bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ negative-type patterning of a GaAs/AlGaAs quantum well using electron beam-induced modification of an InGaAs epitaxial layer mask in Cl2 gas
Authors: Kohmoto S. , Sugimoto Y. , Takado N. , Asakawa K.
Published: July 2002

A GaAs/AlGaAs quantum well structure is in situ patterned by irradiating a thin (50 Å) epitaxial In0.2Ga0.8As mask layer with an electron beam (EB) while exposing the mask to Cl2 gas. This simultaneous EB/Cl2 exposure increases the resistance of the mask to Cl2 etching. However, the parts of the mask only exposed to Cl2 are easily etched off, resulting in a negative-type pattern formation. The etching resistance of the EB/Cl2-exposed area depends on the In content in the InGaAs mask. Possible causes of this are discussed. Using this method, a GaAs/AlGaAs quantum well is fabricated into a dot-matrix pattern.
Electron microscopic and ion scattering studies of heteroepitaxial tin-doped indium oxide films
Authors: Kamei Masayuki , Shigesato Yuzo , Takaki Satoru , Hayashi Yasuo , Sasaki Mikio , Haynes Tony E.
Published: July 2002

The microstructure of heteroepitaxial tin-doped indium oxide (ITO) films were studied in detail. The surface morphology of the heteroepitaxial ITO film consisted of square-shaped, in-plane oriented subgrains (∼300 Å) in contrast to that of the polycrystalline film (characteristic grain-subgrain structure). The subgrain boundaries were predominantly formed along the {110} planes in the ITO film and dislocations were observed primarily along the subgrain boundaries. Ion channeling measurements showed the dislocation density of this film to be approximately 3×1010/cm2, and the angular distribution of the ion channeling yield showed that the subgrains are aligned to within better than 0.3° (standard deviation).
Nanostructure and chemistry of a (100)MgO/(100)GaAs interface
Authors: Bruley J. , Stemmer S. , Ernst F. , Rühle M. , Hsu W.-Y. , Raj R.
Published: July 2002

High-resolution transmission electron microscopy (TEM) shows that MgO films, grown on (001) GaAs by magnetron sputtering, are single crystal with a cube-on-cube relationship with the substrate, even though they are separated from the substrate by an amorphous interlayer. Scanning TEM–energy dispersive x-ray and scanning TEM–electron energy loss spectroscopy analysis of the interlayer shows that it consists of the native oxide of GaAs as well as nanocrystalline MgO. It is proposed that epitaxial MgO nucleated at pin holes produced by volatilization of the native oxide.
Three-terminal bias induced dual wavelength semiconductor light emitter
Authors: Reed F. E. , Zhang D. , Zhang T. , Kolbas R. M.
Published: July 2002

A three-terminal version of a light emitting device, a bias induced color-tunable emitter (BICE), is reported. The three-terminal BICE is a multiwavelength semiconductor light emitter in which the emission wavelength is determined by an applied voltage, while the emission intensity is modulated by an applied current (no optical pumping employed). Device operation is based on the bias dependent injection and collection of electrons and holes in quantum wells. In this letter, three-terminal dual wavelength BICE functionality is demonstrated. The device exhibits coaxial optical output, a large separation of emitted wavelengths (≊570 Å), low operational voltages and currents, and high emission contrast ratios of 159:1 and 1:76 at 77 K.
Low temperature growth of highly doped GaAs:Si by atomic layer molecular beam epitaxy
Authors: Silveira J. P. , Briones F.
Published: July 2002

Two-dimensional growth kinetics characteristic of atomic layer molecular beam epitaxy (ALMBE) allows to extend the range of GaAs growth conditions to low temperatures while preserving excellent crystallinity and layer morphology. In this work we have used ALMBE technique to obtain GaAs layers highly doped with silicon at substrate temperatures from 200 to 400 °C. At these low growth temperatures donor incorporation is excellent and electron densities of 2×1019 cm−3 were reached, limited by the pinning of Fermi level at the DX level. Samples exhibit persistent photoconductivity due to the existence of a DX level resonant with the conduction band.
Characterization of rectifying contacts on natural type IIb diamond
Authors: Hartsell M. L. , Wynands H. A. , Fox B. A.
Published: July 2002

Metal-semiconducting diamond (MS) and metal-insulating diamond-semiconducting diamond (MIS) contacts were fabricated on the same type IIb single crystal diamond. Direct comparisons of MS and MIS structure characteristics were made by analysis of current-voltage and differential capacitance-voltage (C-V) data. Both the MS and MIS contacts exhibited good rectifying characteristics, with a 5 V rectification ratio ≳106. The depletion layer uncompensated acceptor concentration measured in both structures by C-V analysis was ∼1.8×1016 cm−3.
Parametric modeling and measurement of silicon etching in a high density chlorine plasma
Authors: Dane D. , Mantei T. D.
Published: July 2002

The plasma parameter scaling of silicon etching in a high density chlorine discharge has been measured and described by an ion assisted etch model. The measurements were performed in an electron cyclotron resonance chlorine plasma at pressures between 0.5 and 4.0 mTorr. When the Cl neutral atom flux to the wafer is sufficiently high, the etch rate is controlled by the ion power flux to the substrate, JiVs, where Ji is the ion current density and Vs is the plasma sheath potential. There is a threshold value of the ion power flux below which no etching occurs. When the Cl flux is low, the etch rate is controlled by the limited supply of Cl atoms and is approximately independent of the ion power flux.
Imaging of boron dopant in highly oriented diamond films by cathodoluminescence in a transmission electron microscope
Authors: Graham R. J. , Shaapur F. , Kato Y. , Stoner B. R.
Published: July 2002

