bluuebunny/crossref_metadata_2025 huggingface dataset:
Doping effects in reactive plasma etching of heavily doped silicon
Authors: Lee Young H. , Chen Mao-Min , Bright A. A.
Published: July 2002

Etch rates of heavily doped silicon films (n and p type) and undoped polycrystalline silicon film were studied during plasma etching and also during reaction ion etching in a CF4/O2 plasma. The etch rate of undoped Si was lower than the n+-Si etch rate, but higher than the p+-Si etch rate, when the rf inductive heating by the eddy current was minimized by using thermal backing to the water-cooled electrode. This doping effect may be explained by the opposite polarity of the space charge present in the depletion layer of n+-Si and p+-Si during reactive plasma etching.
Phased arrays of buried-ridge InP/InGaAsP diode lasers
Authors: Kapon E. , Lu L. T. , Rav-Noy Z. , Yi M. , Margalit S. , Yariv A.
Published: July 2002

Phase-locked arrays of buried-ridge InP/InGaAsP lasers, emitting at 1.3 μm, were grown by liquid phase epitaxy. The arrays consist of index-guided, buried-ridge lasers which are coupled via their evanescent optical fields. This index-guided structure makes it possible to avoid the occurrence of lower gain in the interchannel regions. As a result, the buried-ridge arrays oscillate mainly in the fundamental supermode, which yields single lobed, narrow far-field patterns. Single lobed beams less than 4° in width were obtained from buried-ridge InP/InGaAsP phased arrays up to more than twice the threshold current.
Amorphous iron zirconium formed by solid state reaction
Authors: Clemens B. M. , Suchoski M. J.
Published: July 2002

We report on the first iron based amorphous alloy formed by the process of solid state reaction. Amorphous iron zirconium was observed to result from thermal anneals of layered crystalline elemental constituents. Starting material was electron beam evaporated with about 50 monolayers of each constituent per layer, which results in an average composition of Fe61Zr39 and a compositional wavelength of 22 nm. Thermal anneals at 623 K were performed in vacuum, and x-ray diffraction was used to determine the structure. A calculated metastable free energy diagram shows the reaction is driven by a large thermodynamic driving force (several kcal/mole).
Evidences that P diffusion in Si is assisted mainly by vacancies
Authors: Mathiot D. , Pfister J. C.
Published: July 2002

A reexamination of some experimental results, including very high concentration phosphorus diffusion with self-interstitial injection, leads to the conclusion that P diffusion is assisted mainly by vacancies. This point is also strengthened by a simple calculation showing that the dominant defect for P diffusion plays the minor role in self-diffusion.
Raman scattering determination of free-carrier concentration and surface space-charge layer in 〈100〉 n-GaAs
Authors: Shen H. , Pollak Fred H. , Sacks R. N.
Published: July 2002

We have used Raman scattering as a nondestructive, contactless method for determining not only the free-carrier concentration N but also the width of the space-charge layer in 〈100〉 n-GaAs with 4×1017 cm−3≤N≤1×1019 cm−3 using as an excitation several different wavelengths of an Ar+ laser. By comparing the intensity at different wavelengths of the uncoupled longitudinal optic phonon mode originating in the space-charge layer with the signal from a piece of undoped 〈100〉 material, it is possible to experimentally evaluate the width of the depletion layer Ls. We find that there is very good agreement between the experimental values and those obtained from a generalized theory for both degenerate and nondegenerate materials. Thus, these experimental results demonstrate that for 〈100〉 III-V semiconductors, Raman scattering can be used as a contactless method to determine the width of the space-charge region for carrier concentrations up to 1×1019 cm−3.
Acoustic wave generation by thermal excitation of small regions
Authors: Kino G. S. , Stearns R. G.
Published: July 2002

Reciprocity theory is used to derive a general formalism for generation of acoustic waves by thermal excitation. It is shown that the most important parameters contributing to the generation include the thermal expansion of the material and its interaction with the volume dilation associated with the acoustic field of the receiving transducer. The excitation of a longitudinal acoustic wave, as a function of angle to the surface normal, is derived directly.
Oxidation condition dependence of surface passivation in high efficiency silicon solar cells
Authors: Blakers A. W. , Green M. A.
Published: July 2002

Several recent high performance silicon solar cells have taken advantage of surface oxide passivation to improve both their short wavelength response and open-circuit voltage. Using low resistivity substrates to minimize base recombination rates, the effect of oxidation conditions upon the passifying properties of thin oxides is quantified. It is shown that emitter recombination in high efficiency cells decreases by a factor of at least 3 and most probably 7 as the oxide growth temperature increases from 825 to 900 °C and the oxide thickness increases from 60 to 100 Å. This increase in performance is at the expense of a slight loss in cell short-circuit current density.
Effect of barrier thickness on the luminescence properties of AlAs/GaAs multiple quantum wells grown by molecular beam epitaxy
Authors: de Miguel J. L. , Fujiwara K. , Tapfer L. , Ploog K.
Published: July 2002

The influence of barrier layer thickness LB for LB >3 nm on the optical properties of all-binary AlAs/GaAs multiple quantum well heterostructures (MQWH) is studied by photoluminescence and excitation spectroscopy measurements at 2 K. In contrast to expectation for a simple coupling between the constituent GaAs quantum wells, MQWH samples with thinner barrier layers show excitonic peaks shifted to higher energies and exhibit a larger splitting between the electron to heavy-hole and electron to light-hole free excitons. This feature remains for different values of the otherwise constant well width within different series and when a small amount of Al is added to the well. Our detailed experimental data indicate that the mechanism responsible for the high-energy shift is intrinsic in nature. This unusual feature demonstrates the inadequacy of photoluminescence and excitation spectroscopy to determine well widths accurately.
Direct detection of magnetostatic wave excitations in magnetostatic wave device structures by Brillouin light scattering
Authors: Srinivasan G. , Patton C. E.
Published: July 2002

