Record gain at 3.1GHz of 4H-SiC high power RF MESFET
In this paper, a very high gain 4H-SiC power MESFET with incorporation of L-gate and source field plate (LSFPMESFET) structures for high power and RF applications is proposed. The influence of L-gate and source field plate structures on saturation current, breakdown voltage (Vb) and small-signal characteristics of the LSFPMESFET was studied by numerical device simulation. The optimized results showed that Vb of the LSFPMESFET is 91% larger than that of the 4H-SiC conventional MESFET (C-MESFET), which meanwhile maintains almost 77% higher saturation drain current characteristics. The maximum output power densities of 21.8 and 5.5W/mm are obtained for the LSFPMESFET and C-MESFET, respectively, which means about 4 times larger output power for the proposed device. Also, the cut-off frequency (fT) of 23.1GHz and the maximum oscillation frequency (fmax) of 85.3GHz for the 4H-SiC LSFPMESFET are obtained compared to 9.4 and 36.2GHz for that of the C-MESFET structure, respectively. The proposed LSFPMESFET shows a new record maximum stable gain exceeding 22.7dB at 3.1GHz, which is 7.6dB higher than that of the C-MESFET. To the best of our knowledge, this is 2.5dB greater than the highest gain yet reported for SiC MESFETs, showing the potential of this device for high power RF applications.
gain 4h-sic mesfet l-gate source field plate frequency