bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of HgTe-CdTe superlattices
Authors: Wu G. Y. , Mailhiot C. , McGill T. C.
Published: July 2002

The first theoretical calculation of the optical properties of HgTe-CdTe superlattices is presented. The envelope function method is used to obtain the superlattice band structure, and then an interpolation scheme is employed to compute ε2(ω) the imaginary part of a dielectric function. The major conclusion is that the optical properties of the superlattice near the band edges are such that the absorption may be comparable to or ever larger than that in the alloys.
Disordering of Ga1−xAlxAs-GaAs quantum well structures by donor sulfur diffusion
Authors: Rao E. V. K. , Thibierge H. , Brillouet F. , Alexandre F. , Azoulay R.
Published: July 2002

We show here, for the first time, that disordering (alloy mixing) on group III sublattice of GaAlAs-GaAs quantum well (QW) structures can be accomplished by the introduction of a group V site substitutional donor impurity. This is achieved by performing donor sulfur diffusions at 850 °C (for varied durations 1 to 14 h) under open-tube conditions in molecular beam epitaxy as well as metalorganic chemical vapor deposition grown GaAlAs-GaAs QW structures. Using simple photoluminescence measurements at room temperature, we provide relevant evidence that the degree of alloy mixing (and so the resulting Al composition) is dependent on the diffused S concentration.
High-power index-guided multiridge waveguide laser array
Authors: Dutta N. K. , Koszi L. A. , Segner B. P. , Craft D. C. , Napholtz S. G.
Published: July 2002

InGaAsP quasi-index-guided multiridge waveguide laser arrays emitting at 1.3 μm have been fabricated. The lasers have threshold currents in the range 300–400 mA at 30 °C and have been operated to pulsed output powers as high as 500 mW. More than 150 mW of output power has been obtained up to an ambient temperature of 60 °C. The lasers emit in multilongitudinal mode with a far-field divergence of ∼15°×45°. A quasi-index-guided laser array of the type described here can be used in applications requiring high-power lasers emitting at 1.3 μm.
Hybrid growth of InGaAsP double-channel planar buried heterostructure lasers
Authors: Temkin H. , Panish M. B. , Logan R. A. , Abeles J. H.
Published: July 2002

Separate confinement InGaAsP structures grown by gas-source molecular beam epitaxy have been used in conjunction with liquid phase epitaxial regrowth to fabricate high-performance buried heterostructure lasers operating at a wavelength of 1.52–1.55 μm. These lasers show room-temperature threshold currents as low as 17 mA, external quantum efficiency as high as 27% per facet, and modulation bandwidth of 1.7–2.0 GHz. Single longitudinal mode operation under cw injection can be maintained up to 8 mW.
Structure of the Al/Al2O3 interface
Authors: Timsit R. S. , Waddington W. G. , Humphreys C. J. , Hutchison J. L.
Published: July 2002

The structure of the interface between aluminum and its amorphous surface oxide has been examined by high resolution electron microscopy. The interface was generated on (111) and (110) Al surfaces with oxide films grown by thermal oxidation in air or by anodization. The roughness of the interface consists of a long-range component originating in the native coarseness of the Al surface, and of a short-range component descriptive of the undulations of the interface over atomic-scale lateral distances. The short-range roughness arose from the presence of ledges on the aluminum at the interface. The ledge heights generally did not exceed two interplanar spacings.
Polycrystalline CuInSe2 photoelectrochemical cells
Authors: Haneman D. , Szot J.
Published: July 2002

Photoelectrochemical cells with short term stability (at least) have been constructed from fracture surfaces of n-type polycrystalline boules of CuInSe2. The recently developed electrolyte of Menezes [Appl. Phys. Lett. 45, 148 (1984)] appeared to have a passivating effect on grain boundaries. Samples with hundreds of boundaries easily attained half the best (12%) single crystal efficiency without any optimization. Microprobe analyses of the treated surfaces showed strong depletion of Cu and incorporation of I but the latter distribution appeared to be nonuniform. Poor fill factors were found on randomly fractured surfaces larger than 1 cm2. Only n-type samples were successful.
High-speed InP optoelectronic switch with a tandem structure
Authors: Hori Yoshikazu , Paslaski Joel , Yi Maobin , Yariv Amnon
Published: July 2002

A tandem-structure InP-optoelectronic switch has been fabricated and studied. This optoelectronic switch is capable of generating short electrical pulses, as well as varying the duration of electrical pulses between 40 and 400 ps (full width at half-maximum). The duration of the electrical pulses and the shortest pulse limit of the new switch are analyzed using a simple electrical model, and good agreement with experimental results has been obtained. The results indicate that the tandem-structure, optoelectronic switch can produce electrical pulses as short as the rise time of a single-structure switch, which is determined only by the electrical circuit time constant of the parallel switch capacitance and transmission line impedance.
Electro-optic phase-sensitive detection of optical emission and scattering
Authors: Genack Azriel Z.
Published: July 2002

Phase-sensitive detection of emission and scattering excited by an intensity modulated laser is achieved using electro-optic demodulation. This method can enhance the frequency range of fluorometric measurements since the response of a sample to light modulated at high frequencies can be measured utilizing only the dc output of the optical detector. Phase resolution is demonstrated by the separation of Raman scattering, which is in phase with the modulated laser, from fluorescence which lags the excitation in phase. Using 30-MHz modulation and multichannel detection, fluorescence-free Raman spectra of toluene are obtained in the presence of intense fluorescence from dissolved fluorol which has a lifetime of 8.5 ns.
Photoluminescence in PbTe-PbEuTeSe multiquantum wells
Authors: Goltsos W. , Nakahara J. , Nurmikko A. V. , Partin D. L.
Published: July 2002