The technique of Brillouin light scattering has been used to detect magnetostatic wave (MSW) excitations in MSW microwave device structures. The present results are for a signal-to-noise enhancer consisting of a microstrip transmission line in contact with a yttrium iron garnet film with the applied magnetic field parallel to the microstrip line. At low input microwave power levels, the MSW spectra at 4 GHz consisted of surface excitations with wave numbers from about 80 to 470 cm−1, with the propagation direction perpendicular to the microstrip line. At high power levels, parametric half-frequency MSW excitations were observed, accompanied by a decrease in the scattering of the surface MSW excitations at the pump frequency.
Capacitance-voltage characteristics of GaAs-AlAs heterostructures
Authors: Woodward T. K. , Schlesinger T. E. , McGill T. C. , Burnham R. D.
Published: July 2002

We report on an experimental study of the temperature and photosensitive capacitance-voltage (C-V) characteristics of GaAs-AlAs-GaAs heterostructures grown by metalorganic chemical vapor deposition. The structures consisted of a layer of AlAs either 2500 or 4000 Å thick sandwiched between layers of GaAs which were a few microns thick. C-V curves were measured at 1 MHz, both with and without illumination. Measurements were made at 77 and 300 K. The C-V showed hysteresis near zero bias with the capacitance being larger when the voltage was swept from reverse to forward bias in the dark. The C-V displayed a light sensitive peak near zero bias. With illumination, the capacitance was greater, and no hysteresis was observed. We explain these phenomena as being due to deep levels near the AlAs-GaAs interface.
Spatial hole burning problems in evanescently coupled semiconductor laser arrays
Authors: Chen Kuo-Liang , Wang Shyh
Published: July 2002

The effect of spatial hole burning on laser arrays is theoretically analyzed. Due to the nonuniformity of the lowest order supermode, carriers are unevenly depleted when this mode is excited. This spatial hole burning in carrier concentration reduces any designed discrimination against higher order supermodes. More and more modes are excited as the power level goes up, resulting in broadened radiation patterns. Even when the lowest order mode oscillation can be guaranteed, spatial hole burning modifies the refractive index profile. The intensity distribution of this mode narrows as power increases. The results are broadened radiation patterns and low quantum efficiency. Two methods to overcome these problems are briefly discussed.
Photoenhanced electron attachment of vinylchloride and trifluoroethylene at 193 nm
Authors: Rossi M. J. , Helm H. , Lorents D. C.
Published: July 2002

We show that the electron attachment properties of a gas mixture of helium containing vinylchloride or trifluoroethylene can be altered from nonattaching to strongly attaching by irradiation with a low-energy laser pulse at 193 nm. These molecules are photodissociated producing vibrationally excited HCl or HF and other fragments that strongly attach low-energy electrons.
High-quality Si-implanted GaAs activated by a two-step rapid thermal annealing technique
Authors: Seo Kwang S. , Dhar Sunanda , Bhattacharya Pallab K.
Published: July 2002

The properties of Si-implanted GaAs activated by halogen lamp annealing have been studied. It is found that consistently better results can be obtained by a two-step annealing technique in which the high-temperature main anneal step is followed by a second anneal at a lower temperature. Mobilities and activations of 4000–4600 cm2/Vs and 50–65%, respectively, are obtained for (3.0–6.5)×1012 cm−2/100 keV 29Si+ implants. These values are among the best reported for lamp-annealed GaAs. Raman spectra confirm the high quality of the annealed crystals.
Lasing transitions in GaAs/GaAs1−xPx strained-layer superlattices with x=0.1–0.5
Authors: Gourley P. L. , Hohimer J. P. , Biefeld R. M.
Published: July 2002

The role of strain in modifying lasing transition energy and gain coefficient in photopumped GaAs/GaAs1−xPx strained-layer superlattices is investigated by examining photoluminescence, excitation, and lasing spectra for samples with x in the range 0.1–0.5. Over this range, the lasing transition energy increases 50 meV, independent of quantum size effects. The compressive biaxial strain present in the GaAs layers is expected to significantly increase the gain coefficient for the ‖3/2,±1/2〉 ‘‘light’’ hole transitions. However, polarization measurements of the lasing spectra show no evidence for lasing on the TM mode ‖3/2,±1/2〉 transitions and show lasing only on the TE mode ‖3/2,±3/2〉 ‘‘heavy’’ hole transitions.
Spectral linewidth of an external-cavity laser diode stabilized by a fiber-optic ring resonator
Authors: Tai Shuichi , Kyuma Kazuo , Nakayama Takashi
Published: July 2002

The spectral linewidth of an external-cavity single-mode GaAs/AlGaAs laser diode was stabilized by controlling the phase of the feedback light, where a fiber-optic ring resonator was used as a linewidth discriminator. The stabilized linewidth is about 500 kHz with a short-term fluctuation of about 30 kHzp−p over a period of 3 h.
0° phase mode operation in phased-array laser diode with symmetrically branching waveguide
Authors: Taneya M. , Matsumoto M. , Matsui S. , Yano S. , Hijikata T.
Published: July 2002

An AlGaAs phased-array laser with a novel index waveguide structure like the letter ‘‘Y’’ is described. In all arrays with such a structure, controllable selection of only 0° phase mode and complete suppression of 180° phase shift mode is achieved up to ∼65 mW in 2%–96% coated devices. The far-field patterns, near-field patterns, and spectra of the array are in good agreement with the theoretical results. The cw threshold currents are ∼100 mA, and the external differential quantum efficiencies are 57% per facet.
Low loss optical waveguides fabricated by thermal nitridation of oxidized silicon
Authors: Zelmon David E. , Boyd Joseph T. , Jackson Howard E.
Published: July 2002

