Passivation layer development for GaN based power devices

In this study, various passivation layers are developed and characterized for gallium nitride (GaN) transistors used in power electronics applications. Dielectric properties of the passivation material on high breakdown voltage devices directly affect both the breakdown voltage and efficiency. That's why, the high voltage strength of the passivation material used has a crucial importance besides the device structure. Silicon nitride and silicon oxide passivation layers were grown with different deposition conditions by plasma enhanced chemical vapor deposition (PECVD) technique. After forming metal-insulator-metal structure with the deposited dielectric thin films, refractive index, dielectric constant, and breakdown voltages were determined, by using ellipsometry, capacitance-voltage and current-voltage measurements, respectively. Thus, the effect of plasma parameters on the optical and electrical properties of the dielectric materials was investigated. The best dielectric strength materials achieved were applied on GaN transistors as passivation layers. And the effect of the passivation layer on the electrical performance of the device was investigated.