Infrared photoluminescence has been studied in a thin (92 Å) PbTe-PbEuTeSe multiquantum well structure. The spectra show good agreement with calculations for the n=1 quantum well transition for a simple two-dimensional electron-hole gas with low-energy broadening consistent with monolayer well width fluctuations. From the measured effective electron temperatures we estimate that the electron-longitudinal optical phonon interaction is significantly reduced in comparison with bulk PbTe.
18.7% efficient (1-sun, AM0) large-area GaAs solar cells
Authors: Werthen J. G. , Hamaker H. C. , Virshup G. F. , Ford C. W.
Published: July 2002

AlGaAs-GaAs heteroface solar cells with areas of 4 cm2 have been fabricated by metalorganic chemical vapor deposition. One-sun, AM0 efficiencies as high as 18.7% and 18.4% have been obtained for p-n and n-p structures, respectively. Both kinds of cell structures are characterized by excellent external quantum efficiencies and their performance is close to that predicted by a realistic computer model. In agreement with the computer model, the n-p cell exhibits a higher short-circuit current density because of its thin, n-type top absorber.
Influence of stress on light-induced effects in amorphous silicon alloys
Authors: Guha S. , den Boer W. , Agarwal S. C. , Hack M.
Published: July 2002

We have studied the effect of stress on light-induced changes in photoconductivity and solar cell performance of amorphous silicon alloys. We find no correlation between degradation and stress in the material.
(100) superlattices of CdTe-Cd0.76Mn0.24Te on (100)GaAs
Authors: Kolodziejski L. A. , Gunshor R. L. , Otsuka N. , Zhang X.-C. , Chang S.-K. , Nurmikko A. V.
Published: July 2002

This letter reports the first growth of (100) CdTe-CdMnTe superlattices. In the past (111) superlattices of CdTe-CdMnTe were grown on (100) GaAs substrates. To consistently achieve the desired (100) epitaxy, three different growth techniques are described. Reflection high-energy electron diffraction is used to observe the initial nucleation of the (100) CdTe film, while transmission electron microscopy is used to investigate the nature of the interface between the epitaxial film and the substrate. The optical properties of these superlattices show interesting differences with the (111) superlattices.
Direct determination of elastic strain in strained-layer superlattices by high-angle x-ray interferences
Authors: Fantner E. J.
Published: July 2002

A novel nondestructive technique for the determination of elastic strains in strained-layer superlattices, which is based on x-ray diffractometry, is described. For the first time, the relative inclination of equivalent lattice planes due to elastic misfit strain in superlattices with small periods exhibiting high-angle x-ray interferences was measured. Sets of theta-twotheta scans with a narrow detector slit were performed for various lattice planes of one crystallographic zone starting at different theta offsets. The value of the angle theta, at which the maximum peak intensity is observed, is a direct measure for the distortion of the strained superlattice layers. It allows the determination of the complete strain status in three dimensions in the individual constituents separately even without knowing the unstrained lattice constant. In addition, this technique is used in the wide temperature range of 10–350 K. It is applied to a study of PbTe-PbSnTe superlattices grown on cleaved (111)-BaF2 in order to determine both the elastic misfit and the temperature-dependent substrate induced strains.
High quality epitaxial GaAs and InP wafers by isoelectronic doping
Authors: Beneking H. , Narozny P. , Emeis N.
Published: July 2002

It is shown that strained isoelectronically doped buffer layers grown on GaAs and InP wafers allow one to reduce the dislocation density drastically by a factor greater than 20. Correspondingly, the photoluminescence efficiency of near-band-edge emission is enhanced by about the same factor. By deep level transient spectroscopy measurements practically no deep levels can be detected in contrast to uncoated wafers. Applied to device fabrication a great improvement is found in comparison to conventionally fabricated optoelectronic and electronic devices.
Elimination of ionized impurity scattering in heavily doped GaxIn1−xAsyP1−y
Authors: Shantharama L. G. , Adams A. R. , Allen E. M. , Greene P. D.
Published: July 2002

Unexpectedly high hole mobilities occur in p-type layers of Ga0.03In0.97As0.07P0.93 grown by liquid phase epitaxy and concurrently doped with high concentrations (1017–1019 cm−3) of Mn and Ge. The temperature dependence of the hole mobility indicates that ionized impurity scattering is insignificant. The effect is attributed to the diffusion of neutral Mn to form donor-acceptor complexes instead of isolated ionized donors and acceptors. Such a model is consistent with observed diffusion profiles into a variety of substrates from Mn-doped epilayers and the presence of ionized impurity scattering where either the donor concentration or the depth of the Mn acceptor level is such that little or no neutral Mn is present.
Analysis of light and current induced effects in hydrogenated amorphous silicon
Authors: Yamagishi H. , Kida H. , Kamada T. , Okamoto H. , Hamakawa Y.
Published: July 2002

A systematic investigation has been made on the changes in mobility-lifetime product and defect density induced by light and current injection in amorphous silicon  p-i-n junction. It has been found that these changes involve the creation and interconversion of two kinds of metastable defects, being induced merely by carrier trapping phenomenon.
26% efficient magnesium-doped AlGaAs/GaAs solar concentrator cells
Authors: Hamaker H. C. , Ford C. W. , Werthen J. G. , Virshup G. F. , Kaminar N. R. , King D. L. , Gee J. M.
Published: July 2002

