Fast Physical Random-Number Generation Based on Room-Temperature Chaotic Oscillations in Weakly Coupled Superlattices

An all-electronic physical random number generator at rates up to $80\mathrm{Gbit}/\mathrm{s}$ is presented, based on weakly coupled $\mathrm{GaAs}/{\mathrm{Ga}}_{0.55}{\mathrm{Al}}_{0.45}\mathrm{As}$ superlattices operated at room temperature. It is based on large-amplitude, chaotic current oscillations characterized by a bandwidth of several hundred MHz and do not require external feedback or conversion to an electronic signal prior to digitization. The method is robust and insensitive to external perturbations and its fully electronic implementation suggests scalability and minimal postprocessing in comparison to existing optical implementations.

Figure 1

(a) Schematic representation of the superlattice (SL) device. (b) A plateau region of the $I\mathrm{\text{−}}V$ curve of the SL consisting of two voltage segments (gray regions) characterized by chaotic current oscillations. Most of the presented measurements were carried out at 4.159 V (dashed vertical line). The inset represents the entire $I\mathrm{\text{−}}V$ range. (c) Spectrum of the chaotic oscillations [11]. Inset: A 100 ns trace of SL current oscillations.

Figure 2

(a) Schematic diagram of the RBG method based on discrete time derivative of the digitized current signal and retention of only a number of least significant bits. (b) An example of the 3rd discrete derivative implementation of the method described in (a), where $A_t$ stands for of the digitized signal. (c) Schematic diagram of the parallel combination RBG method where a minus sign stands for the subtraction, i.e., signal of SL1 minus the signal of SL2.

Figure 3

(a) A 100 ns trace of SL oscillations, digitized at 40 GHz (blue line) and 1.25 GHz (red circles). (b) 1st and 4th order discrete derivatives of the SL oscillations sampled at 1.25 GHz and presented in panel (a). (c) Linear combination of 4 recorded superlattice oscillation traces, digitized at 40 GHz.