  Previous theoretical and experimental work has put forward 50-period
semiconductor superlattices as fast, true random number generators at room
temperature. Their randomness stems from feedback between nonlinear electronic
dynamics and stochastic processes that are intrinsic to quantum transitions.
This work theoretically demonstrates that shorter superlattices with higher
potential barriers contain fully chaotic dynamics over several intervals of the
applied bias voltage compared to the 50-periods device which presented a much
weaker chaotic behavior. The chaos arises from deterministic dynamics, hence it
persists even in the absence of additional stochastic processes. Moreover, the
frequency of the chaotic current oscillations is higher for shorter
superlattices. These features should allow for faster and more robust
generation of true random numbers.
