Chow Chi Fai. / Thesis submitted in: August 2005. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract / Abstract (Chinese) / A cknowledgements / Table of Contents / List of Figures / List of Tables / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- The need for light emission from silicon --- p.1-1 / Chapter 1.2 --- Silicon-based light emitting material 1 - --- p.2 / Chapter 1.3 --- Literature overview --- p.1-4 / Chapter 1.4 --- Project goal --- p.1-10 / Reference --- p.1-11 / Chapter Chapter 2 --- Experimental details / Chapter 2.1 --- Introduction --- p.2-1 / Chapter 2.2 --- Sample preparation techniques --- p.2-1 / Chapter 2.2.1 --- MEVVA ion implantation --- p.2-1 / Chapter 2.2.2 --- PL samples preparation conditions --- p.2-3 / Chapter 2.2.3 --- EL samples preparation conditions --- p.2-4 / Chapter 2.3 --- Characterization techniques --- p.2-7 / Chapter 2.3.1 --- Photoluminescence spectroscopy (PL) --- p.2-7 / Chapter 2.3.2 --- Electroluminescence spectroscopy (EL) --- p.2-9 / Chapter 2.3.3 --- Rutherford backscattering spectroscopy (RBS) --- p.2-10 / Chapter 2.3.4 --- X-ray diffraction (XRD) --- p.2-12 / Chapter 2.3.5 --- Transmission electron microscopy (TEM) --- p.2-13 / Reference --- p.2-15 / Chapter Chapter 3 --- Resutls and Discussions / Chapter 3.1 --- RBS results --- p.3-1 / Chapter 3.2 --- XRD results --- p.3-8 / Chapter 3.3 --- TEM results --- p.3-12 / Chapter 3.3.1 --- Effects of the implantation energy on the microstructure of samples --- p.3-13 / Chapter 3.3.2 --- Effects of the implantation dose on the microstructure of samples --- p.3-16 / Chapter 3.4 --- Photoluminescence results --- p.3-19 / Chapter 3.4.1 --- Effect of implantation energy on the PL --- p.3-19 / Chapter 3.4.2 --- Effect of FA temperature on the PL --- p.3-24 / Chapter 3.4.3 --- Effect of FA duration on the PL --- p.3-26 / Chapter 3.4.4 --- Effect ofRTA duration on the PL --- p.3-28 / Chapter 3.4.5 --- Effect ofRTA temperature on the PL --- p.3-30 / Chapter 3.4.6 --- Effect of implantation dose on the PL --- p.3-32 / Chapter 3.4.7 --- Si band edge enhancement --- p.3-34 / Chapter 3.4.8 --- Photoluminescence spectra as a function of excitation power density --- p.3-37 / Chapter 3.4.9 --- Photoluminescence spectra as a function of measurement temperature --- p.3-45 / Chapter 3.5 --- Electroluminescence results --- p.3-52 / Chapter 3.5.1 --- EL quantum efficiency --- p.3-60 / Reference --- p.3-61 / Chapter Chapter 4 --- Conclusion and future works / Chapter 4.1 --- Conclusion --- p.4-1 / Chapter 4.2 --- Future works --- p.4-2 / Appendix I / Appendix II

A metal-oxide-silicon (MOS) tunneling diode is utilized to embed beta-FeSi 2 precipitates and give strong 1.5 tam electroluminescence at 80 K. And this simple MOS structure with beta-FeSi2 was fabricated by Fe ion implantation and rapid thermal oxidation (RTO) at 900°C, which is fully compatible with ultra-large scale integration (ULSI) processes. / beta-FeSi2 precipitates are also incorporated into a silicon-on-insulator (SOI) rib waveguide and a p+-i-n+ photodetector is monolithically integrated with this SOI rib waveguide. The photoresponse to 1550 nm laser of beta-FeSi2 precipitates was observed and compared to intrinsic silicon. / Beta-phase iron disilicide (beta-FeSi2) is a semiconductor that can act as a light emitting material at the wavelength of 1.55 mum and can also be grown epitaxially on Si substrates. In this thesis, Fe ion implantation into silicon using a metal vapor vacuum arc (MEVVA) ion source was performed to synthesize nano-scale beta-FeSi2 precipitates in silicon matrix. The implantation was performed at ∼-120°C and the effects of silicon substrate and conditions for the following thermal annealing on luminescence properties were studied. The samples were characterized by employing various analytical techniques including Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), atomic force microscope (AFM), photoluminescence (PL), and electroluminescence (EL). / It is found that the PL intensity is optimized in p-100 silicon substrates (with the resistivity of 15-25 O·cm) using Fe ion implantation at a voltage of 80 kV and dosage of 5x1015 cm -2. Formation of beta-FeSi2 can be completed after rapid thermal annealing (RTA) and strong photoluminescence is present. We also found that RTA could maintain the strain in beta-FeSi2 precipitates and there exists an epitaxial relationship between beta-FeSi2 and silicon. Additional furnace annealing at 850°C can relax the strain in beta-FeSi2 precipitates. / The development of both modern microelectronics and lightwave technologies has enabled the establishment of the Internet which has introduced a profound change in our everyday lives. Because of Moore's law, computing today is limited less by the computation ability of microprocessors than by the rate at which the processor can communicate with the outside world. Lightwave technology has had many successes in the long-haul communication field over the past decade. The advantages of lightwave technology over conventional electronics are becoming apparent for shorter and shorter reach applications and lightwave communications may eventually replace copper-based interconnects in microelectronics. To make possible optical interconnects, optical components, especially light emitters may be needed to be integrated on conventional silicon microchips. However, to date, no efficient on-chip silicon-based light emitter is fabricated in silicon photonics. / Sun, Caiming. / Adviser: Hon K. Tsang. