4H-SiC planar MESFETs with F_max of 40 GHz without trapping effect

The high electric breakdown field, high saturated electron drift velocity, and high thermal conductivity make SiC an attractive material for high power microwave devices. In this work, planar 4H-SiC MESFETs were fabricated using ion-implantation and semi-insulating substrate without recess gate etching to eliminate potential damage in the gate region. Ion-implantation was used to obtain a lower contact resistance. The saturation drain current and transconductance were 440 mA/mm and 26 mS/mm, respectively. The maximum oscillation frequency of 40 GHz and the cut-off frequency of 8.2 GHz were obtained by the RF small-signal measurement. The P_1dB of 21.7 dBm and the output power of 1.5 W/mm were also obtained at 2 GHz by the RF large-signal measurement. The fabricated MESFETs showed the charge trapping-free characteristics due to the surface passivation by the thermal oxidation.