bluuebunny/crossref_metadata_2025_split huggingface dataset:
MBE Alloy Clustering Kinetics - A Stochastic Model Study
Authors: Venkatasubramanian R. , Khoie Rahim 
Published: March 2011

ABSTRACTA theoretical study of alloy clustering in an hypothetical diamond cubic alloy, 00.560.5 in which thermodynamics favors phase separation is performed based on a master equation approach. The a-b atom pair interaction is assumed weaker and repulsive (-0.25 eV). It is shown that below 375°C, due to negligible surface migration, there is no clustering of the alloy, but, the surface roughness is very large. In the intermediate temperature range of 300 – 625°C, with increasing temperature, surface migration increases, resulting in more clustering and decreased surface roughness. Above 500°C, due to very high surface migration, complete phase separation and smooth surface result. It is shown that the conventional MBE growth techniques are incompatible with the growth of good quality heterostructures which consist of alloys having large poistive enthalpy of mixing.
Low Temperature In-Situ Processing for Si-MBE
Authors: Ramm Juergen , Beck Eugen , Zueger Albert 
Published: March 2011

ABSTRACTA basic process sequence for low temperature in-situ processing of metal-insulator-semiconductor (MIS) structures in an ultra-high vacuum (UHV) multichamber system is presented. It includes conditioning of the process chamber by plasma heating, in-situ cleaning of silicon wafers, and conventional silicon molecular beam epitaxy (Si-MBE). The in-situ cleaning is achieved by an argon/hydrogen plasma treatment of the wafer surface at temperatures well below 400° C. The native oxide as well as carbon compounds are removed from the silicon surface. Etch rates for SiO2 are determined for various plasma parameters. Without additional cleaning procedures, silicon films are deposited in another process step using a quadrupole mass spectrometer controlled electron beam evaporator. Epitaxial films are obtained for substrate temperatures as low as 500°C on (100) and 600°C on (111) silicon for deposition rates of 0.05 nm/s.
Structural Characterization of Short-Period SimGEn Superlattices by Transmission Electron Microscopy and X-Ray Diffraction
Authors: Jäger W. , Leifer K. , Ehrhart P. , Kasper E. , Kibbel H. 
Published: March 2011

ABSTRACTHigh resolution and analytical transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize short-period strained-layer Sim-Gen superlattices ( m monolayers Si, n monolayers Ge, total number of periods N≤ 145, total thickness ≃ 200 nm). The superlattices were grown by low-temperature molecular beam epitaxy (T = 300–400°C) on different SiGe alloy buffer layers on Si (100)substrates. The combination of these two methods shows that detailed informations can be obtained about superlattice periodicity, interface roughness, strain, and average composition.
Very Thick Coherently Strained GexSi1−x Layers Grown in a Narrow Temperature Window
Authors: Chern C. H. , Wang K. L. , Bai G. , Nicolet M. -A. 
Published: March 2011

ABSTRACTStrain relaxation of GexSi1−x layers is studied as a function of growth temperature. Extremely thick coherently strained layers whose thicknesses exceed more than fifty times of the critical thicknesses predicted by Matthews and Blakeslee's model were successfully grown by MBE. There exits a narrow temperature window from 310 °C to 350 °C for growing this kind of high quality thick strained layers. Below this temperature window, the layers are poor in quality as indicated from RHEED patterns. Above this window, the strain of the layers relaxes very fast accompanied with a high density of misfit dislocations as the growth temperature increases. Moreover, for samples grown in this temperature window, the strain relaxation shows a dependence of the residual gas pressure, which has never been reported before.
Strain-Free GexSi1−x Layers with Low Threading Dislocation Densities Grown on Si Substrates
Authors: Fitzgerald E. A. , Xie Y. H. , Green M. L. , Brasen D. , Kortan A. R. , Mii Y. J. , Michel J. , Weir B. E. , Feldman L. C. , Kuo J. M. 
Published: March 2011