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3703. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Fabrication of integrated photonic devices and circuits in a CMOS-compatible process or foundry is the essence of the silicon photonic platform. Optical devices in this platform are enabled by the high index contrast between silicon and silicon on insulator. These devices offer potential benefits when integrated with existing and emerging high performance microelectronics. Integration of silicon photonics with small footprints and power-efficient and high-bandwidth operation has long been cited as a solution to existing issues in high performance interconnects for telecommunications and data communication. Stemming from this historic application in communications, new applications in sensing arrays, biochemistry, and even entertainment continue to grow. However, for many technologies to successfully adopt silicon photonics and reap the perceived benefits, the silicon photonic platform must extend toward development of a full ecosystem. Such extension includes implementation of low cost and robust electronic-photonic packaging techniques for all applications. In an ecosystem implemented with services ranging from device fabrication all the way to packaged products, ease-of-use and ease-of-deployment in systems that require many hardware and software components becomes possible. With the onset of the Internet of Things (IoT), nearly all technologies—sensors, compute, communication devices, etc.—persist in systems with some level of localized or distributed software interaction. These interactions often require a level of networked communications. For silicon photonics to penetrate technologies comprising IoT, it is advantageous to implement such devices in a hardware-software integrated way. Meaning, all functionalities and interactions related to the silicon photonic devices are well defined in terms of the physicality of the hardware. This hardware is then abstracted into various levels of software as needed in the system. The power of hardware-software integration allows many of the piece-wise demonstrated functionalities of silicon photonics to easily translate to commercial implementation. This work begins by briefly highlighting the challenges and solutions for transforming existing silicon photonic platforms to a full-fledged silicon photonic ecosystem. The highlighted solutions in development consist of tools for fabrication, testing, subsystem packaging, and system validation. Building off the knowledge of a silicon photonic ecosystem in development, this work continues by demonstrating various levels of hardware-software integration. These are primarily focused on silicon photonic interconnects. The first hardware-software integration-focused portion of this work explores silicon microring-based devices as a key building block for greater silicon photonic subsystems. The microring’s sensitivity to thermal fluctuations is identified not as a flaw, but as a tool for functionalization. A logical control system is implemented to mitigate thermal effects that would normally render a microring resonator inoperable. The mechanism to control the microring is extended and abstracted with software programmability to offer wavelength routing as a network primitive. This functionality, available through hardware-software integration, offers the possibility for ubiquitous deployment of such microring devices in future photonic interconnection networks. The second hardware-software integration-focused portion of this work explores dynamic silicon photonic switching devices and circuits. Specifically, interactions with and implications of high-speed data propagation and link layer control are demonstrated. The characteristics of photonic link setup include transients due to physical layer optical effects, latencies involved with initializing burst mode links, and optical link quality. The impacts on the functionalities and performance offered by photonic devices are explored. An optical network interface platform is devised using FPGAs to encapsulate hardware and software for controlling these characteristics using custom hardware description language, firmware, and software. A basic version of a silicon photonic network controller using FPGAs is used as a tool to demonstrate a highly scalable switch architecture using microring resonators. This