Boron-doped, highly oriented, (100) textured diamond films have been examined by cathodoluminescence in a transmission electron microscope to assess the distribution of the defects and boron dopant within the films. Dislocation-related luminescence, which is believed to be unrelated to boron, was found to originate inhomogeneously in the films, from dislocations within single grains and at grain boundaries. Luminescence from donor-acceptor pairs involving boron was imaged with submicron spatial resolution to show that boron dopant is uniformly distributed from grain to grain and within individual grains, in these diamond films. The dislocation density in undoped films grown under similar conditions was found to be much lower than in B-doped films, suggesting that the introduction of B not only results in its incorporation as a dopant, but also gives rise to dislocations.
Charging dynamics of integrated circuit passivation layer probe holes in the electron beam tester
Authors: Phang J. C. H. , Sim K. S. , Chan D. S. H.
Published: July 2002

Numerical simulations show that the sidewall of a probe hole in the SiO2 passivation layer of an integrated circuit charges negatively when a 1 keV beam is probing a test point inside the probe hole. The negative charges on the sidewalls create a local electric field that suppresses the low-energy secondary electrons and at the same time focuses the higher-energy secondary electrons. These potential barrier and lens effects degrade the detected secondary electron signal and may have significant consequences for voltage contrast measurements.
Low-pressure metalorganic vapor phase epitaxy of GaAs using monoethylarsine
Authors: Kachi Tetsu
Published: July 2002

Monoethylarsine has been used for the growth of GaAs by low-pressure metalorganic vapor phase epitaxy in a pressure regime of 400–650 Pa. This operating window promotes improved surface morphologies and higher growth rates (2–3 times) compared to comparable growths at higher operating pressures. Photoluminescence analysis of epitaxial material grown in this pressure range indicates the crystal quality of these films to be optimum. These results are attributed to the suppression of parasitic gas phase side reactions between the arsenic and gallium precursors.
Double resonant behavior of microstrip ring resonator in Tl-based high T
c superconducting films
Authors: Wu S. C. , Yeh C. Y. , Chen F. H. , Tseng T. Y. , Wang C. , Chang H. L. , Wang H. J.
Published: July 2002

High Tc Tl–Ba–Ca–Cu–O superconducting thin films have been made by the dc magnetron sputtering followed by postannealing. In this study, a Tl-based microstrip ring resonator was fabricated by using standard microelectronic photolithographic patterning and wet chemical etching. Experimental results indicated that these ring resonators exhibit the best unloaded Q of 3269 at its resonant frequency of 3.35 GHz and some other samples display the double resonant behavior at 77 K. The frequency difference of the double resonant peaks depends on the input microwave power, and the splitting is ascribed to spatial variations in the film microstructure. The physical properties of the films are about 1 μm thick, as high as 105 K transition temperature, and greater than 105 A/cm2 current density at zero magnetic field and 77 K.
Improved mode stability in low threshold single quantum well native-oxide defined vertical-cavity lasers
Authors: Huffaker D. L. , Shin J. , Deng H. , Lin C. C. , Deppe D. G. , Streetman B. G.
Published: July 2002

Single quantum well active region vertical-cavity surface-emitting lasers (VCSELs) fabricated using a ‘‘native-oxide’’ technique are compared with three quantum well active region VCSELs. The single quantum well active region exhibits improved transverse mode stability under a variety of operating conditions. The suggested reason is due to the reduced gain of the single quantum well, which results in greater lasing mode selectivity. For the single quantum well active region, a continuous wave threshold current of 178 μA at room temperature is measured for a 5 μm diam VCSEL and a pulsed threshold of 160 μA.
Defect generation and suppression during the impurity-induced layer disordering of quantum-sized GaAs/GaInP layers
Authors: Thornton R. L. , Bour D. P. , Treat D. , Ponce F. A. , Tramontana J. C. , Endicott F. J.
Published: July 2002

We have investigated both analytically and experimentally the mechanisms for defect formation during interdiffusion of GaAs and GaInP. We find that the analytical model predicts a critical thickness below which defects are not produced during this highly strained interdiffusion process. Transmission electron microscopy analysis of diffused buried layers of varying thickness exhibits very good qualitative agreement with the analysis developed.
Zone lasers
Authors: Vakhshoori D. , Hong M. , Asom M. , Leibenguth R. E. , Mannaerts J. P. , Wynn J. D.
Published: July 2002

Vertical-cavity zone lasers (Z lasers) operating in 850 and 980 nm have been fabricated. This new class of high power, high efficiency, and large area vertical-cavity lasers has an output light that automatically comes to a focus in a single spot at a particular distance away from the laser output coupler. The light output of the 850-nm Z laser exhibits a spot size of 12 μm in the focal plane for up to several tens of mW with a 0.4-Å spectral width and fixed linear polarization. Through an analysis, ways to enhance the coherence of the Z lasers will be discussed.
Silicon anodic-plasma oxidation during magnetron sputtering of yttria-stabilized zirconia
Authors: Beshenkov V. G. , Marchenko V. A. , Znamenskii A. G.
Published: July 2002

The floating potential Vf was shown to vary in space and time during YSZ (yttria-stabilized zirconia) magnetron deposition onto Si. The Vf gradient causes the substrate to become positively charged with respect to the equilibrium floating potential and undergo anodic-plasma oxidation. Biasing the substrate below the floating potential suppresses SiO2 growth during YSZ film deposition.
A new technique for diagnostics of a radio-frequency parallel-plate remote plasma
Authors: Sano N. , Kohno A. , Hara M. , Sekiya M. , Sameshima T.
Published: July 2002

