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1 Jan 1996

Volume 68, Issue 1, pp. 1-139

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Laser‐heated radiation dosimetry using transparent thermoluminescent glass

Brian L. Justus, Alan L. Huston, and Tommy L. Johnson

Appl. Phys. Lett. 68, 1 (1996); http://dx.doi.org/10.1063/1.116742 (3 pages) | Cited 28 times

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Laser‐stimulated thermoluminescence emission is reported from a novel transparent glass phosphor exposed to γ‐ray or ultraviolet radiation. Laser‐heated radiation dosimetry measurements, using this effect, are reported. A unique laser heating method permits the stimulation of the thermoluminescence without significantly raising the bulk temperature of the glass. © 1996 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
78.60.Kn Thermoluminescence

Investigations of vertical cavity surface emitting laser by photoreflectance spectroscopy

P. D. Berger, C. Bru, T. Benyattou, G. Guillot, A. Chenevas‐Paule, L. Couturier, and P. Grosse

Appl. Phys. Lett. 68, 4 (1996); http://dx.doi.org/10.1063/1.116753 (3 pages) | Cited 31 times

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We report photomodulated reflectance results on vertical cavity surface emitting laser structures. Photoreflectance spectra have been recorded under normal incidence at different temperatures between 9 and 300 K. The structure used is a λ cavity grown in the AlGaAs‐based system emitting at a wavelength near 800 nm. We show that photoreflectance is a unique noninvasive tool to measure accurately the quantum well transition and the cavity mode alignment: both features can be distinguished very well. Furthermore, this technique offers the opportunity to determine the electric field within the undoped region from Franz–Keldysh oscillations, and gives the Al composition of the barrier material in the cavity. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Fd III-V semiconductors

Micromachined ultrasonic transducers: 11.4 MHz transmission in air and more

Igal Ladabaum, B. T. Khuri‐Yakub, and Dimitri Spoliansky

Appl. Phys. Lett. 68, 7 (1996); http://dx.doi.org/10.1063/1.116764 (3 pages) | Cited 16 times

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The fabrication and modeling of novel, capacitive, ultrasonic air transducers is reported. Transmission experiments in air at 11.4, 9.2, and 3.1 MHz are shown to correspond with theory. The transducers are made using surface micromachining techniques, which enable the realization of center frequencies ranging from 1.8 to 11.6 MHz. The bandwidth of the transducers ranges from 5% to 20%, depending on processing parameters. Custom circuitry is able to detect 10 MHz capacitance fluctuations as small as 10−18 F, which correspond to displacements on the order of 10−3 Å, in a bandwidth of 2 MHz with a signal to noise ratio of 20 dB. Such detection sensitivity is shown to yield air transducer systems capable of withstanding over 100 dB of signal attenuation, a figure of merit that has significant implications for ultrasonic imaging, nondestructive evaluation, gas flow and composition measurements, and range sensing. © 1996 American Institute of Physics.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.38.Bs Electrostatic transducers

Observation of inverse reactive ion etching lag for silicon dioxide etching in inductively coupled plasmas

M. F. Doemling, N. R. Rueger, and G. S. Oehrlein

Appl. Phys. Lett. 68, 10 (1996); http://dx.doi.org/10.1063/1.116772 (3 pages) | Cited 23 times

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The slowdown of the oxide etch rate with width of submicrometer structures is known as reactive ion etching (RIE) lag and has been explained by ion shadowing and differential charging of the sidewalls, among other effects [R. A. Gottscho and co‐workers, J. Vac. Sci. Technol. B 10, 2133 (1992)]. Here we show for an inductively coupled high density plasma reactor working in the pressure regime from 6 to 20 mTorr that inverse RIE lag is primarily observed, i.e., the etch rates increase as the width of the microstructures decrease. Inverse RIE lag, which was first discussed by Vitkavage et al. [Tegal Plasma Proceedings Symposium, San Francisco, 1991 (unpublished)], may be explained by considering the neutral flux distribution at the structure bottom. The neutral flux has a stronger dependence on the aspect ratio than the ion flux due to its isotropic velocity distribution. The neutral flux distribution has been modeled and is consistent with etching profiles observed at high pressure. © 1996 American Institute of Physics.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.Cf Surface cleaning, etching, patterning

