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 s elf-oscillations in weakly coupled semiconductor superlattices (SLs). The c alculated frequency is derived from the classical round trip time in one we ll and the tunneling probability through the barrier, using the well and ba rrier width, effective masses and band offsets as well as the resulting ene rgies of the sub- and minibands as input parameters. For all SLs, the measu red frequency dependence on the sample parameters can be well described by our model. For weakly (strongly) coupled SLs, the calculated frequencies ar e somewhat above (below) the observed ones. The changeover from one behavio r to the other occurs for SLs with miniband widths of a few meV.