Radio-Frequency Heating of GaAs and SiC Photoconductive Switch for High-Power Applications

The response of a nonlinear opposed contact GaAs photoconductive switch, which is used in high-power microwave generation, was studied for high-power radio-frequency heating effects and compared with a linear-mode SiC switch. Current-controlled negative resistivity behavior was observed at elevated temperature in both cases. Better thermal conductivity and the absence of a heat sink result in a faster temperature increase and in local thermal carrier generation in SiC. Negative resistivity characteristics leading to unstable filamentation and thermal runaway are therefore more severe and occur at a lower bias in SiC as compared with a GaAs switch. To counter such effects, mechanisms to remove excess heat in switches in high-power application must be devised