AlGaAs/GaAs heteroface solar concentrator cells which exhibit 26% efficiency at 753 sun (AM1.5, 100 mW/cm2) have been fabricated using metalorganic chemical vapor deposition. Magnesium was used as the dopant in the p-type emitter and selenium was used as the n-type dopant. The design parameters of the solar cell were determined with the aid of a computer program which realistically models the performance of such cells.
Broadband operation of coupled-stripe multiple quantum well AlGaAs laser diodes
Authors: Epler J. E. , Jackson G. S. , Holonyak N. , Thornton R. L. , Burnham R. D. , Paoli T. L.
Published: July 2002

A recently developed AlGaAs multiple stripe, multiple quantum well superluminescence light-emitting diode (SLED) with an extremely low reflectivity front-facet coating is operated as a high-power laser in an external grating cavity over an unusually broad tuning range. The SLED diode is operated continuously (cw) in a tuning range Δℏω∼94 meV and a power output from the grating cavity of 75 mW (optical flux ∼500 mW within the compound cavity). Data are presented showing the output power as a function of wavelength at currents of 750 mA (7660 Å<λ<8040 Å) and 1.0 A (7620 Å<λ<8085 Å). The threshold current in pulsed laser operation is measured over a range of 130 meV.
Velocity dependence of maximum substitutional concentrations of In and Bi trapped in rapidly solidified Si
Authors: Campisano S. U. , Poate J. M.
Published: July 2002

The maximum substitutional concentrations of In and Bi that can be trapped in (100) Si by rapid solidification have been measured by Rutherford backscattering and channeling techniques. The In and Bi were implanted in surface layers of Si which were melted by pulsed ruby laser irradiation. The concentration measurements over a liquid-solid interface velocity range of 1–6 m/s have been compared with calculations from morphological stability theory which give the concentrations present at the onset of interface instability.
Origin and effects of interface traps in anodic native oxides on InSb
Authors: Shapira Yoram , Bregman J. , Calahorra Z.
Published: July 2002

We have investigated the wet anodization of InSb under a large variety of oxidation parameters. Results of Auger electron spectroscopy (AES) show that the oxidation produces a mixed oxide film of In2O3 and Sb2O3 containing some unoxidized Sb. 1-MHz capacitance-voltage characteristics show low-frequency-like response of the oxide-semiconductor junction in the inversion region. We have found a strong correlation between this response and the elemental Sb content in the oxide, as revealed by AES. We present a model which explains the role of the elemental Sb in terms of interface traps and charge transfer into the inversion layer. Furthermore, we describe the anodization conditions under which the combined effect is reduced and explain their role. The implications of this observation are discussed.
Effect of oxygen on In0.53Ga0.47As films grown by molecular beam epitaxy
Authors: Stall R. A. , Wunder R. J. , Swaminathan V. , Cox H. M.
Published: July 2002

Incomplete removal of the native oxide from the surface of the InP substrate before growth leads to oxygen incorporation in subsequently grown molecular beam epitaxial In0.53Ga0.47As films. Secondary ion mass spectroscopy profiles indicate highest concentrations near the InP substrate and the InGaAs surface with lower levels in the middle of the epilayer on samples which show oxygen contamination. Electrically such films have low electron mobilities (μ300 K<3000 cm2/V s) and high net free-carrier densities (1016 cm−3<n300 K<1017 cm−3) with substantial freezeout as the temperature is lowered from 300 to 77 K. Photoluminescence from layers with high oxygen incorporation shows low intensity but with no lines or bands that can be ascribed to oxygen at this time.
Growth of thin single crystal NiSi2 films on Si surfaces, a field ion microscope study
Authors: Liu H. F. , Liu H. M. , Tsong T. T.
Published: July 2002

Thin single crystal NiSi2 films have been grown epitaxially on the [111] oriented Si tip surface in ultrahigh vacuum (UHV). A 180° change in the axial symmetry is found for the field ion images taken before and after the growth of the silicide layers. From this observation and a computer simulation of the field ion images we conclude that the Si-NiSi2 interface has the B-type structure. The field ion image of the NiSi2 films is good enough to reveal the atomic structure of the (111) Ni layer.
Five-layer nonlinear waveguide for second harmonic generation
Authors: Duguay M. A. , Weiner J. S.
Published: July 2002

We propose a new two-coupled-waveguide structure for second harmonic generation. An input TEω0 mode is phase matched to a harmonic TM2ω1 mode by varying the separation between the guides. Calculation of conversion efficiency in an AlGaAs structure gives 12% for 10 mW of input power at 1.3 μ over a 2-mm phase-matched length.
Simultaneous diffusion of zinc and indium into GaAs: A new approach for the formation of low resistance ohmic contacts to compound semiconductors
Authors: Shealy J. R. , Chinn S. R.
Published: July 2002

The simultaneous diffusion of zinc and indium into GaAs was performed prior to the deposition of a refractory contact metallization. This has resulted in low resistance contacts to p-type GaAs. We demonstrate that specific contact resistivities as low as 5×10−7 and 2×10−7 Ω cm2 are obtainable for nonalloyed and annealed contacts, respectively, using this technique. These specific contact resistances are the lowest values that have been reported for ohmic contacts to p-type GaAs. Furthermore, the apparatus used here should be easily adapted to the formation of low resistance n-type contacts by substituting for the zinc source a volatile source containing a group VI impurity such as Se or Te.
Use of optical emission spectroscopy to study hexafluoroethane reactive ion beam etching of silicon in the presence of oxygen
Authors: Cox T. I. , Deshmukh V. G. I.
Published: July 2002

By studying the light emission arising from the bombardment of silicon with an ion beam generated from C2F6, we find that emission from excited silicon atoms ejected from the surface is only observed for CF+x ions with energies greater than a threshold value. This is consistent with fragmentation of the CF+x ions on impact and adsorption of the resulting carbon on the silicon surface, thereby preventing the sputtering of silicon atoms. We associated the threshold energy with the appearance of areas of silicon which are free from carbon passivation. Addition of oxygen assists in the removal of this passivating carbon and reduces the observed threshold energies.
Hole trapping and interface state generation during bias-temperature stress of SiO2 layers
Authors: Haywood S. K. , De Keersmaecker R. F.
Published: July 2002

