bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boron Doping in Si-MBE
Authors: Eberl K. , Iyer S. S. , Delage S. L. , Ek B. A. , Cotte J. M. 
Published: March 2011

ABSTRACTWe have investigated p-type doping of Si and SiGc layers in M BE by using two different boron sources. One is a SiB alloy which is prepared in situ by melting elemental boron into Si. Typical B concentrations in the source material are a few percent. Doping levels within 1×1018 cm−3 and 5.5×1019 cm−3 can be adjusted within the temperature range of 350°C to 850°C. No indication of segregation or memory effects is found. The activation is between 90 and 100%. The second p-type doping source investigated is a diborane (B2H6) gas source. Diborane provides doping capability in the range between 1016. to 1020. The incorporation efficiency at 550°C is about 2×10'3. It depends on the diborane exposure and the substrate temperature. The activation at 550°C is above 90%. For lower growth temperatures the activation is considerably reduced. The problem of memory effects is discussed.
Comparison of Growth and Strain Relaxation of Si/Ge Superlattices Under Compressive and Tensile Strain Field
Authors: Wegscheider Werner , Eberl Karl , Abstreiter Gerhard , Cerva Hans , Oppolzer Helmut 
Published: March 2011

ABSTRACTOptimization of growth parameters of short period Si/Ge superlattices (SLs) has been achieved via in situ low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) measurements during homo- and heteroepitaxy on Si (001) and Ge (001) substrates. Transmission electron microscopy (TEM) reveals that pseudomorphic SimGe12-m (m = 9 and 3 for growth on Si and Ge, respectively) SLs with extended planar layering can be prepared almost defect-free by a modified molecular beam epitaxy (MBE) technique. Whereas the SLs on Ge can be deposited at a constant substrate temperature, high-quality growth on Si demands for temperature variations of more than 100°C within one superlattice period. Strain relaxation of these SLs with increasing number of periods has been directly compared by means of TEM. For the compressively strained structures grown on Si we found misfit dislocations of the type 60° (a/2)<110>. Under opposite strain conditions i.e. for growth on Ge, strain relief occurs only by microtwin formation through successive glide of 90° (a/6)<211> Shockley partial dislocations. This is consistent with a calculation of the activation energy for both cases based on a homogeneous dislocation nucleation model.
Structural Characterization of P-I-N Diode Superlattice Structures Grown on <100>, <110>, and <111> Orientation Si Substrates
Authors: Adams P. M. , Bowman R. C. , Arbet-Engols V. , Wang K. L. , Ahn C. C. 
Published: March 2011

ABSTRACTP-I-N diodes whose intrinsic region consists of strained layer superlattices (SLS), separated by 40 nm Si spacers, have been grown by MBE on Si substrates with <100>, <110>, and <111> orientations. These structures have been characterized by x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The dual periodicities in these structures produced unique XRD effects and the quality was highly dependent on substrate orientation. The <100> sample was in general free of defects, whereas the <110> and <111> specimens contained significant numbers of twins and dislocations.
Dislocation Glide Velocity in N- and P-Doped Si1−xGex Layers on Si (001)
Authors: Gibbings C. J. , Tuppen C. G. , Higgs V. 
Published: March 2011

ABSTRACTMisfit dislocation glide velocities in Si.94Ge.06 layers doped to 2.1018cm−2 with boron were measured over the temperature range 500 – 600°C and found to be up to two times slower than that of undoped material. Arsenic doped Si.932Ge.0ee layers on silicon were also studied, and the glide velocity was found to be enhanced by a factor of 80 at the lowest temperature (500°C) and highest doping level (9.1018cm−2) consistent with a decrease in the activation energy for glide from approximately 2eV to 1.3eV as the doping level was increased.
Interface Structure of Ge/Si Superlattices Determined by X-Ray Absorption Fine Structure
Authors: Aebi P. , Tyliszczak T. , Hitchcock A. P. , Baribeau J. -M. , Lockwood D. J. , Jackman T. E. 
Published: March 2011

ABSTRACTWe illustrate the usefulness of the Extended X-ray Absorption Fine Structure (EXAFS) technique to determine the amount of interface mixing and strain condition in the study of (SimGen)p short-period superlattices. It is found that for n < 4, the number of Ge and Si nearest neighbours to Ge atoms is consistent with ∼25% interfacial mixing and that the Ge-Ge bond length corresponds to that of coherently strained Ge. The Si-Ge bond length is shorter, close to that of a strained Si0.25Ge0.75 alloy. For n > 4, the Ge-Ge bond length and the number of Si-Ge nearest neighbours increase significantly consistent with partial relaxation and interdiffusion. Raman scattering spectroscopy and x-ray reflectometry measurements are also presented and are consistent with the conclusions of the EXAFS analysis.
Si-Based Photonic Devices by MBE
Authors: Houghton D. C. , Noël J. -P. , Rowell N. L. 
Published: March 2011

