  We present an asymptotic analysis of the Gunn effect in a drift-diffusion
model---including electric-field-dependent generation-recombination
processes---for long samples of strongly compensated p-type Ge at low
temperature and under dc voltage bias. During each Gunn oscillation, there are
different stages corresponding to the generation, motion and annihilation of
solitary waves. Each stage may be described by one evolution equation for only
one degree of freedom (the current density), except for the generation of each
new wave. The wave generation is a faster process that may be described by
solving a semiinfinite canonical problem. As a result of our study we have
found that (depending on the boundary condition) one or several solitary waves
may be shed during each period of the oscillation. Examples of numerical
simulations validating our analysis are included.