Avalanche hole injection measurements on unstressed metal-oxide-semiconductor capacitors and those having undergone bias-temperature stress (BTS) are compared. The results show that the negative midgap voltage shift (ΔVmg) occurring during negative BTS is due to filling of intrinsic hole traps. Conversely, positive BTS removes any previously trapped holes from the oxide. No evidence was found for hole trap generation at either stress polarity. Interface state generation across the band gap accompanies hole trapping during negative BTS and a characteristic peak is generated in the interface trap distribution at ∼ 0.2 eV above midgap on neutralization or detrapping of these holes during positive BTS.
HgTe-CdTe-InSb heterostructures by molecular beam epitaxy
Authors: Ballingall J. M. , Leopold D. J. , Peterman D. J.
Published: July 2002

HgTe-CdTe heterostructures have been grown by molecular beam epitaxy on (100) InSb substrates. Separate elemental Hg and Te beams were used for the HgTe growth at a substrate temperature of 160 °C. X-ray diffraction measurements indicate that thin epitaxial layers are of high crystalline quality. Secondary-ion mass spectroscopy measurements show substantial In and Sb diffusion into the epitaxial layers with a concentration enhancement at the HgTe-CdTe interface.
Magnetoresistance method to determine GaAs and AlxGa1−xAs mobilities in AlxGa1−xAs/GaAs modulation-doped field-effect transistor structures
Authors: Look D. C. , Norris George B. , Kopp W. , Henderson T. , Morkoç H.
Published: July 2002

Charge carrier mobilities are conveniently measured in simple, homostructure field-effect transistors (FET’s) by means of the geometric magnetoresistance (GMR) technique. Heterostructure FET’s, however, are more complicated because of multiple conducting regions, as well as multiple conducting bands within a given region. We apply a multilayer GMR mobility model to a frequently used heterostructure FET design, namely, the Al0.3Ga0.7As/GaAs modulation-doped FET (MODFET). By analyzing the results at different magnetic fields, we can separate the contributions of the various GaAs subbands and the Al0.3Ga0.7As conduction band. In the particular MODFET structure studied here, the lowest GaAs subband mobility ranges from 5.7×103 cm2/Vs at threshold to 6.9×103 cm2/Vs at saturation, while the Al0.3Ga0.7As mobility is about 5×102 cm2/Vs. This is the first time that the various mobilities in MODFET structures have been separately measured.
Electric field induced shifts and lifetimes in GaAs-GaAlAs quantum wells
Authors: Austin E. J. , Jaros M.
Published: July 2002

We have performed an exact numerical calculation for an isolated GaAs quantum well system subjected to an external electric field. This calculation predicts both the shifts and widths of the Stark resonances. The shift predictions are in agreement with recent experimental results and the width calculations allow the observed decrease in luminescence lifetime with field to be interpreted in terms of the field-induced tunneling of the carriers.
CO2 laser-assisted deposition of boron and phosphorus-doped hydrogenated amorphous silicon
Authors: Bilenchi R. , Gianinoni I. , Musci M. , Murri R. , Tacchetti S.
Published: July 2002

Gas-phase doping of hydrogenated amorphous silicon by CO2 laser-assisted chemical vapor deposition of silane is reported. p-type and n-type doping has been achieved by adding controlled amounts of diborane or phosphine to the reacting mixture in a horizontal flowing gas reactor. Silane molecules decompose by direct resonant absorption of the laser radiation and contribute to the dissociation of the dopant molecules through collisional energy transfers. The occurrence of substitutional doping is confirmed by the change in the dark conductivity by several orders of magnitude as well as by the decrease of its activation energy with increasing dopant gas concentration.
Investigation of the properties of organometallic vapor phase epitaxially grown AlGaAs/GaAs heterostructures using Raman scattering
Authors: Shealy J. R. , Schaus C. F. , Wicks G. W.
Published: July 2002

The growth of AlGaAs/GaAs heterostructures by low pressure organometallic vapor phase epitaxy was studied using Raman spectroscopy on a series of multilayer structures. Growth conditions were chosen to allow the investigation of the effects of growth rate and growth interruption during the formation of each type of interface (aluminum ‘‘turn on’’ and ‘‘turn off’’). This study represents the first report on the use of Raman for the quantitative measurement of the alloy composition in each region of a superlattice structure, where the observation is made that an extended growth interruption is required for the growth of thin GaAs regions (less than 100 Å) over AlGaAs (Al ‘‘turn off’’) while the other interface requires no growth interruption.
A 19% efficient AlGaAs solar cell with graded band gap
Authors: Virshup G. F. , Ford C. W. , Werthen J. G.
Published: July 2002

An Al0.20Ga0.80As solar cell with a band gap graded from 1.64 eV at the junction to 1.72 eV at the surface has been fabricated using metalorganic chemical vapor deposition. An efficiency of 19.2% has been measured under 1-sun, AM2 simulated conditions with an open circuit voltage of 1.18 V, a short circuit density of 14.5 mA/cm2, and a fill factor of 0.83.
Elimination of ‘‘pair’’ defects from GaAs layers grown by molecular beam epitaxy
Authors: Chai Young G. , Pao Y-C. , Hierl T.
Published: July 2002

