Low-k/high-k double stack field plate structures for high-voltage diamond Schottky barrier diodes

We demonstrate diamond Schottky barrier diodes (SBDs) featuring high breakdown voltage enabled by optimized field plate (FP) structures. A double stack FP configuration combining low- and high- permittivity dielectrics is proposed to overcome the limitations of conventional single layer FP designs. The electric field distribution and breakdown characteristics are systematically analyzed using TCAD simulations to design the proposed structure. The model is calibrated first against experimental results to ensure reliability of the simulations. With the total dielectric thickness fixed at 100 nm, the double stack FP structure improves both the breakdown voltage and Baliga's figure of merit compared with single layer FP structures. In particular, the SiO₂ (50 nm)/HfO₂ (50 nm) stack achieves the most uniform electric field redistribution, resulting in optimal breakdown performance featuring a breakdown voltage of 880 V, which is 4 times higher than that of the SBD without a FP. The study provides practical design guidelines for reliable FP engineering in diamond SBDs.