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Hot-electron overcooling and intersubband population inversion in quantum wires

Monte Carlo simulation of hot photoexcited electron relaxation in rectangular quantum wires is carried out. Simulation shows that at the initial stage the electron cooling dynamics is defined by electron-optical phonon interaction and exhibits strong dependence on excitation energy. When electrons are excited above the optical phonon energy they cool down in a subpicosecond time-scale to the bottom of the first subband. Electrons may even occur below thermal equilibrium energy and then slowly (during tens of picoseconds) relax to equilibrium due to interaction with acoustic phonons. At certain excitation energies strong intersubband electron scattering by optical phonons leads to carrier redistribution and intersubband population inversion.