bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Standing Wave and High Resolution Diffraction Study of Si/Ge Superlattices
Authors: Lagomarsino S. , Castrucci P. , Calicchia P. , Cedola A. , Kazimirov A. 
Published: April 2011

ABSTRACTIn modern technology more and more attention is given to epitaxial superlattices. III/V, and more recently Si/Ge superlattices are widely studied because of their applications in integrated optoelectronics. Since the physical properties are strongly dependent on structural characteristics, it is evident that accurate characterization methods are required in order to improve their quality and obtain optimal behavior. X-ray high resolution diffraction is extensively and successfully used to this purpose. In general diffracted intensity is measured close to strong substrate reflections where satellite peaks from superlattice take place. If the crystalline quality, mainly concerning thickness layer uniformity and interface abruptness is good, several orders of diffraction from the superlattice are visible, and fitting based on kinematical or dynamical diffraction can provide information about many structural parameters of the superlattice. However from diffracted intensity the information about the phase of the structure factor is lost. It is well known that the X-ray Standing Wave (XSW) technique can provide direct information about the phase [1]. In this paper we present measurements and calculations relative to the extension of the XSW method to the study of MBE-grown Si/Ge superlattices. The novelty consists in using the superlattice satellite peaks close to a strong reflection from the substrate to form the standing wave field which in turn excites the atoms whose fluorescence is measured. These satellite peaks correspond to high-order diffraction for the superlattice periodicity.
Thermal Mismatch Strain Relaxation Mechanisms and Hysteresis in Pb1−SnxSe-on-CaF2/Si Structures
Authors: Zogg H. , Müller P. , Fach A. , John J. , Paglino C. , Teodoropol S. 
Published: April 2011

ABSTRACTThe strain induced by the thermal mismatch in Pbl−xSnxSe and other IV–VI compound layers on Si(111)-substrates relaxes by glide of dislocations in the main <110> {001}-glide system. The glide planes are arranged with 3-fold symmetry and inclined to the (111)-surface. Despite a high threading dislocation density (> 107 cm−2) in these heavily lattice mismatched structures, the misfit dislocations move easily even at cryogenic temperatures and after many temperature cycles between RT and 77K. The cumulative plastic deformation after these cycles is up to 500%! Despite a pronounced deformation hardening occurs, the structural quality of the layer is only slightly adversely affected as regards additional threading dislocations created. The interaction probability between these dislocations is estimated to be about 10−5.
Strained-Si Mos Field-Effect Transistors: Building Devices on Relaxed -SI1−xGEx Buffer Layers
Authors: Welser Jeffrey J. 
Published: April 2011

ABSTRACTThe experimental application of strained-Si / relaxed-Si1−xGex heterostructures to n-MOSFETs is discussed, focusing on the enhanced mobility provided by the strain. This paper provides an overview of the theoretically-predicted electronic properties of these heterostructures, as well as their growth. Several practical issues which arise in MOS applications are covered, including the effect of the relaxed-Si1−xGex, buffer layers on diode performance, and the observation of self-heating effects in the output characteristics of the MOS transistors.
Capacitance-Voltage Characteristics of p-Si/SiGeC Mos Capacitors
Authors: Rim Kern , Takagi S. , Welser J. J. , Hoyt J. L. , Gibbons J. F. 
Published: April 2011

ABSTRACTThe first measurements of Si/SiGeC valence band offsets have been performed using heterostructure p-type MOS capacitors. Single crystalline epitaxial layers of SiGeC and Si were grown by the rapid thermal CVD technique, limited reaction processing, using ethylene as the carbon source. Films with carbon contents of up to ∼1.2% were studied. X-ray diffraction analysis shows the strain compensating effect of carbon in SiGeC. Substitutionality of carbon in SiGe was also confirmed by Fourier transform infrared spectroscopy measurements. MOS capacitors were fabricated by thermal oxidation (750°C) of the epitaxial Si cap on top of the SiGeC layer. Quasi-static and high frequency capacitance-voltage measurements show wellbehaved characteristics for the samples with carbon contents up to approximately 1%. Onedimensional Poisson simulations of the C-V curves were used to extract the valence band offset between Si and SiGeC. For a fixed germanium fraction, the offset decreases with increasing carbon content. However, for a given lattice mismatch, the offset for Si/Si1−x−yGexCy is larger than the measured value for Si/Si1−zGez.
How Surface Roughening and Dislocation Formation Mutually Influence Each Other During Heteroepitaxial Growth
Authors: Christiansen Silke , Albrecht M. , Michler H. , Strunk H.P. 
Published: April 2011