This letter describes the first optical waveguides fabricated by thermal nitridation of SiO2. This process has allowed us to create layers of silicon oxynitride of about 100-nm thickness in 4.8-μm-thick silicon dioxide layers by exposing thermally oxidized silicon wafers to an ammonia atmosphere for times ranging from one to ten days. Ellipsometric measurements show that the refractive indices of the nitrided layers range from 1.67 to 1.75. Losses for nine optical waveguide samples fabricated with this process range from 0.06 to 0.31 dB/cm.
Properties of carbon films by dc plasma deposition
Authors: Fujii Kazutaka , Shohata Nobuaki , Mikami Masao , Yonezawa Masatomo
Published: July 2002

Perfectly smooth transparent carbon films deposit onto room-temperature silicon wafers in a dc plasma of methane (CH4) and hydrogen (H2). Transmission electron microscope analysis reveals that the films consist primarily of amorphous carbon (a-C). The nearest neighbor C–C bond length of a-C formed at low discharge current densities or low working pressures approaches that of diamond. Electrical resistivity, calculated using V-I curves for the Al-C-Si structure, is more than 1013 Ω cm. A face-centered-cubic phase with a lattice constant of 4.96 Å and diamond, both of which form at relatively high pressures, consist of crystallites having a diameter of about 100 Å.
GaInAs(P)/InP quantum well structures grown by gas source molecular beam epitaxy
Authors: Temkin H. , Panish M. B. , Petroff P. M. , Hamm R. A. , Vandenberg J. M. , Sumski S.
Published: July 2002

We describe optical properties of single and multiple quantum well structures grown by gas source molecular beam epitaxy. Absorption and photoluminescence were used in conjunction with x-ray and transmission electron microscopy techniques to determine the confined particle energy levels and well thicknesses. Well defined exciton transitions were observed in the ternary and quaternary well superlattices even above room temperature. In single well structures energy shifts as large as 260 and 370 meV were observed for GaInAs and GaInAsP wells, respectively. On the basis of these results we estimated that over 50% of the InGaAs/InP band discontinuity resides in the conduction band.
Modulation-doped (Al,Ga)As/AlAs superlattice: Electron transfer into AlAs
Authors: Drummond T. J. , Fritz I. J.
Published: July 2002

A modulation-doped superlattice of n-(Al,Ga)As and undoped AlAs has been grown by molecular beam epitaxy. At cryogenic temperatures, electrons transfer into the undoped AlAs layers and enhanced mobilities as high as 1000 cm2/Vs are observed for the first time. It is shown that by properly accounting for the depth of the donor level in modulation-doped heterostructures reasonably good limits can be set on the gamma point conduction-band discontinuity at the heterojunction. It is found that this discontinuity is approximately 60–65% of the band-gap difference between the two alloys, in good agreement with other recent determinations.
Low loss GaAs optical waveguides grown by the metalorganic chemical vapor deposition method
Authors: Hiruma K. , Inoue H. , Ishida K. , Matsumura H.
Published: July 2002

In order to realize the low loss ridge optical waveguide, high-purity GaAs and Ga1−xAlxAs (0<x<0.1) epitaxial layers were grown by the metalorganic chemical vapor deposition method. The residual free-carrier concentration was reduced to 1014 cm−3 after ten samples had been grown in the same reactor. Ridge optical waveguides fabricated showed propagation losses of 0.8 dB/cm for the GaAs homostructure waveguide and of 0.2 dB/cm for the GaAs-GaAlAs heterostructure waveguide at 1.3-μm wavelength.
Epitaxial growth of FeSi2 in Fe thin films on Si with a thin interposing Ni layer
Authors: Cheng H. C. , Yew T. R. , Chen L. J.
Published: July 2002

Thin interposing Ni layers between Fe thin films and substrate Si have been shown to be very effective in inducing the growth and improving the quality of epitaxial FeSi2 on silicon. The formation of a transition layer with graded concentration is conceived to facilitate the epitaxial growth of FeSi2 on silicon. The thin interposing layer scheme may be extended to promote the epitaxial growth of a number of refractory silicides on silicon.
Implantation disordering of AlxGa1−xAs superlattices
Authors: Gavrilovic P. , Deppe D. G. , Meehan K. , Holonyak N. , Coleman J. J. , Burnham R. D.
Published: July 2002

Data are presented showing that layer disordering of AlxGa1−xAs-GaAs quantum well heterostructures (QWH’s) or superlattices (SL’s) via ion implantation can be effected with a lattice constituent (Al), an inert ion (Kr), or an active impurity (Zn, Si, S, etc.). A doping impurity that diffuses (during annealing) via multiple sites, making column III sites available for Al-Ga interchange, is most effective in layer disordering. However, any implanted ion is itself relatively effective in converting an AlxGa1−xAs-GaAs QWH or SL to bulk-crystal AlyGa1−yAs (0≤y≤x) via damage-induced disordering.
High-frequency constricted mesa lasers
Authors: Bowers J. E. , Hemenway B. R. , Gnauck A. H. , Bridges T. J. , Burkhardt E. G. , Wilt D. P. , Maynard S.
Published: July 2002

InGaAsP cw constricted mesa lasers at 1.3 μm are described which have a small-signal 3-dB bandwidth of 20 GHz at −70 °C. Large-signal pseudorandom modulation at 8 Gb/s resulted in 100% optical modulation. The lasers were gain switched at 12 GHz with 100% optical modulation.
Nitrogen-related deep electron traps in float zone silicon
Authors: Nauka K. , Goorsky M. S. , Gatos H. C. , Lagowski J.
Published: July 2002