ABSTRACTThe prospect of efficient electroluminescence and photodetection in Si-based heterostructures has stimulated considerable interest in recent years. Si-based optoelectronic devices would allow monolithic integration of mature Si technology with optical signal processing. However, Si and epitaxial Si1−xGex/Si (100) alloys are indirect semiconductors and band structure perturbations are necessary to enhance luminescence efficiencies to practical levels. In this review we consider the relative success of the various approaches used to obtain efficient luminescence from Si based heterostructures after first considering the optical properties of Si grown by MBE and doped by several techniques. Exciton binding centers such as isoelectronic defect complexes, zone folding in atomic layer superlattices, e.g. SimGen, and rare earth doping, e.g. Er in Si and Si1−xGex alloys are discussed. The internal quantum efficiencies for the above processes will be compared in both electroluminescence and photoluminescence together with the prospects for room temperature light emission. The twin requirements of band structure engineering and superlative crystal quality extend the challenge to the materials scientist / crystal grower further into the nanoscopic regime. It is a formidable task involving the controlled removal of non-radiative point defects and complexes, controlled introduction of radiative centers, and simultaneous maintenance of coherent interfaces without misfit dislocation injection. Recent progress in our study of intense photoluminescence (wavelength range 1.2 -1.7 μm) from random Si1−xGex alloys (0.53 > × > 0.06) grown by MBE, a 1.5 μm Si0.82Ge0.18/Si LED and a novel Si1−xGex/Si optoelectronic switch will be highlighted.
Integration of Si-MBE and Device Processing
Authors: Gravesteijn D. J. , Van De Walle G. F. A. , Pruijmboom A. , Van Gorkum A. A. 
Published: March 2011

ABSTRACTA review is given of the requirements on MBE-grown layers as far as processing is concerned. Aspects that are considered are: defect density, particulates, background doping and metallic contamination. The stability of the grown layers against thermal anneals is considered. It is shown that normal thermal diffusion in HBT structures is not important, other effects, like transient diffusion following ion implantation, have drastic effects on the grown profiles. As an example the processing of mesa-isolated heterojunction bipolar transistors is treated. It is shown that all-Si transistors can be grown with ideal Gummel plots. The Gummel plots of SiGe HBTs show small non-idealities. The current gain enhancement of the HBTs with respect to the all-Si transistors is shown to be as large as 200 times. Due to transient diffusion, parasitic barriers are formed, that have a detrimental effect on the AC and DC performance.
Characterization and Optical Studies of Short-Period SimGen Superlattices
Authors: Presting H. , Kibbel H. , Kasper E. , Grimmeiss H. G. , Nagesh V. G. 
Published: March 2011

ABSTRACTShort-period SimGen (m monolayer (ML) Si, n ML Ge. n+m<∼40ML∼5.5nm) strained layer superlattices (SLS) are grown on <100> silicon by low temperature molecular beam epitaxy. Various characterization tools such as X-ray diffraction, transmission electron microscopy, Rutherford backscattering, Raman spectroscopy and photocapacitance measurements are used to analyze the growth quality, stram distribution, periodicity, interface sharpness and optical properties of the SLS. Recent photoluminescence experiments give hints of a direct bandgap transition from a 10 ML Si6Ge4 SLS in the near infrared spectral region. I-U and C-U measurements on mesa diodes (Am=2 10−4 cm2) are performed at various temperatures down to T=35K. Photocapacitance measurements show a Wannier-Stark localization of the superlattice states in a p+-n doped Si4Ge4 SLS diode, for the first time observed in type II superlattices. The observed transitions are believed to be defect or impurity related and are discussed in terms of a Wannier-Stark ladder behaviour.
Single and Symmetric Double Two-Dimensional Hole Gases at Si/SiGe Heterojunctions Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Venkataraman V. , Sturm J. C. 
Published: March 2011