ABSTRACTUsing finite elements we quantitatively calculate the inhomogeneous strain distribution associated with the so called crosshatch pattern. This pattern is a twodimensional, pseudoregular surface undulation that generally arises as an intermediate stage of heteroepitaxial growth of low misfitting semiconductor layers. This stage is characterized by an interplay of elastic and plastic relaxation processes. The calculations yield (i) the elastic strain energy density distribution and corresponding degree of elastic relaxation and (ii) the shear stress distribution in the glide system, in which misfit dislocations form. As a main result shear stresses due to the crosshatch pattern within the substrate are identified that cause misfit dislocations to multiply in the substrate.
Implant Enhanced Diffusion of Boron in Silicon Germanium
Authors: Fang Wingra T. C. , Griffin Peter B. , Plummer James D. 
Published: April 2011

ABSTRACTIn this work, the inert and implant enhanced diffusion of boron in silicon germanium (SiGe) was studied by means of a boron box-shaped profile grown inside Si0.905 Ge0.095 or Si0.785Ge0.22 layers. The SiGe layers were capped with silicon for stability and to ensure no lattice damage in the SiGe layers during the implant. Assuming boron moves by interstitial-mediated diffusion in SiGe, the results suggest that decreases in the mobile boron diffusivity, not decreases in interstitial concentration, cause much of the decrease in average boron diffusivity with increasing Ge fraction. Implant enhancements decreased as the germanium percentages increased, possibly indicating higher interstitial concentrations in SiGe than in Si.
Luminescence in Si/Strained Si1−xGex Heterostructures
Authors: Sturm J.C. , Amour A. St. , Lacroix Y. , Thewalt M.L.W. 
Published: April 2011

ABSTRACTThis paper quickly reviews the structure of band-edge luminescence in Si/strained Si1−xGex heterostructures, and then focusses on two recent developments -- the origin of “deep” sub-bandgap luminescence which is sometimes observed in structures grown by Molecular Beam Epitaxy (MBE) and the understanding of the temperature dependence of the band-edge luminescence (up to room temperature). Strong evidence will be presented that the origin of the deep luminescence is radiation damage, and that generated defects are segregated or trapped in the SilxGex layers. The modelling of the temperature dependence by twocarrier numerical simulation is presented for the first time. The work and experimental data show convincingly that the strength of the luminescence at high temperature is controlled by recombination at the top silicon surface, which in turn can be controlled by surface passivation. At high pump powers and low temperatures, Auger recombination reduces the lifetime in the Si1−xGex layers, and leads to a luminescence vs. temperature which is flat up to 250 K and which is reduced only by a factor of three at room temperature.
Heavy Phosphorus Doping in Molecular Beam Epitaxial Grown Silicon and Silicon/Germanium with a Gap Decomposition Source
Authors: Lippert G. , Osten H. J. , KrÜger D. 
Published: April 2011

ABSTRACTDonor-doping in silicon molecular beam epitaxy (MBE) is still an open problem, due to the low solid solubility and the strong segregation behavior (Sb, As) or to the high vapor pressure of the doping elements (P, As). Based on its high solubility elemental P2 would be the best candidate for heavy n-type doping. A new developed phosphorus source, based on the decomposition of solid GaP with a simultaneously mass separation of the parasitic Ga atoms has been applied. Homogenous P-doping higher than 1019 cm3 in Si and strained SiGe has been achieved. No surface accumulation of phosphorus was observed. The parasitic Ga incorporation is about three orders of magnitude below the P concentration. In this paper we will demonstrate the use of such cell to incorporate electrical active phosphorus during MBE growth. The incorporation probabilities into Si and strained SiGe will be compared. The dependence of segregation-/diffusion processes of phosphorus on growth temperature during the MBE will be shown. SIMS investigations on undoped Si layers reveal no P or Ga “memory effect” of the UHV equipment.
Challenges for Sige-Heterotechnology
Authors: Presting H. 
Published: April 2011

