Influence of Nitrogen doping in Vanadium-compensated 4H-SiC on transient photocurrent response for photoconductive microwave generation

High-frequency microwave generation based on PCSS devices requires the fastest possible response speed. In this study, we successfully demonstrated controlled donor level doping in 4H-SiC PCSS devices to reduce the carrier recombination lifetime and enhance high-frequency microwave generation. PCSSs with three different doping of nitrogen concentrations were manufactured and compared. By femtosecond transient absorption spectroscopy (fs-TAS), we observed that the 4H-SiC PCSS devices doped with lower nitrogen concentrations exhibited significantly shorter carrier recombination lifetime and faster response speed, ranging from 137 ps to 118 ps. Furthermore, experiment results demonstrate that if nitrogen doping concentration was below 10 16 cm -3 , the PCSS devices could generate high-frequency microwave up to 10 GHz, with improved response speed and higher photoelectric efficiency. Consequently, by precisely controlling the nitrogen concentration, it is feasible to enhance the response frequency of photoconductive microwaves.