4.4 kV β-Ga2O3 MESFETs with power figure of merit exceeding 100 MW cm-2

beta-Ga2O3 metal-semiconductor field-effect transistors are realized with superior reverse breakdown voltages (V (BR)) and ON currents (I (DMAX)). A sandwiched SiN x dielectric field plate design is utilized that prevents etching-related damage in the active region and a deep mesa-etching was used to reduce reverse leakage. The device with L (GD) = 34.5 mu m exhibits an I (DMAX) of 56 mA mm(-1), a high I (ON)/I (OFF) ratio >10(8) and a very low reverse leakage until catastrophic breakdown at similar to 4.4 kV. A power figure of merit (PFOM) of 132 MW cm(-2) was calculated for a V (BR) of similar to 4.4 kV. The reported results are the first >4 kV class Ga2O3 transistors to surpass the theoretical unipolar FOM of silicon.