Microhollow cathode discharges

K. H. Schoenbach, R. Verhappen, T. Tessnow, F. E. Peterkin, and W. W. Byszewski

Appl. Phys. Lett. 68, 13 (1996); http://dx.doi.org/10.1063/1.116739 (3 pages) | Cited 122 times

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The current–voltage characteristics of hollow cathode discharges and their predischarges in argon under dc and pulsed conditions were found to have a positive slope at pressures up to approximately 50 Torr, and currents up to 20 mA, at a hole diameter of 0.7 mm. In this range of pressure and current, parallel operation of hollow cathode discharges, without ballast, was demonstrated. Scaling to higher pressure is possible by reducing the hole diameter. Pulsed experiments with an array of cathode rings of 75 μm diameter allowed us to obtain parallel operation of more than 50 discharges at a pressure of 350 Torr in air. © 1996 American Institute of Physics.
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52.80.-s Electric discharges

Evolution of the surface cross‐hatch pattern in InxGa1−xAs/GaAs layers grown by metal‐organic chemical vapor deposition

Meeyoung Yoon, Bun Lee, Jong‐Hyeob Baek, Hyo‐Hoon Park, El‐Hang Lee, and Jeong Yong Lee

Appl. Phys. Lett. 68, 16 (1996); http://dx.doi.org/10.1063/1.116740 (3 pages) | Cited 8 times

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The evolution of the cross‐hatch pattern (CHP) in InxGa1−xAs/GaAs heterostructures has been studied. It is found that stress is concentrated at the valleys of the CHP from the results of crack formation at the CHP valleys in the thick GaAs cap layer grown on an InGaAs layer. Residual strain in the InGaAs/GaAs epitaxial layer showing a CHP is confined along the valleys of the CHP with a nonuniform distribution throughout the epitaxial layer. The skeleton of the CHP is formed at the beginning of the rapid strain relaxation period and the depth of the CHP valleys increases after most of the strain has been released. We propose that the development of the CHP in the later stage of the growth takes place by the growth suppression at the CHP valleys due to the high level of stress concentration. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The energetics of {113} stacking fault formation in Si from supersaturated interstitials

Nicolas Cuendet, Timur Halicioglu, and William A. Tiller

Appl. Phys. Lett. 68, 19 (1996); http://dx.doi.org/10.1063/1.116741 (3 pages) | Cited 16 times

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Using a Tersoff‐type empirical potential energy function, the free energy of formation for {113}‐type stacking faults in silicon has been calculated both as a function of stacking fault rod length and width at a variety of temperatures. A particular tetrahedral‐tetrahedral dimer has the lowest free energy of formation at 0 K and this type of stacking fault forms an assemblage of such dimers. The free energy of formation per interstitial in a ribbon fault decreases with ribbon width, ribbon length, and increase of temperature. © 1996 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
61.72.uf Ge and Si
61.80.Jh Ion radiation effects

Investigation of the nucleation mechanism in bias‐enhanced diamond deposition

P. Reinke, P. Kania, P. Oelhafen, and R. Guggenheim

Appl. Phys. Lett. 68, 22 (1996); http://dx.doi.org/10.1063/1.116743 (3 pages) | Cited 24 times

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Polycrystalline diamond films were deposited in a MW‐PECVD reactor employing bias‐enhanced nucleation as pretreatment to promote the subsequent diamond nucleation. The substrate temperature during the bias‐enhanced nucleation was varied between 600° and 760 °C by external heating, while the other deposition parameters namely the microwave input power were kept constant. Likewise, the deposition parameters were not changed in the subsequent diamond growth period throughout the experiment. The films formed during the bias‐enhanced nucleation were analyzed employing electron energy loss spectroscopy (EELS) and scanning electron microscopy (SEM). The nuclei density (ND) obtained for good quality diamond crystals after the nucleation step and an additional growth period increases considerably from 1×106 cm−2 or less to 1×1010 cm−2 in a narrow temperature range between 670 and 700 °C. For temperatures exceeding 700 °C continuous films are formed. The structure of the pretreatment deposit also undergoes considerable changes: the intensity of the diamond plasmon increases with the substrate temperature, which is indicative of an increase in the concentration of diamond crystallites embedded in an otherwise amorphous carbon matrix. Our experiments suggest that diamond crystallites formed during the pretreatment serve as nucleation centers for the subsequent diamond growth. We can also conclude that the variation in the substrate temperature rather than the changes in the microwave input power or, respectively, plasma chemistry, drive the observed structural changes and increase in ND. © 1996 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