In addition to ‘‘oval’’ defects, ‘‘pair’’ defects are observed on molecular beam epitaxially grown GaAs wafers. In this letter it is demonstrated that these defects originate from sulfur on the substrate surface caused by a 4:1:1 (H2SO4:H2O2:H2O) etch. The defects can be completely eliminated by dipping the substrate in 30% HCl solution for 5 min following a sulfuric acid etch.
Degradation-free modulation-doped field-effect transistors grown by organometallic chemical vapor deposition
Authors: Bhat R. , Chan W. K. , Kastalsky A. , Koza M. A. , Davisson P. S.
Published: July 2002

Using AlGaAs and GaAs grown by organometallic chemical vapor deposition (OMCVD), we have fabricated high-transconductance modulation-doped field-effect transistors which do not exhibit the severe electrical degradation in the dark at 77 K that is ordinarily observed in such devices. Such degradation has been attributed to defects in the n+-AlGaAs. Experiments on ohmic test devices using different OMCVD grown structures suggest that the improvement is due to a drastically reduced charge polarization in the n+-AlGaAs layer.
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u compensation of surface acoustic wave filter response
Authors: Cohn R. W. , Wagers R. S.
Published: July 2002

An experimental methodology is demonstrated for compensating the response of surface acoustic wave (SAW) bandpass filters. For a filter on (YZ) LiNbO3, we present measurements of changes in the SAW impulse and frequency response produced by in situ perturbations to the transducer’s apodization. Many transducer electrodes are perturbed in their length to determine filter sensitivity to electrode length variation. A methodology that is adaptive in these length variables is applied to determine the optimal apodization for the compensation of frequency domain sidelobes initially at the −26 dB level. They are deterministically reduced to the −39 dB level.
Room-temperature switching behavior of ferroelectric liquid crystals in thin cells
Authors: Patel J. S.
Published: July 2002

Ferroelectric liquid crystal confined between glass plates with a conductive coating and an alignment promoting layer is examined for bistability and threshold behavior. Bistability and the presence of a dynamic threshold are established in thin cells around 1–2 μm thick. When 1/(pulse width) is plotted versus the voltage of the pulse required to switch the sample, a linear relationship between these two quantities is observed above about 4 V.
Microscopic identification of defects propagating through the center of silicon and indium-doped liquid encapsulated Czochralski grown GaAs using x-ray topography
Authors: Scott M. P. , Laderman S. S. , Elliot A. G.
Published: July 2002

Extended defects in 3×1018 cm−3 Si-doped and 2×1019 cm−3 In-doped GaAs grown by the liquid encapsulated Czochralski technique are investigated using x-ray topography and found to include straight and helicoidal dislocations propagating along the central axis of the ingot. These dislocations are not simply extensions of dislocations in the seed. The defect morphology is explained by strong interaction with native point defects and elastic strain associated with solute segregation at the growing interface.
Rate of formation of silicon dioxide; semiconducting ruthenium silicide
Authors: d’Heurle F. M. , Frampton R. D. , Irene E. A. , Jiang Hao , Petersson C. S.
Published: July 2002

The rate of oxide formation over Ru2Si3, a semiconductor with a band gap of about 1 eV, is about as slow as that for Ir3Si5, another semiconducting silicide, and comparable to the rate observed over silicon itself. This is in opposition to what one obtains over metallic silicides where the linear term of oxidation kinetics is at least an order of magnitude greater than that for silicon. Analysis of these contrasting results leads to the conclusion that the enhanced rate over metallic silicides is due to the greater density of states at the Fermi level which facilitates charge transfer between the oxygen atoms and the oxidizing material. The possibility that the rate of oxidation should depend strongly on the metallic or covalent character of the Si bonding appears to be excluded by the fast oxidation rate observed over NiSi2 and CoSi2.
Molecular beam epitaxial growth of tungsten layers embedded in single crystal gallium arsenide
Authors: Harbison J. P. , Hwang D. M. , Levkoff J. , Derkits G. E.
Published: July 2002

We have been able to fabricate structures which consist of a thin (∼10 nm) polycrystalline W film embedded in surrounding single crystalline GaAs by molecular beam epitaxy (MBE) using an electron beam evaporation source to deposit W metal in an ultrahigh vacuum MBE growth chamber. The entire deposition sequence can take place at elevated temperature (625–700 °C) due to the nonreactive nature of W with respect to GaAs. Reflective high-energy diffraction and transmission electron microscopy indicate that the single crystal GaAs overgrowth proceeds by seeding from the GaAs layer beneath the W through spontaneously occurring perforations in the W layer.
Drawing condition dependences of optical absorption and photoluminescence in pure silica optical fibers
Authors: Hibino Yoshinori , Hanafusa Hiroaki , Sakaguchi Shigeki
Published: July 2002

Drawing-induced absorption at 630 nm and photoluminescence (PL) at 650 nm are investigated for pure synthetic silica optical fibers fabricated under various drawing conditions. It is found that both the absorption peak and the PL intensity increase with increasing drawing tension. These results suggest that the defects responsible for the absorption and the PL are closely related to the nonbridging oxygen defects.
Imaging of oxide precipitates in silicon with ballistic phonons
Authors: Metzger W. , Huebener R. P. , Haug R. J. , Habermeier H.-U.
Published: July 2002

Ballistic phonons were generated at low temperatures in nearly single-crystalline silicon by scanning the specimen surface with an electron beam. At the opposite sample surface the ballistic phonons were detected with two small-area bolometers placed at different locations. For a Si specimen which had been annealed for 150 h at 1050 °C, the ballistic phonon image contained fine structure which could be attributed to oxide precipitates. Comparing the phonon images obtained with the two bolometers, we concluded that the structural inhomogeneities affecting the ballistic phonon propagation were located far from the specimen surface scanned by the electron beam. With these experiments a new principle of three-dimensional tomography based on ballistic phonons has been demonstrated.
Novel ultrahigh resolution silverless photothermal imaging in obliquely deposited amorphous Se-Ge films
Authors: Harshavardhan K. Solomon , Krishna K. N.
Published: July 2002

