Chaotic Current Self-oscillations in Doped, Weakly Coupled Semiconductor Superlattices for True Random Number Generation

A weakly coupled semiconductor superlattice (SL) represents an almost ideal one-dimensional nonlinear dynamical system, the nonlinearity of which is due to sequential resonant tunneling between adjacent quantum wells. A great richness of nonlinear transport behavior has been observed in weakly coupled SLs, including periodic as well as quasi-period current self-oscillations and even driven as well as undriven chaos. Recently, spontaneous chaotic and quasi-periodic self-oscillations have been observed in doped GaAs/(Al,Ga) As SLs with 45% Al at room temperature. Based on this type of SLs, an all-electronic true random number generator has been demonstrated at room temperature with achievable bit rates of up to 80 Gbit/s, about two orders of magnitude larger than typical bit rates for currently available all-electronic true random number generators. The synchronization of chaos using these SLs has been demonstrated as a useful building block for various tasks in secure communications. The realization of chaotic SLs without external feedback and the synchronization among differently structured SLs open up the possibility for advanced secure multi-user communication methods based on large networks of coupled SLs.