Enhanced On-State Performance of Vertical β-Ga 2 O 3 UMOSFETs via MOCVD-Grown Sidewall Regrown Channels

Vertical β-Ga2O3U-shaped trench-gate MOSFETs (UMOSFETs) with a sidewall regrown channel layer are demonstrated to overcome the limited on-state performance in current-blocking-layer (CBL)-based devices caused by etching-induced sidewall damage and deep-level trapping. A conformal unintentionally doped (UID) β-Ga2O3regrown layer is selectively introduced on the trench sidewalls using metal–organic chemical vapor deposition (MOCVD). Electrical measurements and Kelvin probe force microscopy (KPFM) confirm that the regrown layer provides a high-carrier-density conduction path, effectively relocating the channel away from defect-rich etched surfaces and thereby enhancing channel conductivity. As a result, the maximum drain current density (JD,max) increases to 359 A/cm2and 901 A/cm2for devices with 30 nm and 50 nm regrown layers, respectively, while the specific on-resistance (Ron,sp) is reduced from 543.5 mΩ•cm2to 11.8 mΩ•cm2and 7.9 mΩ•cm2. The power figures of merit (PFOM) of the device with 30 nm regenerative layer is 42.5 MW/cm2, which is more than one order of magnitude higher than that of the reference device without regrown-layer. Although the reverse breakdown voltage decreases with increasing regrown-layer thickness due to weakened depletion capability, the results clearly demonstrate the effectiveness of sidewall regrowth as a viable approach for substantially improving the conduction performance of vertical β-Ga2O3UMOSFETs.