Two deep levels (electron traps) associated with nitrogen were identified in high resistivity float zone silicon employing deep level transient spectroscopy. The levels are formed during annealing at high temperatures (≥900 °C). They exhibit activation energies of Ec −0.58 eV and Ec −0.5 eV. The electron capture cross section for the 0.58 eV level is about 5×10−14 cm2. The levels appear to be associated with complexes rather than isolated nitrogen atoms.
PbSnTe multiple quantum well lasers for pulsed operation at 6 μm up to 204 K
Authors: Shinohara Koji , Nishijima Yoshito , Ebe Hiroji , Ishida Akihiro , Fujiyasu Hiroshi
Published: July 2002

Lattice-matched PbSnTe-PbTeSe multiple quantum well lasers fabricated by hot wall epitaxy have been developed. Though the PbSnTe-PbTeSe system is a type I′ superlattice, by using band bending due to doping, laser operation like type I superlattices has been achieved for the first time. The laser worked well in pulsed operation up to 204 K with 6 μm radiation (cw operation at 130 K with 6.6 μm radiation).
Molecular beam epitaxial growth of Si on CoSi2 substrates
Authors: Ditchek B. M. , Salerno J. P. , Gormley J. V.
Published: July 2002

Thin epitaxial films of Si have been grown on single crystal CoSi2 (111) substrates by molecular beam epitaxy. The CoSi2 was found to become atomically clean and suitable for growth upon heating to ≂750 °C in ultrahigh vacuum. Film uniformity and crystalline quality as judged by reflection electron diffraction are maximized by using growth temperatures as low as 400 °C.
Novel organic-on-InP field-effect transistor
Authors: Cheng Chu-Liang , Forrest Stephen R. , Kaplan Martin L. , Schmidt Paul H. , Tell Benjamin
Published: July 2002

We report the first organic-on-inorganic contact barrier semiconductor transistor. InP field-effect transistor similar to metal-semiconductor field-effect transistors was made by vacuum subliming a thin film of N, N′-dimethyl 3,4,9,10-perylenetetracarboxylic diimide onto Si-implanted channel, forming a gate contact. Good pinch-off characteristics and relatively small gate leakage current were obtained. The extrinsic transconductances for these devices are approximately 70–80 mS/mm, with a gate length of 1.5 μm and a channel carrier concentration in the high 1016 cm−3.
High-speed monolithically integrated GaAs photoreceiver using a metal-semiconductor-metal photodiode
Authors: Ito M. , Kumai T. , Hamaguchi H. , Makiuchi M. , Nakai K. , Wada O. , Sakurai T.
Published: July 2002

A planar monolithically integrated GaAs photoreceiver involving a transimpedance preamplifier has been fabricated using a metal-semiconductor-metal (MSM) photodiode. The present MSM photodiode showed a small capacitance of 0.14 pF, which is much smaller than in conventional p-i-n photodiodes, and a high-speed pulse response exhibiting a rise time of 300 ps was demonstrated. It is shown that an MSM photodiode is suitable for monolithic integration due not only to the simple process but also because of its high-speed operation.
High power cw operation of phased array diode lasers with diffraction limited output beam
Authors: Welch D. F. , Scifres D. , Cross P. , Kung H. , Streifer W. , Burnham R. D. , Yaeli J. , Paoli T. L.
Published: July 2002

Phased array diode lasers have been operated emitting predominantly in a single diffraction limited beam with full width at half-maximum of 0.8° in pulsed operation and 0.7° in cw operation and output power of 420 and 350 mW, respectively. The current in these lasers is confined to periodic stripes that are offset by a half period at two positions along the laser. In addition, the stripe width varies monotonically across the device while holding the period constant. The single lobed, far-field pattern occurs at 4° off the facet normal and suggests operation in the lowest order supermode of the asymmetric array.
Variations in interface compound nucleation for Ti-Al ultrathin films on Si substrates
Authors: Han C. C. , Bené R. W.
Published: July 2002

We have determined the structures of compounds nucleated in a series of sequentially sputtered thin bilayer films of Al and Ti on Si substrates for a range of metal thicknesses and for both (100) and (111) substrates. The compound structures were determined by transmission electron microscopy and diffraction, augmented by Auger electron spectroscopy. An annealing temperature of about 380 °C for 30 min was required to produce compound nucleation. For the Ti/Al/Si(100) system it was found that the phases which were nucleated for samples with 30-min, 380 °C anneals varied from TiAl3 to Ti8Al24 to an unknown compound of tetragonal structure (a=b=5.782 Å, c=6.713 Å) as the Al intermediate layer thickness is changed from 200 to 60 to 40 Å. TiAl3 was the compound nucleated at 380 °C for all other cases. Finally, 410 °C annealing of the Al/Ti/Si(100) samples for 30 min resulted in formation of an apparently Al-altered form of TiSi2.
Measurement of optical absorption in single quantum wells using photothermal deflection spectroscopy
Authors: Penna A. F. S. , Shah Jagdeep , DiGiovanni A. E. , Cho A. Y. , Gossard A. C.
Published: July 2002

We report the measurement of the optical absorption spectra of single quantum wells of GaAs (104 Å thick) and InGaAs (75 Å thick) by photothermal deflection spectroscopy. The room-temperature spectra show distinct structure due to heavy- and light-hole excitons in both GaAs and InGaAs samples. The measurements also show that absorption spectra in extremely thin (<10 Å) quantum wells, single heterostructures, or other microstructures with very small absorptance can be obtained by this technique.
Electron irradiation-activated low-temperature annealing of phosphorus-implanted silicon
Authors: Miyao M. , Polman A. , Sinke W. , Saris F. W. , van Kemp R.
Published: July 2002

High-energy (0.2–0.8 MeV, ≊1017 cm−2) electron irradiation-stimulated solid phase regrowth of phosphorus-implanted silicon layers has been observed in the temperature range 350–600 °C. The influence of electron irradiation on the annealing of an isolated damage layer and of a continuous amorphous layer is compared. An ionization effect is found to enhance annealing of trapping centers in the isolated damage region. In addition, a small enhancement of solid phase epitaxial regrowth of the continuous amorphous layer was found, attributed to an elastic displacement effect.
Continuous tunability in three-terminal coupled-cavity lasers
Authors: Corzine S. W. , Coldren L. A. , Burrus C. A. , Koch T. L.
Published: July 2002

