<p>This paper proposes GaN-based Junctionless FinFET as a radiation-hardened device. Such devices possess astounding endurance for high energy radiations and prohibit any prominent alteration in the characteristics. Reliable functioning of such devices is crucial in military and space applications. The influence of radiations of distinct Linear Energy Transfer (LET) parameters varying from 2 MeV.cm²/mg to 10 MeV.cm²/mg have been studied to substantiate the attribute of possessing radiation tolerance at high frequencies. The parameters, namely, surface potential, drain current and SEU generation rate have been accounted to analyze the variation produced due to bombardment of radiations. The device has also been optimized in terms of distinct channel, oxide and gate materials. Moreover, the optimization in terms of varied fin height and fin thickness has been performed to ensure the least possible variation in the device characteristics. The device tolerance in a wide range of temperature has also been studied. A comparative study of the outcomes has been performed with already reported varied device structures, namely, Stacked Gate Junctionless FinFET (SG-JL-FinFET) and L-shaped TFET (LTFET). The obtained results corroborate that the proposed device offers astounding immunity against radiations.</p>