Many optoelectronic modulator designs use waveguides. Coupling light into waveguides requires a difficult alignment step. This dissertation will describe a number of optoelectronic modulators that do not have the tight alignment constraints associated with waveguide-based modulators. The eased alignment constraints may be important for the practical manufacturing and packaging of systems using optical interconnects.

Advanced semiconductor technology is depending on innovation and less on "classical" scaling. SiGe, Ge, and Related Compounds have become a key component of the arsenal in improving semiconductor performance. This issue of ECS Transactions discusses the technology to form these materials, process them, FET devices incorporating them, Surfaces and Interfaces, Optoelectronic devices, and HBT devices.

This cutting-edge book on off-chip technologies puts the hottest breakthroughs in high-density compliant electrical interconnects, nanophotonics, and microfluidics at your fingertips, integrating the full range of mathematics, physics, and technology issues together in a single comprehensive source. You get full details on state-of-the-art I/O interconnects and packaging, including mechanically compliant I/O approaches, fabrication, and assembly, followed by the latest advances and applications in power delivery design, analysis, and modeling. The book explores interconnect structures, materials, and packages for achieving high-bandwidth off-chip electrical communication, including optical interconnects and chip-to-chip signaling approaches, and brings you up to speed on CMOS integrated optical devices, 3D integration, wafer stacking technology, and through-wafer interconnects.

Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.

One possible solution to make viable optoelectronic modulators that meet strict targets down to the scale of on-chip communication is to use germanium-rich materials. Ge/SiGe quantum wells grown on silicon substrates provide the strongest mechanism, the quantum-confined Stark effect (QCSE), and thereby can meet the strictest requirements for optical interconnects, including CMOS-compatibility. Using such a strong effect, Ge-based modulators can be ultra-compact, ultralow-power, large bandwidth and high-speed, making them a strong contender for the future of optoelectronic device integration to solve the bottleneck problem. In this thesis, we will discuss the physical properties of the Ge and SiGe material system then present designs of optoelectronic modulators at the important 1310 nm and 1550 nm communication wavelengths using a program we developed called the Simple Quantum Well Electroabsorption Calculator (SQWEAC). SQWEAC takes the important physical mechanisms present, such as QCSE and indirect absorption, to predict the electroabsorption profile of Ge-based quantum wells. QCSE was experimentally determined on a wide range of samples to show the predictive powers of SQWEAC. Additionally, indirect absorption was also experimentally determined to optimize the physical model for these Ge quantum well devices. In being able to design both 1310 nm and 1550 nm devices using this Ge material system, we provide a platform for designing optoelectronic devices that are Si CMOS compatible and operate over a wide range of wavelengths. These modulators have the capability of providing the large density of information at very low energies per bit required for future interconnect technologies.

Today's computer systems are constrained by the high power consumption and limited bandwidth of inter- and intra-chip electrical interconnections. Optical links could alleviate these problems, provided that the optical and electronic elements are tightly integrated. Most present optical modulators use materials systems that are incompatible with CMOS device fabrication, or rely on weak electrooptic effects that are difficult to utilize for vertical incidence devices. The extremely high communications bandwidth demands of future silicon chips may ultimately require massively parallel free-space optical links based on array integration of such vertical incidence modulators. We have investigated the suitability of surface-normal asymmetric Fabry-Perot electroabsorption modulators for short-distance optical interconnections between silicon chips. These modulators should be made as small as possible to minimize device capacitance; however, size-dependent optical properties impose constraints on the dimensions. We have thus performed simulations that demonstrate how the optical performance of the modulators depends on both the spot size of the incident beam and the dimensions of the device. We also discuss the tolerance to nonidealities such as surface roughness and beam misalignment. The particular modulators considered here are structures based upon the quantum-confined Stark effect in Ge/SiGe quantum wells. We present device designs that have predicted extinction ratios greater than 7 dB and switching energies as low as 10 fF/bit, which suggests that these CMOS-compatible devices can enable high interconnect bandwidths without the need for wavelength division multiplexing. Next, we present experimental results from these Ge/SiGe asymmetric Fabry-Perot modulators. Several approaches were investigated for forming resonant cavities using high-index-contrast Bragg mirrors around the Ge/SiGe quantum well active regions. These include fabrication on double-silicon-on-insulator reflecting substrates, a layer transfer and etch-back process using anodic bonding, and alkaline etching the backside of the Si substrate to leave suspended SiGe membranes. We present results from each of these modulator structures. The best performance is achieved from the SiGe membrane modulators, which are the first surface-normal resonant-cavity reflection modulators fabricated entirely on standard silicon substrates. Electroabsorption and electrorefraction both contribute to the reflectance modulation. The devices exhibit greater than 10 dB extinction ratio with low insertion loss of 1.3 dB. High-speed modulation with a 3 dB bandwidth of 4 GHz is demonstrated. The moderate-Q cavity (Q~600) yields an operating bandwidth of more than 1 nm and permits operation without active thermal stabilization.

"The continually increasing speed of microprocessors over the past forty years has been due in large part to miniaturization. The smaller a transistor is made, the faster it can run, and the more can be packed onto a chip. More recently, the performance of the electrical interconnects, which are responsible for transporting data within the microprocessor and between the microprocessor and memory, has been unable to keep pace. As the interconnect is scaled down along with the transistors, its bandwidth decreases and its latency and power consumption increase. This not only decreases the bandwidth of the interconnect, but also increases both its latency and power consumption. Optical interconnects can directly address these problems by replacing electrical interconnects at the system level. In this work we outline the requirements for a successful optical interconnect, and show that the photonic crystal platform is ideal for optical interconnects. Specifically, we show how photonic crystals can be used to build one of the most basic components of an optical interconnect: the electro-optic modulator, which converts an electrical signal into the optical domain. We will first discuss the potential of photonic crystal slow light for modulation, and then introduce a new multi-channel slow light platform for improved bandwidth. Next we describe the design of a photonic crystal resonator that is embedded entirely in silicon dioxide, which is a fundamental requirement for chip compatibility. This resonator uses a graded cavity design and has a quality factor as high as 300,000. It can be coupled to standard strip waveguides, facilitating the integration of photonic crystal devices with other photonic devices. We will also describe a simplified model of photonic crystal line-defect cavities that can aid in their design. Finally, we propose a design for a low-energy electro-optic modulator based on this graded cavity. Due to the extremely small mode volume possible with photonic crystal resonators, the active region can be on the order of a single cubic wavelength in size. By optimizing a number of parameters, a theoretical switching energy as low as 1 fJ/ bit is possible using this design."--Leaves viii-ix.