Microfabrication of Active Photonic Devices

Abstract

This thesis focuses on the optimization of microfabrication processes used in photonic devices, specifically GaAs wet etching and silicon thermal oxidation. These processes are important for defining patterns and building material platforms for device fabrication. In the first part, wet chemical etching of GaAs was optimized to achieve controlled material removal in both nanometer and micrometer ranges. Different etching recipes based on citric acid and hydrogen peroxide were tested, and their etch rates were measured. The process also includes the optimization of photolithography, particularly the coating conditions and exposure parameters. The results show that wet etching is a reliable method for controlling etch depth in GaAs substrates, while minimizing surface damage, which is important for near-surface quantum dot structures. In the second part, dry thermal oxidation of silicon and silicon-on-insulator (SOI) substrates was studied to develop a multilayer structure consisting of Si/SiO2/YSZ/ CeO2. The oxidation conditions were optimized to control the growth of SiO2, including oxidation through a crystalline YSZ layer. Structural characterization using X-ray diffraction (XRD), X-ray reflectivity (XRR), and electron microscopy confirmed the formation of the multilayer structure. The results show that oxygen can diffuse through the YSZ layer and oxidize the silicon underneath, although at a slower rate than direct oxidation. A multilayer structure was successfully fabricated by combining pulsed laser deposition (PLD) and thermal oxidation processes. Overall, this work demonstrates a fabrication approach that combines optimized etching and oxidation processes for the development of photonic material platforms