Physically Unclonable Function (PUF) emerged as a prominent hardware security solution for Internet of Things (IoTs) devices. PUFs are also used for generating secret keys for cryptography and for low-cost authentication in the high security of integrated circuits (ICs). Some natural variations occur during the manufacture of ICs. These variations are inevitable and uncertain. The PUF generates a different and unique random number by using this variation as the output key for the same input, even though this variation in the output is very small. In this article, a detailed comparative performance analysis of junctionless field effect transistor (JLFET)-based PUF and dopingless JLFET (DLJLFET)-based PUF is presented. A PUF circuit is designed using a five-stage ring oscillator (RO). It is observed that the delay in DLJLFET-based RO is 61 \(\%\) lower and consumes 47 \(\%\) less energy than JFLET-based RO at a supply voltage of 0.5 V because JLFET shows a higher leakage current due to high doping in the channel. Further, we did Monte Carlo simulation for 100 runs and observed that DLJLFET-PUF gives more unique PUF as mean HD is close to 50 \(\%\) and frequency of oscillation of DLJLFET is about 2 times higher than JLFET-PUF so DLJLFET-PUF will take less time during encryption and decryption for incoming and outgoing data, thus the output key generation will be faster.