architecture would not be possible without some semblance of this controller, combined with advanced electronic-photonic packaging. A more advanced deployment of the network interface platform is used to demonstrate a method for accelerating photonic links using out-of-band arbitration. A first demonstration of this platform is performed on a silicon photonic microring router network. A second demonstration is used to further explore the feasibility of full hardware-software integrated photonic device actuation, link layer control, and out-of-band arbitration. The demonstration is performed on a complete silicon photonic network with both spatial switching and wavelength routing functionalities. The aforementioned hardware-software integration mechanisms are rigorously tested for data communications applications. Capabilities are shown for very reliable, low latency, and dynamic high-speed data delivery using silicon photonic devices. Applying these mechanisms to complete electronic-photonic packaged subsystems provides a strong path to commercial manifestations of functional silicon photonic devices.

The exponential growth of data generation–driven in part by the proliferation of applications such as high definition streaming, artificial intelligence, and the internet of things–presents an impending bottleneck for electrical interconnects to fulfill data center bandwidth demands. Links now require bandwidths in excess of multiple Tbps while operating on the order of picojoules per bit, in addition to constraints on areal bandwidth densities and pin I/O bandwidth densities. Optical communications built on a silicon photonic platform offers a potential solution to develop power efficient, high bandwidth, low attenuation, small footprint links, all while building off the mature CMOS ecosystem. The development of silicon photonic foundries supporting multi project wafer runs with associated process design kit components supports a path towards widespread commercial production by increasing production volume while reducing fabrication and development costs. While silicon photonics can always be improved in terms of performance and yield, one of the central challenges is the integration of the silicon photonic integrated circuits with the driving electronic integrated circuits and data generating compute nodes such as CPUs, FPGAs, and ASICs. The co-packaging of the photonics with the electronics is crucial for adoption of silicon photonics in datacenters, as improper integration negates all the potential benefits of silicon photonics. The work in this dissertation is centered around the development of silicon photonic multi chip module transceivers to aid in the deployment of silicon photonics within data centers. Section one focuses on silicon photonic integration and highlights multiple integrated transceiver prototypes. The central prototype features a photonic integrated circuit with bus waveguides with WDM microdisk modulators for the transmitter and WDM demuxes with drop ports to photodiodes for the receiver. The 2.5D integrated prototype utilizes a thinned silicon interposer and TIA electronic integrated circuits. The architecture, integration, characterization, performance, and scalability of the prototype are discussed. The development of this first prototype identified key design considerations necessary for designing multi chip module silicon photonic prototypes, which will be addressed in this section. Finally, other multi chip module silicon photonic prototypes will be overviewed. These include a 2.5D integrated transceiver with a different electronic integrated circuit TIA, a 3D integrated receiver, an active interposer network on chip, and a 2.5D integrated transceiver with custom electronic integrated circuits. Section two focuses on research that supports the development of silicon photonic transceivers. The thermal crosstalk from neighboring microdisk modulators as a function of modulator pitch is investigated. As modulators are placed at denser pitches to accommodate areal bandwidth density requirements in transceivers, this thermal crosstalk will become significant. In this section, designs and results from several iterations of custom microring modulators are reported. Custom microring modulators allow for scaling up the number of channels in microring transceivers by offering the ability to fabricate variable resonances and provide a platform for further innovation in bandwidth, free spectral range, and energy efficiency. The designs and results of higher order modulation format modulators, both microring based and Mach Zehnder based, are discussed. High order modulators offer a path towards scaling transceiver total throughput without having to increase the channel counts or component bandwidth. Together, the work in these two sections supports the development of silicon photonic transceivers to aid in the adoption of silicon photonics into data generating systems.

