  Physical systems exhibiting fast spontaneous chaotic oscillations are used to
generate high-quality true random sequences in random number generators. The
concept of using fast practical entropy sources to produce true random
sequences is crucial to make storage and transfer of data more secure at very
high speeds. While the first high-speed devices were chaotic semiconductor
lasers, the discovery of spontaneous chaos in semiconductor superlattices at
room temperature provides a valuable nanotechnology alternative. Spontaneous
chaos was observed in 1996 experiments at temperatures below liquid nitrogen.
Here we show spontaneous chaos at room temperature appears in idealized
superlattices for voltage ranges where sharp transitions between different
oscillation modes occur. Internal and external noises broaden these voltage
ranges and enhance the sensitivity to initial conditions in the superlattice
snail-shaped chaotic attractor thereby rendering spontaneous chaos more robust.