A new photothermal imaging process which utilizes no silver has been demonstrated in obliquely deposited Se-Ge films. Band-gap irradiation of Se-Ge films has been found to give rise to phases of the type SeOx, GeO, and Se as borne by x-ray initiated Auger electron spectroscopy and x-ray photoelectron spectroscopy. Annealing of SeOx leads to the formation of SeO2. The large (several orders of magnitude) difference in vapor pressures of SeO2 and Se-Ge films results in differential evaporation of the films when annealed around 200 °C, thereby leading to imaging. Such a large contrast in evaporation rates between the exposed and unexposed regions has great potential applications in high resolution image storage and phase holography.
Persistent photoconductivity in quantum well resonators
Authors: Sollner T. C. L. G. , Le H. Q. , Correa C. A. , Goodhue W. D.
Published: July 2002

We have made the first observation of persistent photoconductivity in resonant tunneling structures. The spectral dependence suggests that it arises from Si DX centers in the AlGaAs barriers, and calculations based on a simple model using this assumption agree well with the observations. This effect has been useful in investigating the charge distribution and electric fields near the heterojunction interface and in determining the barrier parameters. The model should help in the design and fabrication of optimized resonant tunneling devices.
Amorphous silicon bulk barrier phototransistor with Schottky barrier emitter
Authors: Chang C. Y. , Wu B. S. , Fang Y. K. , Lee R. H.
Published: July 2002

An amorphous silicon indium tin oxide/n+-i-δ( p+)i/Al Schottky barrier phototransistor was fabricated on a glass substrate, where δ( p+) is the thin (200 Å) p+ base. The operation of the transistor is similar to that of an n+-i-δ( p+)i-n+ amorphous silicon bulk barrier phototransistor. Photogenerated holes are accumulated at the thin base region (barrier valley) and induce a large number of electrons injected from the Schottky barrier due to the hole induced barrier lowering. Varying the emitter and collector i-layer thickness produced different current gains in which a maximum value of 5.6 is obtained for the 300-Å emitter i-layer/p+/3000-Å collector i-layer structure under an input red light intensity of 7.5 mW/cm2.
1.55-μm InGaAsP distributed feedback vapor phase transported buried heterostructure lasers
Authors: Koch T. L. , Bridges T. J. , Burkhardt E. G. , Corvini P. J. , Coldren L. A. , Linke R. A. , Tsang W. T. , Logan R. A. , Johnson L. F. , Kazarinov R. F. , Yen R. , Wilt D. P.
Published: July 2002

1.55-μm single longitudinal mode InGaAsP distributed feedback (DFB) lasers have been fabricated using a vapor phase transported (VPT) buried heterostructure geometry on a liquid phase epitaxially grown broad area DFB base. Lasing thresholds in the 35–65-mA range were obtained, with side mode suppression ratios as high as 39 dB under modulation. The VPT DFB laser has both a good high-speed modulation capability and low wavelength chirping under high-speed modulation, making it an attractive candidate for high bit rate, long-haul optical fiber systems applications, with demonstrated record system performance at both 2 and 4 Gbit/s.
Continuous wave laser assisted chemical material removal from Mo, W, and Si at faint red hot temperatures (700–800 °C)
Authors: Koren Gad
Published: July 2002

cw CO2 and argon ion laser assisted chemical etching of Mo and W in air and Mo, W, and Si in a 7% F2 mixture in He is reported. At room temperature, these materials are hardly etched in air or the F2 mixture. At faint red hot temperatures (700–800 °C), however, they react strongly with the fluorine to produce volatile MoF6, WF6, and SiF4 which allow the etching process to continue. Using 50 W/cm2 of the cw CO2 laser radiation on a 275-μm-thick Si wafer in 30 Torr of the F2 mixture yielded an etch rate of ∼1 μm/s (on both sides) and submicron surface smoothness. Using 4 W of the 4880 Å Ar ion laser beam focused tightly on a 30-μm-thick Mo film in air, perforated the film at a rate of 2 μm/s by producing the volatile MoO3 at the elevated temperature.
Stresses in the InP/Ti/Pt and InP/SiO2/Ti/Pt multilayer systems
Authors: Dautremont-Smith W. C. , Woelfer S. M.
Published: July 2002

The contact metallization of 1000 Å Ti followed by 1500 Å Pt deposited by rf diode sputtering onto InP is found to be of very low stress, as has previously been reported for this metallization on GaAs. This is due to the effect of compressive stress in the Ti film being compensated by tensile stress in the Pt film. However, when Ti is deposited onto SiO2 coated InP, its stress changes sign, becoming highly tensile, of magnitude ∼1×1010 dyne cm−2. Thus its effect becomes additive to that of the Pt film, producing an effective stress in the Ti/Pt bilayer of ∼7×109 dyne cm−2 tensile. Due to moderately low compressive stress in the SiO2, the effective resultant stress for the multilayer of (3000 Å SiO2/Å Ti/1500 Å Pt) on InP(100) remains tensile, of magnitude 1.7×109 dyne cm−2. The origin of the stress reversal in the Ti film appears to be its mode of nucleation and growth, as opposed to the formation of a highly stressed interfacial compound layer.
Tungsten-platinum alloy Schottky barriers on n-type GaAs
Authors: Okumura T. , Tu K. N.
Published: July 2002

