For the last four decades, Si CMOS technology has been advancing with Moore’s law prediction, working itself down to the sub-20 nm regime. However, fundamental problems and limitations arise with the down-scaling of transistors and thus new innovations needed to be discovered in order to further improve device performance without compromising power consumption and size. Thus, a lot of studies have focused on the development of new CMOS compatible architectures as well as the discovery of new high mobility channel materials that will allow further miniaturization of CMOS transistors and improvement of device performance. Pushing the limits even further, flexible and foldable electronics seem to be the new attractive topic. By being able to make our devices flexible through a CMOS compatible process, one will be able to integrate hundreds of billions of more transistors in a small volumetric space, allowing to increase the performance and speed of our electronics all together with making things thinner, lighter, smaller and even interactive with the human skin. Thus, in this thesis, we introduce for the first time a cost-effective CMOS compatible approach to make high-k/metal gate devices on flexible Germanium (Ge) and Silicon-Germanium (SiGe) platforms. In the first part, we will look at the various approaches in the literature that has been developed to get flexible platforms, as well as we will give a brief overview about epitaxial growth of Si1-xGex films. We will also examine the electrical properties of the Si1-xGex alloys up to Ge (x=1) and discuss how strain affects the band structure diagram, and thus the mobility of the material. We will also review the material growth properties as well as the state-of-the-art results on high mobility metal-oxide semiconductor capacitors (MOSCAPs) using strained SiGe films. Then, we will introduce the flexible process that we have developed, based on a cost-effective “trench-protect-release-reuse” approach, utilizing the industry’s most used bulk Si (100) wafers, and discuss how it has been used for getting flexible and semi-transparent SiGe and Ge platforms. Finally, we examine the electrical characteristics of our materials through the fabrication of high-k/metal gate MOSCAPs with SiGe and Ge as channel material. We present their electrical performance on both non- flexible and flexible platform and discuss further improvement that has to be made in order to get better behaving devices for future MOSFET fabrication.

No description available.

Silicon Germanium, SiGe, is an important emerging semiconductor material. In order to optimize growth techniques for SiGe production, such as Liquid Phase Diffusion, LPD, or Melt Replenishment Czochralski, a good understanding of the transport phenomena in the melt is required. In the context of the Liquid Phase Diffusion growth technique, the transport phenomena of silicon in a silicon-germanium melt has been explored. Experiments isolating the dissolution and transport of silicon into a germanium melt have been conducted under a variety of flow conditions. Preliminary modeling of these experiments has also been conducted and agreement with experiments has been shown. In addition, full LPD experiments have also been conducted under varying flow conditions. Altered flow conditions were achieved through the application of a variety of magnetic fields. Through the experimental and modeling work better understanding of the transport mechanisms at work in a silicon-germanium melt has been achieved. / Graduate

Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 54-02, Section: B, page: 0820.

Thesis (Ph. D.)--Washington State University, August 2008. / Includes bibliographical references (p. 66-68).

Thesis (Ph.D.(Physics))--University of Pretoria, 2009. / Includes abstract in English. Includes bibliographical references. Also available online.

L'utilisation de dispositifs thermoélectriques à base de films minces en SiGe est envisagée dans de nombreuses applications comme la micro-génération de puissance ou le refroidissement localisé de composants microélectroniques. Le SiGe possède en effet un net avantage en terme d'integrabilite mais souffre cependant d'un déficit en terme de performances. Dans le cadre de cette thèse, nous nous sommes intéressés à la nanostructuration de ce matériau en super-réseau de boîtes quantiques (SRBQ), celle-ci devant permettre une forte augmentation de son facteur de mérite, rendue possible par une forte altération du transport thermique à l'échelle nanométrique. La réalisation, par un outil CVD de type industriel, à 750 °C, de SRBQ monocristallins lourdement dopés est présentée à partir d'analyses morphologiques (AFM), structurales (MEB, MET) et chimiques (SIMS). Des phénomènes de forts échanges Si-Ge pendant la croissance sont notamment mis en évidence et corrélés avec des mesures de conductivité thermique qui ne démontrent pas un effet significatif des boîtes sur le transport thermique. L'élaboration de structures polycristallines originales est également présentée. Enfin, la question cruciale de la détermination du facteur de mérite est abordée, notamment concernant les problèmes d'incertitudes de mesure. Une / Use of SiGe thin film thermoelectric devices is planed in many applications such as power microgeneration or local cooling of microelectronic components. One main advantage of SiGe relies on its ability to be monolithically integrated in ICs. However, SiGe is affected by a low coefficient of performance. Within the framework of this thesis, we focused on the nanostructuration of this material in the form of quantum dot superlattices (QDSL), which is expected to allow a strong increase of its figure-of-merit, by altering thermal transport at the nanometer scale. The growth of heavily doped monocrystalline QDSL in an industrial CVD tool at 750°C is presented from morphological (AFM), structural (SEM, TEM) and chemical (SIMS) analysis. Strong Si-Ge intermixing phenomenons are notably brought out and correlated with thermal conductivity measurements that do not demonstrate a significant effect of dots on thermal transport. The growth of original polycrystalline structures is also presented. Eventually, the crucial question of the figure-of-merit determination is addressed in particular with regard to the measurement uncertainty problem. One solution consisting in measuring simultaneously several electrical, thermal and thermoelectric parameters on a same sample is put forward and concretely implemented by the simultaneous fabrication of adapted test devices.

