<p>The ringFET devices are investigated for radiation-hardened applications employing advanced semiconductor materials such as SiGe and GaN by conducting 3D TCAD simulations. The most susceptible regions of SiGe and GaN ringFETs are determined by single-event transient (SET) analysis using the interaction of ionizing particles, particularly heavy ions, under varying linear energy transfer (LET) values. The analysis demonstrates that, for both SiGe and GaN devices, the source region exhibits the lowest vulnerability to radiation-induced effects or failures, whereas the channel centre is the most susceptible. Furthermore, the GaN ringFET exhibits superior radiation tolerance compared to SiGe and Si ringFETs, as evidenced by the smaller variations in peak drain current and collected charge under radiation exposure. The inverter circuit implemented with SiGe and GaN ringFETs is also examined under SET conditions, where the GaN-based inverter is observed to exhibit shorter kink duration in transient drain current and reduced collected charge. These findings establish GaN ringFETs as highly suitable for applications requiring robust performance under radiation exposure.</p>