Mitigating the Dominance of Channel Resistance in β -Ga 2 O 3 UMOSFETs via Cell Pitch Scaling

This letter presents a systematic investigation of cell pitch (Lcell) scaling from 10 μm down to 5 μm on the electrical characteristics of vertical β-Ga₂O₃ U-shaped trench gate MOSFETs (UMOSFETs), enabled by a self-aligned gate trench etching process. The analysis of the components of the specific on-resistance (Ron,sp) reveals a critical transition: asLcellis scaled, the drift region resistance surpasses the channel resistance to become the dominant performance-limiting factor. The scaled device with aLcellof 5 μm demonstrates the merits of this strategy, achieving a lowRon,spof 8.7 mΩ·cm² and a high breakdown voltage (Vbr) of 1002 V. These parameters yield a power figure of merit (PFOM) of 115 MW/cm², which is the highest among all the reported vertical β-Ga₂O₃ MOSFETs based on current blocking layer up to date. These findings provide a physical roadmap for future optimization of vertical Ga₂O₃ power transistors, highlighting the importance of drift region engineering in addition to channel optimization.