Escape time model for the current self-oscillation frequencies. in weakly coupled semiconductor superlattices

A semiclassical model was developed to predict the frequencies of current self-oscillations in weakly coupled semiconductor superlattices (SLs). The calculated frequency is derived from the classical round trip time in one well and the tunneling probability through the barrier, using the well and barrier width, effective masses and band offsets as well as the resulting energies of the sub- and minibands as input parameters. For all SLs, the measured frequency dependence on the sample parameters can be well described by our model. For weakly (strongly) coupled SLs, the calculated frequencies are somewhat above (below) the observed ones. The changeover from one behavior to the other occurs for SLs with miniband widths of a few meV.