The continuous tunability of various coupled-cavity semiconductor lasers has been investigated. Monolithic etched groove and cleaved coupled cavity (C3) geometries are included. Using a special method of modulating the laser currents, appreciable tuning ranges have been achieved (∼8 Å) without mode hops. Also, electronic tuning of a laser with no amplitude variation is illustrated. A tuning range of 4 Å with <5% AM depth is observed. Review of the theory and a comparison of the different laser geometries are included.
Artifacts in transmission electron microscope images of artificially layered metallic superlattices
Authors: Baxter C. S. , Stobbs W. M.
Published: July 2002

Both uniform and irregular artificially layered superlattice structures can exhibit a variety of misleading image artifacts in transmission electron microscopy when the layer normal is not perpendicular to the beam direction. These include apparent ‘‘layer dislocations,’’ and the origins of these and other artifacts, as observed in Cu/NiPd superlattices, are discussed.
Continuous wave operation (77 K) of yellow (583.6 nm) emitting AlGaInP double heterostructure laser diodes
Authors: Hino Isao , Kawata Seiji , Gomyo Akiko , Kobayashi Kenichi , Suzuki Tohru
Published: July 2002

Continuous wave lasing operation with the shortest wavelength for semiconductor lasers was obtained from AlGaInP double heterostructure lasers at 77 K. The structure was grown by metalorganic vapor phase epitaxy. Lasing wavelength was 583.6 nm (yellow). Threshold current was 43 mA (1.9 kA/cm2). Magnesium was adopted as a p-type dopant, and was proved to be preferable for a high aluminum composition AlGaInP cladding layer.
Schottky barrier formation on electron beam deposited amorphous Si1−xGex:H alloys and amorphous (Si/Si1−xGex):H modulated structures
Authors: Christou A. , Tzanetakis P. , Hatzopoulos Z. , Kyriakidis G. , Tseng W. , Wilkins B. R.
Published: July 2002

Amorphous Si:H and Si1−xGex:H films were prepared by mixing electron beam evaporated silicon with a molecular beam of germanium from a Knudsen cell and with a beam of ionized hydrogen produced by a 0–3 keV ion source. Aluminum Schottky barriers on two types of samples of (1) amorphous Si1−xGex:H with 0.15<x<0.85 and (2) modulated structures of 50×100 Å layers of amorphous Si:H/a-Si0.8Ge0.2:H (10−5 Torr PH hydrogen) were investigated. Barrier height was found to depend on the Ge concentration and possible Fermi level pinning due to the dangling bond deep level. The modulated structures showed a negative resistance region and a barrier height determined only by the composition of the first layer.
Evidence for amphoteric behavior of Ru on CdTe surfaces
Authors: Bose D. N. , Basu S. , Mandal K. C. , Mazumdar D.
Published: July 2002

Modification of large grain p-CdTe by Ru is shown to reduce the sub-band-gap response and increase minority-carrier diffusion length from 0.67 to 0.92 μm. Contact potential difference (CPD) measurements on n- and p-CdTe show shifts in surface Fermi level in opposite directions corresponding to increase in barrier height in each case. The amphoteric nature of Ru on CdTe surfaces depending on conductivity type is thus inferred. The magnitudes of the changes in CPD are approximately equal to the increase of open circuit voltage Voc observed in photoelectro-chemical cells.
Expanding beam concept for building very large excimer laser amplifiers
Authors: Jacob J. H. , Rokni M. , Klinkowstein R. E. , Singer S.
Published: July 2002

Optical extraction efficiency from conventional lasers and amplifiers with nonsaturable intrinsic absorption is substantially below the maximum efficiency at absorption length products exceeding unity. This result is caused by the fact that high intensities in the amplifier cause saturation of gain but not absorption. In this letter, a new scalable amplifier concept is analyzed which maintains near maximum extraction efficiency as the laser length increases beyond absorption length products of unity.
Dynamic characteristics of dislocations in indium-doped gallium arsenide crystal
Authors: Yonenaga Ichiro , Sumino Koji , Yamada Koji
Published: July 2002

Characteristics in the motion of dislocations generated from scratches in GaAs doped with In at a concentration of 2×1020 atoms/cm3 are investigated and are compared with those in undoped GaAs. α dislocations in In-doped GaAs are found to be immovable under stress lower than 10 MPa in the temperature range 350–750 °C. Such immovability under low stress is not found for β dislocations in In-doped GaAs and for both α and β dislocations in undoped GaAs.
Characteristics and mechanism of 1/f noise in GaAs Schottky barrier field-effect transistors
Authors: Folkes P. A.
Published: July 2002

Measurements of the absolute spectral density of 1/f noise in GaAs Schottky barrier field-effect transistors (MESFET’s) show that 1/f noise consists of a surface component and a separable uncorrelated bulk component. The surface component is caused by trapping of electrons by surface states. The bulk component is correlated with the low field electron mobility and deep level trap concentration versus depletion depth profiles and can only be explained by the random fluctuations in the occupancy of deep level traps in the depletion region. A simple model quantitatively explains the observed characteristics of the bulk component of the noise at a low drain voltage. At normal operating drain voltages the observed 1/f noise characteristics are consistent with the model.
Exciton formation and energy exchange with d-electron states in ZnSe/(Zn,Mn)Se multiple quantum wells
Authors: Hefetz Y. , Goltsos W. C. , Nurmikko A. V. , Kolodziejski L. A. , Gunshor R. L.
Published: July 2002

