Channel recessed 4H-SiC MESFETs with F/sub t/ of 14.5GHz and F/sub max/ of 40GHz

Abstract

Channel recessed 4H-SiC MESFETs have demonstrated excellent small signal characteristics and the effect of Si/sub 3/N/sub 4/ passivation on these devices has been studied in this work. A saturated current of 250-270 mA/mm and a maximum transconductance of 40-45 mS/mm were measured for these devices. The 3-terminal breakdown voltage V/sub ds/ ranges from 120 V to more than 150 V, depending on gate-drain spacing. 2/spl times/200 /spl mu/m devices with 0.45 /spl mu/m gate length show high F/sub t/ of 14.5 GHz and F/sub max/ of 40 GHz. After Si/sub 3/N/sub 4/ passivation, the output power and PAE were increased by 40% and 16%, respectively, for CW power measurement. Other measurements, such as, the change in surface potential and the dispersion of the drain current make it clear that the passivation of SiC MESFETs reduces the surface effects and enhances the RF power performance by suppressing the instability in DC characteristics.