White‐beam synchrotron topographic characterization of flux‐grown KTiOAsO4

W. J. Liu, S. S. Jiang, X. R. Huang, X. B. Hu, C. Z. Ge, J. Y. Wang, J. H. Jiang, and Z. G. Wang

Appl. Phys. Lett. 68, 25 (1996); http://dx.doi.org/10.1063/1.116744 (3 pages) | Cited 16 times

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KTiOAsO4 crystals grown from tungstate fluxes have been studied by white‐beam synchrotron radiation topography. It is shown that growth striations are primary planar defects. By anomalous scattering, ferroelectric domains in KTA are investigated and the ratio of ‖F(004)‖2 to ‖F(004)‖2 is calculated. The mechanisms of domain inversion via 2‐fold axis or n‐glide plane are also discussed in terms of the structural characteristics of KTA. © 1996 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Irreversible light‐enhanced degradation in amorphous silicon solar cells at elevated temperatures

D. E. Carlson and K. Rajan

Appl. Phys. Lett. 68, 28 (1996); http://dx.doi.org/10.1063/1.116745 (3 pages) | Cited 8 times

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An irreversible light‐enhanced degradation has been observed in amorphous silicon solar cells exposed to intense illumination (50 suns) at elevated temperature (≳130 °C). Unlike the light‐induced degradation observed at lower temperatures, the light‐enhanced degradation observed at elevated temperatures is not reversed by annealing and it not suppressed by a strong reverse bias. An analysis of the time decay of the short‐wavelength spectral response at various temperatures indicates that the degradation mechanism is associated with the diffusion of hydrogen at elevated temperatures both in the dark and under intense illumination. © 1996 American Institute of Physics.
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66.30.J- Diffusion of impurities
84.60.Jt Photoelectric conversion

Growth mode, strain relief, and segregation of (Ga,In)Sb on GaSb(001) grown by molecular beam epitaxy

N. Bertru, O. Brandt, M. Wassermeier, and K. Ploog

Appl. Phys. Lett. 68, 31 (1996); http://dx.doi.org/10.1063/1.116746 (3 pages) | Cited 19 times

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We investigate the molecular beam epitaxy of InSb on (001) GaSb by reflection high energy electron diffraction and atomic force microscopy. The growth process is found to follow the Stransky–Krastanov growth scheme with the onset to three‐dimensional growth occurring between 1.7 and 2.8 InSb monolayers depending on substrate temperature. The critical thickness is enhanced at low temperature because of a kinetically limited adatom diffusion length and, apparently, at high temperature because of the thermally activated desorption of In. On the basis of these results, the segregation of In during the growth of (Ga,In)Sb is analyzed in situ, yielding a segregation energy of 0.11 eV. © 1996 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Room temperature operation of a single electron transistor made by the scanning tunneling microscope nanooxidation process for the TiOx/Ti system

K. Matsumoto, M. Ishii, K. Segawa, Y. Oka, B. J. Vartanian, and J. S. Harris

Appl. Phys. Lett. 68, 34 (1996); http://dx.doi.org/10.1063/1.116747 (3 pages) | Cited 177 times

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The single electron transistor (SET) is fabricated using the scanning tunneling microscope (STM) as a fabrication process, and the fabricated SET operates at room temperature. Using the STM tip as a cathode, the surface of the titanium metal can be oxidized, and the few tens of nanometer wide oxidized titanium line can be made. The small island region of the SET of ∼30×∼35 nm2 is formed by the oxidized titanium line. The Coulomb staircase of 150 mV period is observed in the current–voltage characteristics of the SET at room temperature. © 1996 American Institute of Physics.
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85.35.Gv Single electron devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

S. U. Dankowski, D. Streb, M. Ruff, P. Kiesel, M. Kneissl, B. Knüpfer, G. H. Döhler, U. D. Keil, C. B. Sørenson, and A. K. Verma

