DENSITY-OF-STATES AND PHONON-INDUCED RELAXATION OF ELECTRONS IN SEMICONDUCTOR QUANTUM DOTS

To understand the energy relaxation of electrons interacting with both longitudinal-optical (LO) and longitudinal-acoustic (LA) phonons in a semiconductor quantum dot, the electron density-of-states D(E) is cal culated using the Green's-function method taking into account interact ions of all orders and self-consistent level broadening. The D(E) calc ulated for a GaAs dot exhibits sharp peaks (width less than or similar to 0.1 meV) at T=77 K, indicating the absence of fast relaxation in t he usual sense. For level separation near, but not necessarily too clo se to, the LO-phonon energy, the peaks are equally narrow but split by the coherent mixing of electron levels (Rabi splitting). The LA phono ns are much too weak to destroy this coherence. In the time domain, th e electron undergoes rapid (< ps) Rabi flopping between levels.