Finally, we also propose and demonstrate an integrated Mach-Zehnder optical diplexer (IMZOD) for possible use in an integrated silicon optical amplifier. The diplexer is based on two rnultimode interferometers (MMIs) and a Mach-Zehnder interferometer (MZI), and has potential use in an integrated silicon waveguide optical amplifier, to combine or separate the pump signal (1440nm) and probe signal (1556nm) for monolithic implementation of a silicon Raman amplifier. / Helium ion implantation can not only reduce the free-carrier loss, but can also enhance the detection responsivity of below-bandgap wavelengths (1440 1590 nm). We propose and demonstrate an in-line channel power monitor (ICPM) based on helium ion implanted silicon waveguides. The implanted waveguide can detect light at 1440 1590 nm which are normally not detectable by silicon. We study the enhanced photoresponse of helium ion implanted waveguide samples which were annealed at different temperatures and for different durations. / Recently there has been much interest in silicon optical amplifiers and lasers relying on stimulated Raman scattering (SRS), which, despite the much shorter waveguide lengths possible in silicon compared with silica optical fiber, can still provide large optical gain because of the large Raman coefficient of silicon and small mode field areas. However, two-photon absorption (TPA) generated free-carrier absorption (FCA) loss can exceed the Raman gain. In this thesis, experiments and theoretical model will he discussed and analyzed, showing that helium ion implantation can successfully reduce the optical losses due to free-carriers and allow net gain to be attained by continuous-wave (CW)-pumped SRS without requiring external bias to remove the photo-generated free carriers. The theoretical study of dynamics of free carrier lifetime of the silicon waveguides will be described. The effective nonlinear length of the silicon waveguides is defined and studied. The theoretical and experimental studies of the enhanced spectral broaden induced by self-phase-modulation (SPM) are carried out in helium on implanted silicon waveguides. / Silicon-on-insulator (SOI) wafers are an attractive platform for the fabrication of planar lightwave circuits (PLCs) because they offer the potential for low-cost fabrication using mature complementary metal--organic--semiconductor (CMOS) compatible processes developed in the microelectronics industry. At the wavelengths of interest for telecommunications, SOI waveguides can have low optical losses (0.1dB/cm). Besides, the strong optical confinement offered by the high index contrast between silicon (Si) (n=3.45) and silicon dioxide (SiO2) (n=1.45) makes it possible to scale photonic devices to sub-micron level. In addition, the high optical intensity arising from the strong optical confinement inside the waveguide makes it possible to observe nonlinear optical effects, such as Raman and Kerr effects, in chip-scale devices. / We then make use of the ICPM to perform a system application, called optical-burst-and-transient-equalizer (OBTE). The OBTE may provide a compact and low-cost solution to compensate gain-transient, gain-spectrum-tilt and to equalize the upstream packet amplitude in erbium doped fiber amplifier (EDFA) amplified hybrid dense-wavelength-division-multiplexed (DWDM) and time-division-multiplexed (TDM) passive-optical-networks (PONs). The OBTE may be monolithically integrated on SOI platform and is potentially low cost and compact. The OBTE can compensate complicated gain slope shape, which may be generated in cascaded EDFAs or deliberate channel add/drop, based on individual channel equalization. 15-dB receiver sensitivity improvement at 10 Gbit/s bit-error-rate (BER) measurements of 10-9 was achieved by the compensation. / Liu, Yang. / "August 2007." / Adviser: Hon Ki Tsang. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1212. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Silicon photonics is emerging as a promising platform for manufacturing and integrating photonic devices for light generation, modulation, switching and detection. The compatibility with existing CMOS microelectronic foundries and high index contrast in silicon could enable low cost and high performance photonic systems, which find many applications in optical communication, data center networking and photonic network-on-chip. This thesis first develops and demonstrates several experimental work on high speed silicon modulators and switches with record performance and novel functionality. A 8x40 Gb/s transmitter based on silicon microrings is first presented. Then an end-to-end link using microrings for Binary Phase Shift Keying (BPSK) modulation and demodulation is shown, and its performance with conventional BPSK modulation/ demodulation techniques is compared. Next, a silicon traveling-wave Mach- Zehnder modulator is demonstrated at data rate up to 56 Gb/s for OOK modulation and 48 Gb/s for BPSK modulation, showing its capability at high speed communication systems. Then a single silicon microring is shown with 2x2 full crossbar switching functionality, enabling optical interconnects with ultra small footprint. Then several other experiments in the silicon platform are presented, including a fully integrated in-band Optical Signal to Noise Ratio (OSNR) monitor, characterization of optical power upper bound in a silicon microring modulator, and wavelength conversion in a dispersion-engineered waveguide. The last part of this thesis is on network-level application of photonics, specically a broadcast-and-select network based on star coupler is introduced, and its scalability performance is studied. Finally a novel switch architecture for data center networks is discussed, and its benefits as a disaggregated network are presented.

