Level broadening effects in quantum kinetic equations: Hot luminescence from a quantum wire near the optical-phonon-emission threshold

We consider the quantum kinetic equations in a spatially homogeneous situation for cases in which only level shift and broadening are of importance, while coherence phenomena can be neglected. In this case we can formulate the quantum kinetic equations in a form similar to semiclassical Boltzmann rate equations. We also consider a specific problem: Hot luminescence from a quantum wire near the threshold for optical-phonon emission. The problem is first discussed within the framework of the Boltzmann equation. After pointing out the failure of this description, the Boltzmann equations are generalized to a set of quantum kinetic equations, which in turn are solved in order to describe the luminescence spectra.