Analysis and Manufacturing of GaN Trench‐Gate MOSFETs with Thick Bottom Dielectric

Herein, A high‐performance GaN vertical trench‐gate metal‐oxide‐semiconductor field‐effect transistor (MOSFET (UMOSFET)) with polyimide (PI) as the thick‐bottom dielectric (TBD) is numerically studied and experimentally demonstrated. It is demonstrated that the inclusion of TBD can effectively suppress the peak electric field at the bottom corner of the gate trench and prevent premature breakdown of the devices. According to the technology computer‐aided design simulation results, the UMOSFETs with larger TBD thickness ( t TBD ) exhibit enhanced breakdown voltage ( V BR ) with minor expense of specific on‐resistance ( R on,sp ) and a significantly improved Baliga's figure of merit. Compared with the conventional GaN UMOSFETs without TBD, the fabricated GaN UMOSFETs with 500 nm‐thick PI as TBD feature a remarkable 1.5 times enhancement in breakdown voltage V BR to 407 V, highlighting the feasibility and potential of the PI‐TBD to propel the further development of GaN vertical devices toward the inherent material and device ultimate.