 GHz). Over the full frequency range, it is dominated by conductor losses and not by absorption in the dielectric. With these dispersion and attenuation properties, TFMSLs are an attractive alternative to coplanar waveguides, with the additional advantage of immunity against substrate absorption and radiation losses. © 1997 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
42.70.Jk Polymers and organics
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.Jd Polymers; organic compounds

Laser thermoacoustic modulation for space charge measurement

J. L. Franceschi and V. Haas

Appl. Phys. Lett. 70, 2236 (1997); http://dx.doi.org/10.1063/1.118825 (2 pages)

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A new method for measuring the space charge distribution in polymer insulators has been developed. This frequency method is based on the thermoacoustic signal which propagates into the insulator when a chopped laser beam is modulated in intensity and focused on the surface of the sample. This method has been used for measuring space charge distribution in a polyethyleneterephtalate sample. © 1997 American Institute of Physics.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
77.22.Jp Dielectric breakdown and space-charge effects
42.60.Fc Modulation, tuning, and mode locking
77.84.Jd Polymers; organic compounds
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Tip-surface interactions studied using a force controlled atomic force microscope in ultrahigh vacuum

S. P. Jarvis, S.-I. Yamamoto, H. Yamada, H. Tokumoto, and J. B. Pethica

Appl. Phys. Lett. 70, 2238 (1997); http://dx.doi.org/10.1063/1.118826 (3 pages) | Cited 9 times

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A magnetic force has been used to control a partially magnetized atomic force microscope cantilever in ultrahigh vacuum in order to investigate tip-surface interactions. It is shown that forces applied by an oscillating tip can drastically affect the measured response of the lever. In particular the oscillating force influences the measured tip-surface adhesion and can be treated as a simple addition to the static applied force in breaking adhesive bonds. Qualitative differences in force spectroscopy measurements due to the amplitude of the driving oscillation of the lever are presented and an alternative nonintrusive technique introduced. © 1997 American Institute of Physics.  
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Lh Atomic force microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)

Ferroelectric domain gratings and Barkhausen spikes in potassium lithium tantalate niobate

Xiaolin Tong, Amnon Yariv, Min Zhang, Aharon J. Agranat, Rudolf Hofmeister, and Victor Leyva

Appl. Phys. Lett. 70, 2241 (1997); http://dx.doi.org/10.1063/1.118827 (3 pages) | Cited 2 times

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The observation of Barkhausen current spikes during the recording of volume phase holograms in potassium lithium tantalate niobate is reported on. These spikes are due to the ferroelectric domain reversal induced by photorefractive space charge fields. Both “small” (1 nA) and “large” (100 nA) spikes are observed, which correspond to micro and macro domain reversal, respectively. The diffraction efficiency can change as much as 50% during a single macrodomain switching. © 1997 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
77.80.Fm Switching phenomena
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.20.-e Optical properties of bulk materials and thin films
77.80.Dj Domain structure; hysteresis
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Gas-condensation synthesis of nanocrystalline BaTiO3

Shaoping Li, Jeffrey A. Eastman, and Loren J. Thompson

Appl. Phys. Lett. 70, 2244 (1997); http://dx.doi.org/10.1063/1.118828 (3 pages) | Cited 4 times

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Nanocrystalline BaTiO3 has been prepared by a gas-condensation process. BaTiO3 and Ti sources are vaporized simultaneously in either a helium or an oxygen environment using an electron beam evaporation system. The stoichiometry of nanocrystalline BaTiO3 powders can be controlled precisely and reproducibly. Nanocrystalline BaTiO3 powders, with an average particle size of less than 20 nm, can be obtained by postannealing the as-evaporated powders at a temperature of 700 °C. These powders show good sintering behavior with a high density at a sintering temperature as low as 1250 °C. Differential thermal analysis indicated that nanocrystalline BaTiO3was formed through the reaction of Ba/Ti oxidized clusters. Dielectric properties of ceramics from nanocrystalline BaTiO3 are also reported. © 1997 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Strain relaxation and defect formation in heteroepitaxial Si1−xGex films via surface roughening induced by controlled annealing experiments