Alloys of tungsten and platinum were studied as a Schottky contact material on n-type GaAs. Schottky barrier heights for two alloy compositions, W50Pt50 and W80Pt20, were measured by current-voltage, capacitance-voltage, and photoresponse techniques of the barrier heights. The values of the barrier heights from the latter two techniques were 0.90±0.02 eV and did not change with annealing at 350 °C for 20 h. However, the value from the I-V technique changed from about 0.6 to 0.7 eV upon annealing. The W50Pt50 alloy was found to be more stable than the W80Pt20 alloy on GaAs.
Effect of HCl on silicon point defect formation during thermal oxidation of (100) float zone silicon wafers
Authors: Oh Seajin , Tiller W. A. , Hahn SooKap
Published: July 2002

The effect of HCl in an oxidizing ambient on Si interstitial formation during oxidation has been studied. Using an antimony buried marker in (100) Si wafers, self-interstitial generation is directly observed via its influence on Sb diffusion. Adding HCl up to 6 vol % reduces the self-interstitial flux generated at the oxidation front, but it does not completely eliminate it.
Voltage-dependent plasticity in HgCdTe
Authors: Pellegrino Joseph , Galligan J. M.
Published: July 2002

The effect of an applied, time-varying voltage on the plastic behavior of (Hg,Cd)Te has been investigated. We observe that both positive and negative voltages suppress plasticity, with the negative voltage being more effective. The influence of this voltage polarity is strain dependent and provides information on the charge of the mobile dislocations.
Reduced temperature sensitivity AlxGa1−xAs-GaAs quantum well lasers with (Si2)x(GaAs)1−x ‘‘barriers’’
Authors: Jackson G. S. , Deppe D. G. , Hsieh K. C. , Holonyak N. , Hall D. C. , Burnham R. D. , Thornton R. L. , Paoli T. L.
Published: July 2002

The temperature dependence of threshold current of quantum well heterostructure (QWH) laser diodes is reduced by inserting (Si2)x(GaAs)1−x barriers in the active region. Alloy clustering of the (Si2)x(GaAs)1−x barriers, grown by metalorganic chemical vapor deposition, leads to further QW carrier localization and an increase in T0 in the usual expression Jth=J0  exp(T/T0) for the threshold current. Values as high as T0=250–275 °C have been measured.
Ion channeling through a thin Si-liquid interface
Authors: Padmanabhan K. R. , Drallos P. J. , Alexander R. B. , Buchholz J. C.
Published: July 2002

The feasibility of ion channeling through the wall of a thin Si-liquid cell has been investigated. We have shown experimentally that it is possible to channel ions through a thin Si-liquid interface. With water the channeling minimum yield is 0.45 at the interface. This is higher than that required for application of this technique to gain structural information at the solid-liquid interfaces. It is also higher than that required for the determination of preferred positions of deposited impurity atoms at the interface.
Stability of an amorphous SiC/Si tandem solar cell with blocking barriers
Authors: Tawada Y. , Takada J. , Fukada N. , Yamaguchi M. , Yamagishi H. , Nishimura K. , Kondo M. , Hosokawa Y. , Tsuge K. , Nakayama T. , Hatano I.
Published: July 2002

A very stable amorphous SiC/Si (a-SiC/a-Si) heterojunction solar cell has been developed. The cell structure is of multijunction type with blocking barriers for the dopants and metal diffusion. This new tandem cell exhibits excellent stability for both thermal and sunlight conditions. After 2000 h of light exposure, an observable photodegradation is not seen in the cell performance. The improvements are achieved by the low-temperature deposition of first a p a-SiC layer, and by the blocking barriers for dopants and metal diffusion.
Lattice matching at elevated substrate temperature for growth of GaAs films with good electrical properties on CaxSr1−xF2/GaAs(100) structures
Authors: Tsutsui K. , Ishiwara H. , Furukawa S.
Published: July 2002

GaAs films were grown on CaxSr1−xF2/GaAs (100) structures by molecular beam epitaxy using a two-step growth technique and the effects of lattice mismatch between the GaAs and fluoride films at elevated temperature and room temperature were investigated. Electron Hall mobility measurements showed that the lattice matching at elevated temperature is more desirable for device applications.
Very low current threshold GaAs/Al0.5Ga0.5As double-heterostructure lasers grown by chemical beam epitaxy
Authors: Tsang W. T.
Published: July 2002

The first device performance of GaAs/AlxGa1−xAs double-heterostructure lasers grown by chemical beam epitaxy (CBE) is reported. Very low averaged current threshold densities of ∼500 A/cm2 were obtained for wafers with active layer thicknesses of ∼500–1000 Å and confinement layers of Al0.5Ga0.5As. Such current threshold densities were similar to those obtained from the best wafers grown by other techniques. This unequivocally established that CBE is capable of producing high optical quality multilayer heterostructures. Further, extreme device uniformity was also obtained.
Compensation of grain growth enhancement in doped silicon films
Authors: Kim H.-J. , Thompson C. V.
Published: July 2002

In thin films (1140 Å) of silicon doped with phosphorus, secondary or abnormal grain growth leads to bimodal grain size distributions and eventually to grains much larger than (≳25×) the film thickness. The resulting grains have nonrandom texture and are thought to be the result of surface-energy-driven secondary grain growth. The rate of secondary and normal grain growth increases with increasing P content. This rate increase is thought to be due to an increase in the grain boundary mobility. The rate of normal grain growth is unchanged or slightly increased when films are doped with boron. The secondary grain boundary mobility enhancement that occurs due to P doping can be compensated (reduced or eliminated) when films are co-doped with B.
Picosecond studies of electron confinement in simple colored glasses
Authors: Warnock J. , Awschalom D. D.
Published: July 2002

