Silicon nanocrystal devices for silicon photonics

The continued scaling of electronics as predicted by Moore's Law is approaching the point at which interconnects are limiting the improvement in performance gained from decreasing size. Optical interconnects offer one potential solution for the so-called interconnect bottleneck due to their potential to reduce power consumption and improve delay time. However, for optical interconnects to be a realistic solution, they must be compatible with complementary-metal-oxidesemiconductor (CMOS) processing in order to integrate with the extensive infrastructure developed in the electronics industry. The goal of CMOS compatible optical interconnects has driven the development of four major components within the field of silicon photonics: waveguides, modulators, detectors, and light sources. Of these four components, the development of an electrically pumped silicon-based light source has been the most challenging.;Light emission is very inefficient from bulk silicon due to its indirect bandgap. While several potential solutions exist for the development of a silicon-based light source, silicon nanocrystals (Si-ncs) have emerged as one of the most promising approaches. Si-ncs utilize quantum confinement effects to enhance the light emitting capabilities of silicon. Si-ncs can be fabricated using standard CMOS processing techniques and embedded in various host materials, such as SiO2 or Si3N4. Although the insulating properties of these host materials result in low efficiencies, Si-ncs have exhibited the ability to be electrically pumped. Along with their ability to be electrically pumped, Si-ncs may be combined with extrinsic materials such as erbium to produce light emission at telecommunications wavelengths near 1.55 mum. As a result, Si-ncs have emerged as one of the most promising materials for satisfying the necessary requirements for an electrically pumped, CMOS compatible silicon-based light source. In pursuit of this goal, it is important to assess the electrical efficiency of Si-ncs and develop device designs capable of producing a silicon-based laser.;In this work, I present active Si-nc devices with applications in silicon photonics, primarily focused on the development of a silicon-based light source. I first introduce the silicon/silicon dioxide superlattice as a Si-nc material for light emission. I performed extensive material characterization to understand the structure and light emitting capabilities of the material. Subsequently, the Si-nc material was incorporated into traditional light emitting devices (LEDs), which allowed evaluation of the electrical conduction mechanisms, electroluminescence (EL), and device efficiency. I also present distributed Bragg reflector (DBR) cavity-enhanced LEDs. I study the effect of the DBR cavity on the luminescence signals and evaluate the enhancement in the LED efficiency. An alternate electrical pumping scheme based on pulsed excitation was used to further improve the efficiency of the Si-nc LEDs. The pulsed pumping technique utilizes sequential injection of carriers to allow for more reliable operation of the LEDs. I illustrate the advantage of the alternate pumping technique over traditional DC pumping techniques.;After an investigation into several electrically pumped Si-nc devices, I present a concentric microdisk design incorporating the Si-ncs into a two-stage silicon-based laser. The concentric microdisk design leverages the electrical conduction of the Si-ncs and the 1.55 mum emission wavelength of erbium doped glass (Er:SiO2). While some researchers have developed integrated materials combining Si-ncs and Er:SiO2, recent observations of high free carrier absorption (FCA) loss at 1550 nm in Si-nc films may prohibit gain in these films. The two-stage design pursued in this work separates the lasing mode from the Si-nc losses by utilizing EL from the Si-ncs as an optical pump for the Er:SiO2 material. Modeling results for the concentric microdisks outline the requirements for both the Si-nc and Er:SiO2 components of the design. In light of these guidelines, I provide an experimental evaluation of Si-nc microdisks with a focus on the device quality factor.;Although the enhanced FCA effects in Si-ncs present an obstacle in the development of a light source, these effects may be advantageous for other silicon photonic components such as switches and modulators. I illustrate the use of FCA to produce modulation in a Si-nc slot waveguide. A rate equation system was used to model the pump dependent behavior of the device. After fitting the model to the experimental data, I extracted the FCA cross-section of the Si-ncs. Finally, I consider the potential for this device to compete with existing silicon-based modulator technologies.