A new parallel-plate remote plasma reactor was developed, containing a metal grid between the powered and the grounded electrode. Plasma parameters between the grid and a substrate holder have been measured in radio-frequency (13.56 MHz) argon plasmas using another grid with large surface area as a positive electrostatic probe. The electron density is lower than 106 cm−3 at rf power lower than 10 W; this demonstrates that the plasma is effectively confined. The electron energy distribution function is well approximated to a Maxwellian one. The electron temperature decreases as the pressure increases, and it is lower than 3 eV at pressures above 13.3 Pa, in agreement with electron temperatures in conventional plasmas.
Photochemical etching of silicon using monochromatic synchrotron radiation
Authors: Kitamura Osamu , Terakado Shingo , Goto Takashi , Suzuki Shigeo , Tanaka Kenichiro
Published: July 2002

Photochemical etching of single-crystal silicon was studied using monochromatic synchrotron radiation (SR) under the existence of reactive species produced by 2.45 GHz microwave discharge in a mixture of SF6 and Ar. The increases of the etched depth by irradiation of 50, 85, and 130 eV SR were investigated and compared with the total electron yield spectra. The ratios of the increment were found to closely agree with the ratios of the total electron yield of Si fully exposed to reactive species. This suggests that the increments are related to the light absorption of Si having reactive species adsorbed on its surface.
Diamond nucleation on unscratched SiO2 substrates
Authors: Lauten Frederick S. , Shigesato Yuzo , Sheldon Brian W.
Published: July 2002

Enhanced diamond nucleation on fused silica was obtained by using chemical surface pretreatments, instead of prescratching the surface with diamond or another abrasive. One approach was to deposit a thin metal film on the SiO2 substrate. This made it possible to apply a dc bias and obtain significant nucleation during microwave-assisted chemical-vapor deposition. On uncoated silica substrates (i.e., a metal film was not applied), we used a pretreatment step at a lower temperature and lower microwave power to enhance nucleation. The same pretreatment was applied to Si and Mo coated SiO2 substrates, and significant diamond nucleation did not occur. This suggests that the SiO2 substrate is more favorable for nucleation (under these conditions), or that the oxide substrate alters the local plasma chemistry in a way that enhances nucleation.
Resonance enhanced multiphoton ionization detection of SiO desorbing from a Si(111) surface in reaction with O2
Authors: Nakamura Kazutaka G. , Kitajima Masahiro
Published: July 2002

SiO molecule desorbing from Si(111) surface in reaction with pulse O2 molecular beam at the substrate temperature of 1250±50 K is measured with the 2+1 resonance enhanced multiphoton ionization. Vibrationally separated spectrum of the desorbing SiO molecule has been observed. The observed vibrational distribution is estimated to be in equilibrium with the surface temperature.
Parallel quantum point contacts fabricated with independently biased gates and a submicrometer airbridge post
Authors: Sherwin M. E. , Simmons J. A. , Eiles T. E. , Harff N. E. , Klem J. F.
Published: July 2002

Using an integrated airbridge and submicrometer gate post technology, coupled quantum point contacts (QPCs) arranged in a parallel configuration were fabricated. The airbridge and gate post are fabricated by e-beam lithography and Ti/Au evaporation in a single step. Gate post diameters as small as 0.1 μm have been achieved. The two QPCs are fabricated with two conventional gates and a central airbridged gate, each of which can be biased independently. Conductance measurements clearly exhibit coupling of the two QPCs, as the quantized conductance steps are in units of 4 e2/h. Independent measurements of each QPC show conductance steps in units of 2 e2/h.
New synthetic route to the formation of fullerene superconductors
Authors: Hwang J. H. , Mou C. Y. , Sheu H. S. , Wang Y. , Wu M. K.
Published: July 2002

A novel synthetic route to the formation of less air sensitive fullerene superconductors by mixing oxygen-containing alkaline compounds with C60 has been discovered. A high-resolution single-crystal x-ray study on the K-doped samples shows that the ratio of potassium to C60 is not 3:1. The observed stability enhancement and the off-stoichiometry of potassium content may originate from the presence of oxygen which serves as an oxidative agent.
Bandwidth enhanced metal-semiconductor-metal photodetectors based on backgated ip structures
Authors: Greger E. , Reingruber K. , Riel P. , Döhler G. H. , Rosenzweig J. , Ludwig M.
Published: July 2002

We report on theoretical and experimental results on a novel metal-semiconductor-metal (MSM) photodetector with a backgate provided by a p-doped layer. The backgate allows extremely short sweep-out times for the holes, due to strong electric fields normal to the surface. Thus, long tails due to slow moving holes and screening of the external drift fields by hole space charge accumulation at high optical power, which lead to a degradation of the time response of conventional MSM photodetectors, are avoided. The high frequency performance measured up to 8 GHz in the time and frequency domain showed a significant reduction of the bandwidth limiting hole tail compared to standard MSM photodetectors.
Effects of oxygen and hydrogen adsorption on the electron energy loss features of diamond surfaces
Authors: Beerling T. E. , Helms C. R.
Published: July 2002

Electron energy loss spectroscopy has been used to study the surface of diamond and other states of carbon. Other authors have suggested that a loss feature observed at approximately 9 eV may be due to oxygen adsorption on the diamond surface. We report electron energy loss spectroscopy data, in combination with Auger electron spectroscopy data, that shows a correlation of a loss feature at 8.5 eV with adsorbed oxygen on diamond surfaces. Surfaces were oxygenated by low-energy oxygen ion bombardment and oxygen removed by annealing in vacuum and atomic hydrogen. The atomic hydrogen was used to suppress the π loss feature by etching nondiamond carbon and passivating the diamond surface.
Spontaneous formation of Al rich and Ga rich AlxGa1−xAs/AlyGa1−yAs superlattice and strong enhancement of optical properties
Authors: Chin Albert , Hsieh K. Y. , Lin H. Y.
Published: July 2002

