We theoretically investigate dc electron resonant tunneling through an
impurity state in a quantum well assisted by hot acoustical phonons.
Numerical results for the tunneling current, obtained by nonequilibriu
m Green functions, reflect the hot-phonon-induced change in the spectr
um and population of the impurity state. The induced change of the I-V
characteristics has a typical two-peak form, which for larger populat
ions of the level becomes distorted by increased intralevel photon emi
ssions. A qualitative agreement with experiments is obtained.