Passivation of Interface Defects in GaN-Based Metal–Insulator-Semiconductor Devices <i>via In Situ</i> Combined Plasma Pretreatments

Gallium nitride (GaN)-based metal-insulator-semiconductor (MIS) devices are essential for advanced power electronics but face performance limitations due to interface defects at the gate dielectric-semiconductor junction. To address these challenges, this study explored the effects and mechanisms of <i>in situ</i> pretreatments with H₂, N₂, and N₂/H₂ plasmas on GaN surfaces, utilizing an ultrahigh vacuum-interconnected system. A combined plasma treatment method was devised to integrate the benefits of three single plasma processes. <i>In situ</i> X-ray photoelectron spectroscopy and cathodoluminescence characterizations, complemented by <i>ex situ</i> atomic force microscopy analysis, demonstrate that the combined pretreatment effectively and nondestructively reduces carbon and oxygen impurities, compensates nitrogen vacancies, and passivates deep-level defects caused by a nonstoichiometric ratio. Furthermore, capacitance-voltage measurements confirm significant improvements in the electrical performance of the GaN MIS structures. The treatment reduces interface defect density by nearly an order of magnitude compared with untreated surfaces. These results underscore the potential of integrated plasma pretreatments to enhance the GaN-based device reliability and expand their applicability in semiconductor technologies.