True random number generator based on spin-orbit torque magnetic tunnel junctions

True random number generators (TRNGs) play a pivotal role in solving NP-hard problems, neural network computing, and hardware accelerators for algorithms, such as the simulated annealing. In this work, we focus on TRNG based on high-barrier magnetic tunnel junctions (HB-MTJs) with identical stack structure and cell geometry, but employing different spin-orbit torque (SOT) switching schemes. We conducted a comparative study of their switching probability as a function of pulse amplitude and width of the applied voltage. Through experimental and theoretical investigations, we have observed that the Y-type SOT-MTJs exhibit the gentlest dependence of the switching probability on the external voltage. This characteristic indicates superior tunability in randomness and enhanced robustness against external disturbances when Y-type SOT-MTJs are employed as TRNGs. Furthermore, the random numbers generated by these Y-type SOT-MTJs, following XOR pretreatment, have passed the National Institute of Standards and Technology SP800-22 test. This comprehensive study demonstrates the high performance and immense potential of Y-type SOT-MTJs for the TRNG implementations.