The market for higher data rate communication is driving the semiconductor industry to develop new techniques of writing at smaller scales, while continuing to scale bandwidth at low power consumption. The question arises of how to continue to sustain this trend. Silicon photonic (SiPh) devices offer a potential solution to the electronic interconnect bandwidth bottleneck. SiPh leverages the technology commensurate of decades of fabrication development with the unique functionality of next-generation optical interconnects. Finer fabrication techniques have allowed for manufacturing physical characteristics of waveguide structures that can support multiple modes in a single waveguide. By refining modal characteristics in photonic waveguide structures, through mode multiplexing with the asymmetric y-junction and microring resonator, higher aggregate data bandwidth is demonstrated via various combinations of spatial multiplexing, broadening applications supported by the integrated platform. The main contributions of this dissertation are summarized as follows. Experimental demonstrations of new forms of spatial multiplexing combined together exhibit feasibility of data transmission through mode-division multiplexing (MDM), mode-division and wavelength-division multiplexing (MDM-WDM), and mode-division and polarization-division multiplexing (MDM-PDM) through a C-band, Si photonic platform. Error-free operation through mode multiplexers and demultiplexers show how data can be viably scaled on multiple modes and with existing spatial domains simultaneously. This work opens up new avenues for scaling bandwidth capacity through leveraging orthogonal domains available on-chip, beyond what had previously been employed like WDM and time-division multiplexing (TDM). Furthermore, we explore expanding device channel support from two to three arms. Finding that a slight mismatch in the third arm can increase crosstalk contributions considerably, especially when increasing data rate, we explore a methodical way to design the asymmetric y-junction device by considering its angles and multiplexer/demultiplexer arm width. By taking into consideration device fabrication variations, we turn towards optimizing device performance post-fabrication. Through ModePROP simulations, optimizing device performance dynamically post-fabrication is analyzed, through either electro-optical or thermo-optical means. By biasing the arm introducing the slight spectral offset, we can quantifiably improve device performance. Scaling bandwidth is experimentally demonstrated through the device at 3 modes, 2 wavelengths, and 40 Gb/s data rate for 240 Gb/s aggregate bandwidth, with the potential to reduce power penalty per the device optimization process we described. A main motivation for this on-chip spatial multiplexing is the need to reduce costs. As the laser source serves as the greatest power consumer in an optical system, mode-division multiplexing and other forms of spatial multiplexing can be implemented to push its potentially prohibitive cost metrics down. While the device introduces loss, through imperfect mode isolation, as device fabrication improves, tolerance can increase as well. Meanwhile, the rate that laser power consumption increases as supported wavelengths scales is shown to be much faster than the loss introduced by scaling on-chip bandwidth multi-modally. Future generations of ultra-high capacity devices through spatial multiplexing is explored. Already various systems can be implemented multimodally, with the design features serving as useful for other components. Central to photonic network-on-chips, a multimodal switch fabric, composed of microring resonators, is demonstrated to have