Demonstration of Long-Pulse Power Amplification at 1 GHz Using 4H-SiC RF BJTs on a Conductive Substrate

In this letter, we report 4H-SiC RF bipolar junction transistors (BJTs) on an n-type 4H-SiC conductive substrate with, for the first time, RF power amplification at 1 GHz. The devices were fabricated using a double-mesa etch and interdigitated emitter-base finger design. When tested under common-base and pulsed Class AB mode at 1 GHz, the packaged devices with external matching exhibited a 10.1-dB power gain and a 22.9-W output power, with a 40.8% power-added efficiency (PAE) at 1-ms pulsewidth and 10% duty cycle. The RF power density is 313.8 W/cm
²
, normalized to the total emitter finger area. At a longer pulsewidth of 6 ms and the same duty cycle of 10%, devices can still deliver a 16.2-W (222.2 W/cm
²
) output power, with 10-dB gain and 28.3% PAE. The RF performance combined with the lower cost SiC conductive substrate, as compared to the semi-insulating substrate, makes these devices promising for use in power amplifiers for long-pulse L-band radar applications