  Time-dependent current of the electrons excited in the conduction band after
ultrafast interband photogeneration is studied theoretically. The transient
photocurrent is calculated for the nonlinear regime of response to a stationary
electric field. The response demonstrates transient absolute negative
conductivity when the electrons are excited slightly below the optical phonon
energy, while the periodic oscillations of the electric current appear after
formation of the streaming distribution. The quenching of these peculiarities
by the elastic scattering of electrons is also considered.