ABSTRACTWe have grown linearly compositionally graded GexSi1−x structures at high temperatures (700–900°C) on Si substrates to form a surface which resembles a GexSi1−x substrate. We have obtained completely relaxed structures with x≤0.50 and threading dislocation densities in the 105cm−2 - 106cm−2 range. Because of the very low threading dislocation densities, the structures appear dislocation free in conventional transmission electron microscopy (TEM) cross-section and plan view. Employing the electron beam induced current technique (EBIC), we were able to consistently measure these low threading dislocation densities. A direct comparison of two x=0.35 films, one graded in Ge content and one uniform in Ge content, shows that compositional grading decreases the dislocation density by a factor of 100–1000. These. higher quality graded buffers have been used as templates for the subsequent growth of InGaP light emitting diodes (LED) and GexSi1−x/Si two-dimensional electron gas (2DEG) structures. Room temperature operation of orange-red LEDs were obtained at current densities of =600A/cm, and mobilities as high as 96,000 cm2/V-s were achieved at 4.2K in the 2DEG structures.
Characterization of Si1−xGex/Si Heterostructures Using Optically-Detected Magnetic Resonance
Authors: Kennedy T. A. , Glaser E. R. , Trombetta J. M. , Wang K. L. , Chern C. H. , Arbet-Engels V. 
Published: March 2011

ABSTRACTSi1−xGex/Si heterostructures with varying layer-thicknesses have been characterized using photoluminescence and magnetic resonance detected on photoluminescence. Three of the four samples studied exhibit sharp photoluminescence bands at different energies. For a 120 Å Si/40 Å Si1−xGex heterostructure, magnetic resonance of an electron in the Si and of a hole in the Sil. xGex layers were observed. These results indicate cross-interface, or Type II, excitonic recombination. Further, anisotropie magnetic resonance spectra indicate the presence of dangling-bonds defects in the heterostructures.
Growth of Si1−xGex, Strained Layers Using Atmospheric-Pressure CVD
Authors: Namavar F. , Manke J. M. , Kvam E. P. , Sanfacon M. M. , Perry C. H. , Kalkhoran N. M. 
Published: March 2011

ABSTRACTThe objective of this paper is to demonstrate the epitaxial growth of SiGe strained layers using atmospheric-pressure chemical vapor deposition (APCVD). We have grown SiGe layers with various thicknesses and Ge concentrations at temperatures ranging from 800–1000°C. The samples were studied using a variety of methods, including transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD) and Raman spectroscopy (RS). Both HRXRD and RS results indicate that samples with about 10% Ge and a thickness of about 1000 Å are almost fully strained. TEM analyses of these samples indicate a film defect density less than 105/cm2. SIMS results indicate that the oxygen concentration in the epitaxial layers is lower than that found in CZ substrates.Our analyses also indicate that as-grown epitaxial Ge layers several microns thick have a defect density less than 107/cm2. The relatively low defect density in both SiGe and Ge layers grown on Si has been attributed to far higher dislocation glide velocity at the relatively elevated growth temperatures employed in CVD and to very good growth cleanliness.
Fabrication of Bond and Etch Back Silicon on Insulator Using SiGe-MBE and Selective Etching Techniques
Authors: Godbey D. , Palkuti L. , Leonov P. , Krist A. , Wang J. , Twigg M. , Hughes H. , Hobart K. 
Published: March 2011

ABSTRACTUndoped thin layer silicon on insulator has been fabricated using wafer bonding and selective etching techniques using an MBE grown Si0.7Ge0.3 layer as an etch stop. Defect free, undoped 200–350 nm silicon layers are routinely fabricated using this procedure. A new selective silicon-germanium etch has been developed that significantly improves the ease of fabrication of the BESOI material.
Si/Ge Superlattices for Optical Applications: Possibilities, Problems, and Prospects
Authors: Zachai R. 
Published: March 2011

ABSTRACTSi/Ge superlattices offer the possibility to study the influence of various effects on the electronic band structure. Strain, quantization, zone folding, and wave vector mixing effects are expected to create novel optical properties in these Si-based multilayer structures. New optical transitions were observed by various experimental methods like photoluminescence and modulation spectro-scopy. In this article we will review the present state of knowledge of the optical properties of short period strained layer Si/Ge superlattices and discuss the problems and prospects for optical applications.
Well-Resolved Band-Edge Photoluminescence from Strained Si1–xGex Layers Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Sturm J. C. , Schwartz P. V. , Manoharan H. , Mi Q. , Lenchyshyn L. C. , Thewalt M. L. W. , Rowell N. L. , Noël J. -P. , Houghton D. C. 
Published: March 2011

