In this era of global connectivity, the billions of smart devices are in thrust of ultra-low power secure computing systems. In this perspective, Physical Unclonable Functions (PUF) are innovative hardware security primitive as they inherent the indispensable IC manufacture variations to generate trusted random keys. However, the existing CMOS based PUFs are prone to severe attacks as the technology matures the attackers too. While when it comes to emerging devices such as TFET, the lack of stabilization in fabrication process become source of extensive manufacturing variations which leverages PUF with additional advantages of low power and circuit integration density. However, like any other emerging device TFET is also facing problems such as ambipolarity and low driving current. In this paper, for the first time Gate All Around (GAA) structure of large range of III-V and IV semiconductors for physically doped TFET has been analysed in order to find most suitable alternative for CMOS in circuit level designing. We found that due to lattice match Ge/GaAs based GAA TFET has highest driving current(ION) of 1.08×10−3 A at low threshold voltage of 0.29 V and transconductance(gm) of 0.25 (m Ω−1). Also, importance of a GAA structure in low power security applications has been illustrated, as it has OFF current in pico Ampere and parasitic capacitance in atto Farad. Further, the impact of random variations on basic device and inverter characteristics of electrically dominant Ge/GaAs based GAA TFET has been investigated first time for designing delay based Ring Oscillator PUF (ROPUF) and finally, its quality factors have been evaluated.