Cengiz S. Ozkan, William D. Nix, and Huajian Gao

Appl. Phys. Lett. 70, 2247 (1997); http://dx.doi.org/10.1063/1.118819 (3 pages) | Cited 82 times

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Mechanisms of strain relaxation and defect formation during surface roughening in Si1−xGex films grown epitaxially on (100)Si substrates have been investigated by controlled annealing experiments. Epitaxial films 10 nm in thickness and containing 18% Ge, which are subcritical with respect to the formation of misfit dislocations, show strain relaxation through surface roughening on annealing at 850 °C, where surface grooves are aligned along 〈100〉 directions. Other films with 22% Ge and supercritical thicknesses have also been studied, where surface grooves are aligned along 〈110〉 directions. © 1997 American Institute of Physics.
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81.05.Hd Other semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
62.20.F- Deformation and plasticity

On the dynamics of the oxidation-induced stacking-fault ring in as-grown Czochralski silicon crystals

Talid Sinno, Robert A. Brown, Wilfried von Ammon, and Erich Dornberger

Appl. Phys. Lett. 70, 2250 (1997); http://dx.doi.org/10.1063/1.118829 (3 pages) | Cited 10 times

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The behavior of the oxidation-induced stacking-fault ring (OSF ring) in Czochralski (CZ)-grown silicon crystals is predicted based on the dynamics of point defects during growth. Preexponential constants for the equilibrium point defect concentrations and diffusivities are determined by fitting the predictions of the model to a single set of experimental data for OSF-ring dynamics. Other experimental data is well fit by this model. Moreover, point defect properties used are consistent with other estimates. Asymptotic analysis of the point defect model leads to a closed-form expression for the dependence of the OSF-ring location on processing conditions and thermophysical properties of point defects at the melting temperature. These results indicate that differentiation between defect types in CZ-grown material can be done entirely on the basis of point defect dynamics. © 1997 American Institute of Physics.
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81.10.Fq Growth from melts; zone melting and refining
81.05.Cy Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.Nn Stacking faults and other planar or extended defects
81.65.Mq Oxidation
66.30.Lw Diffusion of other defects

Spin-on doping of porous silicon and its effect on photoluminescence and transport characteristics

S. Sen, J. Siejka, A. Savtchouk, and J. Lagowski

Appl. Phys. Lett. 70, 2253 (1997); http://dx.doi.org/10.1063/1.118830 (3 pages) | Cited 11 times

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We have investigated a novel way to dope porous Si layers with (B) and/or (P) using the spin-on doping technique. Under certain conditions, pore filling by the dopant solution was measured to be near 90%–95% leading to a homogeneous coverage of the porous skeleton. Near two orders of magnitude decrease in diode resistance was achievable following rapid thermal activation in a N2 atmosphere of B only or B+P double doped porous Si. Photoluminescence (PL) intensities observed in B+P double doped porous layers were significant. Relative to as-prepared samples, the PL intensities of double doped samples were weaker for porous Si on n-type and stronger for porous Si formed on p-type Si. In both cases, the PL magnitudes after double doping were comparable. © 1997 American Institute of Physics.
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61.72.uf Ge and Si
72.80.Cw Elemental semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology

Fabrication of ZnSe quantum dots under Volmer–Weber mode by metalorganic chemical vapor deposition

M. C. Harris Liao, Y. H. Chang, Y. F. Chen, J. W. Hsu, J. M. Lin, and W. C. Chou

Appl. Phys. Lett. 70, 2256 (1997); http://dx.doi.org/10.1063/1.118831 (3 pages) | Cited 27 times