ABSTRACTWell resolved band-edge luminescence of excitons in silicon-germanium alloy strained layers, quantum wells, and superlattices has been observed in films grown by Rapid Thermal Chemical Vapor Deposition. The signal is due to bound excitons at low temperatures and free excitons at higher temperatures, and has a strong no-phonon signal which is caused by alloy scattering. Bandgaps inferred from photoluminescence agree well with those measured by absorption spectroscopy, inferring that a no-phonon process dominates the band-edge absorption.
GexSi1−x Waveguides Grown by Rapid Thermal Processing Chemical Vator Deposition
Authors: Jung K. H. , Mayer R. A. , Hsieh T. Y. , Campbell J. C. , Kwong D. L. 
Published: March 2011

ABSTRACTWe report the growth and characterization of GexSi1−x films for optical waveguiding. GexSi1−x/Si waveguides were grown by rapid thermal processing chemical vapor deposition. An average attenuation of 3.3 dB/cm was achieved for a 1 μm thick Ge0.04Si0.96 layer patterned into rib waveguides 2000 Å deep with widths of 5 μm. Directional couplers were also fabricated. Average coupling efficiencies of 85% were achieved for 1.5 μm interwaveguide separation.
Modulation Doped Si/SiGe Heterostructures
Authors: Schäffler F. , AG Daimler-Benz 
Published: March 2011

ABSTRACTAn overview of SiGe-based, modulation doped heterostructures is given. Strained layer handling, a prerequisite for realizing both n- and p-type devices, Is treated in terms of band engineering. The main emphasis is put on recent results obtained with high-electron mobility n-type Si/SiGe structures. Hall, Shubnikov-deHaas, and cyclotron resonance measurements are presented. The thermal stability of the heterostructures and the dopant distribution are treated with respect to device applications. Room temperature and 77K dc-measurements on very recent modulation doped field effect transistor (MODFET) implementations using implanted source/drain contacts are discussed. Device concepts with n- and p-type MODFETs combined in a superior complementary layout (CMODFET) are proposed.
Simulations of Ge+ and C+ Implantations to form SiGe/Si HBT and Characterization of SiGe and SiGeC Diodes
Authors: Gupta Ashawant , Waters Jeffrey W. , Cook Carmen , Yang Cary Y. , Fukamia Akira , Shoji Ken-Ichi , Nagano Takahiro 
Published: March 2011

ABSTRACTSimulations of Ge+ and C+ implantations in Si were performed to study bandgap grading in the SiGeC/Si heterojunction bipolar transistor (HBT). Although no bandgap discontinuity was observed at the base-emitter junction, it was found that a wide-bandgap emitter and a narrow-bandgap base with proper bandgap grading were obtainable with implantation. Electrical characterization of SiGe and SiGeC diodes formed by Ge+ and C+ implantations in Si was carried out. Current-voltage (I-V) measurement results confirm that carbon doping improves the crystalline quality of the germanium-implanted layer. On the other hand, capacitance-voltage (C-V) measurements indicate that both germanium and carbon implantations result in considerable dopant deactivation.
Fabrication of CoSi2 Gate Si Permeable Base Transistor Using Si-MBE
Authors: Nakagawa K. , Ohshima T. , Nakamura N. , Miyao M. 
Published: March 2011

ABSTRACTA permeable base transistor (PBT) with submicron grating is fabricated using a Si/COSi2/Si double heterostructure. The high-quality Si/COSi2/Si double heterostructure is formed by two-step moleculer beam epitaxy (i.e. low-temperature MBE and successive high-temperature MBE). The Si and COSi2 interfaces observed by a cross-sectional transmission electron microscope are smooth and atomically abrupt. A new method of patterning COSi2 films is developed. This method uses the difference in surface energies between different crystal orientations. The mutual conductance and cutoff frequency of the PBT are 50 mS/mm and 6 GHz, respectively. These agree with the results of computer simulations. In addition, computer simulations indicate a potential of Si PBT for high frequency application, and a cutoff frequency as high as 90 GHz can be obtained by optimizing the device structure.
Epitaxial Growth of Silicon on CoSi2 (001)/Si (001)
Authors: Xiao Q. F. , Jimenez J. R. , Schowalter L. J. , Luo L. , Mitchell T. E. , Gibson W. M. 
Published: March 2011