Appl. Phys. Lett. 68, 37 (1996); http://dx.doi.org/10.1063/1.116748 (3 pages) | Cited 23 times

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Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT‐GaAs) and AlGaAs (LT‐AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as‐grown LT‐materials, the absorption coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band gap. We observed absorption changes up to 17 000 cm−1 for LT‐GaAs and 9000 cm−1 for LT‐AlGaAs taking place in a two phase process. © 1996 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.40.Fy Semiconductors

Growth and characterization of AlInGaN quaternary alloys

F. G. McIntosh, K. S. Boutros, J. C. Roberts, S. M. Bedair, E. L. Piner, and N. A. El‐Masry

Appl. Phys. Lett. 68, 40 (1996); http://dx.doi.org/10.1063/1.116749 (3 pages) | Cited 39 times

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We report on the deposition of AlyInxGa1−x−yN in the (0<y<0.15) and (0<x<0.14) composition range by metalorganic chemical vapor deposition. AlInGaN quaternary alloys offer a lattice‐matched platform for InGaN‐based light emitting heterostructure devices. Epitaxial growth of AlInGaN on (0001) sapphire substrates has been achieved at 750 °C. Alloy composition, lattice constants, and band gaps were obtained by energy dispersive spectroscopy, x‐ray diffraction, and room temperature PL. Band edge emissions dominate the PL spectra of these quaternary films. Preliminary data suggest that the lattice constant of AlInGaN can be deduced from chemical composition using Vegard’s law, indicating solid solution in the grown quaternary films. © 1996 American Institute of Physics.
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78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Study of deep level defects in n‐GaN by the optical transmission method

L. Balagurov and P. J. Chong

Appl. Phys. Lett. 68, 43 (1996); http://dx.doi.org/10.1063/1.116750 (3 pages) | Cited 19 times

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Absorption coefficient spectra are determined by optical transmission of undoped gallium nitride films, which is used for the density of states distribution. The absorption of n‐type GaN in the region of photon energy lower than the band edge is regarded as attributable to the local deep defect levels. For the photoemission of electrons to the conduction band, two optical threshold energies were detected, approximately at 2.1 eV from one deep level and near 1.1 eV from one or several deep levels. Discussion is centered on the possible participation of either level in the commonly observed 2.2 eV defect luminescence transitions. © 1996 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors

Luminescence quenching in erbium‐doped hydrogenated amorphous silicon

Jung H. Shin, R. Serna, G. N. van den Hoven, A. Polman, W. G. J. H. M. van Sark, and A. M. Vredenberg

Appl. Phys. Lett. 68, 46 (1996); http://dx.doi.org/10.1063/1.116751 (3 pages) | Cited 16 times

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Hydrogenated amorphous silicon thin films are doped with erbium by ion implantation. Room‐temperature photoluminescence at 1.54 μm, due to an intra‐4f transition in Er4+, is observed after thermal annealing at 300–400 °C. Excitation of Er3+ is shown to be mediated by photocarriers. The Er3+ luminescence intensity is quenched by a factor of 15 as the temperature is raised from 10 K to room temperature. Codoping with oxygen (1 at. %) reduces the luminescence quenching to a factor of 7. The quenching is well correlated with a decrease in luminescence lifetime, indicating that nonradiative decay of excited Er3+ is the dominant quenching mechanism as the temperature is increased. © 1996 American Institute of Physics.
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71.55.Jv Disordered structures; amorphous and glassy solids
78.55.Hx Other solid inorganic materials

Oxygen precipitation in Czochralski‐grown silicon wafers during hydrogen annealing

Koji Izunome, Hiroshi Shirai, Kazuhiko Kashima, Jun Yoshikawa, and Akimichi Hojo

Appl. Phys. Lett. 68, 49 (1996); http://dx.doi.org/10.1063/1.116752 (2 pages) | Cited 5 times

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In studying the effect of the ramping process on oxygen precipitation in Czochralski‐grown silicon wafers in hydrogen annealing, we have found that the oxygen precipitate density in the bulk region depends on the ramping‐up rate at temperatures between 900 and 1200 °C. Few oxygen defects are observed when the ramping‐up rate is 30 °C/min or more. Decreasing the ramping‐up rate exponentially increases the oxygen precipitate density. The nucleation for oxygen precipitates can therefore be controlled by adjusting the ramping‐up rate during hydrogen annealing. © 1996 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

