With remarkable attributes of unique polarization characteristics, high electron mobility, and saturation velocity, gallium nitride (GaN) material has emerged as a key contender in the high-performance semiconductor market, paving the way for the future optoelectronics and high-frequency electronics. The oxide/semiconductor interface quality could significantly impact device performance and reliability if not properly managed. This thesis intends to categorize different types of charge trapping effects at the oxide/semiconductor interface and highlight their influence on the device performance. The approach to identify and separate the influence of different oxide traps is suggested based on electrical characterization methods. The quality of the oxide/GaN interface is discussed in the context of experimentally fabricated MOS capacitors on n-type GaN (000), utilizing dielectric materials grown by plasma-enhanced atomic layer deposition. Additionally, this thesis presents findings from the 1st and 2nd generation GaN homojunction tunnel diodes, contributing to the fabrication of MOS capacitors on p-type GaN (0001) substrate for interface quality studies. Lastly, recommendations for optimized device design are provided based on literature survey.