Time-resolved optical measurements at low temperatures reveal finite size effects for excitons trapped in semiconductor microcrystallites embedded in a simple borosilicate glass. The excitation lifetimes are significantly shorter than those in comparable bulk material, with a marked dependence on crystallite size. The results are interpreted as an effect of three-dimensional confinement with ‘‘box’’ dimensions comparable to the exciton diameter.
Measurement of the low-field electron mobility and compensation ratio profiles in GaAs field-effect transistors
Authors: Folkes P. A.
Published: July 2002

A novel technique for measuring the low-field electron mobility as a function of depth into the active layer of a nonuniformly doped GaAs Schottky barrier field-effect transistor (MESFET) has been developed. This technique is based on measurements of the current-voltage characteristics and the transconductance under low-field conditions as well as capacitance-voltage measurements. By comparison of the measured electron mobility with previous theoretical results the compensation ratio profile can be determined. Measurements on ion-implanted and epitaxial GaAs MESFET’s show that, for depths >0.1 μm, the nonuniform mobility profile is correlated with the donor density profile and sensitive to the compensation ratio, indicating that ionized impurity scattering is important over the range of carrier densities typically used in these devices.
Distinction between near infrared optical absorption and light scattering in semi-insulating GaAs
Authors: Skolnick M. S. , Brozel M. R.
Published: July 2002

Simultaneous infrared transmission and laser light scattering experiments on GaAs grown by the liquid encapsulated Czochralski technique are reported. Low-temperature photoquenching experiments are employed to demonstrate in a direct way that the nonuniform infrared images of large diameter GaAs crystals arise from absorption rather than scattering processes.
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u observation of lamp zone melting of Si films on patterned SiO2
Authors: Dutartre D.
Published: July 2002

Using video recording equipment we are able to visualize and study both the melting and freezing interfaces in lamp zone melting recrystallization of silicon on insulator (SOI) films. A so-called ‘‘explosive’’ melting has been observed, corresponding to a noncontinuous advance of the front. We also show the effectiveness of an etched pattern in the underlying SiO2 on the modulation of the solidification front. We thereby confirm the entrainment effect of this pattern. We observe then the effect of the scan speed on the liquid/solid interface morphology together with the entrainment efficiency.
Photopumped laser operation of GaAs doping superlattices
Authors: Vojak B. A. , Zajac G. W. , Chambers F. A. , Meese J. M. , Chumbley P. E. , Kaliski R. W. , Holonyak N. , Nam D. W.
Published: July 2002

The photopumped laser operation of GaAs doping superlattices grown by molecular beam epitaxy is reported. As expected, laser emission is at lower energy than that of bulk undoped GaAs. This emission is attributed to donor to acceptor transitions that occur after the doping superlattice is excited to a flatband condition. Laser operation via electron to hole tunneling and recombination at lower energies, which requires extremely low thresholds, is not observed.
Theoretical study of a 16-μm CO2 downstream-mixing gasdynamic laser: A two-dimensional approach
Authors: Chakravarthy Purandar , Reddy N. M.
Published: July 2002

A 16-μm CO2-N2 downstream-mixing gasdynamic laser, where a cold CO2 stream is mixed with a vibrationally excited N2 stream at the exit of the nozzle, is studied theoretically. The flow field is analyzed using a two-dimensional, unsteady, laminar and viscous flow model including appropriate finite-rate vibrational kinetic equations. The analysis showed that local small-signal gain up to 21.75 m−1 can be obtained for a N2 reservoir temperature of 2000 K and a velocity ratio of 1:1 between the CO2 and N2 mixing streams.
Ion beam mixing in the Al/NixAl1−x/Ni system
Authors: Rimini E. , Nastasi M. , Liu J. , Barbour J. C. , Hirvonen J-P. , Mayer J. W.
Published: July 2002

Thin-film alloy samples of Al/NixAl1−x/Ni (x=0.75, 0.5, 0.25) were irradiated at room temperature and at 160 °C with 280 and 560 keV Xe ions to a dose of 1.1×1016 Xe ions/cm2. The samples were analyzed by Rutherford backscattering spectrometry. In the Al/Ni3Al/Ni configuration the Ni3Al layer mixes more strongly with Al than with Ni. In the Al/NiAl/Ni samples, the NiAl layer mixes substantially with both Al and Ni. In the Al/NiAl3/Ni case, the NiAl3 layer mixes only with Ni. The results differ from thermal annealing behavior and are explained in terms of the thermodynamical driving forces present in the different samples.
Pulsed electron beam annealing of phosphorus-implanted CuInS2
Authors: Lin J. L. , Lue J. T. , Yang M. H. , Hwang H. L.
Published: July 2002

Pulsed electron beam annealing of phosphorus-implanted CuInS2 has been found to be an efficient method in p-type doping of CuInS2. A sheet resistance as low as 10.1 Ω/⧠, a sheet carrier concentration as high as 2.6×1016 cm−2, and a hole mobility as high as 499 cm2/V s have been obtained. The irradiation energy density for the best doping condition was determined to be in the range ∼11–13 J/cm2. Using Van der Pauw/Hall technique in conjunction with a chemical etching technique, effective carrier concentration profiles have been determined with a maximum carrier concentration of 9×1019 cm−3. Excellent p-n CuInS2 homojunctions have been fabricated by electron beam pulse annealing with an ideality factor of 1.75.
Channeling radiation from strained-layer superlattices
Authors: Pathak Anand P. , Balagari Prasanna K. John
Published: July 2002

Possibility to study strained-layer superlattices by observing channeling radiation emitted by relativistic positrons channeled along major crystallographic planes is investigated. A downward shift in the peak frequency and decrease in the linewidth of the channeling radiation peak are predicted.