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The possibility of fabricating quantum dots under Volmer–Weber growth mode is investigated. Layers of ZnSe/ZnS were grown by metalorganic chemical vapor deposition on both Si and GaAs substrates. The images of surface morphology, taken by atomic force microscopy, showed that the layers were grown in three-dimensional islands. Blueshift was observed in the photoluminescence spectra up to room temperature for these samples. This blueshift was shown to originate from the ZnSe islands. The effect of ZnSe growth duration was investigated. It was found that the blueshift increased with shorter ZnSe growth durations, but this near band gap emission disappeared when the ZnSe growth duration was longer than 5 s. Effects of quantum confinement and strain were considered to resolve the origin of the blueshift. Our result suggests that carrier confinement plays a dominant role. © 1997 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.66.Hf II-VI semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Et II-VI semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Improvement in quality of epitaxial Zn0.5Cd0.5Se layers grown on (001) InP substrates by using an InP buffer layer

E. Snoeks, S. Herko, L. Zhao, B. Yang, A. Cavus, L. Zeng, and M. C. Tamargo

Appl. Phys. Lett. 70, 2259 (1997); http://dx.doi.org/10.1063/1.118832 (3 pages) | Cited 9 times

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Zn1−xCdxSe (x ≈ 0.5), a II–VI wide band gap semiconductor, is grown lattice matched by molecular beam epitaxy on (001) InP substrates. The effect of incorporating an InP buffer layer on structural and optical properties of the ZnCdSe films is studied. Transmission electron microscopy shows that a reduction in the density of stacking faults by two orders of magnitude (from 5×109 down to 5×107/cm2) is realized by use of the buffer layer. Grown-in Shockley-type stacking faults are the only defects observed in the ZnCdSe. The (004) x-ray diffraction rocking curve becomes as narrow as 73 arcsec, and the photoluminescence emission peak becomes narrower and more intense. The lower defect density is attributed to the overall improved InP surface allowing for better two-dimensional nucleation of II–VI growth.© 1997 American Institute of Physics.
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81.05.Dz II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Nn Stacking faults and other planar or extended defects
78.55.Et II-VI semiconductors
78.66.Fd III-V semiconductors

Local identification and mapping of the C49 and C54 titanium phases in submicron structures by micro-Raman spectroscopy

I. De Wolf, D. J. Howard, A. Lauwers, K. Maex, and H. E. Maes

Appl. Phys. Lett. 70, 2262 (1997); http://dx.doi.org/10.1063/1.118833 (3 pages) | Cited 18 times

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In this letter, it is shown that micro-Raman spectroscopy allows easy, nondestructive determination of the C49 and C54 phase of titanium silicide with μm resolution within single structures with area dimensions down to 1×1 μm2 and along isolated line structures with widths down to 0.25 μm. The micro-Raman spectroscopy technique is used to study isolated 0.25–5-μm-wide TiSi2 lines with thicknesses as small as 16 nm that are formed in both crystalline Si and polycrystalline Si. The phase mapping ability of the technique is demonstrated on several 80-μm-long, 0.35-μm-wide TiSi2 lines that are part of four-terminal line resistance devices created using complementary metal–oxide–semiconductor processing. © 1997 American Institute of Physics.
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78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.-z Semiconductor devices

The pseudo-ordered structure in light emitting porous and nanocrystalline silicon films

L. C. Wang, X. N. Liu, F. Yan, X. M. Bao, D. Feng, and W. M. Rainforth

Appl. Phys. Lett. 70, 2265 (1997); http://dx.doi.org/10.1063/1.118834 (3 pages)

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The structures of light emitting porous and nanocrystalline silicon films have been investigated using high resolution electron microscopy. A pseudo-ordered structure has been found from the Fourier transformation of the high resolution images after digital processing of the images. The structure description was distinguished from common amorphous and nanocrystalline silicon films. The formation mechanism of the pseudo-ordered structure is described in the letter. © 1997 American Institute of Physics.  
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68.55.-a Thin film structure and morphology
61.43.Gt Powders, porous materials
61.46.-w Structure of nanoscale materials