Long range composition ordering and spontaneous formation of Al rich and Ga rich AlxGa1−xAs/AlyGa1−yAs superlattice were demonstrated. This was observed by cross-sectional transmission electron microscopy (TEM) in a 280 Å Al0.4GaAs quantum well laser diode heterostructure with Al0.7GaAs barriers grown on (111)B GaAs substrates. On the contrary, none of above superstructure was observed by TEM on a side-by-side grown (100) oriented substrate. More evidence is shown in the (111)B Al0.7GaAs barriers which were disordered due to a high growth temperature and did not show any superstructure. 10 K photoluminescence was shown with 32 meV redshift and a 12-times peak intensity enhancement in (111)B orientation.
Evolution of surface topography during metalorganic vapor phase epitaxy of InP/InGaAs/InP quantum well heterostructures
Authors: Epler J. E. , Söchtig J. , Sigg H. C.
Published: July 2002

The evolution of surface topography during epitaxial growth of lattice matched InP/InGaAs/InP on (100) InP substrate is observed using in situ elastic light scattering supported by ex situ atomic force microscopy. A topographically smooth growth transition from InP to InGaAs is observed. However, the InP-on-InGaAs interface exhibits three-dimensional nucleation followed by planarization and two-dimensional epitaxy. The three-dimensional phase is a result of the high surface energy of InP relative to InGaAs. A growth pause after the InGaAs QW increases the transient roughness of the InP surface and increases the thickness of InP required for planarization.
Enhancement in thermal shock resistance of melt-textured YBa2Cu3Ox superconductors by hot isostatic pressing
Authors: Satpathy A. , Lee D. F. , Partsinevelos C. , Salama K. , Selvamanickam V.
Published: July 2002

Thermal shock resistance of melt-textured YBa2Cu3Ox superconductors has been investigated by thermal cycling between 77 and 350 K. The current carrying capability of as-melt-textured specimens is found to drop in three stages by a factor of up to 50% after 60 cycles. To rectify this degradation, a hot isostatic pressing (Hipping) method has been developed to close the microcracks generated during thermal cycling. The critical current (Ic) of specimens that were thermally cycled followed by Hipping is found to increase even above the initial Ic value of its as-melt-textured state. More importantly, Ic of the Hipped specimens is found to be completely insensitive to thermal cycling even after 60 cycles. Indentation measurements revealed that Hipping strengthens the basal plane platelet boundaries in addition to closing the microcracks.
Acoustic and optical properties of thallium ion-exchanged KTiOPO4
Authors: Chu David K. T.
Published: July 2002

Both acoustic and optical properties of thallium ion-exchanged KTiOPO4 (Tl:KTP) plates were examined. Surface acoustic wave (SAW) velocity of the thallium-exchanged z-cut KTP possesses a reduction of 13% from the unchanged KTP. Temperature stability of SAW resonance (1/f0 df/dT) changed from ≊−81 ppm of an untreated z-cut KTP substrate to ≊−121 ppm of a z-cut Tl:KTP substrate. Large optical refractive indices changes at the Tl ion-exchanged surface were observed [Δneff(TE)≊0.3, Δneff(TM)≊0.22]. Tl ion concentration profile from the crystal surface into substrate was also studied using electron beam microscopy and the optical index m-line measurement. Tl-exchanged KTP, therefore, possesses both acoustic and optical waveguiding properties.
High power diode-pumped Nd:YAG regenerative amplifier for picosecond pulses
Authors: Walker D. R. , Flood C. J. , van Driel H. M. , Greiner U. J. , Klingenberg H. H.
Published: July 2002

We demonstrate regenerative amplification of 25-ps full width at half-maximum TEM00 pulses to ≳1 mJ at a 2-kHz repetition rate in a diode-pumped Nd:YAG system. The single pulse energy gain is 74 dB and operation at 5 kHz has delivered ≳3.5 W of average power at λ=1.064 μm. Gain narrowing and self-phase modulation cause significant spectral and temporal broadening, from 70 GHz and 12 ps to ∼100 GHz and 25 ps, respectively, for the shortest amplified pulses.
Effect of grain boundaries on the formation of luminescent porous silicon from polycrystalline silicon films
Authors: Guyader P. , Joubert P. , Guendouz M. , Beau C. , Sarret M.
Published: July 2002

Luminescent porous silicon can be obtained by electrochemical etching under illumination from n-type polycrystalline silicon which has been fabricated by solid phase crystallization of in situ doped amorphous films deposited by low pressure chemical vapor deposition. The analyses of the nanostructures by microscopy show that the pore orientations mainly follow the current flow which is channeled by macropores located at grain boundaries. The luminescence results obtained from this porous polycrystalline silicon are comparable to those obtained from porous samples of single-crystals silicon.
Picosecond pulse generation in the thresholdless optical microlaser
Authors: Mataloni P. , Aiello A. , Murra D. , De Martini F.
Published: July 2002

Picosecond optical pulses have been generated in different kinds of thresholdless dye microlaser operating in high-Q plane microcavities at high pumping rate. The temporal behavior of the system is studied by means of a simple rate equation analysis. It is shown that the buildup time of the output pulse is independent of the cavity finesse. The experiment has been performed by means of a temporally resolved up-conversion technique. A buildup time of the pulse of 3 ps, together with a rise time of 1.5 ps have been measured. These results correspond to a predictable response frequency of 300 GHz.
Direct observation of interface and surface steps in epitaxial films by dark-field transmission electron microscopy
Authors: Loretto D. , Ross F. M. , Lucas C. A. , Wong G. C. L.
Published: July 2002

