High Breakdown Voltage (>3 kV) in β-Ga₂O₃ Lateral MOSFETs Enabled by a Si₃N₄ Terminal Structure

We report a lateral β-Ga₂O₃ MOSFET incorporating a simple Si₃N₄ terminal structure for electric-field management. The main contribution of this work is the demonstration that this process-compatible terminal design can enhance the breakdown performance while preserving the forward conduction characteristics of the device. The epitaxial layer exhibits high crystalline quality, a smooth surface morphology, and favorable carrier transport properties. With the Si₃N₄ terminal structure, the device achieves a breakdown voltage exceeding 3 kV, and the average breakdown field is increased from 0.85 MV/cm to 1.63 MV/cm. Meanwhile, the forward conduction characteristics are well maintained. Electric-field simulations further reveal that the Si₃N₄ terminal structure effectively mitigates electric-field crowding at the gate edge, accounting for the improved breakdown behavior. These results demonstrate that the Si₃N₄-based terminal design provides a simple and effective strategy for simultaneously improving breakdown performance and maintaining forward conduction characteristics in lateral β-Ga₂O₃ MOSFETs.