The practical design of GaN-based Schottky barrier diodes （SBDs） incorporating a field plate （FP） structure necessitates an understanding of their working mechanism and optimization criteria. In this work, the influences of the parameters of FPs upon breakdown of the diode are investigated in detail and the design rules of FP structures for GaN-based SBDs are presented for a wide scale of material and device parameters. By comparing three representative dielectric materials （SiO2, Si3N4 and Al2O3） selected for fabricating FPs, it is found that the product of dielectric permittivity and critical field strength of a dielectric material could be used as an index to predict its potential performance for FP applications.