We have used dark-field transmission electron microscopy to investigate <5 nm thick CaF2 films grown on Si(111) by molecular-beam epitaxy. Images formed with CaF2 [111̄] reflections exhibit contrast at 1/3[111] height steps at the CaF2 surface and at the CaF2/Si interface over large (≳100 μm2), statistically significant areas. Direct evidence for step-flow growth in CaF2 has been obtained.
Characterization of interface topography of the buried Si-SiO2 interface in silicon-on-insulator material by atomic force microscopy
Authors: Crowder S. W. , Griffin P. B. , Plummer J. D.
Published: July 2002

Atomic force microscopy (AFM) has been used to characterize the topography of the buried Si-SiO2 interface in Bonded, single-implant Separation by IMplantation of OXygen (SIMOX), and multiple-implant SIMOX silicon-on-insulator material. The properties of this interface have important implications for processing and for device performance. The root-mean-square surface roughness was found to be 11.4 nm for single-implant material, 2.9 nm for multiple-implant material, and less than 1.5 nm for bonded material.
New properties and applications of electron-beam evaporated silicon in submicron elevated source/drain metal-oxide-semiconductor field-effect transistors
Authors: Mirabedini Mohammad R. , Goodwin-Johansson Scott H. , Massoud Hisham Z.
Published: July 2002

We report the porous nature of electron-beam evaporated silicon on the sidewalls of metal-oxide-semiconductor field-effect transistor (MOSFET) gate spacers. This property was used to develop and fabricate submicron elevated source/drain MOSFETs with 200–500 Å ultrashallow junctions. Using electron-beam evaporated silicon reduces fabrication complexity, overcomes common problems inherent to elevated source/drain MOSFETs, and yields a self-aligned process.
Manipulation of the Ti/Si reaction paths by introducing an amorphous Ge interlayer
Authors: Ma Z. , Xiao H. Z. , Allen L. H. , Park B. J.
Published: July 2002

Evolution of the Ti/a-Ge/Si trilayer reactions has been investigated using transmission electron microscopy and Auger electron spectroscopy. Instead of amorphous phase formation, as usually observed in the Ti/Si bilayer reaction, the crystalline Ti6Ge5 is the first phase observed during the reaction. Preceding the equilibrium C54-Ti(Si,Ge)2, a substitutional solid solution type C49-Ti(Si,Ge)2 forms upon annealing at 550–600 °C, regardless of the replacement of amorphous phase by the crystalline phase. The C49-to-C54 polymorphic transformation occurs at ∼650 °C. The reaction path is also correlated with the change in film resistance obtained from a four-point sheet resistance measurement.
Selective epitaxial growth of GaInP by low-pressure metal-organic chemical-vapor deposition using ethyldimethylindium as In source
Authors: Chan Shih-Hsiung , Sze Simon Ming , Chang Chun-Yen , Lee Wei-I
Published: July 2002

We have demonstrated the feasibility of selective epitaxial growth (SEG) of GaInP using low-pressure metal-organic chemical-vapor deposition (LPMOCVD) with the combination of ethyldimethylindium (EDMIn) and triethylgallium (TEGa) as the group-III sources. Complete selective epitaxy can be achieved at a growth temperature of 675 °C and a growth pressure of 40 Torr. The deposition of Ga-rich polycrystalline GaInP on Si3N4 film occurs at lower temperatures. Although the incorporation efficiency of TEGa into GaInP is much lower than that of trimethylgallium, the combination of EDMIn and TEGa has been found to be a good candidate for SEG of GaInP. Low-temperature photoluminescence shows that the selectively grown epitaxial layer has good optical quality and is useful for light emitting device applications.
Platinumsilicide Schottky barrier infrared detectors with a grating: Dependence of the optical response on wavelength and polarization
Authors: Kapser K. , Deimel P. P. , Platz W. , Prechtel U.
Published: July 2002

Platinumsilicide Schottky diodes on p-Si substrates structured with a dry-etched lamellar grating were fabricated. The grating periods Λ were 3, 4, and 5 μm, and the grating amplitude h ranged from 300 to 1100 nm. Measurements of the optical response Y for TE and TM polarized light were made. A strong dependence of the detector sensitivity on the polarization of the radiation was observed. Enchancement of the responsivity up to 70% was found compared to an unstructured reference sample. Calculations based on an optical model which takes into account the change in absorption due to the grating were made. The results show good agreement with the experimental data.
Hardness of TiO2-MgF2 mixed films prepared by reactive ion-assisted deposition
Authors: Tsai Rung-Ywan
Published: July 2002

The hardness of TiO2-MgF2 mixed films prepared by reactive ion-assisted deposition is strongly related to their compositions and microstructures. Compositions and microstructures of these films are analyzed by the Rutherford backscattering microscopy and transmission electron microscopy, respectively. The hardening of the films with high TiO2 composition has been observed to result from the uniform distribution of small crystalline MgF2 dispersoids within the amorphous TiO2 matrix. The size of all the dispersoids is less than 20 nm. An empirical model is provided to explain the enhancement of hardness of these composite films.
Terahertz radiation from delta-doped GaAs
Authors: Birkedal D. , Hansen O. , So/rensen C. B. , Jarasiunas K. , Brorson S. D. , Keiding S. R.
Published: July 2002