ABSTRACTTwo dimensional hole gases have been investigated in Si/SiGe modulation doped heterostructures grown by RT-CVD for the first time. Single, both normal and inverted, and double heterostructures were studied. The results suggest that any asymmetry due to dopant segregation or autodoping between the normal and inverted structures occurs on a scale of less than 1 nm.
SiGe Heterojunction Bipolar Transistors
Authors: Arienzo Maurizio , Comfort James H. , Crabbé Emmanuel F. , Marame David L. , Iyer Subramanian S. , Meyerson Bernard S. , Patton Gary L. , Stork Johannes M. C. , Sun Yuan-Chen 
Published: March 2011

ABSTRACTStrained layer growth of SiGe on Si by either Molecular Beam Epitaxy (MBE) or various methods of Chemical Vapor Deposition (CVD), including Limited Reaction Processing (LRP) and Ultra High Vacuum CVD (UHV/CVD) have been used to realize narrow bandgap base double heterojunction bipolar transistors (HBTs). This review paper will focus on the fabrication of high performance transistors, and on the material and process challenges facing the implementation of SiGe HBT technology. In particular, the use of SiGe alloys for bandgap engineering of bipolar devices and the development of self-aligned, epitaxial base bipolar device structures will be discussed, including the most recent accomplishment of 75 GHz ƒr heterojunction bipolar transistors, and the record sub-25 ps EC L ring oscillator delay. The design flexibility and trade-offs offered by SiGe heterojunction technology, like junction field/capacitance control, liquid nitrogen operation and complementary processes, arc also reviewed, to assess the leverage of a SiGe base bipolar technology in high speed circuits.
Charge Control in SiGe Quantum-Well MOSFETs and MODFETs
Authors: Hofmann Karl R. 
Published: March 2011

ABSTRACTA one-dimensional charge control model based on the self-consistent numerical solution of the Schroedinger and Poisson equation has been developed for n- and p-channel quantum-well (QW) MOSFETs and MODFETs in the strained-layer SiGe heterostructure material system. Results are presented for prototype QW n-channel MODFET and MOSFET structures experimentally demonstrated in the literature. Side channel formation limits the maximum usable QW channel densities and voltage swings. The optimization of the charge control characteristics of the p-channel QW-MOSFET is achieved by maximizing the Ge content of the QW SiGe layer and minimizing the Si spacer thickness to the oxide. Channel densities on the order of 1×1013cm22 are feasible.
Silicon-Based Long Wavelength Infrared Detectors Fabricated by Molecular Beam Epitaxy
Authors: Lin T. L. , Jones E. W. , George T. , Ksendzov A. , Huberman M. L. 
Published: March 2011

ABSTRACTSiGe/Si heterojunction internal photoemission (HIP) long wavelength infrared (LWIR) detectors have been fabricated by molecular beam epitaxial (MBE) growth of p+ SiGe layers on p-type Si substrates. The SiGe/Si HIP detector offers a tailorable spectral response in the long wavelength infrared regime by varying the SiGe/Si heterojunction barrier. Degenerately doped p+ SiGe layers were grown by MBE using either HBO2 or elemental boron as the dopant source. Improved crystalline quality and lower growth temperatures were achieved for boron-doped SiGe layers as compared with the HBO2-doped layers. The dark current density of the boron-doped HIP detectors was found to be thermionic emission limited and was drastically reduced as compared with that of HBO2-doped HIP detectors. The heterojunction barrier was determined to be 0.066 eV from activation energy analysis of the HIP detectors, corresponding to a 18 μm cutoff wavelength. Photoresponse of the detectors at wavelengths ranging from 2 to 12 μm has been characterized with corresponding quantum efficiencies of 5 – 0.1%.
Optical Properties and Internal Photoemission in Epitaxial Composites of CoSi2 Particles in Silicon
Authors: Jimenez J. R. , Schowalter L. J. , Fathauer R. W. 
Published: March 2011

ABSTRACTAn analysis of optical absorption and internal photoemission in epitaxial CoSi2 particles buried in silicon is carried out. The optical absorption is dominated by the well-known surface plasma resonance, and calculations of the surface plasma frequencies, using the previously measured dielectric constant of CoSi2, agree well with experiment. A model for the photoemission yield is presented which includes the effects of the surface plasmon excitation and decay. The model can reproduce the observed features of the yield in photoresponse experiments. A model for the replenishment of photoemitted carriers is also presented, in which the metal particles acquire a small steady-state charge under illumination.
Carbonization Dynamics of Silicon Surfaces By Hydrocarbon Gas Molecular Beams
Authors: Yoshinobu Tatsuo , Fuyuki Takashi , Matsunami Hiroyuki 
Published: March 2011