Time-resolved photoluminescence at low temperatures has been studied in ZnSe/(Zn,Mn)Se multiple quantum wells and (Zn,Mn)Se thin films, with emphasis on determination of the exciton formation rate and the energy transfer to the Mn-ion d-electron states, the latter contributing to the dominant yellow luminescence in (Zn,Mn)Se. In the quantum well samples which show efficient exciton (blue) emission, the capture of electron-hole pairs to the ZnSe layers on a picosecond timescale is sufficiently rapid to substantially reduce the yellow luminescence.
Study of banded structure in polymer spherulites by polarized micro-Raman spectroscopy
Authors: Tanaka Hajime , Ikeda Teruki , Nishi Toshio
Published: July 2002

Polarized micro-Raman spectroscopy has been used to study polymer blends of poly (ε-caprolactone), poly (vinyl methyl ether), and poly(styrene) for the first time. The banded pattern is attributed to the twist of the lamellae from microscopic (vibrational spectroscopic) measurements on the orientation of the lamellae. Polarized micro-Raman spectroscopy is shown to be a powerful method for studying high order structures of polymers on the molecular level.
Spectral characterization of epitaxial crystal layers, using a fiber stimulated Raman light generator as light source
Authors: Mita Yoh
Published: July 2002

Spectral absorption characteristics in InGaAsP/InP double heterostructure epitaxial crystal layers have been investigated by using stimulated Raman scattering light from silica fiber excited with neodymium:yttrium aluminum garnet laser and by examining the transmitted guided light. The method proved useful in measuring wavelength-dependent optical absorption ranging between 0.1 and 20 cm−1 in epitaxial layers with waveguiding structures as well as characterizing loss in optical waveguides in the wavelength region between 1.06 and 1.7 μm.
Deep level defect study of molecular beam epitaxially grown silicon films
Authors: Xie Y. H. , Wu Y. Y. , Wang K. L.
Published: July 2002

We report the result of the study on the electrically active deep level defects in Si films grown by molecular beam epitaxy. A deep level defect at Ec−0.58 eV is consistently obtained for samples grown on substrates with purposely contaminated surfaces. The observed defects are all located within 3000–5000 Å of the epilayer-substrate interface with concentrations in or below 1014 cm−3 range. Secondary ion mass spectroscopic study results indicate the correlation between the substrate surface residual carbon concentration and the observed defect concentration. These defects appear to be higher order defects rather than the single level defects, as evidenced by the asymmetry of the deep level transient spectra. For samples grown on the substrates cleaned using an established surface cleaning method, no deep level defects within the detection limit (∼1012 cm−3 in our case) are observed.
Auger depth profiling of Ag layer epitaxially grown on Pb(111) surface: A direct evidence of substrate diffusion
Authors: Chen C. H. , Sansalone F. J.
Published: July 2002

Auger depth profiling of an Ag layer grown epitaxially on a Pb(111) surface shows that constant diffusion of Pb occurs and a saturated ordered monolayer of Pb is finally formed on the Ag/vacuum interface. The surface concentration of Pb is found to increase exponentially as a function of time, after the sputtering ion beam was turned off. The time constant of this phenomenon (∼15 s–2.5 min) is dependent on the length of the ion sputtering time and the thermal annealing of the sample prior to the depth profiling. The diffusivity is estimated to be in the range of 2.1×10−12–2.1×10−13 cm2/s at room temperature.
dc and microwave characteristics of a high current double interface GaAs/InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistor
Authors: Henderson T. , Klem J. , Peng C. K. , Gedymin J. S. , Kopp W. , Morkoç H.
Published: July 2002

Extremely large current double interface GaAs/In0.15 Ga0.85 As/Al0.15 Ga0.85 As pseudomorphic modulation-doped field-effect transistors (MODFET’s) grown by molecular beam epitaxy were achieved. The 1-μm gate devices studied have peak current levels (430 mA/mm at 300 K and 483 mA/mm at 77 K) roughly one and a half to two times that found in single interface pseudomorphic MODFET’s. These devices also retain high transconductances over a broad range of gate voltage, peaking at 312 mS/mm at 300 K and 362 mS/mm at 77 K. Further, excellent microwave performance is also obtained with a maximum frequency of oscillation ( fmax) of 37 GHz and a current gain cut-off frequency of as high as 23 GHz at 300 K. An output power level of 14 dBm (1 dB gain compression) was obtained at 6 GHz for a 290-μm gate width. This double interface single quantum well MODFET may be of great importance in millimeter wave power amplifiers.
Epitaxial growth of HgTe by precracking metalorganic mercury and tellurium compounds
Authors: Wang C.-H. , Lu P.-Y. , Williams L. M.
Published: July 2002

Diethyltelluride and dimethylmercury metalorganic sources were precracked for the expitaxial growth of HgTe on CdTe substrates. This method allows metalorganic sources to be decomposed at one temperature while epitaxial growth occurs at a different temperature that is lower. Therefore, the HgTe epitaxial growth can be performed at low temperature and low Hg partial pressure. The growth rate was around 2 μm/h for the growth temperature range 210–270 °C. The HgTe films are single crystalline and have good morphology. Room-temperature carrier concentrations of 2×1017/cm3 and mobilities of 25 000 cm2/V s were obtained for epitaxial layers grown at 240 °C.
Photocurrent response times in undoped amorphous hydrogenated silicon
Authors: Parker M. A. , Schiff E. A.
Published: July 2002

The influence of electrical contacts upon coplanar electrode photocurrent response times has been explored in undoped amorphous hydrogenated silicon (a-Si:H) by measuring contact-induced photocurrents in a virtual ground plane. The results indicate that the relatively long photocurrent response times observed in undoped a-Si:H cannot be attributed to contacts. The response times are evidence that some deep-lying defects in a-Si:H are true electron photocarrier traps and not recombination centers. The discrepancy between long-time coplanar and time-of-flight transient photocurrent measurements upon undoped a-Si:H remains unresolved.
Effect of the silicon doping concentration on the recombination kinetics of D
X centers in Al0.35Ga0.65As
Authors: Caswell N. S. , Mooney P. M. , Wright S. L. , Solomon P. M.
Published: July 2002