Terahertz pulse emission from four different delta-doped molecular beam epitaxially grown GaAs samples is studied. We observe a decrease of the emitted THz pulse amplitude as the distance of the delta-doped layer from the surface is increased, and a change in polarity of the THz pulses as compared to bulk n-type doped GaAs reference samples. The electric fields in the region of the doping layer are investigated by photoreflectance spectroscopy. A careful analysis of Franz–Keldysh oscillations observed in the photoreflectance spectra provides information about the built-in fields on both sides of the delta-doped layer.
Electro-optic modulation using asymmetric Fabry–Perot laser diode amplifiers
Authors: Mitchell N. F. , O’Gorman J. , Hegarty J. , Connolly J. C.
Published: July 2002

We report the use of laser diode amplifiers, whose facets have unequal mirror reflectivities, as asymmetric Fabry–Perot modulators. Due to the presence of optical gain in these devices we observe modulation of reflected light with both large absolute modulation depth and high contrast ratio.
Optical transitions between light hole subbands in InGaAs/InP strained layer multiquantum wells
Authors: Ilouz I. , Oiknine-Schlesinger J. , Gershoni D. , Ehrenfreund E. , Ritter D. , Hamm R. A. , Vandenberg J. M.
Published: July 2002

The observation of light hole intersubband absorption in both p-doped and photoexcited undoped strained InxGa1−xAs/InP (x≂0.35) quantum-well structures is reported. The absorption is polarized along the growth direction and is in agreement with calculations which show that the strain causes the light hole level to be first occupied upon p-doping or photoexcitation. Both impurity bound and free holes transitions are identified.
Magnetometers based on double relaxation oscillation superconducting quantum interference devices
Authors: Adelerhof Derk Jan , Kawai Jun , Tsukada Keiji , Uehara Gen , Kado Hisashi
Published: July 2002

Magnetometers based on double relaxation oscillation superconducting quantum interference devices (SQUIDs) (DROSs) have been fabricated and characterized. The DROSs are based on 2×2 μm2 Nb/AlOx tunnel junctions and have a 25 turn, tightly coupled input coil. The high flux-to-voltage transfer coefficient of 1–2 mV/φ0 facilitates direct voltage readout by a low-noise dc amplifier. The pickup coil consists of a thin-film Nb gradiometer with a baseline of 40 mm and an inductance of 110 nH. The white field noise of the magnetometer was better than 5 ft/√Hz, which is sufficient for magnetoencephalography measurements.
Enhanced mass-transport smoothing of f/0.7 GaP microlenses by use of sealed ampoules
Authors: Swenson J. S. , Fields R. A. , Abraham M. H.
Published: July 2002

A variety of GaP lens arrays have been routinely produced (array dimensions up to 1.5×1.0 cm, 30×50 elements) with high yield, uniformly good finish, and low transmission loss for 0.8 μm<λ<2.5 μm. Microlenses up to 300 μm in diameter with f numbers as low as 0.7 have been fabricated by a new sealed ampoule mass-transport technique. The mesa-step spacing was increased from 10 to 15 μm, with mass-transport smoothing time-at-temperature as short as 8 h, representing a transport-rate 10–40 times higher than previously reported. By additional chemistry control, smoothing of 30 μm spacings has been demonstrated. Only small pieces of phosphorus are required (no phosphine or hydrogen), consequently little safety burden is incurred. Smoothing in the fused quartz ampoules is shown to be self-terminated by wafer oxidation, which is sufficiently delayed by loose-fitting aluminum oxide shielding.
Normally on GaAs/AlAs multiple-quantum well Fabry–Perot transmission modulator with ON/OFF contrast ratios ≳7.4
Authors: Lin Chih-Hsiang , Goossen K. W. , Sadra K. , Meese J. M. , Weng Chun-Jen
Published: July 2002

A normal-incident normally on GaAs/AlAs multiple-quantum well Fabry–Perot transmission modulator is reported. The fabricated modulator achieves ON/OFF transmittance changes larger than 30% and ON/OFF contrast ratios larger than 7.4 at the wavelength of 842.5 nm with a reverse bias voltage of 9 V.
Electroluminescence from carbon-doped GaAs junctions with semi-insulating GaAs
Authors: Tian S. X. , Haneman D. , Nozaki S. , Takahashi K.
Published: July 2002

Electroluminescence (EL) and photoluminescence have been measured from thin film structures of heavily carbon-doped GaAs on crystalline semi-insulating GaAs substrates. EL is only detected when the p-type film is biased positively. From this and the spectral distribution, it is concluded that there are heterojunction interface states at about 50 meV below the conduction band, with a concentration roughly estimated as 1017 cm−3.
Binding and diffusion of a Si adatom around the type A step on Si(001) c(4×2)
Authors: Wang Jun , Drabold D. A. , Rockett A.
Published: July 2002

The results of a simulation are described, using a density functional method, of the diffusion of adatoms on a flat Si(001)c(4×2) surface and around one type of surface step (the SA step). These indicate that there is a moderate additional energy barrier (0.2±0.1 eV) to cross the SA step as compared to the energy for diffusion on a flat surface. The dimer-top lattice site on the lower terrace adjacent to the step edge is stabilized (by 0.15±0.1 eV) with respect to the flat surface result although the most stable binding sites near the step are unaffected. This behavior can be understood based on the disruption of dimer tilt near the step. The results suggest that adatoms are more likely to stop on lattice sites at the SA step edge than on lattice sites on the open surface. This may affect the relative dimer formation rate near the step with respect to the behavior on the flat surface even in the absence of a clear change in binding energy. The effect of the SA step terrace edge on adatom behavior is very short ranged and weak. This is consistent with the relatively small strain field and lack of change in dangling bond density associated with the step edge.
Infrared detection with a ReSi2 thin film photoresistor
Authors: Long Robert G. , Becker James P. , Mahan John E.
Published: July 2002