ABSTRACTCarbonization dynamics of Si surfaces using a hydrocarbon gas molecular beam was investigated. In case of carbonizing atomically clean Si surfaces with C2H2, single crystalline 3C-SiC layers were obtained only In the narrow range of a substrate temperature near 780 °C. Control of surface reaction by a cap of very thin surface oxide layer and gradual increase of substrate temperature during carbonization were found to be effective in forming single crystalline 3C-SiC layers reproducibly.
Dopant Enhanced Low-Temperature Epitaxial Growth by Rapid Thermal Processing Chemical Vapor Deposition
Authors: Hsieh T. Y. , Jung K. H. , Kwong D. L. 
Published: March 2011

ABSTRACTWe have demonstrated, for the first time, that the epitaxial growth temperature can be lowered by dopant incorporation using rapid thermal processing chemical vapor deposition (RTPCVD). Heavily arsenic-doped epitaxial layers with very abrupt dopant transition profiles and relative uniform carrier distribution have been achieved at 800°C. The defect formation is closely related to dopant concentration; the defect density as a function of carrier concentration shows a sharp transition at about 3×1018 cm−3.
Observation of Intersubband Absorption in Boron δ-Doped Si Layers
Authors: Park J. S. , Karunasiri R. P. G. , Wang K. L. , Mii Y. J. , Murray J. 
Published: March 2011

ABSTRACTStrong hole intersubband infrared absorption in δ-doped Si multiple quantum wells is observed. The structures consist of 10 periods of boron doped Si quantum wells and undoped Si barriers. Near 100 % infrared absorption is measured by FTIR spectrometer using waveguide structures. Absorption peaks ranging between 3–7 μm are measured, and these peaks can be tuned by varying the doping concentration in the δ-doped layer. Polarization dependence has been verified to agree with the intersubband selection rule. The estimated peak energy positions using a self-consistency calculation are considerably lower than experimental values, probably due to a large exchange energy of many body effects. This observation suggests multiple quantum well IR detectors using Si- technology.
Applications of In Situ Ellipsometry in RTP Temperature Measurement and Process Control
Authors: Massoud Hisham Z. , Sampson Ronald K. , Conrad Kevin A. , Hu Yao-Zhi , Irene Eugene A. 
Published: March 2011

AbstractThe applications of in situ automated ellipsometry in the measurement and control of temperature in rapid-thermal processing (RTP) equipment are investigated. This technique relies on the accurate measurement of the index of refraction of a wafer using ellipsometry and the strong temperature dependence of the index of refraction to determine the wafer temperature. In principle, this technique is not limited to silicon wafer processing and could be applied to any surface whose index of refraction has a strong and well known temperature dependence. This technique is non-invasive, non-contact, fast, accurate, compatible with ultraclean processing, and lends itself to monitoring the dynamic heating and cooling cycles encountered in rapid-thermal processing.
Characterization of Preclean Induced Surface Damage by Rapid Thermal Processing
Authors: Hsieh T. Y. , Jung K. H. , Kwong D. L. , Koschmieder T. H. , Thompson J. C. 
Published: March 2011

AbstractIn-situ precleaning of the substrate surface plays a critical role in Si epitaxial growth. We have demonstrated that the preclean process can cause considerable surface damage, which strongly depends on process parameters such as system base pressure and temperature. Nomarski optical microscopy, SEM, and optical reflectance were used to characterize the surface morphology. Optical reflectance was more sensitive to surface damage but was also strongly dependent on substrate dopant redistribution after high temperature processing.
The Gettering and Electrical Activity of Ni, Au, and Cu in Epitaxial Si/Si(2%Ge)/Si during RTA
Authors: Zhou Tian-Qun , Buczkowski Andrzej , Radzimski Zbigniew , Rozgonyi George A. 
Published: March 2011

AbstractA study of gettering and electrical activity of metallic impurities Ni, Au and Cu has been carried out on epitaxial Si/Si(2%Ge)/Si wafers containing interfacial misfit dislocations. The impurities were intentionally introduced from a backside deposited thin metal followed by rapid thermal annealing (RTA). Transmission Electron Microscopy (TEM) results indicate that the impurities were gettered along the misfit dislocations in near-surface regions either as Au precipitate colonies, or as NiSi2 and CuSi silicide precipitates. Data from Scanning Electron Microscopy (SEM) in the Electron Beam Induced Current (EBIC) mode revealed that these precipitates dominate the recombination properties of the initially inactive misfit dislocation.
The Effects of Plasma Immersion Ion Implantation on Thermal Hillock Formation
Authors: Pico Carey A. , Tao Jiang , Cheung Nathan 
Published: March 2011