Synthesis of GaN nanocrystals by sequential ion implantation

J. A. Wolk, K. M. Yu, E. D. Bourret-Courchesne, and E. Johnson

Appl. Phys. Lett. 70, 2268 (1997); http://dx.doi.org/10.1063/1.118850 (3 pages) | Cited 18 times

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We have synthesized GaN nanocrystals by sequential implantation of Ga and N ions into a sapphire substrate followed by a postimplantation anneal. The nanocrystals have been identified as the wurtzite phase α-GaN structure by transmission electron microscopy. We also found that the nanocrystals are aligned with the sapphire following the relationship: (0001)sapphire∥(0001)GaN and (11math0)sapphire∥(11math0)GaN. The use of a sapphire substrate allows for the measurements of optical properties, and near band-edge luminescence and the yellow band are observed in photoluminescence spectroscopy.
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81.05.Ea III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.55.Cr III-V semiconductors
61.46.-w Structure of nanoscale materials
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing

Differential reflectance spectroscopy of GaAlAs thin films and GaAs bulk under externally applied temperature gradient

N. Dai, J. F. Feng, L. Y. Chen, X. Q. Liu, W. Lu, and J. L. Zhong

Appl. Phys. Lett. 70, 2271 (1997); http://dx.doi.org/10.1063/1.118835 (3 pages)

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Using vibrating optical beam, differential reflectance (DR) spectra have been obtained on GaAlAs thin films and GaAs bulk subjected to an externally applied temperature gradient. The DR spectra reveal all the critical points, namely, E0 and E0+Δ0 in GaAlAs and E0, E0+Δ0 and E1 in GaAs in the given energy range under study whereas, without the temperature gradient, DR spectra measured on homogeneous materials are structureless. The DR technique shows better sensitivity than photoreflectance on thin epilayers. Our investigation suggests that, combined with the application of a field gradient, DR can be made extremely useful for the characterization of semiconductors. © 1997 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
78.66.Fd III-V semiconductors

Observation of singly ionized selenium vacancies in ZnSe grown by molecular beam epitaxy

S. D. Setzler, M. Moldovan, Zhonghai Yu, T. H. Myers, N. C. Giles, and L. E. Halliburton

Appl. Phys. Lett. 70, 2274 (1997); http://dx.doi.org/10.1063/1.118836 (3 pages) | Cited 13 times

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Electron paramagnetic resonance (EPR) has been used to investigate singly ionized selenium vacancy VSe+ centers in ZnSe epilayers grown by molecular beam epitaxy (MBE). The study included undoped and nitrogen-doped films. Spectra taken at 8 K and 9.45 GHz, as the magnetic field was rotated in the plane from [100] to [010], showed an isotropic signal at g=2.0027±0.0004 with a linewidth of 5.8 G. In the two samples where this signal was observed, estimates of concentration were approximately 1.1×1017 and 6.3×1017 cm−3. The appearance of the EPR signal correlated with an increase in the Zn/Se beam equivalent pressure ratio (during growth) in undoped films and with an increase in the nitrogen concentration in doped films. We conclude that the singly ionized selenium vacancy may be a dominant point defect in many MBE-grown ZnSe layers and that these defects may play a role in the compensation mechanisms in heavily nitrogen-doped ZnSe thin films. © 1997 American Institute of Physics.
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61.72.J- Point defects and defect clusters
76.30.Mi Color centers and other defects
61.72.S- Impurities in crystals
61.66.Fn Inorganic compounds

Schottky barrier detectors on GaN for visible–blind ultraviolet detection

Q. Chen, J. W. Yang, A. Osinsky, S. Gangopadhyay, B. Lim, M. Z. Anwar, M. Asif Khan, D. Kuksenkov, and H. Temkin

Appl. Phys. Lett. 70, 2277 (1997); http://dx.doi.org/10.1063/1.118837 (3 pages) | Cited 123 times