Infrared detection was accomplished with the narrow bandgap semiconductor (∼0.1 eV), ReSi2. Photoresistors were fabricated from a polycrystalline ReSi2 film grown on a silicon substrate. A light-induced decrease in resistance was observed, which was due both to film photoconductivity and to a light-sensitive contact resistance. The relative spectral response (measured at 10 K) in the wavelength range from 3000 to 6000 nm roughly follows the number of photons absorbed as estimated from the optical absorption coefficient of ReSi2. Thus, the sample is a quantum, rather than thermal, detector. The mechanism of detection is believed to be the intrinsic band-to-band photogeneration of excess free carriers, leading to photoconductivity and to the reduction in contact resistance. It is suggested that ReSi2 offers the potential for a new intrinsic semiconductor infrared detector technology, which may be integrated on a silicon chip, and whose absorption edge is well into the far-infrared range.
Detection of simultaneous lattice expansion and contraction in low-energy, H-implanted InP
Authors: Fatemi M. , Molnar B. , Dietrich H. B. , Anderson W. T.
Published: July 2002

We report the observation of simultaneous lattice expansion and contraction in InP implanted with low-energy protons, using the high-resolution x-ray rocking-curve technique. For implantation with 260 keV, 1×1016 protons/cm2, the volume of the crystal extending from the surface to approximately 1.6 μm deep is contracted with a mean effective strain of −7×10−5, while the proton containing region is expanded to a maximum positive strain of about 7×10−4.
Light polarizer based on antiresonant reflecting layers in a directional coupler
Authors: Li Xiangshan , Deck R. T.
Published: July 2002

We propose a design for a TE–TM polarization splitter based on the addition of antiresonant reflecting layers to the two adjacent channel walls of a standard directional coupler. The geometry of the proposed splitter is relatively easy to fabricate and should allow for an almost total separation between the TE and TM modes of a guided light wave. The analysis of the guided modes of the splitter serves to illustrate the efficiency of the ‘‘resonance method’’ for determining the modes of an arbitrary structure.
Superconductor–insulator–superconductor quasiparticle tunneling current in Ba1−xKxBiO3 grain-boundary junctions on SrTiO3 bicrystal substrates
Authors: Yamamoto Tetsuya , Suzuki Seiji , Takahashi Kazuhiko , Yoshisato Yorinobu , Maekawa Shigero
Published: July 2002

We have prepared Ba1−xKxBiO3 grain-boundary junctions on SrTiO3 bicrystal substrates and observed the quasiparticle tunneling current for a superconductor–insulator–superconductor (SIS) junction. The current–voltage (I–V) characteristics were investigated by using a gap-energy distribution model to consider the effect of the inhomogeneity of Δ at the grain-boundary junction interface. The broadening of the I–V characteristics around the gap voltage of a SIS junction and its temperature dependence could be explained by assuming the Gaussian distribution of gap energies with Δ0(0)=3.8 meV and δΔ=0.8 meV, where Δ0(0) and δΔ denoted the mean value and variance of the distribution, respectively.
Nonresonant third-order nonlinear optical susceptibility of CdS clusters encapsulated in zeolite A and X
Authors: Sugimoto Noriaki , Koiwai Akihiko , Hyodo Shi-aki , Hioki Tatsumi , Noda Shoji
Published: July 2002

Nonresonant third-order harmonic generation from CdS clusters encapsulated in zeolite A and X was observed at a fundamental wavelength of 1900 nm. To avoid scattering from the surfaces of the small zeolite crystals, the powder samples were dispersed in a liquid with nearly the same refractive index as that of the samples. The third-order optical susceptibilities of CdS-encapsulated zeolite A and X estimated from the intensity of their Maker fringe patterns were 4.1×10−12 and 1.1×10−11 esu, respectively. These values were slightly smaller than those reported for the 1.5 nm surface-capped CdS cluster. The hyperpolarizabilities of CdS clusters encapsulated in zeolite A and X were estimated by assuming the Lorentz local field to be in the range of 380–480×10−36 and 270–390×10−36 esu, respectively.
Light scattering spectral behavior of liquid crystal dispersions in silica glasses
Authors: Otón J. M. , Pena J. M. S. , Serrano A. , Levy D.
Published: July 2002

Dispersions of nematic liquid crystal microdroplets in silica glasses have been obtained by sol-gel processes, forming gel-glass dispersed liquid crystals (GDLCs). GDLC microdroplet size may be adjusted precisely by controlling the sol-gel reaction. This allows the preparation of scattering media with different spectral response, which can be further modified by reorienting the liquid crystal microdroplets with external electric fields. Opaque/transparent and dichroic GDLC thin films have been prepared. An extension of the general scattering theory is used for explaining their optical behavior.
Quantitative measurement of the microwave distribution in superconducting tunnel junctions
Authors: Gerber R. , Quenter D. , Doderer T. , Kruelle C. A. , Huebener R. P. , Müller F. , Niemeyer J. , Pöpel R. , Weimann T.
Published: July 2002

Low temperature scanning electron microscopy offers the possibility to measure the microwave distribution inside Josephson tunnel junctions in a quantitative way. The junctions are coupled to an external microwave source. Our results confirm the established model for the propagation of microwaves inside the junction stripline. Our method yields microwave specific parameters of the junction such as wavelength, microwave attenuation, reflection coefficients, and phase shifts.
Imaging and profiling surface microstructures with noninterferometric confocal laser feedback
Authors: Lu Chun-Hung , Wang Jyhpyng , Deng King-Li
Published: July 2002