ABSTRACTHeterostructure devices composed of silicon, silicon-germanium or germanium layers have substantially broadened the spectrum of the well established Si microelectronics. The achieved results for devices, such as the SiGe base heterobipolar transistor (SiGe HBT), the n-. and p-channel SiGe modulation doped field effect transistor (SiGe MODFET) and optoelectronic devices (SiGe LED and photodiode) point to the outstanding potential of this novel heterosystem. Today the SiGe HBT is the world fastest Si based transistor with a wide application area from conventional microelectronic applications to microwave power generation in a frequency regime where up to now only III-V semiconductor devices have prevailed. In addition novel SiGe optoelectronic devices, such as SiGe LED and Si/Ge photodetector in the near infrared spectral region (1.3µ) could pave the way for Si based optical interconnect devices monolithically integrated on a Si IC chip (chip to chip coupling). Growth aspects, strain effects, band alignment and novel bandstructure effects in this material system will be reviewed, its effect on the device performance will be discussed.
Structural Properties of InAs/AlSb Superlattices
Authors: Jenichen B. , Neuroth H. , Brar B. , Kroemer H. 
Published: April 2011

ABSTRACTShort-period (InAs)6/(AlSb)6 superlattices (SL) with AlAs-like and InSb-like interfaces (IF) grown on a relaxed AlSb buffer layer are studied by X-ray reflectivity and diffractometry measurements. Reflectivity measurements reveal average IF roughnesses between 0.6 and 1.0 nm. Measurements of the diffuse scattering show that the roughness is highly correlated from layer to layer. Triple crystal area scans illustrate that the inhomogeneous deformation of the buffer layer leads to a certain symmetric peak broadening. In the case of AlAs-like IFs an additional broadening of the SL peaks reveals lattice parameter gradients over the superlattice. This asymmetric peak broadening may be attributed to a further relaxation of the superlattice, which is inhomogeneous with depth. The diffusion of As into the AlSb layers leads to a peak shift and modifies the intensity ratios of the different satellite reflections. The best structural quality is achieved for superlattices with InSb-like IFs.
Dynamics of Surface Segregation During InGaAs Mbe
Authors: Evans Keith R. , Kaspi R. , Ehret J.E. , Skowronski M. 
Published: April 2011

ABSTRACTThe dynamics of In surface segregation during molecular beam epitaxy growth of In.22Ga.78As/GaAs quantum wells (QWs) are studied by temperature-programmed desorption (TPD). The TPD spectra show two In peaks: a low temperature (low-T5) peak and a high temperature (high-T5) peak, which arise from desorption of surface segregated In and dissociation of the underlying InGaAs lattice, respectively. Integration of the low-Ts peak provides quantitative determination of the surface segregated In population ΘIn, as a function of InGaAs layer thickness, incident arsenic dimer flux [(Fi(As2)], InGaAs growth temperature, and GaAs cap thickness. The surface segregated In population ΘIn, is observed to grow with InGaAs thickness, until reaching a temperature-dependent steady state value between 1.0 and 2.0 monolayers after approximately ten monolayers of growth, and then decays during GaAs overlayer growth. The variation of ΘIn with thickness closely mimics the resulting vertical composition profile, which is characterized by an In-depleted bottom interface and segregation of In into the GaAs cap. Based on these results, a sequence of: 1) In predeposition, 2) InGaAs growth, and 3) thermal desorption of Eh is proposed to produce a more square InGaAs/GaAs QW than can be obtained by more standard MBE approaches.
Surfactant-Mediated Growth of Aigaas by Molecular Beam Epitaxy
Authors: Kaspi Ron , Evans Keith R. , Reynolds Don C. , Brown Jeff , Skowronski Marek 
Published: April 2011

ABSTRACTAntimony was used as a surfactant during solid-source molecular beam epitaxy of AIGaAs layers. A steady-state surface-segregated population of Sb was maintained at the AIGaAs growth surface by providing a continuous Sb2 flux to compensate for loss due to thermal desorption. Above ∼ 650 °C, the incorporation rate of Sb was negligible, thereby allowing the deposition of AlGaAs layers despite the presence of Sb at the surface. A significant improvement in the optical quality of Al0.24Ga0 76As layers was observed by photoluminescence. In addition, extended reflection high energy electron diffraction oscillations and a reduction in Al0.24Ga0.76As surface roughness was observed when Sb was employed as a surfactant.
On thon the Photoemission from Quantum Confined Strained III–V Systems
Authors: Ghatak Kamakhya P. , Nag B. , Mazumder G. 
Published: April 2011