The mechanism of iron gettering in boron‐doped silicon

P. A. Stolk, J. L. Benton, D. J. Eaglesham, D. C. Jacobson, J.‐Y. Cheng, J. M. Poate, S. M. Myers, and T. E. Haynes

Appl. Phys. Lett. 68, 51 (1996); http://dx.doi.org/10.1063/1.116754 (3 pages) | Cited 21 times

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High‐energy B implantation was used to introduce gettering layers into float‐zone Si wafers contaminated with 2×1014 Fe/cm3. Secondary ion mass spectrometry shows that about 5% of the Fe contamination is collected at the 4 μm deep peak of a 4×1014/cm2, 3.3 MeV B implant after annealing at 1000 °C for 1 h. Deep level transient spectroscopy demonstrates that increasing the gettering B dose from 4×1012 to 4×1014/cm2 reduces the Fe concentration from 3×1012 to below ∼1010/cm3 in the 1–3 μm deep region from the surface, indicating very efficient gettering. Measurements of the Fe depth profile imply that the depletion of Fe near the gettering layer occurs upon cooling down from 1000 °C. The gettering behavior can be qualitatively understood in terms of a Fermi‐level‐enhanced pairing reaction between Fe and B. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
61.72.Yx Interaction between different crystal defects; gettering effect
66.30.J- Diffusion of impurities

Monolayer control in the growth of (Al,Ga)Sb/GaSb single quantum wells: Application to the band offset and Γ–L crossover problems

M. Leroux and J. Massies

Appl. Phys. Lett. 68, 54 (1996); http://dx.doi.org/10.1063/1.116755 (3 pages) | Cited 12 times

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This letter reports the growth by molecular beam epitaxy of AlxGa1−xSb/GaSb single quantum wells on GaSb substrates. Barrier compositions and well thicknesses are determined in situ using reflection high energy electron diffraction. The luminescence energies of wells with width increasing by a two monolayer increment, with either an odd or even number of monolayers, are intercalated, further evidencing the thickness control. For pseudomorphic AlxGa1−xSb/GaSb heterostructures, a heavy hole valence band offset in meV of (275±75)x is estimated. For an Al barrier composition of 0.31, the confinement induced Γ–L crossover occurs at a well thickness of 12 monolayers. © 1996 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Spatial distribution of the luminescence in GaN thin films

F. A. Ponce, D. P. Bour, W. Götz, and P. J. Wright

Appl. Phys. Lett. 68, 57 (1996); http://dx.doi.org/10.1063/1.116756 (3 pages) | Cited 219 times

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The spatial dependence of the luminescence intensities at the band edge (364 nm) and at the ‘‘yellow’’ defect‐band (centered at 560 nm) regions for epitaxial GaN films have been studied using cathodoluminescence microscopy at room temperature. The films were grown by metalorganic chemical vapor deposition on (0001) sapphire substrates and were not intentionally doped. Significant nonuniformities in the band‐to‐band and in the yellow band emissions were observed. Yellow luminescence in small crystallites appears to originate from extended defects inside the grains and at low‐angle grain boundaries. The size of band‐to‐band emission sites correlates with low‐angle grain sizes observed by transmission electron microscopy. © 1996 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors

Stark effect in individual luminescent centers observed by tunneling luminescence

J. Lindahl, M.‐E. Pistol, L. Montelius, and L. Samuelson

Appl. Phys. Lett. 68, 60 (1996); http://dx.doi.org/10.1063/1.116757 (3 pages) | Cited 23 times

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We have measured photon emission from individual luminescent states in GaInP/InP heterostructures, containing InP dots, using local injection from a scanning tunneling microscope tip. By changing the tip‐sample bias we are able to see the Stark shift of the emission peaks, as well as the onset of impact ionization. We find that the exciton diffusion length is about 1 μm, while the minority carrier diffusion length is much less in our samples. Below the threshold for impact ionization the excitation is extremely local, limiting the excitation to one or a few quantum dots. © 1996 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.60.Hk Cathodoluminescence, ionoluminescence

