Control of noise-induced oscillations in superlattices by delayed feedback

The dominant noise source, which effects the electron dynamics in semiconductor nano-structures, is shot noise, which is associated with the tunneling of individual carriers across a potential barrier. We consider noise-induced dynamics of electrons in a superlattice, which consists of alternating layers of two semiconductor materials with different band gaps. The parameters are fixed in the regime below the Hopf bifurcation of spatio-temporal oscillations, where in the absence of noise the system rests in a fixed point. It is shown that in this case noise applied to the superlattice can induce quite coherent oscillations of the current through the device. While the regularity of these oscillations depends on the noise intensity, their dominant frequency remains almost constant with variation of the noise level in the system. Further, we demonstrate that a time-delayed feedback scheme that was previously used to control purely temporal oscillations induced by noise, can not only enhance or deteriorate the regularity of stochastic spatio-temporal patterns but also allows for the manipulation of the system's timescales with varying time delay.