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We report on the fabrication and characterization of vertical geometry transparent Schottky barrier ultraviolet detectors based on n−/n+-GaN structures grown over sapphire substrates. Spectral responsivity measurements were made using illumination through the UV transparent Schottky barrier metal. A responsitivity as high as 0.18 A/W was measured for wavelengths shorter than the absorption edge of GaN. The detector speed was RC limited and the fall time was 118 ns. The 1/f noise is identified to be the main noise contribution. At 300 Hz, we measure the noise equivalent power at less than 4×10−9 W. © 1997 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.70.+m Noise processes and phenomena

Metal–oxide–semiconductor capacitors formed by oxidation of polycrystalline silicon on SiC

J. Tan, M. K. Das, J. A. Cooper, and M. R. Melloch

Appl. Phys. Lett. 70, 2280 (1997); http://dx.doi.org/10.1063/1.119262 (2 pages) | Cited 40 times

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A method to form SiO2/SiC metal–oxide–semiconductor structures by oxidation of a thin polycrystalline silicon (polysilicon) layer deposited on SiC is demonstrated. The oxidation time used is sufficient to oxidize all the polysilicon while short enough at 1050 °C to insure insignificant oxidation of the underlying SiC. Since the oxidation of SiC is highly anisotropic, this method allows uniform oxide formation on a nonplanar SiC surface. The SiO2/SiC interface quality is comparable to that obtained with thermal oxidation. © 1997 American Institute of Physics.
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81.05.Hd Other semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
73.20.At Surface states, band structure, electron density of states

Ultraviolet-sensitive, visible-blind GaN photodiodes fabricated by molecular beam epitaxy

J. M. Van Hove, R. Hickman, J. J. Klaassen, P. P. Chow, and P. P. Ruden

Appl. Phys. Lett. 70, 2282 (1997); http://dx.doi.org/10.1063/1.118838 (3 pages) | Cited 82 times

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GaN p–i–n photovoltaic diode arrays were fabricated from epitaxial films deposited on sapphire by molecular beam epitaxy. Peak UV responsivity was 0.11 A/W at 360 nm, corresponding to 48% internal quantum efficiency. Visible rejection over 400–800 nm was 3–4 orders of magnitude. Typical pulsed time response was measured at 8.2 μs. Spectral response modeling was performed to analyze the photocurrent contributions from photogenerated carrier drift in the depletion region and from minority carrier diffusion in the p and n layers. With the model, a maximum internal quantum efficiency of 55% at 360 nm was calculated for the photovoltaic diode structure. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.60.Dw Photodiodes; phototransistors; photoresistors
72.40.+w Photoconduction and photovoltaic effects

B diffusion and clustering in ion implanted Si: The role of B cluster precursors

L. Pelaz, M. Jaraiz, G. H. Gilmer, H.-J. Gossmann, C. S. Rafferty, D. J. Eaglesham, and J. M. Poate

Appl. Phys. Lett. 70, 2285 (1997); http://dx.doi.org/10.1063/1.118839 (3 pages) | Cited 105 times

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A comprehensive model for B implantation, diffusion and clustering is presented. The model, implemented in a Monte Carlo atomistic simulator, successfully explains and predicts the behavior of B under a wide variety of implantation and annealing conditions by invoking the formation of immobile precursors of B clusters, prior to the onset of transient enhanced diffusion. The model also includes the usual mechanisms of Si self-interstitial diffusion and B kick-out. The immobile B cluster precursors, such as BI2 (a B atom with two Si self-interstitials) form during implantation or in the very early stages of the annealing, when the Si interstitial supersaturation is very high. They then act as nucleation centers for the formation of B-rich clusters during annealing. The B-rich clusters constitute the electrically inactive B component, so that the clustering process greatly affects both junction depth and doping level in high-dose implants. © 1997 American Institute of Physics.
Show PACS
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
85.40.Ry Impurity doping, diffusion and ion implantation technology
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
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