ABSTRACTEpitaxial Si layers have been grown under a variety of growth conditions on CoSi2 (001) by molecular beam epitaxy (MBE). The structural properties of the Si overgrowth were studied by in-situ Reflection High Energy Electron Diffraction (RHEED), as well as ex-situ MeV4He+ ion channeling and High Resolution Transmission Electron Microscopy (HRTEM). Strong influences of the CoSi2 surface reconstruction on the Si overgrowth have been observed. RHEED studies show islanding growth of Si on the CoSi2 (001) (3/√2 × √2)R45 reconstructed surface, but smooth growth of Si on the CoSi2 (001) {√2 × √2)R45 reconstructed surface, under the same growth conditions. The growth of Si on thin layers of CoSi2 (2nm-6nm) with (√2 × √2)R45 reconstructed surface at 460°C results in high crystalline quality for the Si top layer, as indicated by good channeling minimum yield (Xmin < 6%), but cross-sectional TEM shows that the CoSi2 layers are discontinuous. We also report preliminary results on Si grown on a 2 × 2 reconstructed CoSi2 (001) surface.
RTP-CVD of Si Materials and Devices for ULSI Applications
Authors: Kwong D. L. , Hsieh T. Y. , Jung K. H. 
Published: March 2011

ABSTRACTRapid thermal processing chemical vapor deposition (RTP-CVD) has received considerable attention because of its ability to reduce many of the processing problems associated with thermal exposure in conventional chemical vapor deposition, while still retaining the ability to grow high quality epitaxial layers. In this paper, the principles of the RTP-CVD system are described, followed by results of experiments on in-situ cleaning, undoped Si epitaxy and in-situ doped Si epitaxy, and selective Si deposition using oxide masks. Our results show that RTP-CVD is capable of growing high quality, epitaxial layers with sharp, dopant transition profiles. Selective deposition was achieved without the use of HC1. We also studied the growth and characterization of GexSi1−x films for optical waveguiding.
The Synthesis and Stability of Si1−yQy Alloys and Strained Layer Superlattices
Authors: Iyer S. S. , Eberl K. , Goorsky M. S. , Legoues F. K. , Cardone F. , Ek B. A. 
Published: March 2011

ABSTRACTWe have synthesized Si1−yQy layers and strained layer superlattices on Si (100) with C concentrations of up to a few percent using Solid Source Molecular Beam Epitaxy. The presence of C even in small quantities is known to disrupt the epitaxy of Si. We show that under conditions of high Si flux for a given C/Si flux ratio, defect-free epitaxy results. However, exceeding a critical C/Si flux ratio leads to disruption of epitaxy, initially via twinning and subsequently by amorphous growth. Growth temperature also plays a significant role in preventing twinning and islanding. Low growth temperature also suppresses the precipitation of β-SiC and leads to the formation of pseudomorphic Si1−yQy random alloys. The layers are characterized by X-ray diffraction, Secondary Ion Mass spectroscopy, and Transmission Electron Microscopy. We have also studied the thermal stability of strained layer superlattices and find that the layers are stable to about 800°C (for y = 0.003). Between 800°C and 1000°C, the layers relax by interdiffusion. Above 1000°C, silicon carbide precipitation occurs and the carbide layers nucleate and grow at high C content regions of the film.
Electronic Structures for (Si)m (GaP)n Superlattices
Authors: Lin-Chung P. J. 
Published: March 2011

ABSTRACTThis paper reports on a tight-binding calculation of the band structures of the Si-GaP superlattice (SL) systems with emphasis on the results of the band gap properties. This calculation finds that the SLs grown onto the [110] or [111] oriented substrate do not produce direct gap materials. On the other hand, some of the [001] oriented SLs become direct gap materials when either an interface (IF) state is created at the P and Si IF, or a confined state in the Si occurs with only Ga and Si atoms forming all the IF.
Electrical and Optical Properties of Si and Si1−xGex, Alloy Grown by the Ultra-High Vacuum Vapour Phase Epitaxy Method
Authors: Leong W. Y. , Robbing D. J. , Glasper J. L. , Canham L. T. , Carline R. , Calcott P. 
Published: March 2011

ABSTRACTEpitaxial growth and p-type doping in Si and Si1−xGex alloy by the ultra-high vacuum vapour phase epitaxy (UHV-VPE) method using SiH4/GeH4/B2H/H2 mixture is reported. Growth temperatures as low as 610°C were studied for Ge contents between x=0 to 0.25. Secondary Ion Mass Spectroscopy (SIMS) data of boron dopant profiles in si and Si1−xGex structures are presented. Strong luminescence attributed to the strained Si1−xGex alloy is obtained. The bandgap in the alloy layer obtained from our luminescence data is compared with published data. Unambiguous electroluminescence from a Si1−xGex multiple quantum well p-n structure grown by UHV-VPE, supported by the photoluminescence and photoconductivity measurement, is reported for the first time.
An Overview of Doping Strategies in Si:MBE
Authors: Kubiak Richard , Parry Carl 
Published: March 2011