error-free operation of 1x2 switching of 10 Gb/s data. These contributions aim to scale bandwidth to ultra-high capacity, while ameliorating any imperfect design, through multiple routes conjoined with on-chip spatial multiplexing, and they constitute the bulk of this dissertation. For the latter part, we turn to the issue of integrating a photonic device for dynamic power reallocation in a system. Specifically, we utilize a 4x4 nonblocking switch fabric composed of Mach-Zehnder interferometers that switch both electro-optically and thermo-optically at ns and μs rates respectively. In order to demonstrate an intelligent platform capable of dynamically multicasting data and reallocating power as needed by the system, we must first initialize the switch fabric to control with an electronic interface. A dithering mechanism, whereby exact cross, bar, and sub-percentage states are enforced through the device, is described here. Such a method could be employed for actuating the device table of bias values to states automatically. We then employ a dynamic power reallocation algorithm through a data acquisition unit, showing real-time channel recovery for channels experiencing power loss by diverting power from paths that could tolerate it. The data that is being multicast through the system is experimentally shown to be error-free at 40 Gb/s data rate, when transmitting from one to three clients and going from automatic bar/cross states to equalized power distribution. For the last portion of this topic, the switch fabric was inserted into a high-performance computing system. In order to run benchmarks at 10 Gb/s data ontop of the switch fabric, a newer model of the control plane was implemented to toggle states according to the command issued by the server. Such a programmable mechanism will prove necessary in future implementations of optical subsystems embedded inside larger systems, like data centers. Beyond the specific control plane demonstrated, the idea of an intelligent photonic layer can be applied to alleviate many kinds of optical channel abnormalities or accommodate for switching based on different patterns in data transmission. Besides spatial-multiplexing, expanding on-chip bandwidth can be accomplished by extension of the wavelength detection regime to a longer regime. Experimental demonstration of photodetection at 1.9 μm is shown with Si+-doped Si photodetectors at 1 Gb/s data operation featuring responsivities of .03 AW−1 at 5 V bias. The same way of processing these Si ribbed waveguide photodetectors can garner even longer wavelength operation at 2.2 μm wavelength. Finally, the experimental demonstration of a coherent perfect absorption Si modulator is exhibited, showing a viable extinction ratio of 24.5 dB. Using this coherent perfect absorption mechanism to demodulate signals, there is the added benefit of differential reception. Currently, an automated process for data collection is employed at a faster time scale than instabilities present in fibers in the setup with future implementations eliminating the off-chip phase modulator for greater signal stability. The field of SiPh has developed to a stage where specific application domains can take off and compete according to industrial-level standards. The work in this dissertation contributes to experimental demonstration of a newly developing area of mode-division multiplexing for substantially increasing bandwidth on-chip. While implementing the discussed photonic devices in dynamic systems, various attributes of integrated photonics are leveraged with existing electronic technologies. Future generations of computing systems should then be designed by implementing both system and device level considerations.