ABSTRACTThe effect of shallow (< 500 Å) implanted ions on the formation of thermal hillocks in thin (5000 Å) patterned Al9 9w%Si1w%, films was studied. The ions were implanted by plasma immersion ion implantation (PIII) and the gases (N2, O2, and Ar) used in the implantation ranged from completely inert to highly reactive with Al. The voltages used to accelerate the ionized molecules were 2.5 kV to 30 kV. This corresponds to implant depths of 50 Å to 400 Å. The nominal doses were adjusted to achieve a ∼20% dopant concentration over the fullwidth- at-half-maximum of the calculated implant profile. Following implant, the samples were sintered at 450°C for 30 minutes and inspected for thermal hillock formation by scanning electron microscopy. We find that PIII is effective in suppressing thermal hillock formation for implant depths greater than 60 Å.
The Kinetics of Electromigration Damage in Copper Films Studied by Isothermal Resistance Change Analysis
Authors: Park C. W. , Vook R. W. 
Published: March 2011

ABSTRACTElectromigration damage is one of the primary causes of the failure of interconnects in VLSI circuits. In this work, the response of Cu films to electromigration stress has been studied by an isothermal electrical resistance method. Accurate temperature measurement and control of Cu stripes stressed at elevated temperatures and high current densities were accomplished by use of a thin film thermistor. The activation energy and current density exponent were measured for vacuum evaporated Cu films and the values that were obtained are 0.79±0.02eV and 3.6±0.2, respectively. Scanning electron micrographs of stripes that underwent electromigration damage showed many voids in the cathode region, hillocks in the anode region, and both voids and hillocks in the rest of the stripe. The activation energies of two aluminum stripes were also measured by the same method. An average value of 0.54±0.02eV was obtained.
Void Growth as a Function of Residual Stress Level in Thin, Narrow Aluminum Lines
Authors: Korhonen M. A. , Børgesen P. , Paszkiet C. A. , Lee J. K. , Li Che-Yu 
Published: March 2011

ABSTRACTHigh tensile stresses develop in passivated aluminum line metallizations on silicon substrates after excursion to elevated temperatures. The principal mechanisms to relax these stresses at room temperature are plastic deformation and grain boundary void growth. It is shown that stress relaxation and void growth are intimately connected.
Silicon Carbide Whisker Reinforced Aluminum with Improved Temperature Resistance Due to the Use of a Phosphate Binder
Authors: Chiou Jeng-Maw , Chung D.D.L. 
Published: March 2011

AbstractSilicon carbide whisker reinforced aluminum with improved temperature resistance, increased tensile strength and decreased coefficient of thermal expansion was obtained by using a phosphate binder instead of a commonly used silica binder for preparing the SiC whisker preform, to which liquid aluminum was infiltrated in order to form the composite. The composite is attractive for applications as a heat sink with a low coefficient of thermal expansion.
On The Electronic Contribution to Elastic Constants of Ultrathin Films of P-Type Si
Authors: Ghatak Kamaxhya P , De Badal 
Published: March 2011

AbstractIn this paper we have formulated the electronic contribution to the elastic constants in ultrathin films of p-Si by considering the influences of heavy, light and split-off holes respectively. We have suggested an experimental method of determining the same in degenerate materials having arbitrary dispersion laws. The elastic constants increase with increasing hole concentration in an oscillatory way and decrease with increasing film thickness. The theoretical formulation is in agreement with the suggested experimental method of determining second and third order elastic constants.
Microstructure and Mechanical Behavior of Magnetron Sputtered Al-Cu Films
Authors: Lin Tsann , Raman V. 
Published: March 2011

AbstractWe have investigated the microstructure, electrical resistivity and mechanical behavior of DC magnetron sputtered A1-4wt%Cu films. The substrate temperatures were varied systematically from room temperature to 500 °C. Scanning and transmission electron microscopy of the sputtered films show that the top surface of the films sputtered at low temperatures (< 200 °C) exhibits a pure Al-like fine grain morphology. In contrast, sputter deposition at higher temperatures (> 300 °C) produces films that are characterized at the top surface by a distribution of θ’-A12Cu precipitates with a platelet morphology. The mechanical behavior of the sputtered films were investigated by performing indentation tests using a depth-sensing technique.