ABSTRACTIn this paper we have studied the photoemission from quantum wells (QW), quantum wells wires (QWWs) and quantum dots (QDs) of quantum confined strained III–V compounds on the basis of a newly formulated electron dispersion law. It is found taking such quantum confined Hg1–xCdxTe and In1–xGaxAsyP1–y lattice matched InP as examples that the photoemission increases with increasing energy of the incident photons in a ladder like manner and also exhibits oscillatory dependences with changing electron concentration and film thickness respectively for all types quantum confinement. The photoemitted current is greatest in strained QDs and least in unstrained QWs. In addition the theoretical results are in agreement with the experimental datas as given elsewhere.
Spatial Concentrations of Silicon Atoms in RF Discharges of Silane
Authors: Roth R. M. , Spears K. G. , Wong G. 
Published: April 2011

AbstractA capacitively coupled rf glow discharge of silane in argon was studied to determine the spatial concentration of silicon atoms. Laserinduced fluorescence was used to determine the ground state concentration profiles. The fluorescence profiles clearly show the sharp boundaries of the sheath regions. The dc bias voltage, silane mole fractions, flow rates, and chamber pressure were all varied to establish the sensitivity of the silane profiles. The existing theory of sheath formation is used to qualitatively understand the existence of sharp spatial boundaries and the sensitivity of the anode sheath region to plasma chemistry.
Effects of the Combined Exposure of Silicon to Beams of Low-Energy Argon Ions and Halogen-Containing Molecules
Authors: Kolfschoten A. W. 
Published: April 2011

AbstractThis paper reviews our results of modulated ion beam studies of the ion-assisted etching of Si. It is shown that the experimental data of the Si(C12, Ar+) reactive system can be described by a model based upon an ion-bombardment induced amorphousness of the Si substrate and the formation of a mixed surface region of several atomic layers of chlorine, argon and silicon. It is also shown that the model is in general agreement with the experimental data of the Si(XeF2, Ar+) and C(H, Ar+) systems.
Cl2 Chemically Assisted Sputter-Etching of Permalloy
Authors: Vasile M. J. , Mogab C. J. 
Published: April 2011

AbstractRedeposition-free patterns have been etched in 3000Å thick permalloy films using the technique of chemically assisted sputter-etching. This technique involves the simultaneous adsorption of a reactant gas from a molecular beam source and normally incident argon ion bombardment. Experimental conditions with Cl2 adsorption can be maintained to etch the permalloy at 80Å/min and to etch positive photoresist at 110Å/min. These etch rates are not significantly different from rates obtained with argon ion milling, even though the permalloy surface is known to incorporate Cl2. Re-deposited material observed with Cl2 chemically assisted sputtering has been shown to be water soluble, and can be completely removed from feature side-walls prior to stripping the resist. Linewidth measurements show that no feature broadening occurs on 2 micron line and space patterns, within the precision of the measurement (±0.2 micron).
Applications of Optical Emission Spectroscopy to Semiconductor Processing
Authors: Shabushnig John G. , Demko Paul R. , Savage Richard N. 
Published: April 2011

AbstractOptical emission spectroscopy (OES) has proven to be a valuable tool in the development and production of state-of-the-art semiconductor devices. Application to the plasma etching of a variety of materials necessary for integrated circuit fabrication is discussed, with particular emphasis placed on etch endpoint analysis. The utility of OES techniques in monitoring photolithographic processes is also presented.
Silane Discharge Gas and Surface Reactions
Authors: Gallagher Alan 
Published: April 2011

AbstractIn order to control the quality and properties of hydrogenated amor-phous silicon (a–Si:H) semiconductors produced by discharge deposition, we would like to control the gas species produced in the discharge and to understand how these deposit and influence the film properties. One would like to separately consider the gas processes that yield the mix of species arriving at the surface, and then the surface processes. I will somewhat follow that separation here, but it appears that many of the species found in the gas may, in fact, be released from the surface. Thus, the gas species appear to result from gas and surface reactions, and a sequential separation is actually not possible. Similarly, the study of the surface deposition process requires forming various radical species as well as an a–Si:H surface, which inevitably will involve the gas processes. Thus we really have coupled problems.
Fabrication of Semiconductor Nanostructures With an Atomic Force Microscope
Authors: Snow E. S. , Campbell P. M. 
Published: April 2011