Lo, Ming Gai Stanley. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 131-135). / Abstracts in English and Chinese. / Title Page --- p.i / Abstract --- p.ii / Acknowledgements --- p.v / Table of Contents --- p.vii / List of Figures --- p.ix / List of Tabic --- p.xiv / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Photonic Integrated Circuits --- p.1 / Chapter 1.2 --- Silicon Photonics --- p.7 / Chapter 1.3 --- Optical Modulators --- p.15 / Chapter 1.4 --- Modulation Mechanisms in Silicon --- p.19 / Chapter 1.5 --- Motivation --- p.27 / Chapter 1.6 --- Thesis Outline --- p.28 / Chapter Chapter 2: --- Use of Silicon-bascd Modulators in Radio-over-fiber Optical Links --- p.29 / Chapter 2.1 --- Modeling of Linearity of Silicon Carrier Depletion-based Modulators --- p.31 / Chapter 2.2 --- Modeling of Dependence of Linearity on Various Diode Structures --- p.45 / Chapter 2.3 --- Experiment of Radio-over-Fiber Signal Transmission by a Carrier-Injection Silicon Microring Modulator --- p.52 / Chapter 2.3.1 --- Device Fabrication --- p.53 / Chapter 2.3.2 --- Experimental Setups --- p.59 / Chapter 2.3.3 --- Experimental Results --- p.61 / Chapter 2.4 --- Summary --- p.66 / Chapter Chapter 3: --- Novel Diode Structures and T-Rail Travelling-Wave Electrodes to Enhance the Performance of Depletion-based Modulators --- p.67 / Chapter 3.1 --- Requirements of Diode Design for Depletion-based Optical Modulators --- p.70 / Chapter 3.2 --- Diode Design Principle --- p.72 / Chapter 3.3 --- Modeling Results of Vertical-Junction p-n Diodes --- p.79 / Chapter 3.4 --- Fabrication Process of the Silicon Modulator --- p.88 / Chapter 3.5 --- Experimental Results of the Fabricated Devices --- p.92 / Chapter 3.6 --- T-Rail Travelling-Wave Electrodes --- p.102 / Chapter 3.6.1 --- The Limiting Factors to the Speed of Depletion-based Modulators --- p.102 / Chapter 3.6.2 --- The Design Principle of T-Rail Travelling-Wave Electrodes --- p.104 / Chapter 3.6.3 --- The Fabricated Devices --- p.111 / Chapter 3.7 --- Summary --- p.112 / Chapter Chapter 4: --- Conclusion and Future Work --- p.113 / Chapter 4.1 --- Conclusion --- p.113 / Chapter 4.1.1 --- Use of Silicon-based Modulators in Radio-over-fiber Optical Links --- p.113 / Chapter 4.1.2 --- Novel Diode Structures and T-Rail Travelling-Wave Electrodes to Enhance the Performance of Depletion-based Modulators --- p.114 / Chapter 4.2 --- Future Work --- p.116 / Chapter Appcndix-A --- List of Symbols --- p.118 / Chapter Appcndix-B --- List of Abbreviations --- p.120 / Chapter Appcndix-C --- Principles of Various Optical Structures of Modulators --- p.123 / Chapter Appcndix-D --- Modeling of Refractive Index Change by Free-Carrier Plasma Dispersion Effcct --- p.127 / Reference --- p.131 / Publication List --- p.136

M.Sc. (Physics) / Amorphous silicon is one of the most promising materials for large area solar cells for terestrial photovoltaic applications. Unfortunately these cells suffer from two serious problems: the efficiencies drop when laboratory processes are scaled up and the cells degrade after some exposure to sunlight. The exact causes of these two problems are still unknown. In this project some aspects of the latter problem were investigated. The photo-degradation was investigated by illuminating films of a-Si:H with simulated sunlight for different periods of time and then thermally annealing them. The change in the optical properties were investigated with the aid of optical transmission spectroscopy. The films were also characterized by Fourier Transform Infra-Red (FTIR) spectroscopy. The change in the electrical properties of the intrinsic films was determined as function of temperature and total photon flux. No change in the optical properties could be detected. The illumination had-no effect on the FTIR measurements. It seems as if the hydrogen is not involved in the microscopic processes leading to the Staebler-Wronski Effect (SWE). The effect of the photo-degradation manifests itself in a drop in the the dark conductivity and photoconductivity over the total temperature range that was investigated. The observed phenomena are explained in terms of photo-induced deep levels in the gap. The Fermi level shifts to the middle of the gap due to these defect states, causing a drop in the free carrier concentration and conductivity. The measurements of photoconductivity as function of photon energy show that these defect levels increase the absorption coefficient in the long wavelength region, but they also decrease the lifetime of the photo-generated carriers. The photo-induced defects were investigated with the CPM-technique. It was found that the light introduced defects deep in the band gap. The concentration of the defects increases with illumination, but saturates after about 24 hours of illumination. The defects could be annealed almost completely. The microscopic processes causing the photo-degradation of α Si:H solar cells were investigated by comparing the different theoretical models explaining the SWE with the results obtained during this project.

D.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract