  We report the results of molecular dynamics simulation of a spatiotemporal
evolution of the locally photoexcited electrons and holes localized in two
separate layers. It is shown that the ring-shaped spatial pattern of
luminescence forms due to the strong in-layer Coulomb interaction at high
photoexcitation power. In addition, the results predict (i) stationary spatial
oscillations of the electron density in quasi one-dimensional case and (ii)
dynamical phase transition in the expansion of two-dimensional electron cloud
when threshold electron concentration is reached. A possible reason of the
oscillations and a theoretical interpretation of the transition are suggested.
