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The recent development of 8-in Gallium Nitride on Silicon (GaN-on-Si) wafers has facilitated cost effective, large-scale manufacturability of GaN-based electronics. Leveraging its wide band gap, capability to support a two dimensional electron gas (2DEG) layer, and strong built-in polarization effects, GaN-based electronic devices have become a viable cost-effective successor to silicon-based devices for high-performance applications where the large bandgap and high breakdown field are required. The advantageous properties of GaN-on-Si material, however, have yet to be utilized for photonic integrated circuit applications. Therefore, the exploration of GaN for efficient on-chip optical modulation and switching applications is examined. In order to effectively characterize GaN’s capabilities for optical modulation and switching, GaN-based Mach-Zehnder modulators are designed and fabricated. Through simulating the propagating optical modes supported in a GaN-based Mach-Zehnder structure, the geometry of the device is designed to optimize optical modal overlap with the 2DEG layer while maintaining single-mode performance. Through electrical and optical characterization, the effective electro-optic coefficient and Vπ length are measured. These measurements provide a method of benchmarking GaN-based photonic devices for their optical modulation and switching efficiency.