The Trade-Off Between Microwave Frequency and Output Power in SiC Photoconductive Switches Based on Carrier Lifetime

The trade-off between microwave frequency and output power in VCSI 4H-silicon carbide (SiC) photoconductive semiconductor switch (PCSSs), based on carrier lifetime is investigated. PCSSs with two different vanadium doping concentrations are fabricated and tested across a frequency range of 0.5–2 GHz. The output power and modulation depth ratio trends with microwave frequency indicate a trade-off between microwave frequency and output power. The two devices exhibit output powers of approximately 40 W (@0.5 GHz) and 160 W (@0.5 GHz), respectively. Employing transient absorption (TA) techniques, the carrier lifetime of the two devices is determined to be 30 and 460 ps, revealing a relationship between longer carrier lifetime and increased output power. Nevertheless, the longer carrier lifetime also leads to a lower modulation depth ratio. Furthermore, when carrier lifetime ceases to be the primary constraining factor for the device’s frequency response, the upper cut-off frequency is constrained by the interstage capacitance.