The recombination (electron capture) kinetics of the ionized DX center in AlxGa1−xAs have been measured as a function of temperature and silicon doping concentration. It is shown that for x≂0.35, the silicon concentration dependence of the recombination kinetics is dominated by effects of the electron distribution in the conduction band, and is insensitive to changes in the trap characteristics. In a model kinetic calculation consistent with the data the trap is found to capture through a level 0.202 eV from the bottom of the conduction band with a width of 0.045 eV, independent of DX center concentration.
Electron spin resonance of [11̄1], [1̄11], and [111̄] oriented dangling orbital P
b0 defects at the (111) Si/SiO2 interface
Authors: Stesmans A.
Published: July 2002

The observation of (111) Si/SiO2 interface Pb0 defects (modeled as 0Si≡Si3) with dangling bonds positioned along [11̄1], [1̄11], and [111̄] from low-temperature (T≲30 K) electron spin resonance measurements is reported. This is connected with the particular structure (SiOx) of the attendant very near-Si interfacial transition region for the oxidation method invoked. Some instructive information as to the precise atomic modeling of the Si/SiO2 interface is inferred.
Low-temperature annealed contacts to very thin GaAs epilayers
Authors: Patrick W. , Mackie W. S. , Beaumont S. P. , Wilkinson C. D. W.
Published: July 2002

A low-temperature annealing process has been developed for the fabrication of low resistivity ohmic contacts to very thin (<0.2 μm) n+ GaAs epilayers. It is shown that by altering the relative amounts of Ni in the commonly used AuGe/Ni/Au contact system, the anneal temperature can be reduced from the standard 420–450 °C to 320 °C or less without deterioration in specific contact resistance. The specific contact resistances were evaluated using the modified transmission line model.
Linewidth characteristics of fiber-extended-cavity distributed-feedback lasers
Authors: Liou K.-Y. , Jhee Y. K. , Eisenstein G. , Tucker R. S. , Ku R. T. , Shen T. M. , Chakrabarti U. K. , Anthony P. J.
Published: July 2002

A 1.55-μm wavelength InGaAsP distributed feedback (DFB) laser with an antireflection coated facet has been coupled to a single-mode fiber with a reflective end to construct a compact narrow-linewidth source. The linewidth of the DFB laser is reduced by a factor of 1000 to 70 kHz at 1 mW output with a 5.5-cm fiber length. The fiber mirror to DFB laser coupling parameters required for narrow-linewidth operation are presented.
GaInAs-InP multiquantum well structures grown by metalorganic gas phase epitaxy with adducts
Authors: Scholz F. , Wiedemann P. , Benz K. W. , Tränkle G. , Lach E. , Forchel A. , Laube G. , Weidlein J.
Published: July 2002

We report the first successful growth of GaInAs-InP multiquantum well structures by metalorganic gas phase epitaxy with adducts in one single reactor. The properties of the two-dimensional electron gas in these samples were studied in detail by photoluminescence measurements and Shubnikov–de Haas experiments.
Hydrogenation of the ‘‘new oxygen donor’’ traps in silicon
Authors: Hölzlein K. , Pensl G. , Schulz M. , Johnson N. M.
Published: July 2002

Hydrogenation was performed at moderate temperatures (≤300 °C) on Czochralski-grown Si samples that contained high concentrations of the oxygen-related ‘‘new donor’’ (ND) traps. From deep level transient spectroscopy, a comparison of spectra from untreated reference and hydrogenated material reveals that two different types of defect states contribute to the continuous energy distribution of the ND traps. The experimental and theoretical results further establish the ‘‘SiOx interface’’ model for the ND defects.
Temperature-dependent pinning at the Al/n-GaAs(110) interface
Authors: Kendelewicz T. , Williams M. D. , Chin K. K. , McCants C. E. , List R. S. , Lindau I. , Spicer W. E.
Published: July 2002

It is shown that at the Al/n-GaAs(110) interface grown in ultrahigh vacuum at −80 °C the Fermi level remains unpinned at least up to a 3 monolayer coverage. In contrast, at room temperature the pinning near midgap is established after a deposition of approximately 1 monolayer of Al. The low-temperature behavior is correlated with the growth of a more uniform overlayer which inhibits cluster and defect formation. This result provides a critical test of models of Schottky barrier formation.
High-energy stimulated emission in GaAs quantum wells coupled with (Si2)x(GaAs)1−x barriers (ℏω≳E
L, E
X)
Authors: Hsieh K. C. , Kaliski R. W. , Holonyak N. , Burnham R. D. , Thornton R. L. , Paoli T. L.
Published: July 2002

Data are presented showing that a small GaAs quantum well (Lz≊80 Å), the middle third of which is replaced with a (Si2)x(GaAs)1−x ‘‘barrier’’ (27 Å, x≳0.2), is capable of stimulated emission (77 K) at energies ℏω≳EL(Si+GaAs), EX(Si+GaAs).
I
n s
i
t
u investigation of the nucleation of microcrystalline Si
Authors: Collins R. W.
Published: July 2002

I n situ ellipsometry experiments have been used to probe the structural changes that occur in the initial stages of the growth of microcrystalline silicon ( μc-Si) on single-crystal Si substrates. The initial nucleation of μc-Si appears to occur at well-dispersed sites and ∼100 Å of material with significantly different optical properties than the bulk is buried at the film/substrate interface. The different optical structure of this interface layer is attributed to voids which are trapped when crystalline nuclei merge. These results are contrasted with recent data for hydrogenated amorphous silicon which show that nuclei converge after about 50 Å, leaving material with bulklike optical properties at the substrate interface.
Comparison of buried oxide in silicon by oxygen implantation made by wafer and beam scanning
Authors: Mogro-Campero A. , Love R. P. , Lewis N. , Hall E. L. , McConnell M. D.
Published: July 2002

