71 W (19.7 W/mm) SiC BJTs for long-pulse UHF radar applications

In this paper, we present 71 W SiC bipolar junction transistors (BJTs) using state of the art technology. The devices were fabricated on a commercial n-type 4H–SiC substrate using a double-mesa etch and interdigitated emitter–base finger design. When operating under common-emitter configuration and long pulse RF conditions of 15 ms pulse width and 25% duty cycle, the packaged devices without internal matching exhibited 8.5 dB power gain and 71 W output power with a 50.7% power added efficiency (PAE) at 500 MHz. The power density is 19.7 W/mm normalized to total emitter finger length. The normally-off characteristic and superior long pulse RF performance makes these SiC transistors promising for use in compact power amplifiers in long-pulse UHF radar systems.