Direct comparison of GaAs surface morphology between migration enhanced epitaxy and molecular beam epitaxy using in situ scanning electron microscopy

Yoshikazu Homma, Hiroshi Yamaguchi, and Yoshiji Horikoshi

Appl. Phys. Lett. 68, 63 (1996); http://dx.doi.org/10.1063/1.116758 (3 pages) | Cited 10 times

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We have used scanning electron microscopy (SEM) for real‐time‐observation to compare the surface evolution during the early stage growth of GaAs with molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE), at the substrate temperature of 500 °C. Surface roughness during MEE growth is about 1 ML and much smaller than during MBE growth. Immediately after growth termination, monolayer steps can be seen and the surface recovers to initial smoothness in MEE, while islands do not disappear without higher temperature annealing in MBE. Present results confirm high surface atom mobility in MEE growth. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Low temperature selective silicon epitaxy by ultra high vacuum rapid thermal chemical vapor deposition using Si2H6, H2 and Cl2

Katherine E. Violette, Patricia A. O’Neil, Mehmet C. Öztürk, Kim Christensen, and Dennis M. Maher

Appl. Phys. Lett. 68, 66 (1996); http://dx.doi.org/10.1063/1.116759 (3 pages) | Cited 18 times

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We present the use of the Si2H6/H2/CL2 chemistry for selective silicon epitaxy by rapid thermal chemical vapor deposition (RTCVD). The experiments were carried out in an ultrahigh vacuum rapid thermal chemical vapor deposition reactor. Epitaxial layers were grown selectively with growth rates above 150 nm/min at 800 °C and 24 mTorr using 10% Si2H6 and H2 and Cl2 with a minimum Si:Cl ratio of 1. Excellent selectivity with respect to SiO2 and Si3N4 was obtained indicating that very low Cl2 partial pressures are sufficient to preserve selectivity. In situ doping results with B2H6 show that sharp doping transitions and a wide range of B concentrations can be obtained with a slight B incorporation rate reduction with Cl2 addition. Our results indicate that UHV‐RTCVD with the Si2H6/H2/Cl2 chemistry yields highly selective Si epitaxy with growth rates well within the practical throughput limits of single wafer manufacturing and with a potential to reduce the Cl content below the levels used in conventional SiH2Cl2 based selective epitaxy processes. © 1996 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Preparation of three‐dimensionally oriented polycrystalline Si film

G. Q. Di, H. Lin, N. Uchida, Y. Kurata, K. Koumoto, and S. Hasegawa

Appl. Phys. Lett. 68, 69 (1996); http://dx.doi.org/10.1063/1.116760 (3 pages) | Cited 2 times

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The crystal structure and morphology of polycrystalline Si films deposited using a plasma‐enhanced chemical vapor deposition method, have been investigated by x‐ray diffraction and atomic force microscopy. When the 〈110〉‐oriented films were prepared at 690 °C with a hydrogen dilution ratio H2/SiH4=3 and rf power of 20 W, it was found that the grains with almost the same size are uniformly distributed within the film, and their shapes in a top view become rectangular. The longer sides of rectangles stand in line in the direction of gas flow (the plasma also spreads in this direction), indicating that the gas‐flow direction and the plasma assist the growths of essentially three‐dimensionally oriented grains. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electroabsorption field imaging between coplanar metal contacts on semi‐insulating semiconductor epilayers

D. D. Nolte, N. P. Chen, M. R. Melloch, C. Montemagno, and N. M. Haegel

Appl. Phys. Lett. 68, 72 (1996); http://dx.doi.org/10.1063/1.116761 (3 pages) | Cited 7 times

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We use excitonic electroabsorption field imaging to study the electric field distribution between coplanar gold Schottky contacts on semi‐insulating photorefractive AlGaAs epilayers. The field imaging shows consistently large localized enhancements of the electric field adjacent to the anode, followed by a region of reduced field. Complex behavior occurs at the cathode, with high‐field regions extending far from the contact. These inhomogeneous near‐contact field profiles are determined by the superposition of both diffused and drifted charge which affect the performance of many optoelectronic devices that use planar contacts or striplines on semi‐insulating substrates. © 1996 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Sx Metal-semiconductor-metal structures
78.66.Fd III-V semiconductors
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