Exploiting the sensitivity and the self-aligning features of the confocal laser-feedback technique and the convenience of superluminescent laser diodes, we developed an optical method for imaging and profiling surface microstructures with a depth resolution as great as 20 nm. The incoherent, noninterferometric nature of the technique enables fast open-loop operation and large dynamic range. Measurements of calibrated semiconductor surface microstructures and optical ridge waveguides are demonstrated.
Electrostatic plasma injection switch
Authors: Chung M. , Kunhardt E. E.
Published: July 2002

A low pressure gas discharge switch operating in the 0.1–0.7 Torr range and triggered by electrostatic plasma injection is described. The trigger and cathode electrodes are coaxial cylinders, with the trigger electrode (the inner cylinder) being divided into resistively isolated sections. The anode electrode is collinear with both of these electrodes. Commutation is initiated by the generation of a plasma in the trigger-cathode region, with subsequent injection into the anode–cathode space. This injection is driven by self-generated voltage gradients between the sections of the trigger electrode. Results from measurements of the characteristics (plasma injection speed, electron density and temperature, anode and trigger current, and voltage wave forms) of a test device operated at hold-off voltages of up to 17 kV and currents up to 5 kA are presented.
Cryogenic sample stage for the Cameca IMS-3f ion microscope
Authors: Bernius Mark T. , Chandra Subhash , Morrison George H.
Published: July 2002

A simple and inexpensive cold stage developed for use with the Cameca IMS-3f ion microscope is described. It is easy to use, and temperatures near to that of liquid nitrogen are obtained. Data are presented showing the first analysis of frozen hydrated biological samples with the ion microscope.
InAsSb/InAlAs strained quantum-well lasers emitting at 4.5 μm
Authors: Choi H. K. , Turner G. W. , Le H. Q.
Published: July 2002

Strained quantum-well lasers emitting at 4.5 μm have been fabricated. The laser structure, grown on a GaSb substrate by molecular beam epitaxy, consists of compressively strained InAsSb active layers and tensile-strained InAlAs barrier layers, surrounded by AlAsSb cladding layers. Under electrical injection, the laser exhibited pulsed operation up to 85 K, with threshold current density of 350 A/cm2 at 50 K. Under optical pumping, the laser operated pulsed up to 144 K, with peak power at 95 K of 0.54 W.
Optical properties of CdTe/CdZnTe wires and dots fabricated by a final anodic oxidation etching
Authors: Gourgon C. , Dang Le Si , Mariette H. , Vieu C. , Muller F.
Published: July 2002

A two step etching process has been used to fabricate wire and dot nanostructures from CdTe/CdZnTe quantum wells with high optical qualities. Wires and dots are first etched by the usual process of electron beam lithography and ion beam etching then, anodic oxidation is used to etch nanostructures to their final lateral sizes. We have observed remarkable improvements in the optical properties of these nanostructures as compared to the single step etching process. Their photoluminescence spectra are similar to that of the reference quantum well, with an exciton linewidth of about 3 meV, even for the smallest wires (100 nm) and dots (250 nm) which were studied.
Femtosecond investigations of spectral hole burning in semiconductor lasers
Authors: Sun Chi-Kuang , Golubovic Boris , Choi Hong-Kyun , Wang Christine A. , Fujimoto James G.
Published: July 2002

An investigation of spectral hole burning effects is reported in the gain region of InGaAs/AlGaAs strained-layer single quantum well diode lasers, using a heterodyne nondegenerate pump-probe technique. This technique permits simultaneous measurement of the femtosecond dynamics and spectral dependence of transient gain in semiconductor lasers. At high bias current, strong spectral hole burning effects were observed.
Boron-induced morphology changes in silicon chemical vapor deposition: A scanning tunneling microscopy study
Authors: Wang Yajun , Hamers Robert J.
Published: July 2002

Scanning tunneling microscopy has been used to investigate the influence of surface boron on silicon growth via chemical vapor deposition (CVD). The presence of boron-induced reconstructions on the Si(001) surface dramatically changes the surface morphology during subsequent CVD growth of silicon using disilane at 815 K. Boron-induced reconstructions inhibit the lateral diffusion of silicon atoms from terraces to step edges, leading to greatly enhanced island nucleation, and also reduce the local surface reactivity toward disilane. Strong segregation of boron to the growth surface allows the enhanced island nucleation to persist to subsequent terraces during multilayer CVD growth of silicon, producing a rough but epitaxial surface.
Epitaxial growth of cubic AlN films on (100) and (111) silicon by pulsed laser ablation
Authors: Lin Wen-Tai , Meng Ling-Cheng , Chen Guo-Ju , Liu Hok-Shin
Published: July 2002

Epitaxial growth of cubic AlN thin films on (100) and (111) silicon substrates by pulsed laser ablation is reported. The epitaxial AlN films can be grown at temperatures above 630 °C in 100–300 mTorr of N2. The epitaxial orientation relationships are (100)AlN//(100)Si and [010]AlN//[010]Si, and (111)AlN//(111)Si and [011̄]AlN//[011̄]Si. The growth of microtwins on (111) planes of AlN was also observed. In the present study, for the AlN thin films grown on (100)Si at around 680 °C in 100 mTorr of N2, the epitaxial growth can cover about 90% of the film region.
Composition modulated structures in bulk-growth Hg0.8Cd0.2Te
Authors: Liao X. Z. , Shi T. S.
Published: July 2002

High-resolution transmission electron microscopy and selected area electron diffraction have been used to study Hg0.8Cd0.2Te wafer. Two kinds of chemical composition modulated structures were found. One is a one-dimensional modulation with modulated wave vector q*=(a*−b*)/5.6 and the other two-dimensional modulation with modulated wave vectors q1*=(a*−b*)/5.6 and q2*=(a*−b*)/11.2−0.22c*. Both structures have a common modulated wavelength of 2.54 nm.