In solids under irradiation with femtosecond laser pulses, photoabsorption produces a strongly nonequilibrium highly
energetic electrons gas. We study theoretically the ionization of the electronic subsystem of either a semiconductor
(silicon) or a metal (aluminum) target, exposed to an ultra-short laser pulse (pulse duration ~10 fs) of VUV-XUV
photons. We developed a numerical simulation technique, based on the classical Monte-Carlo method, to obtain transient
distributions of electrons within conduction band. We extend the Monte-Carlo method in order to take into account
quantum effects such as the electronic band structure, Pauli's exclusion principle for electrons in the conduction band and
for holes within the valence band (for semiconductors), and free-free electron scattering (for metals).
In the presented work, the temporal distribution of the energy density of excited and ionized electrons were calculated.
The transient dynamics of electrons is discussed regarding the differences between semiconductors and metals. It is
demonstrated that for the case of semiconductors, since a part of the energy is spent to overcome ionization potentials,
the final kinetic energy of free electrons at the end of the laser pulse is much less than the total energy provided by the
laser pulse. In contrast, for metals all the energy is present as kinetic energy in the electronic subsystem, unless the
photon energy is greater that an ionization potential of a deep atomic shell. In the latter case, a part of the energy is
shortly kept by deep-shell holes, and is released back to the electrons by Auger-processes on femtosecond timescales.