  Evolution of the nonequilibrium carriers excited in the process of decay of
surface plasmon polaritons in metal is described for each step, from the
carrier generation to their extraction from the metal. The relative importance
of various carrier generating mechanism is discussed. It is shown that both
carrier generation and their decay are inherently quantum processes as for
realistic illumination conditions no more than a single SPP per nanoparticle
exists at a given time. As a result, the distribution of non-equilibrium
carriers cannot be described by a single temperature. It is also shown that the
originally excited carriers that have not undergone a single electron-electron
scattering event, are practically the only ones that contribute to the
injection. The role of the momentum conservation in the carrier extraction is
discussed and it is shown that if all the momentum conservation rules are
relaxed, it is the density of states in the semiconductor/dielectric that
determines the ultimate injection efficiency. A set of recommendations aimed at
improving the efficiency of plasmonic-assisted photodetection and (to a lesser
degree) photocatalysis is made in the end.
