In an increasingly crowded frequency spectrum with strong interfering signals, the distortion performance, or the linearity, of RF circuits is key to their ability to reject strong intermodulation terms that can corrupt the weak but desired carrier signal. A standard figure-of-merit for small-signal linearity is the Input/Output Third Order Intercept Point (IIP3/OIP3), which represents the input/output power level at which the power of fundamental frequency (PFUND) become equal to that of the third-order intermodulation product (P3rd). Clearly, a higher IIP3 number yields improved linearity, and is highly desirable for many circuits. The thesis will focus on describing the issues that can stem in telecommunication systems from these non-linearities. These non-linearities can be modeled by using a rigorous mathematical expansion based on the Volterra Series. The thesis will "demystify" the Volterra series so that it could be readily understood by the circuit designer, without over burdening him with too much mathematics. Using this series, the distortion performance of an amplifier will be quantified based on IIP3 metrics as described above. Having identified sources of non-linearities, and quantifying the effect of each non-linearity on total IIP3 of an amplifier, the thesis will focus on mitigating these non-linearity sources to increase the overall IIP3 of an amplifier. The techniques discussed to do this are based on both novel device design as well as novel circuit techniques. The amplifiers under discussion will all be SiGe based, due to their exemplary RF performances (comparable to III-V devices) at the fraction of the cost.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references (p.64-66).

SixGe1-x is a promising alloy semiconductor material that is gaining importance in the semiconductor industry primarily due to the fact that silicon and germanium form a binary isomorphous system and hence its properties can be adapted to suit the needs of a particular application. Liquid phase diffusion (LPD) is a solution growth technique which has been successfully used to grow single crystals of SixGe1-x. The first part of this thesis discusses the development of a fixed grid solver to simulate the LPD growth under zero gravity condition. Initial melting is modeled in order to compute the shape of the initial growth interface along with temperature and concentration distribution. This information is then used by the solidification solver which in turn predicts the onset of solidification, evolution of the growth interface, and temperature and concentration fields as the solidification proceeds. The results are compared with the previous numerical study conducted using the dynamic grid approach as well as with the earth based experimental results. The predicted results are found to be in good qualitative agreement although certain noticeable differences are also observed owing to the absence of convective effects in the fixed grid model. The second part investigates the effects of crucible translation on the LPD technique using the dynamic grid approach. The case of constant pulling is examined first and compared with the available experimental results. Then a dynamic pulling profile obtained as a part of simulation process is used to achieve the goal of nearly uniform composition crystal. The effect of crucible translation on the interface shape, growth rate, and on the transport process is investigated. Finally, the effect of magnetic field on the LPD growth is examined. / Graduate

No description available.

There are significant differences between experiment and theoretical calculations of the electronic structure of GaSb/GaAs self-assembled quantum dots. Using a multi-band effective mass approximation it is shown that the influence of size and geometry of quantum dots has little or no effect in determining the hydrostatic strain. Furthermore, the valenceband ground state energies of the quantum dots studied are surprisingly consistent. This apparent paradox attributed to the influence of biaxial strain in shaping the heavy-hole and light-hole potentials. Consequently, it is shown that a simple, hydrostatically derived potential is insufficient to accurately describe the electronic structure of such quantum dots. In addition, using the latest experimental results measuring the conductionband offset, it has been shown that much better experimental contact may be achieved for the magnitude of the transition energies derived compared to theoretically derived transition energies. The transition energies of Si/Ge self-assembled quantum dots has also been calculated. In particular, a range of quantum dot structures have been proposed that are predicted to have an optical response in the 3-5 micron range.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: John D. Cressler; Committee Member: John Papapolymerou; Committee Member: Shyh-Chiang Shen.

Schwerpunkte der Arbeit waren die Synthese und in-situ Charakterisierung metastabiler Modifikationen der Elemente Silicium und Germanium, sowie die Darstellung binärer Silicide und Germanide der Erdalkali- und Seltenerdmetalle unter Druck (bis 20 GPa) und bei hoher Temperatur (bis 2200 K). Dabei konnten die Phasenbeziehungen von Allotropen des Germaniums näher beleuchtet werden und es gelang, eine neue Germaniummodifikation, Ge(hR8), in-situ strukturell zu charakterisieren. Die neu dargestellten metastabilen binären Silicide und Germanide unterteilen sich strukturell in solche, die clathratartige Tetrel-Netzwerke mit einer Koordinationszahl von drei und vier enthalten und in jene, bei denen die Anzahl benachbarter Tetrelatome vier übersteigt. So konnten beispielsweise Netzwerke dargestellt werden, die acht homonukleare Silicium oder Germanium Kontakte im Netzwerk aufweisen. Neben der strukturellen Charakterisierung standen die Bestimmungen der elektrischen Leitfähigkeit und des Magnetismus, sowie die Ermittlung der thermischen Eigenschaften im Focus der Arbeit. / Key aspects of the present work were the synthesis and in-situ characterization of metastable modifications of elemental silicon and germanium as well as the preparation of binary silicides and germanides of the alkaline earth and rare earth metals under pressure (up to 20 GPa) and at elevated temperatures (up to 2200 K). In that process the phase relations of germanium allotropes could be examined more closely and led to the preparation of a new germanium modification, Ge(hR8), which could be structurally characterized by in-situ experiments. The prepared silicides and germanides can be structurally separated in those containing clathrate-like networks with a coordination number of three and four and those which contain more neighbors in the network than four e.g., eight homonuclear silicon or germanium contacts in the network of CeSi5 and CeGe5. Beside the structural characterization the determination of the electrical resistivity and the magnetical properties as well as the analysis of the thermal behavior were in focus of the work.

