Quantum communication networks rely on quantum memory devices to enable long-distance entanglement distribution. Erbium is a promising candidate for quantum memory due to its telecom C-band optical transition, which allows seamless integration with existing fiber-optic infrastructure. However, challenges such as spin coherence limitations, material integration, and non-radiative decay mechanisms must be addressed to realize practical Er-based quantum memory systems. This dissertation investigates the development of erbium-doped titanium oxide integrated with silicon photonics as a platform for quantum memory. A primary focus is the deposition and characterization of Er-doped thin films using atomic layer deposition (ALD), providing a scalable and CMOS-compatible approach to quantum memory fabrication. The integration of Er-doped materials into photonic crystal cavities enables Purcell enhancement, significantly improving optical readout efficiency. The optical measurements provide essential insights into cavity-ion quantum electrodynamics. In particular, the experiment of isolating single erbium ions establish a crucial foundation for realizing spin-photon interfaces, enabling the integration of quantum memories into CMOS-compatible quantum photonic platforms. This work plays a pivotal role in advancing hybrid quantum system integration, a critical step toward enabling scalable and distributed quantum networks. By developing a fully CMOS-compatible platform, this research not only enhances the feasibility of practical quantum memory technologies but also lays the groundwork for next-generation quantum communication infrastructure, accelerating the realization of global quantum networks. Beyond quantum technologies, this thesis also explores broader advancements in photonics, including a novel dynamic quenching method for single-photon avalanche diodes (SPADs) and the development of mechanically stable, ultra-thin anti-reflective coatings (ARCs) for displays. Both studies demonstrate technological progress through innovative integration strategies and process development, contributing to the evolution of photonic engineering.