Buried oxide in silicon was formed by high dose oxygen implantation using either slow mechanical wafer scanning or the usual rapid beam scanning. Transmission electron microscopy and Auger depth profiling were used to characterize the samples after high-temperature annealing: 1150 °C for 2 h, followed by 1210 °C for 6 h. Oxygen-denuded zones of single crystal silicon are formed for both types of samples in the upper region of the top silicon layer (for the wafer-scanned samples, an oxygen-denuded zone had not formed after the usual 1150 °C anneal for 2 h). The dislocation density in the top silicon layer was much lower (<107 cm−2) for wafer-scanned samples than for beam-scanned samples (2×109 cm−2). The density of oxide precipitates in the top silicon layer and of silicon ‘‘islands’’ within the buried oxide was greater for wafer-scanned samples. These microstructural differences may produce differences in electrical properties.
Chloride vapor phase epitaxial growth of high-purity GaInP
Authors: Hoshino Masataka , Kodama Kunihiko , Kitahara Kuninori , Ozeki Masashi
Published: July 2002

High-purity GaInP alloy was grown by chloride vapor phase epitaxy (Ga/In/PCl3/H2 system) with two separate metal source regions. The alloy composition could be precisely controlled by using separate regions for Ga and In metals. From the photoluminescence and Hall effect analysis, epitaxial layers lattice matched to GaAs substrates showed high emission efficiency, the full width at half-maximum of the free-exciton luminescence was as narrow as 7.4 meV at 77 K (3.8 meV at 4.2 K), and the low impurity concentration was below 1.5×1015 cm−3.
Tunable single pass gain in titanium-activated lithium germanium oxide
Authors: Loiacono G. M. , Shone M. F. , Mizell G. , Powell Richard C. , Quarles G. J. , Elouadi B.
Published: July 2002

Laser-pumped single pass gain measurements were made on crystals of titanium-activated lithium germanium oxide between about 388 and 524 nm. Gain was observed throughout this spectral region with a peak cross section of about 1.7×10−19 cm2 near 450 nm.
Si film as an annealing cap for Si-implanted GaAs
Authors: Shim Tae Earn , Itoh Tadatsugu , Yamamoto Yasuhiro , Suzuki Setsu
Published: July 2002

A Si film formed by vacuum deposition as an annealing cap for a Si-implanted GaAs substrate has been studied. GaAs substrates implanted with 3×1013 Si ions/cm2 at 100 keV were furnace annealed with Si caps at temperatures between 750 and 900 °C for 15 min. The existence of Ga and/or As atoms in the Si cap film was not detected in the Rutherford backscattering spectra of the Si films after annealing. The differential Hall measurement showed that the carrier concentration profile distributed within the ion implanted region. The Si cap film has feasible characteristics for annealing of Si-implanted GaAs.
Using focused ion beam damage patterns to photoelectrochemically etch features in III-V materials
Authors: Cummings K. D. , Harriott L. R. , Chi G. C. , Ostermayer F. W.
Published: July 2002

A method of patterning n-type GaAs, InP, InGaAs, and InGaAsP by photoelectrochemical (PEC) etching in conjunction with a submicron focused ion beam (FIB) at low dose is described. The ion beam is used to produce damage in a desired pattern in the material. Subsequent PEC etching of the material reveals the ion induced features in relief. The procedure is highly sensitive, requiring a dose of only 5×109 ions/cm2 for the differential etch to become apparent. The sensitivity allows rapid pattern generation in our FIB system.
Oxygen precipitation in antimony-doped silicon wafers
Authors: d’Aragona F. Secco , Fejes P. L.
Published: July 2002

Measurements of oxygen concentration as well as preferential etching of lightly and medium Sb-doped wafers show that for high-temperature (1050 °C) anneals the oxygen precipitation is inversely dependent on the dopant concentration, while it is independent of the dopant concentration for low-temperature (650 °C) anneals. This is interpreted on the basis of a heterogeneous versus homogeneous precipitation mechanism.
All-optical power limiting of CO2 laser pulses using cascaded optical bistable elements
Authors: Walker A. C. , Kar A. K. , Ji Wei , Keller U. , Smith S. D.
Published: July 2002

We report the first all-optical power limiter based on cascaded InSb étalons. The power limiting effect is due to a dispersive nonlinearity in InSb at room temperature as a result of generation of free carriers through two-photon absorption of 10 μm radiation. The efficiency and dynamic range of this all-optical circuit are discussed.
Silver ion-exchanged, buried, glass optical waveguides with symmetric index profile
Authors: Lagu R. K. , Ramaswamy R. V.
Published: July 2002

Symmetrical buried waveguides with fiberlike refractive index profiles using Ag+-Na+ exchange have been realized in soda-lime-silicate glass substrates. A simple scanning electron microscope technique to determine the silver ion (refractive index) profile is also reported.
Chemical etching for the evaluation of hydrogenated amorphous silicon films
Authors: Chu T. L. , Chu Shirley S.
Published: July 2002

Chemical etching using a 1:5:40 HF-HNO3-CH3COOH solution has been used for the evaluation of hydrogenated amorphous silicon (a-Si:H) films. The dissolution rate of a-Si:H films and the structural features brought out by etching have revealed significant differences in the properties of a-Si:H films deposited in hydrogen and helium atmospheres. Unintentionally contaminated a-Si:H films have also been found to show considerably higher dissolution rate than intrinsic films, and the dissolution rate measurements may be used to optimize the deposition conditions.