Current oscillation in superlattices with different miniband widths

We report on current oscillation at microwave frequencies in n-doped wide-miniband GaAs/AlAs superlattices. We found that, with increasing miniband width (16--72 meV), the oscillation frequency increased (from 2 to 53 GHz). An analysis of the current transport, making use of the continuity and Poisson equation, indicates that the current oscillation was due to propagating dipole domains and that the oscillation frequency corresponded to the transit frequency of the domains.