Junctionless tunnel field effect transistor (JLTFET) is one of the most promising devices due to its exceptional performance as it combines the advantages of JLFET (junctionless field effect transistor) and TFET (tunneling field effect transistor). In this study, 20 nm JLTFET is proposed, and for the first time, the device performance is investigated by exposing it to heavy ion radiation for a lower and higher dose of LET values. The most sensitive location for the radiation study is found to be the channel region. The parameters, collected charge ( Q C ), transient peak current ( I peak ), and bipolar gain ( β ) are extracted with respect to time and found to be totally insensitive for lower dose whereas less sensitive for higher dose of LET values. This is due to the maximum electron density prevailing for a higher dose at a particular time instant. The same study is repeated for a varying temperature range from 100 K to 500 K and found that the device is insensitive for lower temperature and lower dose of LET values. It is good to mention that at a lower temperature, subthreshold swing (SS) and β gets decreased whereas for higher temperature, threshold voltage ( V th ) follows a decreasing trend which makes the device suitable for radiation hardening applications.