No description available.

Heteroepitaxial SiGe(C) layers have attracted immense attention as a material for performance boost in state of the art electronic devices during recent years. Alloying silicon with germanium and carbon add exclusive opportunities for strain and bandgap engineering. This work presents details of epitaxial growth using chemical vapor deposition (CVD), material characterization and integration of SiGeC layers in MOS devices. Non-selective and selective epitaxial growth of Si1-x-yGexCy (0≤x≤0.30, 0≤y≤0.02) layers have been performed and optimized aimed for various metal oxide semiconductor field effect transistor (MOSFET) applications. A comprehensive experimental study was performed to investigate the growth of SiGeC layers. The incorporation of C into the SiGe matrix was shown to be strongly sensitive to the growth parameters. As a consequence, a much smaller epitaxial process window compared to SiGe epitaxy was obtained. Incorporation of high boron concentrations (up to 1×1021 atoms/cm3) in SiGe layers aimed for recessed and/or elevated source/drain (S/D) junctions in pMOSFETs was also studied. HCl was used as Si etchant in the CVD reactor to create the recesses which was followed (in a single run) by selective epitaxy of B-doped SiGe. The issue of pattern dependency behavior of selective epitaxial growth was studied in detail. It was shown that a complete removal of pattern dependency in selective SiGe growth using reduced pressure CVD is not likely. However, it was shown that the pattern dependency can be predicted since it is highly dependent on the local Si coverage of the substrate. The pattern dependency was most sensitive for Si coverage in the range 1-10%. In this range drastic changes in growth rate and composition was observed. The pattern dependency was explained by gas depletion inside the low velocity boundary layer. Ni silicide is commonly used to reduce access resistance in S/D and gate areas of MOSFET devices. Therefore, the effect of carbon and germanium on the formation of NiSiGe(C) was studied. An improved thermal stability of Ni silicide was obtained when C is present in the SiGe layer. Integration of SiGe(C) layers in various MOSFET devices was performed. In order to perform a relevant device research the dimensions of the investigated devices have to be in-line with the current technology nodes. A robust spacer gate technology was developed which enabled stable processing of transistors with gate lengths down to 45 nm. SiGe(C) channels in ultra thin body (UTB) silicon on insulator (SOI) MOSFETs, with excellent performance down to 100 nm gate length was demonstrated. The integration of C in the channel of a MOSFET is interesting for future generations of ultra scaled devices where issues such as short channel effects (SCE), temperature budget, dopant diffusion and mobility will be extremely critical. A clear performance enhancement was obtained for both SiGe and SiGeC channels, which point out the potential of SiGe or SiGeC materials for UTB SOI devices. Biaxially strained-Si (sSi) on SiGe virtual substrates (VS) as mobility boosters in nMOSFETs with gate length down to 80 nm was demonstrated. This concept was thoroughly investigated in terms of performance and leakage of the devices. In-situ doping of the relaxed SiGe was shown to be superior over implantation to suppress the junction leakage. A high channel doping could effectively suppress the source to drain leakage. / <p>QC 20100715</p>

A background investigation of the total-dose radiation tolerance of a third generation complementary SiGe:C BiCMOS technology platform was performed. Tolerance was quantified under proton and X-ray radiation sources for both the npn and pnp HBT, as well as for an operational amplifier built with these devices. Furthermore, a technique known as junction isolation radiation hardening was proposed and tested with the goal of improving the SEE sensitivity of the npn by reducing the charge collected by the subcollector in the event of a direct ion strike. Three independent systems were designed, including: 1) a charge amplification channel developed as part of a remote electronics unit for the lunar environment, 2) variable bias circuitry for a self-healing radar receiver, and 3) an ultra-fast x-ray detector for picosecond scale time-domain measurements of evolving chemical reactions. The first two projects capitalized on the wide-temperature performance and radiation tolerance of the SiGe HBT, allowing them to operate under extreme environmental conditions reliably and consistently. The third design makes use of the high-frequency capabilities of the HBT, particularly in emitter-coupled logic (ECL) configurations. Findings concerning the performance of these systems and implications for future research are discussed.