No description available.

<p> As modern digital communications evolve, the requirements imposed on the systems than are required to transmit/receive the signals involved become more stringent. Amplifiers are required to provide gain from low frequencies, sometimes down to DC, up to high frequencies in the order of few to tens of gigahertz. Not only is the gainbandwidth product to be enhanced, but also the amplifier should introduce minimal distortion to the signal and consume as low power as possible. </p> <p> Distributed amplification is a multi-stage broadband circuit technique that may provide such a function. In distributed amplifiers, inter-stage transmission lines provide the capability to reach higher operational frequencies by absorbing the parasitic capacitances of the transistors used. Unlike other broadband topologies that trade-off gain and bandwidth, distributed amplifiers do not, but rather, the trade-off is between gain and delay. As gain stages are added, the gain increases as the bandwidth remains the same but the signal delay is increased. </p> <p> This work considers the silicon germanium (SiGe) heterojunction bipolar transistor (HBT) implementation of distributed amplifiers. SiGe HBTs incorporate a thin SiGe base with Ge profiling to achieve high cut-off frequencies. SiGe BiCMOS processes are silicon based and hence have the major advantage of integrability to the low cost CMOS process unlike ill-V compound semiconductors. Hence, SiGe is a promising technology capable of bridging the performance gap between silicon and m-v semiconductors. </p> <p> The proposed amplifier achieves an approximately flat gain of 6.5 dB and a noise figure of 5.8-9 dB throughout the -3 dB passband of 10.5 GHz. The power consumed is 12.2 mW, significantly lower than previously published results by up to an order of magnitude is some cases. The group delay of the amplifier was found to be approximately constant in the passband at -60 ps. </p> <p> For the first time, temperature measurements are preformed on SiGe HBT DAs. Analysis show that the gain falls drastically with temperature increase due to deterioration in input matching caused by the significant change in the transistors input impedance with temperature. Similarly the NF, increases with temperature due to the decrease in gain. Moreover, noise analysis of SiGe HBT DAs is investigated, producing simulations predicting the NF of the proposed amplifier giving insight as to how noise may be reduced in future designs. </p> / Thesis / Master of Applied Science (MASc)

Silicon photonics offers great benefits in terms of cost, performance and power consumption. This is increasingly important as the demand for internet bandwidth continues to grow. Optical detection in silicon photonics is performed via the integration of germanium, one of the more challenging integration steps during fabrication. This thesis describes research into a novel technique to grow silicon-germanium on silicon and its application in waveguide detectors and research performed into the application of germanium at extended wavelengths of light. Chapter 1 provides a brief introduction to silicon photonics and chapter 2 covers background material on p-n and p-i-n detectors as well as germanium growth on silicon and it’s applications in silicon photonics. Chapter 3 presents work done on a germanium condensation technique using high fluence ion implantation, suitable for straightforward silicon-germanium fabrication. Using this technique a crystalline layer of silicon-germanium with a high concentration of 92% germanium was demonstrated. In addition a semi-empirical model was developed using a segregation coefficient, an enhanced linear oxidation rate and transient enhanced diffusion. This technique was then used to fabricate a photodetector for operation at a wavelength of 1310 nm. While the responsivity of the detector of 0.01 A/W was modest, this work presents the first demonstration of a detector fabricated in this way, and as such provides a foundation for future improved devices. Chapter 4 presents work done on p-i-n germanium detectors to increase their detection limit in the thulium doped fibre amplifier band. This work originally focused on using mid-bandgap lattice defects introduce via ion implantation to improve the detection limit. However, during this experimental work it was determined that the unimplanted samples had a responsivity of 0.07 A/W at 1850 nm and 0.02 A/W at 2000 nm which was higher than that of the defect implanted samples and so the unimplanted samples were investigated further. From this work it was found that the absorption of the germanium detectors was 0.003 μm-1 at 1900 nm, which is approximately a factor of 10 greater than that of bulk germanium. The increased responsivity and absorption coefficient were attributed to tensile strain in the germanium. In Chapter 5 Raman spectroscopy was employed in order to investigate the detectors described in chapter 4 and confirm the presence of tensile strain. When compared with Raman spectra from a bulk germanium sample it was found that the detectors were experiencing 0.27 to 0.48 % tensile strain, consistent with the enhanced absorption at extended wavelengths. Nanowire bridges were then fabricated in germanium and silicon-germanium and characterized using Raman spectroscopy. Germanium was found to have enhanced strain in the nanowire with an enhancement of up to 13.5 demonstrated, whereas for the silicon-germanium samples the structures were shown to reduce the compressive strain in the samples. It is concluded that strain engineering is a very promising route for the development of extended wavelength detectors integrated with silicon photonic systems. / Thesis / Doctor of Philosophy (PhD)