ABSTRACTThis paper reviews the diverse methods used to achieve doping during MBE of Si and SiGe, and the incorporation processes involved. The optimum choice of dopant and methodology depends on the most appropriate growth conditions for a given structure. At growth temperatures exceeding 750°C, Potential Enhanced n-type doping of coevaporated Sb is capable of achieving high resolution structures, at doping levels up to mid-1019 cm−3. At lower temperatures, such as those most suited to SiGe growth, Sb-doping becomes a formidable challenge, due to the high accumulated equilibrium coverages required. Low energy ion implantation appears to be the favoured route for good control, p-type B-doping can readily be achieved by coevaporation of compounds or, to avoid oxygen incorporation at low temperatures, the element. A “designer” chart for B-doping of Si is presented.
An Investigation of Boron Incorporation in SiGe MBE
Authors: Parry C. P. , Kubiak R. A. , Newstead S. M. , Whall T. E. , Parker E. H. C. 
Published: March 2011

ABSTRACTThe performance of many Si/SiGe devices, particularly those involving modulation doped quantum wells, will depend on the quality of the matrix and doping interfaces involved. These may be adversely affected by profile smearing of Ge and the dopant. A study of boron incorporation in SiGe, as a function of substrate temperature and Ge fraction, shows a marked difference in profile smearing for boron in Si and in the SiGe alloy. This is shown to be associated with a reduction in the temperature for transition from equilibrium to kinetically limited accumulation in the alloy.
In-Situ TEM Observation of Electromigration Damage by Surface or Interface Diffusion in Al and Al Alloy Films
Authors: Chang C. Y. , Vook R. W. 
Published: March 2011

ABSTRACTIn-situ transmission electron microscope (TEM) electromigration damage (EMD) tests were performed on pure Al films which were thermally evaporated onto oxidized silicon wafers under different deposition conditions. Three different aluminum alloy films, Al-2wt%Cu, Al-8wt%Cu, and Al-2wt%Cu-lwt%Si were also examined. TEM images were recorded photographically and by a video camcorder. The sample stripes were stressed by a high DC current density (≈1.5 MA/cm2). A linear temperature ramp (5°C/min) was supplied by an external, computer controlled heater. The morphology of EMD-induced voids was found to be strongly dependent on microstructure. In small grain size Al stripes, EMD occurred by the formation of void “fingers” which propagated in an almost random manner. In large grain size Al and Al alloy stripes, the EMD-elongated voids propagated approximately parallel to each other and along the field direction. They were preceded with clearly identifiable local thinning. The thinned regions often had crystallographic edges. Contrary to the commonly held belief that EMD occurs only by a grain boundary diffusion mechanism, the present study clearly shows that surface or interface diffusion was the dominant, latter stage EMD failure mode in large grain size films.
A Statistical Characterization of Electromigration-Induced Open Failures in 2-Level Metal Structures
Authors: Kahn H. , Thompson C. V. 
Published: March 2011

ABSTRACTA new electromigration test structure has been designed and fabricated which allows statistical characterization of current-induced open failures at vias, under varying current flow geometries. Results for a 2-level Al-Cu metallization system with W-filled 1.0 μm vias reveal no differences in via lifetimes for parallel, anti-parallel, or perpendicular current flows. However, a factor of 7 improvement in the total average via resistance produces an order of magnitude improvement in lifetimes. Line reliability remains superior to the reliability of the vias, indicating that the vias are the “weak links” in the system.A model for evaluating temperature and current density effects which incorporates the atomic flux equation has been developed and used to make reliability predictions for extrapolations to operating conditions. The model suggests that the median time to failure of a 2-level ietal structure with an average via resistance of two ohms will be 2.7×1017 hours for operating conditions of 2×105 A/cm2 and 125°C.
The Effect of a Passivation Over-Layer on Tile Mechanisms of Stress Relaxation in Continuous Films and Narrow Lines of Aluminum
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu 
Published: March 2011

ABSTRACTStress relaxation was studied in bare and nitride-covered continuous films and narrow lines of aluminum. The rate of relaxation in unpassivated metallizations is shown to be consistent with a dislocation-controlled mechanism. Relaxation in passivated lines appears to depend on grain boundary diffusion-controlled void growth. In passivated continuous films, two rate-controlling mechanisms appear to operate in sequence.