In this work, we demonstrated Ga2O3-based power MOSFETs grown on c-plane sapphire substrates using in-situ TEOS doping for the first time. Theβ-Ga2O3:Si epitaxial layers were formed by the metalorganic chemical vapor deposition (MOCVD) with a TEOS as a dopant source. The depletion-mode Ga2O3power MOSFETs are fabricated and characterized, showing the increase of the current, transconductance, and breakdown voltage at 150 °C. In addition, the sample with the TEOS flow rate of 20 sccm exhibited a breakdown voltage of more than 400 V at RT and 150 °C, indicating that the in-situ Si doping by TEOS in MOCVD is a promising method for Ga2O3power MOSFETs.