ABSTRACTAn AFM-based nanolithography process is described. We employ the local electric field of a metal-coated AFM tip which is operated in air to selectively oxidize regions of a H-passivated Si surface. The resulting oxide, ∼ 3 nm thick, is used as a mask for selective etching of the unoxidized regions of Si. This AFM-based fabrication process is fast, reliable, simple to perform and is well suited for device fabrication. We apply this technique to the fabrication of Si and GaAs nanostructures, as well as to the fabrication of a nanometer-scale Si side-gated transistor. In addition, we discuss the ultimate resolution limits of the technique.
SPM-Based Lithography for Electronics Device Fabrication: New Strategies and Directions
Authors: Dagata J. A. 
Published: April 2011

ABSTRACTDirect patterning of a semiconductor surface to produce an ultrathin oxide mask has proven to be a promising approach for integrating lithographic methods based on scanned probe microscopy (SPM) into existing electronics device processing. The resulting masks are capable of withstanding the necessary etching and thermal cycling required for pattern development. Recent work has validated the concept for the fabrication of silicon devices. The current challenges which face this active research area will now require a detailed, predictive understanding of the mechanism responsible for oxidation within an SPM junction in order for the process to optimized with respect to write speed, resolution, and reliability.
Creating Three-Dimensionally Confined Nanoscale Strained Structures Via Substrate Encoded Size-Reducing Epitaxy and the Enhancement of Critical Thickness for Island Formation
Authors: Konkar A. , Madhukar A. , Chen P. 
Published: April 2011

ABSTRACTSubstrate encoded size-reducing epitaxy (SESRE) is utilized to fabricate, in-situ, threedimensionally confined InAs volumes on <100> oriented square mesas patterned onto GaAs(001) substrates. As a function of InAs deposition thickness two remarkable results are found: (i) the strain relief available in mesas of linear size ≤ 100 nm allows the mesa top InAs layers up to thickness ∼ 11 ML to remain coherent and maintain 2D morphology even though on unpatterned substrates onset of 3D island formation at ∼ 2 ML InAs is well documented. (ii) With increasing deposition, once the InAs thickness on mesa tops of linear size ∼ 75 nrn reaches ∼ 11 ML, no further growth occurs even for deposition amounts in excess of twice this value. This suggests complete migration of In away from the mesa top to the sidewalls once the InAs thickness on the mesa top reaches ∼ 11 ML even though, at the early stages of deposition, In migrates from the sidewalls to the mesa top. A strain-induced “self-limiting” growth behavior on sub 100nm mesas is thus indicated for the first time.
Probing the Limits of Silicon-Based Nanoelectronics
Authors: Wind S. J. , Taur Y. , Mii Y. , Frank D. J. , Wong H.-S. , Buchanan D. A. , Rishton S. A. , Bucchignano J. J. , Lii Y. , Jenkins K. A. 
Published: April 2011

ABSTRACTThe ability to reduce device features to increasingly smaller dimensions offers the potential for remarkable circuit performance and low power consumption. CMOS (Complementary Metal-Oxide-Semiconductor) devices with 100 nm channel lengths offer a 2X performance gain over 0.25 μm technology at a reduced power supply as well as the potential for a 20X reduction in active power at comparable performance levels. Continued scaling of devices beyond 100 nm dimensions faces various fundamental limitations. Overcoming these limitations will require technological innovation in both device design and fabrication.
Silicon Nanofabrication and Chemical Modification by UHV-STM
Authors: Lyding J. W. , Shen T.-C. , Abeln G. C. , Wang C. , Foley E. T. , Tucker J. R. 
Published: April 2011

ABSTRACTPatterning on the 10 Å size scale has been achieved with a UHV-STM for Si(100)-2×1:H surfaces. Hydrogen passivation serves as a monolayer resist which the STM locally desorbs, exposing clean Si(100)-2×1 for selective chemistry. Two mechanisms have been identified for hydrogen removal by STM electrons: in the field emission regime direct electron stimulated desorption of hydrogen occurs whereas, in the lower energy tunneling regime, hydrogen desorption results from vibrational excitation of the Si-H bond at high tunneling currents. Furthermore, we find that atomic hydrogen is liberated in contrast to molecular hydrogen evolved during thermal desorption. Selective oxidation and nitridation of the STM-patterned areas has been achieved.